Abstract:
A user-controlled interactive computer display system and method is disclosed for manipulating a hierarchy of information (a topmost node and a number of subordinate nodes, each with only one superior node). This display system and method allows a hierarchical arrangement of information to be constructed and changed with a minimum of steps and errors because positional information about each node is handled implicitly by the system.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to user-controlled interactive computer display systems, specifically to a display system and method for constructing and editing a hierarchical arrangement of information. 
     PRIOR ART 
     In a user-controlled interactive computer display system it is desirable to insulate the user from the computer and how the computer itself works. The object is to provide a display system and method that relates directly to the work at hand, allowing the user to learn quickly how to operate the display system, then work efficiently words the completion of his or her task. This is especially important for display systems used by people who have minimal computer experience. 
     Proven display systems and methods exist for constructing and manipulating textual documents, free-form graphics drawings, and tables of numbers. Such is not the case for hierarchical diagrams or representations such as corporate organization charts, work break-down structures, and decision trees. 
     Traditional display systems and methods for working with hierarchical representations fall into three groups: editors for an indented or subscripted list of items (such a list scheme is described by Donald E. Knuth, Fundamental Algorithms, Addison-Wesley, 1973), prompting systems that query the user for nodes in the representation one at a time (e.g., Diagram-Master (TM) by Decision Resources), and systems that allow the user to construct a purely graphic image of the representation (draw/paint display systems, e.g., PC Paint Plus (TM) by Mouse Systems Corp.). 
     These display systems and methods of the prior art have the disadvantage of requiring the user to explicity specify the positional information about a node. This is a time consuming step that must be performed repeatedly as the hierarchy is constructed and edited. The resulting error rate is high. 
     For applications that require a diagrammatic output such as an organization chart, the trend has been to develop display systems that allow the user to draw an image of the diagram on the display device of the computer. This technique has the advantage of being easy for the inexperienced user to understand because he is simply copying on to the display device a representation from his everyday experience. However, the other prior art systems and methods require a user to maintain the overall image of the diagram in his or her head. This is not any easy task, especially when editing the hierarchy. 
     Unfortunately, the price paid for ease-of-use is very high. Since the costs to process purely graphic image are prohibitively high, the user is forced to do much of the hard work of positioning the nodes, positioning the descriptive information in the nodes, and drawing the connecting lines. Consequently, the overall speed of draw/paint display systems is very slow. Draw/paint systems have other well known disadvantages: they require specialized and more expensive display hardware (which most users do not possess), editing is limited to copying or erasing then redrawing, and the information the user has painstakingly input cannot be used for other tasks. For example, a user doing an organization chart may want the computer to sum the salaries of the individuals represented in the chart. This is not possible with draw/paint systems of the prior art. 
     Thus, there exists a need for a new method that is intuitive to learn, quick to use, and flexible in its application. 
     Accordingly, it is the object of this invention to provide an improved method for displaying a hierarchy that overcomes the disadvantages of the prior art. 
     In particular, it is an object of the invention to accept information about the nodes of the hierarchy in a way that allows it to be stored in a database. The information can then be used for a variety of purposes once it has been entered. Another object is to place minimal demands on the hardware of the computer display system so that the broadest possible cross-section of equipment can support the invention. 
     Most importantly, it is an object of this invention to eliminate the need for the user to provide explicit positional information about each node. There should not even be a requirement to know that positional information exists, or how to provide it. By eliminating the need for such an expertise in constructing hierarchies, a broader selection of people can build them. By eliminating the steps associated with providing positional information, hierachies can be constructed and changed much more quickly and accurately. 
     SUMMARY OF THE INVENTION 
     A computer display system and method is disclosed that has particular application to the construction and manipulation of hierarchical representations. A computer is programmed to provide an area on the display screen where information about a single, superior node in the representation can be entered and remembered by the computer. Adjacent to this area (below in the present embodiment) another area is created where subordinate nodes can be created, identified and stored by the computer. By using a command key or menu selection in the present embodiment, the user can instantly change the contents of the display to that of any other node above, below, or beside the currently displayed node. In other words, the user can navigate around the representation at will. In such a way, a hierarchical representation can quickly be entered into the computer. The user always sees one node and its subordinate nodes. Subsequent processing can modify the nodes and their relationship to one another by editing their contents, changing their order or interconnections, performing calculations on values assigned to them, and formatting their representation for printed output. 
