Patent Publication Number: US-2009235156-A1

Title: Document processing device and document processing method

Description:
TECHNICAL FIELD 
     The present invention relates to a document processing apparatus and a document processing method, and particularly to a user interface for editing and processing a structured document. 
     BACKGROUND ART 
     XML has been attracting attention as a format that allows the user to share data with other users via a network. This encourages the development of applications for creating, displaying, and editing XML documents (see Patent document  1 , for example). The XML documents are created based upon a vocabulary (tag set) defined according to a document type definition. 
     [Patent Document  1 ] 
     Japanese Patent Application Laid-open No. 2001-290804 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     The XML technique allows the user to define vocabularies as desired. In theory, this allows a limitless number of vocabularies to be created. It does not serve any practical purpose to provide dedicated viewer/editor environments for such a limitless number of vocabularies. However, there is a demand for a technique for improving the ease-of-use of editing a document, even if the document is described in a minor vocabulary used by a small number of users. 
     The present invention has been made in view of such a situation. Accordingly, it is a general purpose of the present invention to provide a processing environment suitable for allowing a structured document to be processed. 
     Means for Solving the Problems 
     In order to solve the aforementioned problems, a document processing apparatus according to an aspect of the present invention comprises: a document readout unit which reads out an XML document described in a first vocabulary; a mapping relation creating unit which detects elements or attributes included in the XML document, and which creates definition data that defines a mapping relation for mapping the elements or the attributes thus detected to those of a second vocabulary that differs from the first vocabulary; an operation input unit which allows a user to input an instruction; and a display processing unit which displays a description structure of at least any one of the elements and the attributes included in the definition data is displayed in a window displayed on a screen using block-shaped objects in a visually comprehensible form. 
     Each of the first vocabulary and the second vocabulary may be a form of XML, examples of which include XHTML, SVG, MathML, etc. The displaying/editing environment for the second vocabulary may be provided in the form of a plug-in. Also, an arrangement may be made in which in a case that a document described in a vocabulary for which there is no available plug-in is to be displayed or edited, definition data is created for mapping the vocabulary to another vocabulary for which there is an available plug-in. Thus, even in a case that a vocabulary cannot be handled by the document processing apparatus, such an arrangement allows a document described in such a vocabulary to be properly displayed. Furthermore, with such an arrangement, the definition data can be easily created and edited via a graphical user interface, thereby allowing the mapping between the vocabularies to be performed in a simpler manner. Such a technique provides a method for handling the theoretically limitless number of vocabularies that can be created, and is thereby endowed with great significance in the field of XML. The definition data may be described in a script language or the like. 
     With such an arrangement, a graphical user interface is used in a step for creating the definition data used for mapping between multiple vocabularies. Furthermore, the description structure of the elements or the attributes specified in the definition data is represented in the form of an inclusion relation among the objects. Such an arrangement allows the user to comprehend the description structure in an intuitive manner. 
     Also, an arrangement may be made in which the display processing unit displays a window including a menu that provides options on a screen, which allows display formats to be applied to the elements and the attributes. With such an arrangement, the operation input unit may receive an instruction to select any one from among the display format options from the menu and an instruction to select any one from among the objects thus displayed. Upon acquisition of the selection instruction, the mapping relation creating unit adds a description, which is an instruction to apply the display format thus selected to the element or the attribute that corresponds to the object thus selected, to the definition data. 
     Such an aspect allows the user to specify a style and so forth via a graphical user interface in a simple manner in a step for creating the definition data used for mapping between multiple vocabularies, instead of manual input according to conventional techniques. 
     Note that any combination of the aforementioned components or any manifestation of the present invention realized by modification of a method, a device, a system, a computer program, a recording medium for storing a computer program, and so forth, is effective as an embodiment of the present invention. 
     ADVANTAGES 
     The present invention provides the advantage of enabling structured documents described in various vocabularies to be displayed or processed in a simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram which shows a configuration of a document processing apparatus according to the background technique. 
         FIG. 2  is a diagram which shows an example of an XML document which is a processing target. 
         FIG. 3  is a diagram which shows an example in which the XML document shown in  FIG. 2  is mapped to a table described in HTML. 
         FIG. 4(   a ) is a diagram which shows an example of a definition file used for mapping the XML document shown in  FIG. 2  to the table shown in  FIG. 3 . 
         FIG. 4(   b ) is a diagram which shows an example of a definition file used for mapping the XML document shown in  FIG. 2  to the table shown in  FIG. 3 . 
         FIG. 5  is a diagram which shows an example of a screen on which the XML document, which has been described in a marks managing vocabulary and which is shown in  FIG. 2 , is displayed after having been mapped to HTML according to the correspondence shown in  FIG. 3 . 
         FIG. 6  is a diagram which shows an example of a graphical user interface provided by a definition file creating unit, which allows the user to create a definition file. 
         FIG. 7  is a diagram which shows another example of a screen layout created by the definition file creating unit. 
         FIG. 8  is a diagram which shows an example of an editing screen for an XML document, as provided by the document processing apparatus. 
         FIG. 9  is a diagram which shows another example of an XML document which is to be edited by the document processing apparatus. 
         FIG. 10  is a diagram which shows an example of a screen on which the document shown in  FIG. 9  is displayed. 
         FIG. 11(   a ) is a diagram which shows a basic configuration of a document processing system. 
         FIG. 11(   b ) is a block diagram which shows an overall block configuration of a document processing system. 
         FIG. 11(   c ) is a block diagram which shows an overall block configuration of a document processing system. 
         FIG. 12  is a diagram which shows a document management unit in detail. 
         FIG. 13  is a diagram which shows a vocabulary connection sub-system in detail. 
         FIG. 14  is a diagram which shows a relation between a program invoker and other components in detail. 
         FIG. 15  is a diagram which shows a structure of an application service loaded to the program invoker in detail. 
         FIG. 16  is a diagram which shows a core component in detail. 
         FIG. 17  is a diagram which shows a document management unit in detail. 
         FIG. 18  is a diagram which shows an undo framework and an undo command in detail. 
         FIG. 19  is a diagram which shows the operation in which a document is loaded to the document processing system. 
         FIG. 20  is a diagram which shows an example of a document and a representation of the document. 
         FIG. 21  is a diagram which shows a relation between a model and a controller. 
         FIG. 22  is a diagram which shows a plug-in sub-system, a vocabulary connection, and a connector, in detail. 
         FIG. 23  is a diagram which shows an example of a VCD file. 
         FIG. 24  is a diagram which shows a procedure for loading a compound document to the document processing system. 
         FIG. 25  is a diagram which shows a procedure for loading a compound document to the document processing system. 
         FIG. 26  is a diagram which shows a procedure for loading a compound document to the document processing system. 
         FIG. 27  is a diagram which shows a procedure for loading a compound document to the document processing system. 
         FIG. 28  is a diagram which shows a procedure for loading a compound document to the document processing system. 
         FIG. 29  is a diagram which shows a command flow. 
         FIG. 30  is a diagram which shows an example of a first XML document. 
         FIG. 31  is a diagram which shows a rendering screen displaying a structure of the relation among multiple elements and attributes included in the definition data in the form of an inclusion relation among blocks. 
         FIG. 32  is a diagram which shows an example of a floating window displayed for allowing the user to set a style for the element or the attribute. 
         FIG. 33  is a diagram which shows an example of the definition data thus edited. 
         FIG. 34  is a diagram which shows the rendered result obtained by converting a first document into a second document with reference to the definition data. 
         FIG. 35  is a functional block diagram which shows a basic configuration of a document processing apparatus according to an embodiment. 
     
    
    
     REFERENCE NUMERALS 
     
         
         
           
               20  document processing apparatus 
               3300  rendering display window 
               3310  parent block 
               3312  first child block 
               3314  second child block 
               3316  first setting box 
               3318  second setting box 
               3320  first grandchild block 
               3322  second grandchild block 
               3324  third grandchild block 
               3330  third setting box 
               3332  fourth setting box 
               3334  fifth setting box 
               3340  attribute block 
               3342  addition box 
               3350  style palette window 
               3352  style menu 
               3354  details field 
               3400  VC processing unit 
               3402  document readout unit 
               3404  mapping relation creating unit 
               3406  mapping processing unit 
               3408  display processing unit 
               3410  candidate storage unit 
               3412  data output unit 
               3414  operation input unit 
               3416  processing control unit 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Description will be made below regarding the background technique for the present invention before detailed description of the present embodiment. 
     (Background Technique) 
       FIG. 1  illustrates a structure of a document processing apparatus  20  according to the background technique. The document processing apparatus  20  processes a structured document where data in the document are classified into a plurality of components having a hierarchical structure. Represented in the background technique is an example in which an XML document, as one type of a structured document, is processed. The document processing apparatus  20  is comprised of a main control unit  22 , an editing unit  24 , a DOM unit  30 , a CSS unit  40 , an HTML unit  50 , an SVG unit  60  and a VC unit  80  which serves as an example of a conversion unit. In terms of hardware components, these unit structures may be realized by any conventional processing system or equipment, including a CPU or memory of any computer, a memory-loaded program, or the like. Here, the drawing shows a functional block configuration which is realized by cooperation between the hardware components and software components. Thus, it would be understood by those skilled in the art that these function blocks can be realized in a variety of forms by hardware only, software only or the combination thereof. 
     The main control unit  22  provides for the loading of a plug-in or a framework for executing a command. The editing unit  24  provides a framework for editing XML documents. Display and editing functions for a document in the document processing apparatus  20  are realized by plug-ins, and the necessary plug-ins are loaded by the main control unit  22  or the editing unit  24  according to the type of document under consideration. The main control unit  22  or the editing unit  24  determines which vocabulary or vocabularies describes the content of an XML document to be processed, by referring to a name space of the document to be processed, and loads a plug-in for display or editing corresponding to the thus determined vocabulary so as to execute the display or the editing. For instance, an HTML unit  50 , which displays and edits HTML documents, and an SVG unit  60 , which displays and edits SVG documents, are implemented in the document processing apparatus  20 . That is, a display system and an editing system are implemented as plug-ins for each vocabulary (tag set), so that when an HTML document and an SVG document are edited, the HTML unit  50  and the SVG unit  60  are loaded, respectively. As will be described later, when compound documents, which contain both the HTML and SVG components, are to be processed, both the HTML unit  50  and the SVG unit  60  are loaded. 
     By implementing the above structure, a user can select so as to install only necessary functions, and can add or delete a function or functions at a later stage, as appropriate. Thus, the storage area of a recording medium, such as a hard disk, can be effectively utilized, and the wasteful use of memory can be prevented at the time of executing programs. Furthermore, since the capability of this structure is highly expandable, a developer can deal with new vocabularies in the form of plug-ins, and thus the development process can be readily facilitated. As a result, the user can also add a function or functions easily at low cost by adding a plug-in or plug-ins. 
     The editing unit  24  receives an event, which is an editing instruction, from the user via the user interface. Upon reception of such an event, the editing unit  24  notifies a suitable plug-in or the like of this event, and controls the processing such as redoing this event, canceling (undoing) this event, etc. 
     The DOM unit  30  includes a DOM provider  32 , a DOM builder  34  and a DOM writer  36 . The DOM unit  30  realizes functions in compliance with a document object model (DOM), which is defined to provide an access method used for handling data in the form of an XML document. The DOM provider  32  is an implementation of a DOM that satisfies an interface defined by the editing unit  24 . The DOM builder  34  generates DOM trees from XML documents. As will be described later, when an XML document to be processed is mapped to another vocabulary by the VC unit  80 , a source tree, which corresponds to the XML document in a mapping source, and a destination tree, which corresponds to the XML document in a mapping destination, are generated. At the end of editing, for example, the DOM writer  36  outputs a DOM tree as an XML document. 
     The CSS unit  40 , which provides a display function conforming to CSS, includes a CSS parser  42 , a CSS provider  44  and a rendering unit  46 . The CSS parser  42  has a parsing function for analyzing the CSS syntax. The CSS provider  44  is an implementation of a CSS object and performs CSS cascade processing on the DOM tree. The rendering unit  46  is a CSS rendering engine and is used to display documents, described in a vocabulary such as HTML, which are laid out using CSS. 
     The HTML unit  50  displays or edits documents described in HTML. The SVG unit  60  displays or edits documents described in SVG. These display/editing systems are realized in the form of plug-ins, and each system is comprised of a display unit (also designated herein as a “canvas”)  56  and  66 , which displays documents, a control unit (also designated herein as an “editlet”)  52  and  62 , which transmits and receives events containing editing commands, and an edit unit (also designated herein as a “zone”)  54  and  64 , which edits the DOM according to the editing commands. Upon the control unit  52  or  62  receiving a DOM tree editing command from an external source, the edit unit  54  or  64  modifies the DOM tree and the display unit  56  or  66  updates the display. These units have a structure similar to the framework of the so-called MVC (Model-View-Controller). With such a structure, in general, the display units  56  and  66  correspond to “View”. On the other hand, the control units  52  and  62  correspond to “Controller”, and the edit units  54  and  64  and DOM instance corresponds to “Model”. The document processing apparatus  20  according to the background technique allows an XML document to be edited according to each given vocabulary, as well as providing a function of editing the HTML document in the form of tree display, The HTML unit  50  provides a user interface for editing an HTML document in a manner similar to a word processor, for example. On the other hand, the SVG unit  60  provides a user interface for editing an SVG document in a manner similar to an image drawing tool. 
