Abstract:
A computer system includes a database containing a plurality of data documents stored thereon, each data document containing at least one data field, and an archive system for electronically archiving data documents originating from the database. The database includes a control table stored thereon containing change rule information pertaining to the at least one data field of a data document archived in the archive system.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of electronic data processing, and more particularly to a computer system, a database for storing electronic data and a method to operate a database system. 
     RELATED APPLICATIONS 
     Priority is claimed to European Patent Application No. 04 004 155.0, filed Feb. 24, 2004, the content of which is incorporated herein by reference. 
     BACKGROUND 
     Today, data is almost entirely processed electronically by means of large computer systems. Particularly in the field of operating a business, a large amount of data covering all aspects of a business, particularly in the context with customers, orders, billing, machine or device data etc., accumulate over time. In order not to overload the database of the computer system, there is usually the wish to delete data that is not needed anymore, e.g. data concerning a finished business activity or process. However, very often there exists a legal requirement to keep such data over a given time period, which can be five years and even longer. As a solution hereto, software developers created so-called archive systems in which all kind of data and data documents can be archived once they are not needed in the database anymore. However, there is the drawback that archived data cannot be changed or altered anymore as the archive system usually is a read-only medium. Therefore, users tend to keep even data which could be archived in the regular productive database because they want to be able to perform certain changes as there are cases in which it is desirable to alter archived data. This leads to a situation in which data archiving is not performed as soon as it should (or could) be done, in order to ensure system performance and to keep the database size at a reasonable and preferably constant level. 
     The only possibility to change archived data today is to reload such data into the database, perform necessary changes and archiving the data again after it has been changed. This results in a very high administrative and time wise effort and is a potential source of error. 
     SUMMARY 
     Consistent with embodiments of the present invention, a database stores a plurality of data documents and is interconnected with archive systems for electronically archiving data documents originating from the database. The database comprises a control table containing change rule information pertaining to the at least one data field of a data document archived in the archive system. Upon retrieving and opening a data document which is archived in an archive system, change rule information pertaining to the retrieved archive data document is retrieved from a database interconnected with the archive system and displayed together with the retrieved archived data document. 
     It is to be understood that in the context of this invention, the term “data document” defines any entity of structured data comprising at least one data field and the term “archive system” defines a read-only medium on which data documents originating from a database are archived, the data to be archived being initially written on the read-only medium. Further, the term “control table” relates to a computer-implemented control element which operates on the basis of a table or matrix. 
     An archived data document may thus be retrieved together with control information defining which of the data fields contained in the retrieved data document can be subject to an alteration. The change rule information stored in the database automatically sets the data fields that can be subject to an alteration in a change mode once the data document is retrieved from the archive system and displayed on the monitor of a user. The remaining data fields which cannot be subject to an alteration remain in their non-change mode. This enables a user to easily effect changes to an archived data document. 
     In an embodiment, any alteration to a data field which can be subject to an alteration is stored separately in the database, e.g. in a log element. This allows a detailed history of all changes effected to a given data document to be kept and ensures that changes are correctly displayed upon a later retrieval of a changed data document. 
     The invention also covers a computer program with program coding means which are suitable for carrying out a process according to the invention as described above when the computer program is run on a computer. The computer program itself as well as stored on a computer-readable medium is claimed. 
     Further features and embodiments of the invention will become apparent from the description and the accompanying drawings. 
     It will be understood that the features mentioned above and those described hereinafter can be used not only in the combination specified but also in other combinations or on their own, without departing from the scope of the present invention. 
     The invention is schematically illustrated in the drawings by means of an embodiment by way of example and is hereinafter explained in detail with reference to the drawings. It is understood that the description is in no way limiting on the scope of the present invention and is merely an illustration of a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram of a computer system consistent with the invention; 
         FIG. 2  illustrates a data document archived in a database system according to the invention; 
         FIG. 3  is a schematic block diagram illustrating retrieval and display of the archived data document shown in  FIG. 2 ; and 
         FIG. 4  illustrates how changes to the archived data document of  FIG. 3  are saved in a log table consistent with the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The invention is illustrated by means of one possible embodiment in which a computer system  10  comprises a client computer  24  and a database system  12  (cf.  FIG. 1 ). The database system  12  comprises a database  14  and an archive system  22 , the latter being interconnected with the database  14 . A plurality of data documents  16  is stored on the database  14 . As already explained above, data documents which are not needed on database  14  anymore can be archived in the archive system  22 . Thus, the archive system serves as an off-load for the database. The archive system  22  typically is a read-only medium. 
     As already mentioned above, there are numerous situations in which a user might experience the need to perform changes or alterations to a data document which is already archived. According to the invention, such alterations are made possible by change rule information pertaining to the data documents archived in the archive system. 
     Exemplary embodiment are now described in more detail with reference to  FIGS. 2 to 4 . 
       FIG. 2  shows a data document  26 . 1  which is archived in the archive system  22  (cf. also  FIG. 3 ). The data document  26 . 1  comprises a plurality of data fields which are distributed on different tabs. In the illustration of  FIG. 2 , a tab  28  with the header “Doc lines” is shown, further tabs of the shown data document  26 . 1  having the headers “Hdr data” ( 30 ) and “Doc. overview” ( 32 ). 