     The present invention provides such an improvement in speed, that it can be used to perform &#34;what if&#34; analysis not before possible on hierarchical representations. Users can quickly edit their hierarchy to compare one alternative to another. 
    
    
     DESCRIPTION OF THE DRAWING 
     FIG. 1 is a block schematic diagram of the preferred embodient of the present invention; and 
     FIG. 2 is a graphic representation of a frame which displays information about a node and its subordinate nodes; and 
     FIG. 3 is a graphic representation of a frame which displays information about a staff-level node; and 
     FIG. 4 is a graphic representation of a frame which displays information about a terminal node at the lowest possible level of the hierarchy; and 
     FIG. 5 is a graphic representation of a frame with sample information in some of its data-entry fields; and 
     FIG. 6 is a graphic representation of a display of index information about a sample hierarchy; and 
     FIG. 7 is a graphic representation of a display of a map of a sample hierarchy; and 
     FIGS. 8, 8A, 8B, and 8C comprise a logic flow diagram illustrating the operation of the preferred embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For clarity of description only, the invention will be described as embodied to produce common office organization charts. Of course it should be understood changes to the data entry field(s) such as, but not limited to, their: identification label, type (text, numeric only, multiple choice, date only, etc.), size or length, position relative to one another within their area, and quantity can make the invention appropriate for entirely different applications such as work breakdown structures, decision trees, and outlines, etc. The performance of different kinds of operations (such as statistical or arithmetic operations) on the contents of the data entry fields can also make the invention appropriate for entirely different applications. 
     The following definitions are applicable to the description: 
     Node 
     An element that has two types of information associated with it. Positional information that describes its spatial relationship to other nodes and descriptive information that allows it to represent something to an observer. 
     Hierarchy 
     A single topmost or root node which has no superior and an indefinite plurality (which can be zero) of subordinate nodes such that each node has one and only one immediate superior node and such that each subordinate node is in some way ordered relative to its sibling nodes (those nodes with the same immediate superior). Thus, the positional information for each node includes, at a minimum, two pieces: superior node and position relative to siblings. This type of hierarchy represents an ordered or plane tree. 
     Branch 
     A sub-hierarchy including a node and all of the directly or indirectly connected nodes below it, if any. 
     Frest 
     A plurality of hierarchies. 
     Referring now to FIG. 1, there is shown a schematic diagram of the preferred embodiment of the present invention that includes a central processing unit 11 which is connected to and controls the display device 13 in response to inputs supplied to the CPU 11 via the user&#39;s manipulation of the keyboard (or mouse or other input device) 15. 
     The CPU accesses addresses memory 18 which contains information that is supplied via the keyboard 15, mass storage 27, or network 29 and instructions for manipulation of that information in accordance with the operating sequences of the present invention. These operating sequences are directed toward developing a specific database 17 of hierarchical information under command of the hierarchy processor 19 (described in detail later herein). The hierarchy processor 19 interacts with the CPU 11 to display an image 21 on the display device 13 that can allow a hierarchy to be constructed and changed under control of the user. The image 21 that is displayed includes one or more primary representations of the data as shown in FIG. 2. 
     This representation is referred to as a frame 74. Each frame is uniquely identified by the positional information of the node whose descriptive information is displayed in the superior node box 40. In this embodiment the frame represents a work group. The term work group refers to an individual manager and the people reporting directly to him or her. 
     The subordinate nodes box 42 is the lower box in a frame 74. It contains an ordered list (according to the position in which they were entered) of the subordinate nodes (as identified by a subset of the information contained about them in the database) whose superior node identifies the current frame, herein referred to as the current superior node. (It is described below how indirectly connected nodes are in certain conditions listed.) The user can enter as many subordinate nodes as the current superior node has (up to 16 in the present embodiment although the number can be indefinitely large by providing means to scroll or page through additional entries). The subordinate nodes box 42 expands and contracts depending on the number of subordinate nodes. The nodes will appear in a corresponding order on the printed chart as they appear top-to-bottom in the subordinate nodes box 42 on the screen. 
     The fields for descriptive information, i.e., superior node name field 44, superior node title field 46, and superior node comment field 48, have self explanatory labels such as Name 45, Title 47, and Comment 49. However, they may be used for other information. 