     The VC unit  80  includes a mapping unit  82 , a definition file acquiring unit  84  and a definition file generator  86 . The VC unit  80  performs mapping of a document, which has been described in a particular vocabulary, to another given vocabulary, thereby providing a framework that allows a document to be displayed and edited by a display/editing plug-in corresponding to the vocabulary to which the document is mapped. In the background technique, this function is called a vocabulary connection (VC). In the VC unit  80  the definition file acquiring unit  84  acquires a script file in which the mapping definition is described. Here, the definition file specifies the correspondence (connection) between the nodes for each node. Furthermore, the definition file may specify whether or not editing of the element values or attribute values is permitted. Furthermore, the definition file may include operation expressions using the element values or attribute values for the node. Detailed description will be made later regarding these functions. The mapping unit  82  instructs the DOM builder  34  to generate a destination tree with reference to the script file acquired by the definition file acquiring unit  84 . This manages the correspondence between the source tree and the destination tree. The definition file generator  86  offers a graphical user interface which allows the user to generate a definition file. 
     The VC unit  80  monitors the connection between the source tree and the destination tree. Upon reception of an editing instruction from the user via a user interface provided by a plug-in that handles a display function, the VC unit  80  first modifies a relevant node of the source tree. As a result, the DOM unit  30  issues a mutation event indicating that the source tree has been modified. Upon reception of the mutation event thus issued, the VC unit  80  modifies a node of the destination tree corresponding to the modified node, thereby updating the destination tree in a manner that synchronizes with the modification of the source tree. Upon reception of a mutation event that indicates that the destination tree has been modified, a plug-in having functions of displaying/editing the destination tree, e.g., the HTML unit  50 , updates a display with reference to the destination tree thus modified. Such a structure allows a document described in any vocabulary, even a minor vocabulary used in a minor user segment, to be converted into a document described in another major vocabulary. This enables such a document described in a minor vocabulary to be displayed, and provides an editing environment for such a document. 
     An operation in which the document processing apparatus  20  displays and/or edits documents will be described herein below. When the document processing apparatus  20  loads a document to be processed, the DOM builder  34  generates a DOM tree from the XML document. The main control unit  22  or the editing unit  24  determines which vocabulary describes the XML document by referring to a name space of the XML document to be processed. If the plug-in corresponding to the vocabulary is installed in the document processing apparatus  20 , the plug-in is loaded so as to display/edit the document. If, on the other hand, the plug-in is not installed in the document processing apparatus  20 , a check shall be made to see whether a mapping definition file exists or not. And if the definition file exits, the definition file acquiring unit  84  acquires the definition file and generates a destination tree according to the definition, so that the document is displayed/edited by the plug-in corresponding to the vocabulary which is to be used for mapping. If the document is a compound document containing a plurality of vocabularies, relevant portions of the document are displayed/edited by plug-ins corresponding to the respective vocabularies, as will be described later. If the definition file does not exist, a source or tree structure of a document is displayed and the editing is carried out on the display screen. 
       FIG. 2  shows an example of an XML document to be processed. According to this exemplary illustration, the XML document is used to manage data concerning grades or marks that students have earned. A component “marks”, which is the top node of the XML document, includes a plurality of components “student” provided for each student under “marks”. The component “student” has an attribute “name”, and contains, as child elements, the subjects “japanese”, “mathematics”, “science”, and “social_studies”. The attribute “name” stores the name of a student. The components “japanese”, “mathematics”, “science” and “social_studies” store the test scores for the subjects Japanese, mathematics, science, and social studies, respectively. For example, the marks of a student whose name is “A” are “90” for Japanese, “50” for mathematics, “75” for science and “60” for social studies. Hereinafter, the vocabulary (tag set) used in this document will be called “marks managing vocabulary”. 
     Here, the document processing apparatus  20  according to the background technique does not have a plug-in which conforms to or handles the display/editing of marks managing vocabularies. Accordingly, before displaying such a document in a manner other than the source display manner or the tree display manner, the above-described VC function is used. That is, there is a need to prepare a definition file for mapping the document, which has been described in the marks managing vocabulary, to another vocabulary, which is supported by a corresponding plug-in, e.g., HTML or SVG. Note that description will be made later regarding a user interface that allows the user to create the user&#39;s own definition file. Now, description will be made below regarding a case in which a definition file has already been prepared. 
       FIG. 3  shows an example in which the XML document shown in  FIG. 2  is mapped to a table described in HTML. In an example shown in  FIG. 3 , a “student” node in the marks managing vocabulary is associated with a row (“TR” node) of a table (“TABLE” node) in HTML. The first column in each row corresponds to an attribute value “name”, the second column to a “Japanese” node element value, the third column to a “mathematics” node element value, the fourth column to a “science” node element value and the fifth column to a “social_studies” node element value. As a result, the XML document shown in  FIG. 2  can be displayed in an HTML tabular format. Furthermore, these attribute values and element values are designated as being editable, so that the user can edit these values on a display screen using an editing function of the HTML unit  50 . In the sixth column, an operation expression is designated for calculating a weighted average of the marks for Japanese, mathematics, science and social studies, and average values of the marks for each student are displayed. In this manner, more flexible display can be effected by making it possible to specify the operation expression in the definition file, thus improving the users&#39; convenience at the time of editing. In this example shown in  FIG. 3 , editing is designated as not being possible in the sixth column, so that the average value alone cannot be edited individually. Thus, in the mapping definition it is possible to specify editing or no editing so as to protect the users against the possibility of performing erroneous operations. 
       FIG. 4(   a ) and  FIG. 4(   b ) illustrate an example of a definition file to map the XML document shown in  FIG. 2  to the table shown in  FIG. 3 . This definition file is described in script language defined for use with definition files. In the definition file, definitions of commands and templates for display are described. In the example shown in  FIG. 4(   a ) and  FIG. 4(   b ), “add student” and “delete student” are defined as commands, and an operation of inserting a node “student” into a source tree and an operation of deleting the node “student” from the source tree, respectively, are associated with these commands. Furthermore, the definition file is described in the form of a template, which describes that a header, such as “name” and “japanese”, is displayed in the first row of a table and the contents of the node “student” are displayed in the second and subsequent rows. In the template displaying the contents of the node “student”, a term containing “text-of” indicates that editing is permitted, whereas a term containing “value-of” indicates that editing is not permitted. Among the rows where the contents of the node “student” are displayed, an operation expression “(src:japanese+src:mathematics+scr:science+scr:social_studies) div 4” is described in the sixth row. This means that the average of the student&#39;s marks is displayed. 
       FIG. 5  shows an example of a display screen on which an XML document described in the marks managing vocabulary shown in  FIG. 2  is displayed by mapping the XML document to HTML using the correspondence shown in  FIG. 3 . Displayed from left to right in each row of a table  90  are the name of each student, marks for Japanese, marks for mathematics, marks for science, marks for social studies and the averages thereof. The user can edit the XML document on this screen. For example, when the value in the second row and the third column is changed to “70”, the element value in the source tree corresponding to this node, that is, the marks of student “B” for mathematics are changed to “70”. At this time, in order to have the destination tree follow the source tree, the VC unit  80  changes a relevant portion of the destination tree accordingly, so that the HTML unit  50  updates the display based on the destination tree thus changed. Hence, the marks of student “B” for mathematics are changed to “70”, and the average is changed to “55” in the table on the screen. 
     On the screen as shown in  FIG. 5  commands like “add student” and “delete student” are displayed in a menu as defined in the definition file shown in  FIG. 4(   a ) and  FIG. 4(   b ). When the user selects a command from among these commands, a node “student” is added or deleted in the source tree. In this manner, with the document processing apparatus  20  according to the background technique, it is possible not only to edit the element values of components in a lower end of a hierarchical structure but also to edit the hierarchical structure. An edit function for editing such a tree structure may be presented to the user in the form of commands. Furthermore, a command to add or delete rows of a table may, for example, be linked to an operation of adding or deleting the node “student”. A command to embed other vocabularies therein may be presented to the user. This table may be used as an input template, so that marks data for new students can be added in a fill-in-the-blank format. As described above, the VC function allows a document described in the marks managing vocabulary to be edited using the display/editing function of the HTML unit  50 . 
       FIG. 6  shows an example of a graphical user interface, which the definition file generator  86  presents to the user, in order for the user to generate a definition file. An XML document to be mapped is displayed in a tree in a left-hand area  91  of a screen. The screen layout of an XML document after mapping is displayed in a right-hand area  92  of the screen. This screen layout can be edited by the HTML unit  50 , and the user creates a screen layout for displaying documents in the right-hand area  92  of the screen. For example, a node of the XML document which is to be mapped, which is displayed in the left-hand area  91  of the screen, is dragged and dropped into the HTML screen layout in the right-hand area  92  of the screen using a pointing device such as a mouse, so that a connection between a node at a mapping source and a node at a mapping destination is specified. For example, when “mathematics,” which is a child element of the element “student,” is dropped to the intersection of the first row and the third column in a table  90  on the HTML screen, a connection is established between the mathematics node and a “TD” node in the third column. Either editing or no editing can be specified for each node. Moreover, the operation expression can be embedded in a display screen. When the screen editing is completed, the definition file generator  86  generates definition files, which describe connections between the screen layout and nodes. 
     Viewers or editors which can handle major vocabularies such as XHTML, MathML and SVG have already been developed. However, it does not serve any practical purpose to develop dedicated viewers or editors for such documents described in the original vocabularies as shown in  FIG. 2 . If, however, the definition files for mapping to other vocabularies are created as mentioned above, the documents described in the original vocabularies can be displayed and/or edited utilizing the VC function without the need to develop a new viewer or editor. 
       FIG. 7  shows another example of a screen layout generated by the definition file generator  86 . In the example shown in  FIG. 7 , a table  90  and circular graphs  93  are created on a screen for displaying XML documents described in the marks managing vocabulary. The circular graphs  93  are described in SVG. As will be discussed later, the document processing apparatus  20  according to the background technique can process a compound document described in the form of a single XML document according to a plurality of vocabularies. That is why the table  90  described in HTML and the circular graphs  93  described in SVG can be displayed on the same screen. 
       FIG. 8  shows an example of a display medium, which in a preferred but non-limiting embodiment is an edit screen, for XML documents processed by the document processing apparatus  20 . In the example shown in  FIG. 8 , a single screen is partitioned into a plurality of areas and the XML document to be processed is displayed in a plurality of different display formats at the respective areas. The source of the document is displayed in an area  94 , the tree structure of the document is displayed in an area  9 S, and the table shown in  FIG. 5  and described in HTML is displayed in an area  96 . The document can be edited in any of these areas, and when the user edits content in any of these areas, the source tree will be modified accordingly, and then each plug-in that handles the corresponding screen display updates the screen so as to effect the modification of the source tree. Specifically, display units of the plug-ins in charge of displaying the respective edit screens are registered in advance as listeners for mutation events that provide notice of a change in the source tree. When the source tree is modified by any of the plug-ins or the VC unit  80 , all the display units, which are displaying the edit screen, receive the issued mutation event(s) and then update the screens. At this time, if the plug-in is executing the display through the VC function, the VC unit  80  modifies the destination tree following the modification of the source tree. Thereafter, the display unit of the plug-in modifies the screen by referring to the destination tree thus modified. 
     For example, when the source display and tree-view display are implemented by dedicated plug-ins, the source-display plug-in and the tree-display plug-in execute their respective displays by directly referring to the source tree without involving the destination tree. In this case, when the editing is done in any area of the screen, the source-display plug-in and the tree-display plug-in update the screen by referring to the modified source tree. Also, the HTML unit  50  in charge of displaying the area  96  updates the screen by referring to the destination tree, which has been modified following the modification of the source tree. 
     The source display and the tree-view display can also be realized by utilizing the VC function. That is to say, an arrangement may be made in which the source and the tree structure are laid out in HTML, an XML document is mapped to the HTML structure thus laid out, and the HTML unit  50  displays the XML document thus mapped. In such an arrangement, three destination trees in the source format, the tree format and the table format are generated. If the editing is carried out in any of the three areas on the screen, the VC unit  80  modifies the source tree and, thereafter, modifies the three destination trees in the source format, the tree format and the table format. Then, the HTML unit  50  updates the three areas of the screen by referring to the three destination trees. 
     In this manner, a document is displayed on a single screen in a plurality of display formats, thus improving a user&#39;s convenience. For example, the user can display and edit a document in a visually easy-to-understand format using the table  90  or the like while understanding the hierarchical structure of the document by the source display or the tree display. In the above example, a single screen is partitioned into a plurality of display formats, and they are displayed simultaneously. Also, a single display format may be displayed on a single screen so that the display format can be switched according to the user&#39;s instructions. In this case, the main control unit  22  receives from the user a request for switching the display format and then instructs the respective plug-ins to switch the display. 
       FIG. 9  illustrates another example of an XML document edited by the document processing apparatus  20 . In the XML document shown in  FIG. 9 , an XHTML document is embedded in a “foreignObject” tag of an SVG document, and the XHTML document contains an equation described in MathML. In this case, the editing unit  24  assigns the rendering job to an appropriate display system by referring to the name space. In the example illustrated in  FIG. 9 , first, the editing unit  24  instructs the SVG unit  60  to render a rectangle, and then instructs the HTML unit  50  to render the XHTML document. Furthermore, the editing unit  24  instructs a MathML unit (not shown) to render an equation. In this manner, the compound document containing a plurality of vocabularies is appropriately displayed.  FIG. 10  illustrates the resulting display. 