     A data document  26 . 1  is a structured data document with a plurality of data fields. When archiving the data document  26 . 1  in the archive system  22 , the structure of the data document  26 . 1  is retained unchanged. That means that the archived data document  26 . 1  has exactly the same structure as it can be seen on the display when the data document  26 . 1  is loaded from the archive system  22 . The exact knowledge of the structure and the arrangement of the data document  26 . 1  makes it possible to adapt thereto a control equipment as for example a log table and a control table as it is described in more detail with reference to  FIGS. 3 and 4 . 
     On the tab “Doc lines”  28 , various data fields are displayed, such as the data field  34  “cancellation” and, on sub-tab  36  “Cust/Acct” data fields  38  “BusPartner”,  40  “Contract Acct”,  42  “Contract”,  44  “Division” etc. 
     Upon retrieval of the data document  26 . 1  from the archive system  22 , a control table  18  is loaded from the database  14 . The control table  18  contains change rule information pertaining to the various data fields of the data documents  26 . 1 ,  26 . 2 ,  26 . 3 , . . . archived in the archive system  22 . For example in the embodiment illustrated in  FIG. 3 , the control table  18  comprises information that identifies a given archive object (which in the example shown in  FIG. 3  is object  1  identical with the shown data document  26 . 1 ) and a table name (which in the example is “tab 1”) to identify the data field. 
     Further, the control table  18  contains information regarding given data fields which can be subject to a change or alteration after the according data document has already been archived. In the example shown in  FIG. 3 , data field “cancel” is identified in the third column “field” of control table  18 . This means that data field  34  “cancellation” of tab  1  of object  1  (=data document  26 . 1 ) can be subject to a change. None of the other data fields  38 ,  40 ,  42 ,  44 , . . . is identified in the control table and thus cannot be subject to any changes or alterations. 
     Arrows A 1  and A 2  in  FIG. 3  illustrate that the data document  26 . 1  from the archive system and the control table  18  from the database  14  are retrieved together and processed for display on the client  24 . Client  24  is interconnected with the database  14  by means of appropriate elements which are well known to the person skilled in the art, e.g. appropriate hardware and software such as a processing unit and/or server and interfaces. 
     Processing of the retrieved data document  26 . 1  and the control table  18  for display on the client computer  24  comprises an evaluation of the change rule information of the control table and a merging of the obtained information with the data document  26 . 1  to be displayed by appropriate evaluation and merger means. The display can be effected in such a manner that every data field of the data document  26 . 1  which can be subject to a change is shown in an active status (e.g. underlaid in white as shown in  FIG. 2  for active data field  34 ) or in a non-active status (e.g. underlaid in grey as shown for non-active data fields  38 ,  40 ,  42 ,  44  in  FIG. 2 ). 
     In case a change or alteration to a data field which can be subject to a change is performed (such as illustrated in  FIG. 4  for the data field  34  in which the cancellation indicator is set with an “x”), the change is stored according to the invention in the log table  20  as indicated by arrow A 3  in  FIG. 4 . 
     The log table  20  comprises information which allows the identification of a given data field (data field  34  in the example illustrated in  FIGS. 2 to 4 ) according to the information contained in the control table  18  plus the additional information pertaining to the new content of this data field after the alteration. 
     In the example shown in  FIG. 4 , the log table  20  therefore comprises in its fourth column bearing the header “new” the indication “x” for the new content of the cancellation data field  34 . The indication of the new content of the changed data field is related to an archive key (first column of the log table  20 ) which serves to identify the given data document containing the changed data field. 
     It has to be noted that the changes which have been affected to any data field in the data document  26 . 1  are not archived together with the data document  26 . 1  in the archive system  22 , but separately as appropriate entries within the log table  20 . Whenever the data document  26 . 1  is loaded from the archive system  22  the log table  20  is also loaded from the database together with the changes which have been made to the data document  26 . 1  in the past. The content of the log table  20  is merged with the data document  26 . 1  in such a way that the change last effected to the data document  26 . 1  is appropriately displayed at the data field which has been concerned by that change. The data document  26 . 1  is, however, always archived in its original state without any changes. The changes are simultaneously stored within the log table  20  which can always be loaded from the database whenever the data document  26 . 1  is retrieved from the archive system  22 . 
     As can also be seen in  FIG. 3 , the information contained in the log table  20  is also evaluated and merged with the information drawn from the data document  26 . 1  and the control table  18  (arrow A 3 ). In the depiction of  FIG. 3 , the log table is still void and thus has no effect on the display of the archived data document  26 . 1 . However, once there was a change to any data field in the data document  26 . 1  (as the change of the cancellation data field  34  described above with reference to  FIG. 4 ), in a subsequent retrieval and display of the archived data document after the change has been effected, the content of the log table  20  in the example of  FIG. 4  the entry “x”) would be considered and the change to the data field would be displayed. 
     The control table according to the invention is a class-oriented table (as to the data objects or documents concerned), and the log table according to the invention is a document-specific table. 
     The invention therefore provides a system and a method to process archived data without actually changing the archived data documents so that the original state of the data document is reproducible at any time. The control table according to the invention allows for a maximum of customization. It also provides for a high level of security as all changes are stored in the log table.