     The fields for descriptive information, i.e., superior node name abbreviation field 50a, superior node title abbreviation field 50b, and superior node comment abbreviation field 50c (labeled Abbrev 51a, 51b, 51c) are for abbreviations of the information the user enters in the corresponding fields 44, 46, 48. The invention may use these abbreviations when printing the chart if there is difficulty making the chart fit on the page size requested. Entering abbreviations is entirely optional. Once the node has been created, changes to the descriptive information fields only change the descriptive information stored in the database 17 of FIG. 1. 
     The superior node level field 52, labeled Chart Level 53 contains positional information about a node indicating the node&#39;s level in the hierarchy. The top level is defined as 1. The topmost node&#39;s immediate subordinate nodes are at level 2 and so on. The superior node level field 52 defaults to a value one greater than the chart level for the current superior node. If the node is to be placed at an even lower level the user can specify a larger number. The user is disallowed from entering a number less than or equal to the level of the node&#39;s superior node. The specification of a number different than the default or previous value always involves creation or destruction of nodes. In the present embodiment, nodes invisible to the user (they are never displayed) are created to hold a place at each level of the hierarchy between the superior node and the actual (real-world) subordinate. Correspondingly, said invisible nodes are destroyed if the user reduces the number of intervening levels. 
     The invention also provides for staff level nodes, i.e., employees. A staff level node is a terminal node that cannot have subordinate nodes, consequently, the staff frame as shown in FIG. 3 is displayed differently on the display device 13. Staff level nodes are identified with an S in the node&#39;s level field 71 or 58a. Arbitrarily, the current embodiment has a limit of 99 levels. A node at the 99th level is also a terminal node displayed as shown in FIG. 4. 
     The value in the superior node line type field 54 of FIG. 2, labeled Line Type 55, indicates whether the current superior node is connected to its superior (in the final printed output) with a solid line (S), a dotted line (D), or no line at all (N). The present embodiment of the invention defaults to a solid line. Display of the superior node line type field 54, and label 55 is suppressed if the hierarchy&#39;s topmost node is the current superior node since that node has no node to be connected to. This field is highly peculiar to the application of the present embodiment. 
     In accordance with the present invention, the subordinate node name field 56a and label 57a, subordinate node level field 58a and label 59a, and subordinate node line type field 60a and label 61a contain a subset of the information describing the subordinate node. The ordinal of the subordinate node 64a shows the subordinate node&#39;s order from top-to-bottom starting with 1. 
     FIG. 5 shows a frame as displayed with sample information in the fields. The potential subordinate node row 62 is the bottom-most row of fields in the subordinate nodes box 42. It is not associated with any existing node and serves as a means as described below to add new nodes. It is displayed unless the maximum number of subordinate nodes is already assigned to the current superior node. 
     With reference to FIG. 2, the scale 66 allows the user to estimate the length in characters of the information entered into superior node fields 44, 46, and 48. The length of these fields has an impact on the printed size of the chart. The top connecting line 68 is shown if the current superior node has a superior of its own and if the line type of the current superior node is not &#34;None&#34;. The top connecting line 68 is dotted if the line type of the current superior node is &#34;Dotted&#34;. Staff frames have a side connecting line 69 in place of a top connecting line 68. The side connecting line 69 in FIG. 3 behaves like the top connecting line 68. The box connector 70 graphically connects the superior nodes box 40 and the subordinate nodes box 42. One bottom connecting line 72a is displayed for each subordinate node in the subordinate nodes box 42 that has at least one subordinate node of its own. Lines 68, 69, 70, and 72a help the user reference the frame to a diagram of a hierarchy such as an office organization chart. 
     Referring now to FIGS. 8A and 8B, there is shown the overall flow through the display system. When the system is loaded into addressable memory 18, it is in the &#34;Main Menu&#34; state. From the &#34;Main Menu&#34; the user can do such things as access the mass storage 27, exit the system, or choose to work on a hierarchy. Under receiving a request from the user to work on a hierarchy there is first a test 81 to ascertain whether a hierarchy exists. If no hierarchy exists, a hierarchy is established by creating a topmost node 83. A topmost node has positional information indicating that it has no superior. 