     The displayed menu may be switched corresponding to the position of the cursor (carriage) during the editing of a document. That is, when the cursor lies in an area where an SVG document is displayed, the menu provided by the SVG unit  60 , or a command set which is defined in the definition file for mapping the SVG document, is displayed. On the other hand, when the cursor lies in an area where the XHTML document is displayed, the menu provided by the HTML unit  50 , or a command set which is defined in the definition file for mapping the HTML document, is displayed. Thus, an appropriate user interface can be presented according to the editing position. 
     In a case that there is neither a plug-in nor a mapping definition file suitable for any one of the vocabularies according to which the compound document has been described, a portion described in this vocabulary may be displayed in source or in tree format in the conventional practice, when a compound document is to be opened where another document is embedded in a particular document, their contents cannot be displayed without the installation of an application to display the embedded document. According to the background technique, however, the XML documents, which are composed of text data, may be displayed in source or in tree format so that the contents of the documents can be ascertained. This is a characteristic of the text-based XML documents or the like. 
     Another advantageous aspect of the data being described in a text-based language, for example, is that, in a single compound document, a part of the compound document described in a given vocabulary can be used as reference data for another part of the same compound document described in a different vocabulary. Furthermore, when a search is made within the document, a string of characters embedded in a drawing, such as SVG, may also be search candidates. 
     In a document described in a particular vocabulary, tags belonging to other vocabularies may be used. Though such an XML document is generally not valid, it can be processed as a valid XML document as long as it is well-formed. In such a case, the tags thus inserted that belong to other vocabularies may be mapped using a definition file. For instance, tags such as “Important” and ‘Most Important’ may be used so as to display a portion surrounding these tags in an emphasized manner, or may be sorted out in the order of importance. 
     When the user edits a document on an edit screen as shown in  FIG. 10 , a plug-in or a VC unit  80 , which is in charge of processing the edited portion, modifies the source tree. A listener for mutation events can be registered for each node in the source tree. Normally, a display unit of the plug-in or the VC unit  80  conforming to a vocabulary that belongs to each node is registered as the listener. When the source tree is modified, the DOM provider  32  traces toward a higher hierarchy from the modified node. If there W is a registered listener, the DOM provider  32  issues a mutation event to the listener. For example, referring to the document shown in  FIG. 9 , if a node which lies lower than the &lt;html&gt; node is modified, the mutation event is notified to the HTML unit  50 , which is registered as a listener to the &lt;html&gt; node. At the same time, the mutation event is also notified to the SVG unit  60 , which is registered as a listener in an &lt;svg&gt; node, which lies upper to the &lt;html&gt; node. At this time, the HTML unit  50  updates the display by referring to the modified source tree. Since the nodes belonging to the vocabulary of the SVG unit  60  itself are not modified, the SVG unit  60  may disregard the mutation event. 
     Depending on the contents of the editing, modification of the display by the HTML unit  50  may change the overall layout. In such a case, the layout is updated by a screen layout management mechanism, e.g., the plug-in that handles the display of the highest node, in increments of display regions which are displayed according to the respective plug-ins. For example, in a case of expanding a display region managed by the HTML unit  50 , first, the HTML unit  50  renders a part managed by the HTML unit  50  itself, and determines the size of the display region. Then, the size of the display area is notified to the component that manages the screen layout so as to request the updating of the layout. Upon receipt of this notice, the component that manages the screen layout rebuilds the layout of the display area for each plug-in. Accordingly, the display of the edited portion is appropriately updated and the overall screen layout is updated. 
     Then, further detailed description will be made regarding functions and components for providing the document processing  20  according to the background technique. In the following description, English terms are used for the class names and so forth. 
     A. Outline 
     The advent of the Internet has resulted in a nearly exponential increase in the number of documents processed and managed by users. The Web (World Wide Web), which serves as the core of the Internet, provides a massive storage capacity for storing such document data. The Web also provides an information search system for such documents, in addition to the function of storing the documents. In general, such a document is described in a markup language. HTML (HyperText Markup Language) is an example of a popular basic markup language. Such a document includes links, each of which links the document to another document stored at another position on the Web. XML (eXtensible Markup Language) is a popular further improved markup language. Simple browsers which allow the user to access and browse such Web documents have been developed using object-oriented programming languages such as Java (trademark). 
     In general, documents described in markup languages are represented in a browser or other applications in the form of a tree data structure. This structure corresponds to a tree structure obtained as a result of parsing a document. The DOM (Document Object Model) is a well-known tree-based data structure model, which is used for representing and processing a document. The DOM provides a standard object set for representing documents, examples of which include an HTML document, an XML document, etc. The DON includes two basic components, i.e., a standard model which shows how the objects that represent the respective components included in a document are connected to one another, and a standard interface which allows the user to access and operate each object. 
     Application developers can support the DOM as an interface for handling their own data structure and API (Application Program Interface). On the other hand, application providers who create documents can use the standard interface of the DOM, instead of using the DOM as an interface for handling their own API. The capacity of the DOM to provide such a standard interface has been effective in promoting document sharing in various environments, particularly on the Web. Several versions of the DOM have been defined, which are used in different environments and applications. 
     A DOM tree is a hierarchical representation of the structure of a document, which is based upon the content of a corresponding DOM. A DOM tree includes a “root”, and one or more “nodes” branching from the root. In some cases, an entire document is represented by a root alone. An intermediate node can represent an element such as a table, or a row or a column of the table, for example. A “leaf” of a DOM tree generally represents data which cannot be further parsed, such as text data, image data, etc. Each of the nodes of the DOM tree may be associated with an attribute that specifies a parameter of the element represented by the node, such as a font, size, color, indent, etc. 
     HTML is a language which is generally used for creating a document. However, HTML is a language that provides formatting and layout capabilities, and it is not meant to be used as a data description language. The node of the DOM tree for representing an HTML document is defined beforehand as an HTML formatting tag, and in general, HTML does not provide detailed data description and data tagging/labeling functions. This leads to a difficulty in providing a query format for the data included in an HTML document. 
     The goal of network designers is to provide a software application which allows the user to make a query for and to process a document provided on the Web. Such a software application should allow the user to make a query for and to process a document, regardless of the display method, as long as the document is described in a hierarchically structured language. A markup language such as XML (eXtensible Markup Language) provides such functions. 
     Unlike HTML, XML has a well-known advantage of allowing the document designer to label each data element using a tag which can be defined by the document designer as desired. Such data elements can form a hierarchical structure. Furthermore, an XML document can include a document type definition that specifies a “grammar” which specifies the tags used in the document and the relations between the tags. Also, in order to define the display method of such a structured XML documents CSS (Cascading Style Sheets) or XSL (XML Style Language) is used. Additional information with respect to the features of the DOM, HTML, XML, CSS, XSL, and the related languages can be acquired via the Web, for example, from “http://www.w3.org/TR/”. 
     XPath provides common syntax and semantics which allow the position of a portion of an XML document to be specified. Examples of such functions include a function of traversing a DOM tree that corresponds to an XML document. This provides basic functions for operating character strings, values, and Boolean variables, which are related to the function of displaying an XML document in various manners. XPath does not provide a syntax for how the XML document is displayed, e.g., a grammar which handles a document in the form of text in increments of lines or characters. Instead of such a syntax, XPath handles a document in the form of an abstract and logical structure. The use of XPath allows the user to specify a position in an XML document via the hierarchical structure of a DOM tree of the XML document, for example. Also, XPath has been designed so as to allow the user to test whether or not the nodes included in a DOM tree match a given pattern. Detailed description of XPath can be obtained from http://www.w3.org/TR/xpath. 
     There is a demand for an effective document processing system based upon the known features and advantages of XML, which provides a user-friendly interface which handles a document described in a markup language (e.g., XML), and which allows the user to create and modify such a document. 
     Some of the system components as described here will be described in a well-known GUI (Graphical User Interface) paradigm which is called the MVC (Model-View-Controller) paradigm. The MVC paradigm divides a part of an application or an interface of an application into three parts, i.e., “model”, “view”, and “controller”. In the GUI field, the MVC paradigm has been developed primarily for assigning the roles of “input”, “processing”, and “output”. 
     [input]→[processing]→[output] 
     [controller]→[model]→[view] 
     The MVC paradigm separately handles modeling of external data, visual feedback for the user, and input from the user, using a model object (M), a view object (V), and a controller object (C). The controller object analyzes the input from the user input via a mouse and a keyboard, and maps such user actions to a command to be transmitted to the model object and/or the view object. The model object operates so as to manage one or more data elements. Furthermore, the model object makes a response to a query with respect to the state of the data elements, and operates in response to an instruction to change the state of the data elements. The view object has a function of presenting data to the user in the form of a combination of graphics and text. 
     B. Overall Configuration of the Document Processing System 
     In order to make clear an embodiment of the document processing system, description will be made with reference to  FIGS. 11 through 29 . 
       FIG. 11(   a ) shows an example of a configuration comprising components that provide the basic functions of a kind of document processing system according to a conventional technique as will be mentioned later. A configuration  10  includes a processor in the form of a CPU or a microprocessor  11  connected to memory  12  via a communication path  13 . The memory  12  may be provided in the form of any kind of ROM and/or RAM that is currently available or that may be available in the future. In a typical case, the communication path  13  is provided in the form of a bus. An input/output interface  16  for user input devices such as a mouse, a keyboard, a speech recognition system, etc., and a display device  15  (or other user interfaces) is connected to the bus that provides communication with the processor  11  and the memory  12 . Such a configuration may be provided in the form of a standalone device. Also, such a configuration may be provided in the form of a network which includes multiple terminals and one or more servers connected to one another. Also, such a configuration may be provided in any known form. The present invention is not restricted to a particular layout of the components, a particular architecture, e.g., a centralized architecture or a distributed architecture, or a particular one of various methods of communication between the components. 
     Furthermore, description will be made below regarding the present system and the embodiment regarding an arrangement including several components and sub-components that provide various functions. In order to provide desired functions, the components and the sub-components can be realized by hardware alone, or by software alone, in addition to various combination of hardware and software. Furthermore, the hardware, the software, and the various combinations thereof can be realized by general purpose hardware, dedicated hardware, or various combinations of general purpose and dedicated hardware. Accordingly, the configuration of the component or the sub-component includes a general purpose or dedicated computation device for executing predetermined software that provides a function required for the component or the sub-component. 
       FIG. 11(   b ) is a block diagram which shows an overall configuration of an example of the document processing system. Such a document processing system allows a document to be created and edited. Such a document may be described in a desired language that has the functions required of a markup language, such as XML etc. Note that some terms and titles will be defined here for convenience of explanation. However, the general scope of the disclosure according to the present invention is not intended to be restricted by such terms and titles thus defined here. 
     The document processing system can be classified into two basic configurations. A first configuration is an “execution environment”  101  which provides an environment that allows the document processing system to operate. For example, the execution environment provides basic utilities and functions that support both the system and the user during the processing and management of a document. A second configuration is an “application”  102  that comprises applications that run under an execution environment. These applications include the documents themselves and various representations of the documents. 
     1. Execution Environment 
     The key component of the execution environment  101  is the ProgramInvoker (program invoking unit)  103 . The ProgramInvoker  103  is a basic program, which is accessed in order to start up the document processing system. For example, upon the user logging on and starting up the document processing system, the ProgramInvoker  103  is executed. The ProgramInvoker  103  has: a function of reading out and executing a function added to the document processing system in the form of a plug-in; a function of starting up and executing an application; and a function of reading out the properties related to a document, for example. However, the functions of the ProgramInvoker  103  are not restricted to these functions. Upon the user giving an instruction to start up an application to be executed under the execution environment, the ProgramInvoker  103  finds and starts up the application, thereby executing the application. 
     Also, several components are attached to the ProgramInvoker  103 , examples of which include a plug-in sub-system  104 , a command sub-system  105 , and a resource module  109 . Detailed description will be made below regarding the configurations of such components. 
     a) Plug-in Sub-System 
     The plug-in sub-system is used as a highly flexible and efficient configuration which allows an additional function to be added to the document processing system. Also, the plug-in sub-system  104  can be used for modifying or deleting functions included in the document processing system. Also, various kinds of functions can be added or modified using the plug-in sub-system. For example, the plug-in sub-system  104  allows an Editlet (editing unit) to be added, which supports functions of allowing the user to edit via the screen. Also, the Editlet plug-in supports the functions of allowing the user to edit a vocabulary added to the system. 
     The plug-in sub-system  104  includes a ServiceBroker (service broker unit)  1041 . The ServiceBroker  1041  manages a plug-in added to the document processing system, thereby mediating between the service thus added and the document processing system. 
     Each of the desired functions is added in the form of a Service  1042 . Examples of the available types of Services  1042  include: an Application Service; a ZoneFactory (zone creating unit) Service; an Editlet (editing unit) Service; a CommandFactory (command creating unit) Service; a ConnectXPath (XPath management unit) Service; a CSSComputation (CSS calculation unit) Service; etc. However, the Service  1042  is not restricted to such services. Detailed description will be made below regarding these Services, and regarding the relation between these Services and other components of the system, in order to facilitate understanding of the document processing system. 
     Description will be made below regarding the relation between a plug-in and a Service. The plug-in is a unit capable of including one or more ServiceProviders (service providing units). Each ServiceProvider has one or more classes for corresponding Services. For example, upon using a plug-in having an appropriate software application, one or more Services are added to the system, thereby adding the corresponding functions to the system. 
     b) Command Sub-System 
     The command sub-system  105  is used for executing a command relating to the processing of a document. The command sub-system  105  allows the user to execute the processing of the document by executing a series of commands. For example, the command sub-system  105  allows the user to edit an XML DOM tree that corresponds to an XML document stored in the document processing system, and to process the XML document, by issuing a command. These commands may be input by key-strokes, mouse-clicks, or actions via other valid user interfaces. In some cases, when a single command is input, one or more sub-commands are executed. In such a case, these sub-commands are wrapped in a single command, and the sub-commands are consecutively executed. For example, let us consider a case in which the user has given an instruction to replace an incorrect word with a correct word. In this case, a first sub-command is an instruction to detect an incorrect word in the document. Then, a second sub-command is an instruction to delete the incorrect word. Finally, a third function is an instruction to insert a correct word. These three sub-commands may be wrapped in a single command. 
     Each command may have a corresponding function, e.g., an “undo” function described later in detail. Such a function may also be assigned to several basic classes used for creating an object. 
     The key component of the command sub-system  105  is a CommandInvoker (command invoking unit)  1051  which operates so as to allow the user to selectively input and execute the commands.  FIG. 11(   b ) shows an arrangement having a single CommandInvoker. Also, one or more CommandInvokers may be used. Also, one or more commands may be executed at the same time. The CommandInvoker  1051  holds the functions and classes required for executing the command. In the operation, the Command  1052  is loaded in a Queue  1053 . Then, the CommandInvoker  1051  creates a command thread for executing the commands in sequence. In a case that no Command is currently being executed by the CommandInvoker, the Command  1052  provided to be executed by the CommandInvoker  1051  is executed. In a case that a command is currently being executed by the CommandInvoker, the new Command is placed at the end of the Queue  1053 . However, each CommandInvoker  1051  executes only a single command at a time. In a case of failure in executing the Command thus specified, the CommandInvoker  1051  performs exception handling. 
     Examples of the types of Commands executed by the CommandInvoker  1051  include: an UndoableCommand (undoable command)  1054 ; an AsynchronousCommand (asynchronous command)  1055 ; and a VCCommand (VC command)  1056 . However, the types of commands are not restricted to those examples. The UndoableCommand  1054  is a command which can be undone according to an instruction from the user. Examples of UndoableCommands include a deletion command, a copy command, a text insertion command, etc. Let us consider a case in which, in the course of operation, the user has selected a part of a document, following which the deletion command is applied to the part thus selected. In this case, the corresponding UndoableCommand allows the deleted part to be restored to the state that it was in before the part was deleted. 
     The VCCommand  1056  is stored in a Vocabulary Connection Descriptor (VCD) script file. The VCCommand  1056  is a user specified Command defined by a programmer. Such a Command may be a combination of more abstract Commands, e.g., a Command for adding an XML fragment, a Command for deleting an XML fragment, a Command for setting an attribute, etc. In particular, such Commands are provided with document editing in mind. 
     The AsynchronousCommand  1055  is a command primarily provided for the system, such as a command for loading a document, a command for storing a document, etc. AsynchronousCommands  1055  are executed in an asynchronous manner, independently of UndoableCommands and VCCommands. Note that the AsynchronousCommand does not belong to the class of undoable commands (it is not an UndoableCommand). Accordingly, an AsynchronousCommand cannot be undone. 
     c) Resource 
     The Resource  109  is an object that provides several functions to various classes. Examples of such system Resources include string resources, icon resources, and default key bind resources. 
     2. Application Component 
     The application component  102 , which is the second principal component of the document processing system, is executed under the execution environment  101 . The application component  102  includes actual documents and various kinds of logical and physical representations of the documents included in the system. Furthermore, the application component  102  includes the configuration of the system used for management of the documents. The application component  102  further includes a UserApplication (user application)  106 , an application core  108 , a user interface  107 , and a CoreComponent (core component)  110 . 
     a) User Application 
     The UserApplication  106  is loaded in the system along with the ProgramInvoker  103 . The UserApplication  106  serves as an binding agent that connects a document, the various representations of the document, and the user interface required for communicating with the document. For example, let us consider a case in which the user creates a document set which is a part of a project. Upon loading the document set, an appropriate representation of the document is created. The user interface function is added as a part of the UserApplication  106 . In other words, with regard to a document that forms a part of a project, the UserApplication  106  holds both the representation of the document that allows the user to communicate with the document, and various other document conditions. Once the UserApplication  106  has been created, such an arrangement allows the user to load the UserApplication  106  under the execution environment in a simple manner every time there is a need to communicate &amp; with a document that forms a part of a project. 
     b) Core Component 
     The CoreComponent  110  provides a method which allows a document to be shared over multiple panes. As described later in detail, the Pane displays a DOM tree, and provides a physical screen layout. For example, a physical screen is formed of multiple Panes within a screen, each of which displays a corresponding part of the information. With such an arrangement, a document displayed on the screen for the user can be displayed in one or more Panes. Also, two different documents may be displayed on the screen in two different Panes. 
     As shown in  FIG. 11(   c ), the physical layout of the screen is provided in a tree form. The Pane can be a RootPane (root pane)  1084 . Also, the Pane can be a SubPane (sub-pane)  1085 . The RootPane  1084  is a Pane which is positioned at the root of a Pane tree. The SubPanes  1085  are other Panes that are distinct from the RootPane  1084 . 
     The CoreComponent  110  provides a font, and serves as a source that provides multiple functional operations for a document. Examples of the tasks executed by the CoreComponent  110  include movement of a mouse cursor across the multiple Panes. Other examples of the tasks thus executed include a task whereby a part of the document displayed on a Pane is marked, and the part thus selected is duplicated on another Pane. 
     c) Application Core 
     As described above, the application component  102  has a structure that comprises documents to be processed and managed by the system. Furthermore, the application component  102  includes various kinds of logical and physical representations of the documents stored in the system. The application core  108  is a component of the application component  102 . The application core  108  provides a function of holding an actual document along with all the data sets included in the document. The application core  108  includes a DocumentManager (document manager, document managing unit)  1081  and a Document (document)  1082  itself. 
     Detailed description will be made regarding various embodiments of the DocumentManager  1081 . The DocumentManager  1081  manages the Document  1082 . The DocumentManager  1081  is connected to the RootPane  1085 , the SubPane  1085 , a ClipBoard (clipboard) utility  1087 , and a SnapShot (snapshot) utility  1088 . The ClipBoard utility  1087  provides a method for holding a part of the document which is selected by the user as a part to be added to the clipboard. For example, let us consider a case in which the user deletes a part of a document, and stores the part thus deleted in a new document as a reference document. In this case, the part thus deleted is added to the ClipBoard. 
     Next, description will also be made regarding the SnapShot utility  1088 . The SnapShot utility  1088  allows the system to store the current state of an application before the state of the application changes from one particular state to another state. 
     d) User Interface 
     The user interface  107  is another component of the application component  102 , which provides a method that allows the user to physically communicate with the system. Specifically, the user interface allows the user to upload, delete, edit, and manage a document. The user interface includes a Frame (frame)  1071 , a MenuBar (menu bar)  1072 , a StatusBar (status bar)  1073 , and a URLBar (URL bar)  1074 . 
     The Frame  1071  serves as an active region of a physical screen, as is generally known. The Menubar  1072  is a screen region including a menu that provides selections to the user. The StatusBar  1073  is a screen region that displays the status of the application which is being executed. The URLBar  1074  provides a region which allows the user to input a URL address for Internet navigation. 
     C. Document Management and Corresponding Data Structure 
       FIG. 12  shows a configuration of the DocumentManager  1081  in detail. The DocumentManager  1081  includes a data structure and components used for representing a document in the document processing system. Description will be made regarding such components in this sub-section using the MVC paradigm for convenience of explanation. 
     The DocumentManager  1081  includes a DocumentContainer (document container)  203  which holds all the documents stored in the document processing system, and which serves as a host machine. A tool kit  201  attached to the DocumentManager  1081  provides various tools used by the DocumentManager  1081 . For example, the tool kit  201  provides a DomService (DOM service) which provides all the functions required for creating, holding, and managing a DOM that corresponds to a document. Also, the tool kit  201  provides an IOManager (input/output management unit) which is another tool for managing the input to/output from the system, Also, a StreamHandler (stream handler) is a tool for handling uploading a document in the form of a bit stream. The tool kit  201  includes such tools in the form of components, which are not shown in the drawings in particular, and are not denoted by reference numerals. 
     With the system represented using the MVC paradigm, the model (M) includes a DOM tree model  202  of a document. As described above, each of all the documents is represented by the document processing system in the form of a DOM tree. Also, the document forms a part of the DocumentContainer  203 . 
     1. DOM Model and Zone 
     The DOM tree which represents a document has a tree structure having Nodes (nodes)  2021 . A Zone (zone)  209 , which is a subset of the DOM trees includes a region that corresponds to one or more Nodes within the DOM tree. For example, a part of a document can be displayed on a screen. In this case, the part of the document that is visually output is displayed using the zone  209 . The Zone is created, handled, and processed using a plug-in which is so-called ZoneFactory (Zone Factory=Zone creating unit)  205 . While the Zone represents a part of the DOM, the Zone can use one or more “namespaces”. It is well known that a namespace is a set that consists of unique names, each of which differs from every other name in the namespace. In other words, the namespace does not include the same names repeated. 
     2. Facets and the Relation Between Facets and Zones 
     A Facet  2022  is another component included in the model (M) component of the MVC paradigm. The Facet is used for editing the Node in the Zone. The Facet  2022  allows the user to access the DOM using a procedure that can be executed without affecting the content of the Zone. As described below, such a procedure executes an important and useful operation with respect to the Node. 
     Each node has a corresponding Facet. With such an arrangement, the facet is used for executing the operation instead of directly operating the Node in the DOM, thereby maintaining the integrity of the DOM. On the other hand, let us consider an arrangement in which an operation is performed directly on the Node. With such an arrangement, multiple plug-ins can change the DOM at the same time, leading to a problem that the integrity of the DOM cannot be maintained. 
     The DOM standard stipulated by the World Wide Web Consortium (W3C) defines a standard interface for operating a Node. In practice, unique operations particular to each vocabulary or each Node are required. Accordingly, such unique operations are preferably provided in the form of an API. The document processing system provides such an API particular to each Node in the form of a Facet which is attached to the Node. Such an arrangement allows a useful API to be attached to the DOM according to the DOM standard. Furthermore, with such an arrangement, after a standard DOM has been installed, unique APIs are attached to the DOM, instead of installing a unique DOM for each vocabulary. This allows various kinds of vocabularies to be uniformly handled. Furthermore, such an arrangement allows the user to properly process a document described using a desired combination of multiple vocabularies. 
     Each vocabulary is a set of tags (e.g., XML tags), which belong to a corresponding namespace. As described above, each namespace has a set of unique names (in this case, tags). Each vocabulary is handled as a sub-tree of the DOM tree which represents an XML document. The sub-tree includes the Zone. In particular cases, the boundary between the tag sets is defined by the Zone. The Zone  209  is created using a Service which is called a ZoneFactory  205 . As described above, the Zone  209  is an internal representation of a part of the DOM tree which represents a document. In order to provide a method that allows the user to access a part of such a document, the system requires a logical representation of the DOM tree. The logical representation of the DOM allows the computer to be informed of how the document is logically represented on a screen. A Canvas (canvas)  210  is a Service that operate so as to provide a logical layout that corresponds to the Zone. 
     On the other hand, a Pane  211  is a physical screen layout that corresponds to a logical layout provided by the Canvas  210 . In practice, the user views only a rendering of the document, through text or images displayed on a screen. Accordingly, there is a need to use a process for drawing text and images on a screen to display the document on a screen. With such an arrangement, the document is displayed on a screen by the Canvas  210  based upon the physical layout provided from the Pane  211 . 
     The Canvas  210  that corresponds to the Zone  209  is created using an Editlet  206 . The DOM of the document is edited using the Editlet  206  and the Canvas  210 . In order to maintain the integrity of the original document, the Editlet  206  and the Canvas  210  use the Facet that corresponds to one or more Nodes included in the Zone  209 . The Facet is operated using a Command  207 . 
     In general, the user communicates with a screen by moving a cursor on a screen or typing a command. The Canvas  210 , which provides a logical layout on a screen, allows the user to input such cursor operations. The Canvas  210  instructs the Facet to execute a corresponding action. With such a relation, the cursor sub-system  204  serves as a controller (C) according to the MVC paradigm with respect to the DocumentManager  1081 . The Canvas  210  also provides a task for handling an event. Examples of such events handled by the canvas  210  include: a mouse click event; a focus movement event; and a similar action event occurring in response to the user operation. 
     3. Outline of the Relation Between Zone, Facet, Canvas, and Pane. 
     The document in the document processing system can be described from at least four points of view. That is to say, it can be seen as: 1) a data structure for maintaining the content and structure of a document in the document processing system, 2) means by which the user can edit the content of the document while maintaining the integrity of the document, 3) a logical layout of the document on a screen, and 4) a physical layout of the document on the screen. The components of the document processing system that correspond to the aforementioned four points of view are the Zone, Facet, Canvas, and Pane, respectively. 