     There are a large number of ways to consistently specify the positional information about this topmost node and the other nodes in a hierarchy which, in the present invention, is an ordered or plane tree. The preferred embodiment is a triply-linked data structure wherein pointers are established to a node&#39;s superior, leftmost subordinate, and adjacent right sibling. With a triply-linked data structure, a change in the positional information of one node changes the positional information of other nodes. For example, to add a rightmost node to a group of existing siblings, the new node will have null pointers to leftmost subordinate and adjacent right sibling; the pointer to the node&#39;s superior will hold the address of the current superior node. Additionally, the new node&#39;s left sibling must have its adjacent right sibling pointer changed from null to the address of the new node as entered in the database 17. This approach provides extremely high speed when polling the database 17 (even to find the left adjacent sibling for which there is no pointer is a quick calculation) with some speed penalties when changing the positional information. The trade-off is favorable because polling is an extremely frequent activity while changing the positional information is rare and generally performed when speed is not an issue. 
     Manipulation of a triply-linked data structure is well covered by the literature (see for example, Knuth, Fundamental Algorithms). 
     Alternatively, a four-way-linked data structure could be used to describe the positional information of each node. To the three links described above we would add a link to the left adjacent sibling. This would speed operations where the finding the left adjacent sibling was important, but the additional storage overhead and added complexity in changing the positional information may make this alternative data structure less attractive than the embodiment described above. On the other hand, a doubly-linked structure would be sufficient to define our hierarchy (we would give up from the triply-linked structure the pointer to leftmost subordinate), but it is believed the processing burden for many common operations would result in unacceptable performance. Though not favored, these and other data structures can be used to implement the invention. 
     A memory allocation scheme is used in developing the database 17 according to the present invention. A fixed array of C-language structures which include positional and descriptive information (name, title, comment, etc.) is defined and allocated. Pointers to the elements of this array are used to initialize a stack. A pop routine indicates the next available structure when a node is created. A push routine returns the memory space from a destroyed node back to the available pool of memory space. The C-language function malloc could alternatively be used to allocate and assign memory for the information. 
     Node creation in the database 17 refers to obtaining a pointer to an available block of memory from the stack and storing the proper positional information at that location. Node destruction refers to erasing the contents of the memory block and pushing the pointer to the block back on the stack. Updating the database, as later discussed, is a more generic operation which includes updating both the positional and descriptive information about the node as required. 
     Referring again to the flow chart of FIGS. 8A and 8B, at this time, the topmost node has no subordinate nodes or descriptive information about itself (other than default values of information as applicable). The topmost node is designated as the current superior node. 
     In all cases, a hierarchy 81 now exists and a current superior node has been designated. System flow proceeds to the functional block that generates the screen image of a frame 84. Specifically, the database 17 is polled for descriptive information about the current superior node and that information is displayed in the appropriate fields on display device 13. Then the database is polled for the subordinate nodes of the current superior node (if any) and the required descriptive information about them. This information is displayed in the subordinate nodes box 42. A potential subordinate node row 62 is also displayed in the subordinate nodes box 42 if the current superior node has fewer than the maximum number of subordinate nodes. This row has only default descriptive information in its fields; it is not associated with a node. Other background information that may be desired to complete the image of a frame is generated and displayed. 
     If the current superior node has just been changed, the cursor is placed in the superior node name field, else its position depends on the previous history of the system. 
     User input and editing within a given field is handled with a buffered editor that waits for and responds to user edits, but does not update the database until the field is exited. System behavior depends on the field in which the editor is called as described below. 
     If the cursor 86 is in the superior node box 40, the editor is called for the appropriate field and the system awaits user input. If the edits make a legal change 96 in the superior node level field 52, then the appropriate number of nodes will be created or destroyed 102 and the subordinate node level field(s) 58a values will be updated 106. Edits to other fields will result in simple updates 100 to the database 17. If the cursor 88 is in the potential subordinate node row when the field editor is called 92, any change or addition 98 results in the creation/addition of at least one node 104, more if the subordinate node level field 58a is legally changed. The database 17 will be updated 100 if information is added to the subordinate node name field 56a. If the cursor 88 is elsewhere in the subordinate nodes box 42, the editor 94 is called for the appropriate field. If the edits make a legal change 96 in the subordinate node level field 58a, then the appropriate number of nodes will be created or destroyed 102. Edits to other fields will result in simple updates 100 to the database 17. 