     4. Undo Sub-System 
     As described above, all modifications made to the document (e.g., document editing procedures) are preferably undoable. For example, let us consider a case in which the user executes an editing operation, and then determines that the modification thus made to the document should be undone. Referring to  FIG. 12 , the undo subsystem  212  provides an undo component of a document management unit. With such an arrangement, an UndoManager (undo manager=undo management unit)  2121  holds all the undoable operations for the document which the user can select to be undone. 
     Let us consider a case in which the user executes a command for replacing a word in a document by another word, following which the user determines that, on reflection, the replacement of the word thus effected should be undone. The undo sub-system supports such an operation. The UndoManager  2121  holds such an operation of an UndoableEdit (undoable edit)  2122 . 
     5. Cursor Sub-System 
     As described above, the controller unit of the MVC may include the cursor sub-system  204 . The cursor sub-system  204  receives the input from the user. In general, such an input provides command input and/or edit operation. Accordingly, with respect to the DocumentManager  1081 , the cursor sub-system  204  serves as the controller (C) component according to the MVC paradigm. 
     6. View 
     As described above, the Canvas  210  represents the logical layout of a document to be displayed on a screen. In a case that the document is an XHTML document, the Canvas  210  may include a box tree  208  that provides a logical representation of a document, which indicates how the document is displayed on a screen. With respect to the DocumentManager  1081 , the box tree  208  may be included in the view (V) component according to the MVC paradigm. 
     D. Vocabulary connection 
     The important feature of the document processing system is that the document processing system provides an environment which allows the user to handle an XML document via other representations to which the document has been mapped. With such an environment, upon the user editing a representation to which the source XML document has been mapped, the source XML document is modified according to the edit operation while maintaining the integrity of the XML document. 
     A document described in a markup language, e.g., an XML document is created based upon a vocabulary defined by a document type definition. The vocabulary is a set of tags. The vocabulary can be defined as desired. This allows a limitless number of vocabularies to be created. It does not serve any practical purpose to provide dedicated viewer/editor environments for such a limitless number of vocabularies. The vocabulary connection provides a method for solving this problem. 
     For example, a document can be described in two or more markup languages. Specific examples of such markup languages used for describing a document include: XHTML (eXtensible HyperText Markup Language), SVG (scalable Vector Graphics), MathML (Mathematical Markup Language), and other markup languages. In other words, such a markup language can be handled in the same way as is the vocabulary or the tag set in XML. 
     A vocabulary is processed using a vocabulary plug-in. In a case that the document has been described in a vocabulary for which there is no available plug-in in the document processing system, the document is mapped to a document described in another vocabulary for which a plug-in is available, thereby displaying the document. Such a function enables a document to be properly displayed even if the document has been described in a vocabulary for which there is no available plug-in. 
     The vocabulary connection has a function of acquiring a definition file, and a function of mapping from one vocabulary to another different vocabulary based upon the definition file thus acquired. With such an arrangement, a document described in one vocabulary can be mapped to a document described in another vocabulary. As described above, the vocabulary connection maps a document described in one vocabulary to another document described in another vocabulary for which there is a corresponding display/editing plug-in, thereby allowing the user to display and edit the document. 
     As described above, in general, each document is described by the document processing system in the form of a DOM tree having multiple nodes. The “definition file” describes the relations among the different nodes. Furthermore, the definition file specifies whether or not the element values and the attribute values can be edited for each node. Also, the definition file may specify an expression using the element values and the attribute values of the nodes. 
     Using the mapping function by applying the definition file, a destination DOM tree can be created. As described above, the relation between the source DON tree and the destination DOM tree is created and held. The vocabulary connection monitors the relation between the source DOM tree and the destination DOM tree. Upon reception of an editing instruction from the user, the vocabulary connection modifies the corresponding node included in the source DOM tree. Subsequently, a “mutation event” is issued, which gives notice that the source DOM tree has been modified. Then, the destination DOM tree is modified in response to the mutation event. 
     The use of the vocabulary connection allows a relatively minor vocabulary used by a small number of users to be converted into another major vocabulary. Thus, such an arrangement provides a desirable editing environment, which allows a document to be properly displayed even if the document is described in a minor vocabulary used by a small number of users. 
     As described above, the vocabulary connection sub-system which is a part of the document processing system provides a function that allows a document to be represented in multiple different ways. 
       FIG. 13  shows a vocabulary connection (VC) sub-system  300 . The VC sub-system  300  provides a method for representing a document in two different ways while maintaining the integrity of the source document. For example, a single document may be represented in two different ways using two different vocabularies. Also, one representation may be a source DOM tree, and the other representation may be a destination DOM tree, as described above. 
     1. Vocabulary Connection Sub-System 
     The functions of the vocabulary connection sub-system  300  are provided to the document processing system using a plug-in which is called a VocabularyConnection  301 . With such an arrangement, a corresponding plug-in is requested for each Vocabulary  305  used for representing the document. For example, let us consider a case in which a part of the document is described in HTML, and the other part is described in SVG. In this case, the vocabulary plug-in that corresponds to HTML and the vocabulary plug-in that corresponds to SVG are requested. 
     The VocabularyConnection plug-in  301  creates a proper VCCanvas (vocabulary connection canvas)  310  that corresponds to a document described in a proper Vocabulary  305  for the Zone  209  or the Pane  211 . Using the VocabularyConnection  301 , a modification made to the Zone  209  within the source DOM tree is transmitted to the corresponding Zone within another DOM tree  306  according to a conversion rule. The conversion rule is described in the form of a vocabulary connection descriptor (VCD). Furthermore, a corresponding VCManager (vocabulary connection manager)  302  is created for each VCD file that corresponds to such a conversion between the source DOM and the destination DOM. 
     2. Connector 
     A Connector  304  connects the source node included within the source DOM tree and the destination node included within the destination DON tree. The Connector  304  operates so as to monitor modifications (changes) made to the source node included within the source DOM tree and the source document that corresponds to the source node. Then, the Connector  304  modifies the corresponding node of the destination DOM tree. With such an arrangement, the Connector  304  is the only object which is capable of modifying the destination DON tree. Specifically, the user can modify only the source document and the corresponding source DOM tree. With such an arrangement, the Connector  304  modifies the destination DOM tree according to the modification thus made by the user. 
     The Connectors  304  are logically linked to each other so as to form a tree structure. The tree structure formed of the Connectors  304  is referred to as a ConnectorTree (connector tree). The connector  304  is created using a Service which is called a ConnectorFactory (connector factory=connector generating unit)  303 . The ConnectorFactory  303  creates the Connectors  304  based upon a source document, and links the Connectors  304  to each other so as to create a ConnectorTree. The VocabularyConnectionManager  302  holds the ConnectorFactory  303 . 
     As described above, a vocabulary is a set of tags for a namespace. As shown in the drawing, the VocabularyConnection  301  creates the Vocabulary  305  for a document. Specifically, the Vocabulary  305  is created by analyzing the document file, and then creating a proper VocabularyConnectionManager  302  for mapping between the source DOM and the destination DOM. Furthermore, a proper relation is created between the ConnectorFactory  303  for creating the Connectors, the ZoneFactory  205  for creating the Zones  209 , and the Editlet  206  for creating the Canvases. In a case that the user has discarded or deleted a document stored in the system, the corresponding VocabularyConnectionManager  302  is deleted. 
     The Vocabulary  305  creates the VCCanvas  310 . Furthermore, the connectors  304  and the destination DOM tree  306  are created corresponding to the creation of the VCCanvas  310 . 
     The source DOM and the Canvas correspond to the Model (M) and the View (V), respectively. However, such a representation is useful only in a case that the target vocabulary allows a document to be displayed on a screen. With such an arrangement, the display is performed by the vocabulary plug-in. Such a vocabulary plug-in is provided for each of the principal vocabularies, e.g., XHTML, SVG, and MathML. Such a vocabulary plug-in is used for the target vocabulary. Such an arrangement provides a method for mapping a vocabulary to another vocabulary using a vocabulary connection descriptor. 
     Such mapping is useful only in a case that the target vocabulary can be mapped, and a method has been defined beforehand for displaying such a document thus mapped on a screen. Such a rendering method is defined in the form of a standard defined by an authority such as the W3C. 
     In a case that the processing requires vocabulary connection, the VCCanvas is used. In this case, the view for the source cannot be directly created, and accordingly, the Canvas for the source is not created. In this case, the VCCanvas is created using the ConnectorTree. The VCCanvas handles only the conversion of the event, but does not support display of the document on a screen. 
     3. DestinationZone, Pane, and Canvas 
     As described above, the purpose of the vocabulary connection sub-system is to create and hold two representations of a single document at the same time. With such an arrangement, the second representation is provided in the form of a DOM tree, which has been described as the destination DOM tree. The display of the document in the form of the second representation requires the DestinationZone, Canvas, and Pane. 
     When the VCCanvas is created, a corresponding DestinationPane  307  is also created. Furthermore, a corresponding DestinationCanvas  308  and a corresponding BoxTree  309  are created. Also, the VCCanvas  310  is associated with the Pane  211  and the Zone  209  for the source document. 
     The DestinationCanvas  308  provides a logical layout of a document in the form of the second representation. Specifically, the DestinationCanvas  308  provides user interface functions such as a cursor function and a selection function, for displaying a document in the form of a destination representation of the document. The event occurring at the DestinationCanvas  308  is supplied to the Connector. The DestinationCanvas  308  notifies the Connector  304  of the occurrence of a mouse event, a keyboard event, a drag-and-drop event, and events particular to the destination representation (second representation). 
     4. Vocabulary Connection Command Sub-System 
     The vocabulary connection (VC) sub-system  300  includes a vocabulary connection (VC) command sub-system  313  in the form of a component. The vocabulary connection command sub-system  313  creates a VCCommand (vocabulary connection command)  315  used for executing a command with respect to the vocabulary connection sub-system  300 . The VCCommand can be created using a built-in CommandTemplate (command template) and/or created from scratch using a script language supported by a script sub-system  314 . 
     Examples of such command templates include an “If” command template, “When” command template, “Insert” command template, etc. These templates are used for creating a VCCommand. 
     5. XPath Sub-System 
     An XPath sub-system  316  is an important component of the document processing system, and supports the vocabulary connection. In general, the Connector  304  includes XPath information. As described above, one of the tasks of the vocabulary connection is to modify the destination DOM tree according to the change in the source DOM tree. The XPath information includes one or more XPath representations used for determining a subset of the source DOM tree which is to be monitored to detect changes and/or modifications. 
     6. Outline of Source DOM Tree, Destination DOM Tree, and ConnectorTree 
     The source DOM tree is a DOM tree or a Zone of a document described in a vocabulary before vocabulary conversion. The source DOM tree node is referred to as the source node. 
     On the other hand, the destination DOM tree is a DOM tree or a Zone of the same document as that of the source DOM tree, and which is described in another vocabulary after having been converted by mapping, as described above in connection with the vocabulary connection. Here, the destination DOM tree node is referred to as the destination node. 
     The ConnectorTree is a hierarchical representation which is formed based upon the Connectors that represent the relation between the source nodes and the destination nodes. The Connectors monitor the source node and the modifications applied to the source document, and modify the destination DOM tree. The Connector is the only object that is permitted to modify the destination DOM tree. 
     E. Event Flow in the Document Processing System 
     In practice, the program needs to respond to the commands input from the user. The “event” concept provides a method for describing and executing the user action executed on a program. Many high-level languages, e.g., Java (trademark) require events, each of which describes a corresponding user action. On the other hand, conventional programs need to actively collect information for analyzing the user&#39;s actions, and for execution of the user&#39;s actions by the program itself. This means that, after initialization of the program, the program enters loop processing for monitoring the user&#39;s actions, which enables appropriate processing to be performed in response to any user action input by the user via the screen, keyboard, mouse, or the like. However, such a process is difficult to manage. Furthermore, such an arrangement requires a program which performs loop processing in order to wait for the user&#39;s actions, leading to a waste of CPU cycles. 
     Many languages employ distinctive paradigms in order to solve such problems one of these paradigms is event-driven programming, which is employed as the basis of all current window-based systems. In this paradigm, all user actions belong to sets of abstract phenomena which are called “events”. An event provides a sufficiently detailed description of a corresponding user action. With such an arrangement, in a case that an event to be monitored has occurred, the system notifies the program to that effect, instead of an arrangement in which the program actively collects events occurring according to the user&#39;s actions. A program that communicates with the user using such a method is referred to as an “event-driven” program. 
     In many cases, such an arrangement handles an event using a “Event” class that acquires the basic properties of all the events which can occur according to the user&#39;s actions. 
     Before the use of the document processing system, the events for the document processing system itself and a method for handling such events are defined. With such an arrangement, several types of events are used. For example, a mouse event is an event that occurs according to the action performed by the user via a mouse. The user action involving the mouse is transmitted to the mouse event by the Canvas  210 . As described above, it can be said that the Canvas is the foremost level of interaction between the user and the system. As necessary, this foremost Canvas level hands over the event content to the child levels. 
     On the other hand, a keystroke event is issued from the Canvas  210 . The keystroke event acquires a real-time focus. That is to say, a keystroke event always involves an operation. The keystroke event input to the Canvas  210  is also transmitted to the parent of the Canvas  210 . Key input actions are processed via other events that allows the user to insert a character string. The event for handling the insertion of a character string occurs according to the user action in which a character is input via the keyboard. Examples of “other events” include other events which are handled in the same way as a drag event, a drop event, and a mouse event. 
     1. Handling of an Event Outside of the Vocabulary Connection 
     An event is transmitted using an event thread. The state of the Canvas  210  is modified upon reception of an event. As necessary, the Canvas  210  posts the Command  1052  to the CommandQueue  1053 . 
     2. Handling of an Event within the Vocabulary Connection 
     An XHTMLCanvas  1106 , which is an example of the DestinationCanvas, receives events that occur, e.g., a mouse event, a keyboard event, a drag-and-drop event, and events particular to the vocabulary, using the VocabularyConnection plug-in  301 . The connector  1104  is notified of these events. More specifically, the event passes through a SourcePane  1103 , a VCCanvas  1104 , a DestinationPane  1105 , a DestinationCanvas  1106  which is an example of the DestinationCanvas, a destination DOM tree, and a ConnectorTree, within the VocabularyConnection plug-in, as shown in  FIG. 21(   b ). 
     F. ProgramInvoker and the Relation Between ProgramInvoker and Other Components 
       FIG. 14(   a ) shows the ProgramInvoker  103  and the relation between the ProgramInvoker  103  and other components in more detail. The ProgramInvoker  103  is a basic program executed under the execution environment, which starts up the document processing system. As shown in  FIG. 11(   b ), the UserApplication  106 , the ServiceBroker  1041 , the CommandInvoker  1051 , and the Resource  109  are each connected to the ProgramInvoker  103 . As described above, the application  102  is a component executed under the execution environment. Also, the ServiceBroker  1041  manages the plug-ins, which provide various functions to the system. On the other hand, the CommandInvoker  1051  executes a command provided from the user, and holds the classes and functions for executing the command. 
     1. Plug-in and Service 
     A more detailed description will be made regarding the ServiceBroker  1041  with reference to  FIG. 14(   b ). As described above, the CommandInvoker  1041  manages the plug-ins (and corresponding services), which allows various functions to be added to the system. The Service  1042  is the lowermost layer, having a function of adding the features to the document processing system, and a function of modifying the features of the document processing system. A “Service” consists of two parts, i.e., a part formed of ServiceCategories  401  and another part formed of ServiceProviders  402 . As shown in  FIG. 14(   c ), one ServiceCategory  401  may include multiple corresponding ServiceProviders  402 . Each ServiceProvider operates a part of, or the entire functions of, the corresponding ServiceCategory, Also, the ServiceCategory  401  defines the type of Service. 
     The Services can be classified into three types, i.e., a “feature service” which provides predetermined features to the document processing system, an “application service” which is an application executed by the document processing system, and an “environment” service that provides the features necessary throughout the document processing system. 
       FIG. 14(   d ) shows an example of a Service. In this example, with respect to the Category of the application Service, the system utility corresponds to the ServiceProvider. In the same way, the Editlet  206  is the Category, and an HTMLEditlet and the SVGEditlet are the corresponding ServiceProviders. Also, the ZoneFactory  205  is another Service Category, and has a corresponding ServicePtovider (not shown). 
     As described above, a plug-in adds functions to the document processing system. Also, a plug-in can be handled as a unit that comprises several ServiceProviders  402  and the classes that correspond to the ServiceProviders  402 . Each plug-in has dependency specified in the definition file and a ServiceCategory  401 . 
     2. Relation Between the ProgramInvoker and the Application 
       FIG. 14(   e ) shows the relation between the ProgramInvoker  103  and the UserApplication  106  in more detail. The required documents and data are loaded from the storage. All the required plug-ins are loaded in the ServiceBroker  1041 . The ServiceBroker  1041  holds and manages all the plug-ins. Each plug-in is physically added to the system. Also, the functions of the plug-in can be loaded from the storage. When the content of a plug-in is loaded, the ServiceBroker  1041  defines the corresponding plug-in. Subsequently, a corresponding UserApplication  106  is created, and the UserApplication  106  thus created is loaded in the execution environment  101 , thereby attaching the plug-in to the ProgramInvoker  103 . 
     G. The Relation Between the Application Service and the Environment 
       FIG. 15(   a ) shows the configuration of the application service loaded in the ProgramInvoker  103  in more detail. The CommandInvoker  1051 , which is a component of the command sub-system  105 , starts up or executes the Command  1052  in the ProgramInvoker  103 . With such a document processing system, the Command  1052  is a command used for processing a document such as an XML document, and editing the corresponding XML DOM tree. The CommandInvoker  1051  holds the classes and functions required to execute the Command  1052 . 
     Also, the ServiceBroker  1041  is executed within the ProgramInvoker  103 . The UserApplication  106  is connected to the user interface  107  and the CoreComponent  110 . The CoreComponent  110  provides a method which allows all the Panes to share a document. Furthermore, the CoreComponent  110  provides a font, and serves as a tool kit for the Pane. 
       FIG. 15(   b ) shows the relation between the Frame  1071 , the MenuBar  1072 , and the StatusBar  1073 . 
     H. Application Core 
       FIG. 16(   a ) provides a more detailed description of the application core  108 , which holds the whole document, and a part of the document, and the data of the document. The CoreComponent  110  is attached to the DocumentManager  1081  for managing the documents  1082 . The DocumentManager  1081  is the owner of all the documents  1082  stored in memory in association with the document processing system. 
     In order to display a document on a screen in a simple manner, the DocumentManager  1081  is also connected to the RootPane  1084 . Also, the functions of the Clipboard  1087 , a Drag&amp;Drop  601 , and an Overlay  602  are attached to the CoreComponent  110 . 
     The SnapShot  1088  is used for restoring the application to a given state. Upon the user executing the SnapShot  1088 , the current state of the application is detected and stored. Subsequently, when the application state changes, the content of the application state thus stored is maintained.  FIG. 16(   b ) shows the operation of the SnapShot  1088 . With such an arrangement, upon the application switching from one URL to another, the SnapShot  1088  stores the previous state. Such an arrangement allows operations to be performed forward and backward in a seamless manner. 
     I. Document Structure within the DocumentManager 
       FIG. 17(   a ) provides a more detailed description of the DocumentManager  1081 , and shows the DocumentManager holding documents according to a predetermined structure. As shown in  FIG. 11(   b ), the DocumentManager  1081  manages the documents  1082 . With an example shown in  FIG. 17(   a ), one of the multiple documents is a RootDocument (root document)  701 , and the other documents are SubDocuments (sub-documents)  702 . The DocumentManager  1081  is connected to the RootDocument  701 . Furthermore, the RootDocument  701  is connected to all the SubDocuments  702 . 
     As shown in  FIG. 12  and  FIG. 17(   a ), the DocumentManager  1081  is connected to the DocumentContainer  203 , which is an object for managing all the documents  1082 . The tools that form a part of the tool kit  201  (e.g., XML tool kit) including a DOMService  703  and an IOManager  704  are supplied to the DocumentManager  1081 . Referring to  FIG. 17(   a ) again, the DOM service  703  creates a DON tree based upon a document managed by the DocumentManager  1031 . Each document  705 , whether it is a RootDocument  701  or a SubDocument  702 , is managed by a corresponding DocumentContainer  203 . 
       FIG. 17(   b ) shows the documents A through E managed in a hierarchical manner. The document A is a RootDocument. On the other hand, the documents B through D are the SubDocuments of the document A. The document E is the SubDocument of the document D. The left side in  FIG. 17(   b ) shows an example of the documents displayed on a screen according to the aforementioned hierarchical management structure. In this example, the document A, which is the RootDocument, is displayed in the form of a base frame. On the other hand, the documents B through D, which are the SubDocuments of the document A, are displayed in the form of sub-frames included in the base frame A. On the other hand, the document E, which is the SubDocument of the document D, is displayed on a screen in the form of a sub-frame of the sub-frame D. 
     Referring to  FIG. 17(   a ) again, an UndoManager (undo manager=undo management unit)  706  and an UndoWrapper (undo wrapper)  707  are created for each DocumentContainer  203 . The UndoManager  706  and the UndoWrapper  707  are used for executing an undoable command. Such a feature allows the user to reverse a modification which has been applied to the document according to an editing operation. Here, the modification of the SubDocument significantly affects the RootDocument. The undo operation performed under such an arrangement gives consideration to the modification that affects other hierarchically managed documents, thereby preserving the document integrity over all the documents managed in a particular hierarchical chain, as shown in  FIG. 17(   b ), for example. 
     The UndoWrapper  707  wraps undo objects with respect to the SubDocuments stored in the DocumentContainer  203 . Then, the UndoWrapper  707  connects the undo objects thus wrapped to the undo object with respect to the RootDocument. With such an arrangement, the UndoWrapper  707  acquires available undo objects for an UndoableEditAcceptor (undoable edit acceptor=undoable edit reception unit)  709 . 
     The UndoManager  706  and the UndoWrapper  707  are connected to the UndoableEditAcceptor  709  and an UndoableEditSource (undoable edit source)  708 . Note that the Document  705  may be the UndoableEditSource  708  or a source of an undoable edit object, as can be readily understood by those skilled in this art. 
     J. Undo Command and Undo Framework 
       FIG. 18(   a ) and  FIG. 18(   b ) provide a more detailed description with respect to an undo framework and an undo command. As shown in  FIG. 18(   a ), an UndoCommand  801 , RedoCommand  802 , and an UndoableEditCommand  803  are commands that can be loaded in the CommandInvoker  1051 , and which are serially executed. The UndoableEditCommand  803  is further attached to the UndoableEditSource  708  and the UndoableEditAcceptor  709 . Examples of such undoableEditCommands include a “foo” EditCommand  804  and a “bar” EditCommand  805 . 
     1. Execution of UndoableEditCommand 
       FIG. 18(   b ) shows execution of the UndoableEditCommand. First, let us consider a case in which the user edits the Document  705  using an edit command. In the first step S 1 , the UndoableEditAcceptor  709  is attached to the UndoableEditSource  708  which is a DOM tree of the Document  705 . In the second step S 2 , the Document  705  is edited using an API for the DOM according to a command issued by the user. In the third step S 3 , a listener of the mutation event is notified of the modification. That is to say, in this step, the listener that monitors all modifications made to the DOM tree detects such an edit operation. In the fourth step S 4 , the UndoableEdit is stored as an object of the UndoManager  706 . In the fifth step S 5 , the UndoableEditAcceptor  709  is detached from the UndoableEditSource  708 . Here, the UndoableEditSource  708  may be the Document  705  itself. 
     K. Procedure for Loading a Document to the System 
     Description has been made in the aforementioned sub-sections regarding various components and sub-components of the system. Description will be made below regarding methods for using such components.  FIG. 19(   a ) shows the outline of the operation for loading a document to the document processing system. Detailed description will be made regarding each step with reference to examples shown in  FIGS. 24 through 28 . 
     In brief, the document processing system creates a DOM based upon the document data which is provided in the form of a binary data stream. First, an ApexNode (apex node=top node) is created for the targeted part of the document, which is a part of the document that belongs to the Zone. Subsequently, the corresponding Pane is identified. The Pane thus identified generates the Zone and Canvas from the ApexNode and the physical screen. Then, the Zone creates a Facet for each node, and provides the necessary information to the Facets. On the other hand, the Canvas creates a data structure for rendering the nodes based upon the DOM tree. 
     More specifically, the document is loaded from a storage  901 . Then, a DOM tree  902  of the document is created. Subsequently, a corresponding DocumentContainer  903  is created for holding the document. The DocumentContainer  903  is attached to the DocumentManager  904 . The DOM tree includes the root node, and in some cases includes multiple secondary nodes. 
     Such a document generally includes both text data and graphics data. Accordingly, the DOM tree may include an SVG sub-tree, in addition to an XHTML sub-tree The XHTML sub-tree includes an ApexNode  905  for XHTML. In the same way, the SVG sub-tree includes an ApexNode  906  for SVG. 
     In Step  1 , the ApexNode  906  is attached to a Pane  907  which is a logical layout of the screen. In Step  2 , the Pane  907  issues a request for the CoreComponent which is the PaneOwner (pane owner=owner of the pane)  908  to provide a ZoneFactory for the ApexNode  906 . In Step  3 , in the form of a response, the PaneOwner  908  provides the ZoneFactory and the Editlet which is a CanvasFactory for the ApexNode  906 . 
     In Step  4 , the Pane  907  creates a Zone  909 . The Zone  909  is attached to the Pane  907 . In Step  5 , the Zone  909  creates a Facet for each node, and attaches the Facets thus created to the respective nodes. In Step  6 , the Pane  907  creates a Canvas  910 . The Canvas  910  is attached to the Pane  907 . The Canvas  910  includes various Commands. In Step  7 , the Canvas  510  creates a data structure for rendering the document on a screen. In a case of XHTML, the data structure includes a box tree structure. 
     1. MVC of the Zone 
       FIG. 19(   b ) shows the outline of a structure of the Zone using the MVC paradigm. In this case, with respect to a document, the Zone and the Facets are the input, and accordingly the model (M) includes the Zone and the Facets. On the other hand, the Canvas and the data structure for rendering a document on a screen are the output, in the form of an image displayed on a screen for the user. Accordingly, the view (V) corresponds to the Canvas and the data structure. The Command executes control operations for the document and the various components that correspond to the document. Accordingly, the control (C) includes the Commands included in the Canvas. 
     L. Representation of a Document 
     Description will be made below regarding an example of a document and various representations thereof. The document used in this example includes both text data and image data. The text data is represented using XHTML, and the image data is represented using SVG.  FIG. 20  shows in detail the relation between the components of the document and the corresponding objects represented in the MVC. In this example, a Document  1001  is attached to a DocumentContainer  1002  for holding the Document  1001 . The document is represented in the form of a DOM tree  1003 . The DOM tree includes an ApexNode  1004 . 