     If the user exits field editing 180, 110 with a keystroke that moves the cursor to another field in either the superior node box 40 or the subordinate nodes box 42, then a small loop is made to resume editing at the chosen field. Otherwise all possible paths of flow rejoin and a test is performed 112 to establish whether the user wants to invoke a command. If the test fails, the flow returns to the &#34;Main Menu&#34; operating state. If the user has chosen to invoke a command 112, flow passes through a series of tests 114, 118, 130, 138, 154, 170 to identify the particular command. A description of each command follows: 
     The user can navigate from one frame 74 to another. The navigation operations 116 are several in number. At the user&#39;s direction, they can show the frame of the node at the same level to the left or right of the current superior node, to the frame of the current node&#39;s superior, to the frame of the topmost node of the hierarchy, or to the frame of one of the current node&#39;s subordinate nodes. If the current frame is already at the extreme of the selected navigation direction, the display image remains unchanged. 
     If the cursor is in the superior node&#39;s box 40 when the command to navigate down is invoked, the frame of the superior node&#39;s leftmost subordinate node (at the highest level of subordinate nodes) will be displayed. If the node identified in the superior node&#39;s box 40 has no subordinate nodes, the leftmost frame of the next lower level will be displayed. These conventions for navigating down in the hierarchy are arbitrary and could be modified as desired to establish different conventions. In the present embodiment, animation is used to slide portions of the new frame images into place from the appropriate direction. This enhances the users illusion that he is actually moving about a hierarchy. 
     The user can also navigate directly to another frame by making a randomly chosen node the current superior node. In the present embodiment this is possible by choosing a navigation command to display a list of the nodes alphabetized by the first field of descriptive test FIG. 6. The invention will navigate directly to the node selected by the user. 
     All of the navigation commands operate by changing the value 116 of the memory address (a pointer in the C-language) that identifies the node known as the current superior node. The system loops to the display frame step 84 and places the cursor in the top, leftmost field 44 of the new current superior node&#39;s frame 74. The user has the impression that the representaiton of the entire hierarchy can move at his command while at any one time he views a portion (the frame 74) through a window. 
     The command to insert 118, the creation of a new node at the cursor location, has a behavior that depends on the box in which the cursor is currently located. If the cursor 102 is anywhere in the superior node box 40 when the insert command is invoked, a node will be created above the current superior node 122 with appropriate changes to the positional information of attached nodes. The new node becomes the current superior node 124 and the screen is updated. The new image of the superior node&#39;s box 40 will of course be empty of descriptive information other than defaults peculiar to the application of the present embodiment. All nodes directly or indirectly subordinate to the new node will be moved down in the hierarchy one level. If the cursor 120 is anywhere in the subordinate nodes box 42 when the insert command 118 is invoked, a node will be created 128 between the node the cursor is on (or the potential subordinate node row 62) and the one above it (if one exists). The cursor will stay on the new node which will have no descriptive information other than defaults peculiar to the application of the present embodiment. The positional information of the new node&#39;s siblings will be adjusted appropriately. 
     The present invention allows hierarchies to be merged in a manner similar to insertion of a new node. Another hierarchy selected by name 132 (from the mass storage 27 in the current embodiment) is merged by inserting 136 it&#39;s topmost node at the current cursor location. This process follows the conventions of the insertion operation except that the sursor 134 must be in the subordinate nodes box 42 (as an arbitrary restriction according to the preferred embodiment). 
     The delete command 138 destroys the existence of the node the cursor is on. If the node the cursor is on has subordinate nodes 140, the user is asked to specify 144 whether the subordinate nodes are also to be deleted. If the user requests that subordinate nodes be deleted, the node the cursor is on defines the top of a branch which is deleted 146. If the user does not want to delete the subordinates, the subordinate nodes are inserted in order as subordinate nodes of the deleted node&#39;s superior 152. In all cases, the positional information of previously attached and still existing nodes is updated 146, 152. The current superior node is unchanged if the cursor 150 was located in the subordinate nodes box 42. If the cursor was in the superior node box 40, the topmost deleted node&#39;s superior becomes the current superior node 148. There must be one and only one topmost node in each hierarchy. The preferred embodiment of the invention cannot handle a forest of hierarchies at one time. For that reason the topmost node in the hierarchy can be deleted only if it has exactly one subordinate node connected directly 142. In contrast, if the topmost node, having several subordinate nodes, were deleted as an individual, that would result in those subordinate nodes being topmost nodes in several independent hierarchies. 