     The ApexNode is indicated by a solid circle. Each of the nodes other than the ApexNode is indicated by an empty circle. Each Facet used for editing the node is indicated by a triangle, and is attached to the corresponding node. Here, the document includes text data and image data. Accordingly, the DOM tree of the document includes an XHTML component and an SVG component. The ApexNode  1004  is the top node of the XHTML sub-tree. The ApexNode  1004  is attached to an XHTMLPane  1005  which is the top pane for physically representing the XHTML component of the document. Furthermore, the ApexNode  1004  is attached to an XHTMLZone  1006  which is a part of the DON tree of the document. 
     Also, the Facet  1041  that corresponds to the Node  1004  is attached to the XHTMLZone  1006 . The XHTMLZone  1006  is attached to the XHTMLPane  1005 . The XHTMLEditlet creates a XHTMLCanvas  1007  which is a logical representation of the document. The XHTMLCanvas  1007  is attached to the XHTMLPane  1005 . The XHTMLCanvas  1007  creates a BoxTree  1009  for the XHTML component of the Document  1001 . Various commands  1008  necessary for holding and displaying the XHTML component of the document are added to the XHTMLCanvas  1007 . 
     In the same way, an ApexNode  1010  of the SVG sub-tree of the document is attached to an SVGZone  1011  which is a part of the DOM tree of the document  1001 , and which represents the SVG component of the document. The ApexNode  1010  is attached to an SVGPane  1013  which is the top Pane for physically representing the SVG part of the document. An SVGCanvas  1012  for logically representing the SVG component of the document is created by the SVGEditlet, and is attached to an SVGPane  1013 . The data structure and the commands for rendering the SVG component of the document on a screen are attached to the SVGCanvas. For example, this data structure may include circles, lines, and rectangles, and so forth, as shown in the drawing. 
     While description has been made regarding the representation of a document with reference to  FIG. 20 , further description will be made regarding a part of such examples of the representations of the document using the above-described MVC paradigm with reference to  FIG. 21(   a ).  FIG. 21(   a ) shows a simplified relation between M and V (MV) with respect to the XHTML components of the document  1001 . In this case, the model is the XHTMLZone  1101  for the XHTML component of the Document  1001 . The tree structure of the XHTMLZone includes several Nodes and the corresponding Facets. With such an arrangement, the corresponding XHTMLZone and the Pane are a part of the model (M) component of the MVC paradigm. On the other hand, the view (V) component of the MVC paradigm corresponds to the XHTMLCanvas  1102  and the BoxTree that correspond to the XHTML component of the Document  1001 . With such an arrangement, the XHTML component of the document is displayed on a screen using the Canvas and the Commands included in the Canvas. Note that the events occurring due to the keyboard action and the mouse input proceed in the opposite direction to that of the output. 
     The SourcePane provides an additional function, i.e., serves as a DOM owner.  FIG. 21(   b ) shows the operation in which the vocabulary connection is provided for the components of the Document  1001  shown in  FIG. 21(   a ). The SourcePane  1103  that serves as a DOM holder includes a source DOM tree of the document. The ConnectorTree  1104  is created by the ConnectorFactory, and creates the DestinationPane  1105  which also serves as an owner of the destination DOM. The DestinationPane  1105  is provided in the form of the XHTMLDestinationCanvas  1106  having a box tree layout. 
     M. The Relation Between Plug-in Sub-System, Vocabulary Connection, and Connector 
       FIGS. 22(   a ) through  22 ( c ) provide further detailed description with respect to the plug-in sub-system, the vocabulary connection, and the Connector, respectively. The Plug-in sub-system is used for adding a function to the document processing system or for replacing a function of the document processing system. The plug-in sub-system includes the ServiceBroker  1041 . A ZoneFactoryService  1201  attached to the ServiceBroker  1041  creates a Zone that corresponds to a part of the document. Also, an EditletService  1202  is attached to the ServiceBroker  1041 . The EditletService  1202  creates a Canvas that corresponds to the Nodes included in the Zone. 
     Examples of the ZoneFactories include an XHTMLZoneFactory  1211  and an SVGZoneFactory  1212 , which create an XHTMLZone and an SVGZone, respectively. As described above with reference to an example of the document, the text components of the document may be represented by creating an XHTMLZone, on the other hand, the image data may be represented using an SVGZone. Examples of the EditletService includes an XHTMLEditlet  1221  and an SVGEditlet  1222 . 
       FIG. 22(   b ) shows the vocabulary connection in more detail. The vocabulary connection is an important feature of the document processing system, which allows a document to be represented and displayed in two different manners while maintaining the integrity of the document. The VCManager  302  that holds the ConnectorFactory  303  is a part of the vocabulary connection sub-system. The ConnectorFactory  303  creates the Connector  304  for the document. As described above, the Connector monitors the node included in the source DOM, and modifies the node included in the destination DOM so as to maintain the integrity of the connection between the two representations. 
     A Template  317  represents several node conversion rules. The vocabulary connection descriptor (VCD) file is a template list which represents several rules for converting a particular path, an element, or a set of elements that satisfies a predetermined rule into another element. All the Templates  317  and CommandTemplates  318  are attached to the VCManager  302 . The VCManager is an object for managing all the sections included in the VCD file. A VCManager object is created for each VCD file. 
       FIG. 22(   c ) provides further detailed description with respect to the Connector. The ConnectorFactory  303  creates a Connector based upon the source document. The ConnectorFactory  303  is attached to the Vocabulary, the Template, and the ElementTemplate, thereby creating a VocabularyConnector, a TemplateConnector, and an ElementConnector, respectively. 
     The VCManager  302  holds the ConnectorFactory  303 . In order to create a Vocabulary, the corresponding VCD file is read out. As described above, the ConnectorFactory  303  is created. The ConnectorFactory  303  corresponds to the ZoneFactory for creating a Zone, and the Editlet for creating a Canvas. 
     Subsequently, the EditletService for the target vocabulary creates a VCCanvas. The VCCanvas also creates the Connector for the ApexNode included in the source DOM tree or the Zone. As necessary, a Connector is created recursively for each child. The ConnectorTree is created using a set of the templates stored in the VCD file. 
     The template is a set of rules for converting elements of a markup language to other elements. For example, each template is matched to a source DOM tree or a Zone. In a case of a suitable match, an apex Connector is created. For example, a template “TA/*/D” matches all the branches starting from the node A and ending with the node D. In the same way, a template “//B” matches all the “B” nodes from the root. 
     N. Example of VCD File with Respect to ConnectorTree 
     Further description will be made regarding an example of the processing with respect to a predetermined document. In this example, a document entitled “MySampleXML” is loaded in the document processing system.  FIG. 23  shows an example of the VCD script for the “MySampleXML” file, which uses the VCManager and the ConnectorFactoryTree. In this example, the script file includes a vocabulary section, a template section, and a component that corresponds to the VCManager. With regard to the tag “vcd:vocabulary”, the attribute “match” is set to “sample:root”, the attribute “label” is set to “MySampleXML”, and the attribute “call-template” is set to “sample template”. 
     In this example, with regard to the VCManager for the document “MySampleXML”, the Vocabulary includes the apex element “sample:root”. The corresponding UI label is “MySampleXML”. In the template section, the tag is “vcd:template”, and the name is set to “sample:template”. 
     O. Detailed Description of an Example of a Method for Loading a File to the System 
       FIGS. 24 through 28  provide a detailed description regarding loading the document “MySampleXML” in the system. In Step  1  shown in  FIG. 24(   a ), the document is loaded from a storage  1405 . The DOMService creates a DOM tree and a DocumentContainer  1401  that corresponds to the DocumentManager  1406 . The DocumentContainer  1401  is attached to the DocumentManager  1406 . The document includes an XHTML sub-tree and a MySampleXML sub-tree. With such a document, the ApexNode  1403  in the XHTML sub-tree is the top node of the XHTML sub-tree, to which the tag “xhtml:html” is assigned. On the other hand, the ApexNode  1404  in the “MySampleXML” sub-tree is the top node of the “MySampleXML” sub-tree, to which the tag “sample:root” is assigned. 
     In Step S 2  shown in  FIG. 24(   b ), the RootPane creates an XHTMLZone, Facets, and a Canvas. Specifically, a Pane  1407 , an XHTMLZone  1408 , an XHTMLCanvas  1409 , and a BoxTree  1410  are created corresponding to the ApexNode  1403 . 
     In Step S 3  shown in  FIG. 24(   c ), the tag “sample:root” that is not understood under the XHTMLZone sub-tree is detected, and a SubPane is created in the XHTMLCanvas region. 
     In Step  4  shown in  FIG. 25 , the SubPane can handle the “sample:root”, thereby providing a ZoneFactory having a function of creating an appropriate zone. The ZoneFactory is included in the vocabulary, and the vocabulary can execute the ZoneFactory. The vocabulary includes the content of the VocabularySection specified in “MySampleXML”. 
     In Step  5  shown in  FIG. 26 , the Vocabulary that corresponds to “MySampleXML” creates a DefaultZone  1601 . In order to create a corresponding Editlet for creating a corresponding Canvas, a SubPane  1501  is provided. The Editlet creates a VCCanvas. The VCCanvas calls the TemplateSection including a ConnectorFactoryTree. The ConnectorFactoryTree creates all the connectors that form the ConnectorTree. 
     In Step S 6  shown in  FIG. 27 , each Connector creates a corresponding destination DOM object. Some of the connectors include XPath information. Here, the XPath information includes one or more XPath representations used for determining a partial set of the source DOM tree which is to be monitored for changes and modifications. 
     In Step S 7  shown in  FIG. 28 , the vocabulary creates a DestinationPane for the destination DOM tree based upon the pane for the source DOM. Specifically, the DestinationPane is created based upon the SourcePane. The ApexNode of the destination tree is attached to the DestinationPane and the corresponding Zone. The DestinationPane creates a DestinationCanvas. Furthermore, the DestinationPane is provided with a data structure for rendering the document in a destination format and an Editlet for the DestinationPane itself. 
       FIG. 29(   a ) shows a flow in a case in which an event has occurred at a node in the destination tree that has no corresponding source node. In this case, the event acquired by the Canvas is transmitted to an ElementTemplateConnector via the destination tree. The ElementTemplateConnector has no corresponding source node, and accordingly, the event thus transmitted does not involve an edit operation for the source node. In a case that the event thus transmitted matches any of the commands described in the CommandTemplate, the ElementTemplateConnector executes the Action that corresponds to the command. On the other hand, in a case that there is no corresponding command, the ElementTemplateConnector ignores the event thus transmitted. 
       FIG. 29(   b ) shows a flow in a case in which an event has occurred at a node in the destination tree that has been associated with a source node via a TextOfConnector. The TextOfConnector acquires the text node from the node in the source DOM tree specified by the XPath, and maps the text node to the corresponding node in the destination DOM tree. The event acquired by the Canvas, such as a mouse event, a keyboard event, or the like, is transmitted to the TextOfConnector via the destination tree. The TextofConnector maps the event thus transmitted to a corresponding edit command for the corresponding source node, and the edit command thus mapped is loaded in the CommandQueue  1053 . The edit commands are provided in the form of an API call set for the DOM executed via the Facet. When the command loaded in the queue is executed, the source node is edited. When the source node is edited, a mutation event is issued, thereby notifying the TextOfConnector, which has been registered as a listener, of the modification of the source node. Then, the TextOfConnector rebuilds the destination tree such that the destination node is modified according to the modification of the source node. In this stage, in a case that the template including the TextOfConnector includes a control statement such as “for each”, “for loop”, or the like, the ConnectorFactory reanalyzes the control statement. Furthermore, the TextOfConnector is rebuilt, following which the destination tree is rebuilt. 
     EMBODIMENT 
     A document processing apparatus according to the present embodiment edits definition data that defines the mapping relation which is used as a reference for converting a first XML document described in a vocabulary into a second XML document described in another vocabulary. In particular, the document processing apparatus displays a rendering screen which displays the definition data in a simple and visually comprehensible form. Furthermore, the document processing apparatus provides a graphical user interface (which will be referred to as “GUI” hereafter) which allows the user to edit the definition data via the rendering screen. Such an arrangement offers an environment which allows the user to edit the definition data while visually confirming the structure of the template described in the definition data. Here, the latter vocabulary is a vocabulary for which a plug-in for displaying or editing is available, examples of which include XHTML. 
       FIG. 30  shows an example of a first XML document. In the example shown in this drawing, an “entire diary” element which is the root element includes a “title” element and a “diary” element. The “diary” element includes an “header” element, a “date” element, and a “body” element. The “date” element includes a “weather” attribute. On the other hand, the “diary” element has been repeatedly input. 
       FIG. 31  shows a rendering screen which displays the structure of the relation among multiple elements and attributes specified in the definition data in the form of an inclusion relation among blocks. The rendering display window  3300  provides the relation among the elements and attributes extracted from the editing-target definition data in a visually comprehensible form. Such an arrangement allows the user to easily edit the definition data by operating the objects displayed on the rendering display window  3300  via a mouse. The rendering display window  3300  allows the user to perform simple editing operations, example of which mainly include: deletion or addition of an element or an attribute; setting whether or not repetition of a specified element is permitted; setting a style for each element. With such an arrangement, the rendering display window  3300  allows the user to input an instruction to add or delete an element or attribute via a menu within a floating menu, a context menu, or a main menu of an application, which are not shown in this drawing. 