     The move command 154 is a two step process in the preferred embodiment. The user first invokes the move command 156 when the cursor is on the topmost node of the branch to be moved 158. Then the user moves the cursor to the location where the topmost node of the branch previously identified is to be inserted and invokes the move command once more. If the branch to be moved has move than one node 162 and the cursor 164 is not in the same subordinate nodes box 42 as that of the topmost node of the branch to be moved, the user is asked whether to move the entire branch or just the topmost node 166. If the user requests to move just the topmost node, a negative choice at 166, that action is performed 160. The convention in the current embodiment is to leave a node without descriptive information in the moved node&#39;s place to which the moved node&#39;s previous subordinates are connected. Otherwise, the entire branch is moved 168. The positional information of all affected nodes on both ends of the operation is updated 160 and 168 (the conventions used to update the positional information of the moved node are the same as for inserting a new node). If the cursor is in the superior node box 169, then the moved node becomes the current superior node 171. 
     The Show Entire Chart command 170 displays a map of the hierarchy in the form illustrated in FIG. 7. It is very useful for viewing where the current superior node is with regard to the rest of the hierarchy. A window is made to appear over a part of the current frame. Each regular node will appear as a small square 190. Each staff node will appear as a dash 192. The current superior node may be made to blink on and off. 
     Other conventional operations may be included such as saving the hierarchy to mass storage 27, retrieving a hierarchy from mass storage 27, erasing the entire hierarchy, or processing the data 17 constructed according to the invention (for example, to format and print an organization chart). It is also possible in the current embodiment to perform most of these operations on part of the hierarchy by identifying the topmost node to be processed and by indicating how many levels down from that node to process. 
     As an additional disclosure, the User&#39;s Guide for the present embodiment of the invention is included below as an appendix. It should be noted that the User&#39;s guide uses slightly different terminology for its description because it was written for a non-technical individual. Nodes are referred to as employees, persons, or positions and superior nodes are referred to as managers. Navigation is referred to as &#34;moving between work groups&#34; and the merging of two charts is referred to as appending. 
     The present invention as configured may be used to build an office organization chart. During operation, the user is presented with a manageable piece of what can be an indefinitely large hierarchy. The user can make changes to this piece without having to consider the effect of these changes on other parts of the hierarchy. In fact, the user does not even need to known that his changes will have an effect. The system stores information about the entire hierarchy and makes changes as necessary, based on the user&#39;s modifications. Once the user has established the structure of the hierarchy, global operations such as formatting and printing an organization chart can be performed as if the user was operating on a single node. 
     In particular, the user can add a node simply by typing a name into the potential subordinate node row 62 under the appropriate manager. This is intuitive to the user because the frame displayd to him effectively represents an organization chart even though it is not. The most important point is that the user&#39;s intended action is unambiguous to the system; the system knows that the current superior node defines the superior node pointer and the system can calculate the sibling pointers since it is known that the additional node is the rightmost of the existing subordinates. Therefore, the positional information about the node is implicitly extracted from the user and automatically recorded by the system. The user is not even required to known that a node has positional information, nor is the user required to know the rules of constructing a hierarchy from nodes. The expertise in these arcane matters is subsumed by the system and method, freeing the user to concentrate on the task at hand. 
     In addition, configuring such a hierarchical chart requires fewer steps than in the prior art wherein the position information must be explicity stated by the user. Thus the prior art requires more steps that must be learned and repeated for every iteration. 
     Similar advantages are obtained when inserting, merging, or moving nodes. It is intuitive to the user that a request to perform a node insertion when the cursor is in the superior node box 40 of the frame 74 will result in a new node being placed above the superior node. On the other hand, if the cursor is in the subordinate nodes box 42 of the frame 74, it is intuitive to the user that a request to perform a node insertion will result in a new node between the existing adjacent nodes. The system has all the information it requires since the cursor location on the display device 13 uniquely defines the nodes affected by the insertion. In the prior draw/paint art, wherein an actual graphic image of the hierarchy is being worked on, it would be ambiquous to the user and to the system which type of insertion was to occur because these prior art systems don&#39;t distinguish between the two types of nodes (current superior node or subordinate node) at any one time. Additional commands are required, lengthening the learning process and/or the time to perform the operation. In fact, it is common that an insertion in the draw/paint prior art requires the user to manually move or erase and redraw portions of the hierarchy to make room for a new node. ##SPC1##