     In the present example, the elements and attributes extracted from the definition data are: the “entire diary” element which is the parent element; the “title” element and the “diary” element, each of which is a child element of the parent element; the “header” element, the “date” element, and the “body” element, each of which is a child element of the “diary” element, i.e., a grandchild element of the “entire diary” element; and the “@weather” attribute which is an attribute of the “date” element. 
     The rendering display window  3300  displays a parent block  3310 , a first child block  3312 , a second child block  3314 , a first grandchild block  3320 , a second grandchild block  3322 , a third grandchild block  3324 , and an attribute block  3340 . These blocks are displayed in the form of boxes, differing in color one from another. With such an arrangement, the positional relation and the inclusion relation among the blocks represent the relation among the corresponding elements or attributes or the tree structure. Furthermore, the size or the shape of the block indicates whether the block represents an element or an attribute. Here, a tag name is displayed at an upper-left portion of each block, which corresponds to the name of the element or the attribute. In a case that repetition is permitted for the element that corresponds to a block, a checkbox is displayed at an upper-right portion of the block, which allows the user to set whether or not repetition can be made. With such an arrangement, in a case that the user has checked the checkbox, a loop setting is set. The loop setting is set using a “for-each” element in XSLT, for example. 
     First, the “entire diary” element is displayed in the form of the parent block  3310 . The “title” element, which is a child element of the “entire diary” element is displayed in the form of the first child block  3312  included in the parent block  3310 . The parent-child relation between the “entire diary” element and the “title” element is represented by the corresponding inclusion relation between the parent block  3310  and the first child block  3312 . Note that such an arrangement allows the user to add a block in the first child block  3312  in the form of a child block thereof. A first setting box  3316  is displayed at an upper-right portion of the first child block  3312 . In a case that the user has checked the checkbox in the first setting box  3316 , the system allows the user to set a loop setting for the “title” element. 
     The “diary” element, which is a child element of the “entire diary” element, is displayed in the parent block  3310  in the form of the second child block  3314  included in the parent block  3310 . The parent-child relation between the “entire diary” element and the “diary” element is represented by the corresponding inclusion relation between the parent block  3310  and the second child block  3314 . Also, such an arrangement allows the user to add a block in the second child block  3314  in the form of a child block thereof. A second setting box  3318  is displayed at an upper-right portion of the second child block  3314 . As shown in the drawing, in a case that the user has checked the checkbox in the second setting box  3318 , the system allows the user to set a loop statement for the “diary” element. Furthermore, as shown in the drawing, an “addition” box  3342  is displayed at a lower-right portion of the second child block  3314 , which indicates that the system permits the user to repeatedly input each sub-element included in this element. 
     The “header” element, which is a first child element of the “diary” element, is displayed in the second child block  3314  in the form of the first grandchild block  3320 . The parent-child relation between the “diary” element and the “header” element is represented by the corresponding inclusion relation between the second child block  3314  and the first grandchild block  3320 . Also, such an arrangement allows the user to add a block in the first grandchild block  3320  in the form of a child block thereof. A third setting box  3330  is displayed at an upper-right portion of the first grandchild block  3320 . In a case that the user has checked the checkbox in the third setting box  3330 , the system allows the user to set a loop setting for the “header” element. 
     The “date” element, which is a second child element of the “diary” element, is displayed in the second child block  3314  in the form of the second grandchild block  3322 . The parent-child relation between the “diary” element and the “date” element is represented by the corresponding inclusion relation between the second child block  3314  and the second grandchild block  3322 . Also, such an arrangement allows the user to add a block in the second grandchild block  3322  in the form of a child block thereof. A fourth setting box  3332  is displayed at an upper-right portion of the second grandchild block  3322 . In a case that the user has checked the checkbox in the fourth setting box  3332 , the system allows the user to set a loop setting for the “date” element. 
     The “body” element, which is a third child element of the “diary” element, is displayed in the second child block  3314  in the form of the third grandchild block  3324 . The parent-child relation between the “diary” element and the “body” element is represented by the corresponding inclusion relation between the second child block  3314  and the third grandchild block  3324 . Also, such an arrangement allows the user to add a block in the third grandchild block  3324  in the form of a child block thereof. A fifth setting box  3334  is displayed at an upper-right portion of the third grandchild block  3324 . In a case that the user has checked the checkbox in the fifth setting box  3334 , the system allows the user to set a loop setting for the “body” element. 
     The “weather” attribute, which is an attribute of the “date” element, is displayed in the second grandchild block  3322  in the form of the attribute block  3340 . The relation between the “date” element and the “@weather” attribute is represented by the corresponding inclusion relation between the second grandchild block  3322  and the attribute block  3340 . The system does not permit the user to add a child element in the attribute. Accordingly, the attribute block  3340  is displayed in the shape of a narrow block having no space for allowing the user to add any item in the block, which notifies the user that the system does not permit the user to add a child block. 
     The system allows the user to set a style, i.e., a display format for each block displayed on the rendering display window  3300 . The system allows the user to set the style by selecting a floating window shown in the next drawing. Note that this drawing shows no menu provided to the rendering display window  3300 . However, a menu including the root element names and the vocabulary names may be displayed. Also, another menu may be provided for allowing the user to add the top element for the additional element. On the other hand, let us consider a case in which new definition data is created. In this case, after the setting of the definition data name and the namespace, the rendering display window  3300  is displayed. In this stage, the rendering display window  3300  has a single block displayed with a large size approximately the same as the overall size of the rendering display window  3300 . 
       FIG. 32  shows an example of a floating window which is displayed for allowing the user to set a style for an element or an attribute. A style palette window  3350  displays a style menu  3352  and a details field  3354 . The style menu  3352  provides multiple kinds of style options. The details field  3354  displays the style sample thus selected via the style menu  3352 , and a color in which the block is displayed in the rendering display window  3300 . 
     The style menu  3352  provides the style options such as a “&lt;table&gt;” option, a “&lt;b&gt;” option, an “&lt;a&gt;” option, a “&lt;u&gt;” option, an “&lt;h1&gt;” option, an “&lt;h2&gt;” option, an “&lt;h3&gt;” option, etc., which are represented by the names such as “table”, “bold”, “link”, “underline”, “header 1”, “header 2”, “header 3”, etc. This drawing shows a case in which the user has selected the “header 1”, which corresponds to “&lt;h1&gt;”, from the style menu  3352 . The system allows the user to define a user&#39;s own style, and to register the user&#39;s own style thus defined as the option of the style menu  3352 . For example, such an arrangement allows the user to define a user&#39;s own style which specifies both the “underline” option that corresponds to the “&lt;u&gt;” tag and the “bold” option that corresponds to the “&lt;b&gt;” tag, with a new name “important part”, for example. With such an arrangement, the system may provide a method for allowing the user to define such a user&#39;s own style as follows. That it to say, upon the user selecting a “customize” menu from among the options of an unshown main menu, a corresponding option screen is opened, which allows the user to directly input a tag. Also, the style menu  3352  provides particular styles which can be applied only to an element, but cannot be applied to any attribute. For example, the “table” style can be applied to only an element. 
     The details field  3354  displays the character string to which the style has been applied and the style name, which serve as a sample that allows the user to visually confirm the style thus selected from the style menu  3352 . With such an arrangement, a particular color or a particular icon is assigned to each style included in the style menu  3352 . With the present embodiment, a background color and a character color are assigned to each style. With such an arrangement, the details field  3354  displays a description of the background color and the character color assigned to the style thus selected via the style menu  3352 . In this stage, upon the user selecting a block that corresponds to any one of the elements or the attributes displayed on the rendering display window  3300 , the style thus selected via the style palette window  3350  is applied to the block thus selected. Furthermore, the background color and the character color assigned to the style thus selected are applied to the selected block displayed on the rendering display window  3300 . 
     Note that the style menu  3352  further includes styles such as a “date” style, a “numeral” style, a “paragraph” style, a “numbered list” style, an “itemizing” style, etc. The system permits the user to specify the font size, the kind of the font, the background color, the character color, etc., for each style. Also, the system may restrict the input value. Examples of such restrictions include: restriction of the data input to only a date format; restriction of the numeral input to only a numerical value; restriction of the numeral input by setting a maximum value or a minimum value; etc. 
       FIG. 33  shows an example of the definition data thus edited. As shown in  FIG. 12 , a loop setting is set for the “diary” element in the rendering display window  3300 . Also, as shown in this drawing, “for-each element” is set for the element  3360 . Furthermore, the styles selected from the style palette window  3350  shown in  FIG. 32  are applied to a part of the blocks displayed on the rendering display window  3300 . Specifically, as shown in this drawing, the “&lt;h1&gt;” style is applied to the node  3362 , and the “&lt;p&gt;” style is applied to the node  3364 . 
       FIG. 34  shows the rendered result obtained by converting the first document into the second document with reference to the definition data, In the rendering display window  3300 , a character string “January diary” which is the element value of the “title” element is displayed in the form of a header with a large character size according to the “&lt;h1&gt;” tag. Furthermore, the rendering display window  3300  displays the contents of the “diary” element according to the loop setting. Specifically, first, the rendering display window  3300  displays: “January 1”, which is the element value of the “date” element; “fair”, which is the “@weather” attribute of the “date” element; and a character string “It is fair today” which is the element value of the “body” element. Subsequently, the rendering display window  3300  displays: “January 2”, which is the element value of the next “date” element; “rainy”, which is the “@weather” attribute of the “date” element; and a character string “It is rainy today” which is the element value of the “body” element. 
       FIG. 35  is a functional block diagram which shows a basic configuration of the document processing apparatus  20  according to the embodiment. In particular, description, will be made with reference to this drawing, mainly regarding a function of editing the definition data. With the document processing apparatus  20 , a VC processing unit  3400  converts a first XML document described in a first vocabulary into a second XML document described in a second vocabulary. Furthermore, the VC processing unit  3400  provides a function of creating and editing the definition data used as a reference for the mapping. The VC processing unit  3400  includes a document readout unit  3402 , a mapping relation creating unit  3404 , a display processing unit  3408 , a candidate storage unit  3410 , a data output unit  3412 , an operation input unit  3414 , and a processing control unit  3416 . Such a configuration can be realized by hardware components, e.g., by actions of a CPU, memory, or by software components, e.g., by actions of a program loaded into the memory. Here, the drawing shows a functional block configuration realized by both hardware components and software components operating in cooperation. Accordingly, such functional blocks can be realized by hardware components alone, software components alone, or various combinations thereof, which can be readily conceived by those skilled in this art. 
     The operation input unit  3414  receives instructions from the user via input devices such as a keyboard, a mouse, and so forth. For example, let us consider a case in which the operation input unit  3414  receives an instruction with respect to repeated input. In this case, the operation input unit  3414  receives an instruction according to the user&#39;s operation via the checkbox such as the first setting box  3316 , the second setting box  3318 , or the like. On the other hand, let us consider a case in which the operation input unit  3414  receives an instruction with respect to style. In this case, the operation input unit  3414  receives a selection instruction from the user to select the style and to select the element or the attribute to which the style is to be applied. The processing control unit  3416  controls each component of the VC processing unit  3400  based upon the instructions from the user acquired by the operation input unit  3414 . 
     The document readout unit  3402  reads out a first XML document described in a first vocabulary and stores the first XML document thus read out in the memory. In general, the term “first vocabulary” as used here represents a local vocabulary for which no dedicated viewer is available. The first XML document is a target document which is to be converted into another XML document described in the second vocabulary. Specifically, in the present embodiment, the XML document as shown in  FIG. 30  corresponds to the first XML document. 
     The mapping relation creating unit  3404  detects the elements or the attributes included in the first XML document read out by the document readout unit  3402 . The mapping relation creating unit  3404  creates definition data for mapping the elements or the attributes thus detected to those of the second vocabulary. In a case that the document readout unit  3402  has read out the first XML document as a new document, the mapping relation creating unit  3404  performs pre-processing, i.e., creates definition data including only a description of the basic elements. Subsequently, let us consider a case in which the operation input unit  3414  has acquired an instruction according to the user&#39;s operation via the checkbox such as the first setting box  3316 , the second setting box  3318 , or the like, thus checked. In this case, a statement of the “for-each element” is added to the definition data according to the operation. On the other hand, upon reception of a selection instruction to select the style or an instruction to select the element or the attribute to which the style is to be applied, an XHTML tag is added to the definition data based upon the selection instruction. The candidate storage unit  3410  stores the style options. 
     The display processing unit  3408  displays the rendering display window  3300  and the style palette window  3350  on a monitor screen. Furthermore, the display processing unit  3408  instructs the rendering display window  3300  to display the first XML document, the contents of the definition data, the contents after mapping, and so forth, in a rendered form. The data output unit  3412  outputs the definition data externally. 
     Note that the VC processing unit  3400  may be provided in the form of a part of the document processing apparatus  20  according to the background technique. With such an arrangement, the VC unit  80  shown in  FIG. 1  may be replaced by the VC processing unit  3400 . 
     Description has been made regarding the present invention with reference to the embodiments. The above-described embodiments have been described for exemplary purposes only, and are by no means intended to be interpreted restrictively. Rather, it can be readily conceived by those skilled in this art that various modifications may be made by making various combinations of the aforementioned components or processes, which are also encompassed in the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a document processing apparatus for displaying or processing a structured document.