Non-modal database system with methods for incremental maintenance

• US 5,893,125 A
• Filed: 09/22/1997
• Issued: 04/06/1999
• Est. Priority Date: 01/27/1995
• Status: Expired due to Fees

• Current Assignee: Borland Software Corporation (Open Text Corporation)
• Original Assignee: Borland International, Inc. (Open Text Corporation)
• Inventors: Shostak, Robert
• Primary Examiner(s): FETTING, ANTON W
• Application Number:
  US08/935,163
• Time in Patent Office: 561 Days
• Field of Search: 707/3-5, 707/505-509, 707/511
• US Class Current: 715/206
• CPC Class Codes: G06F 16/284 Relational databases

Abstract

A database system with methodology providing "live" views of a database is described. In response to a user request (e.g., query) to display information from the database according to user-specified criteria, the system registers and displays a view (e.g., user-designed form and/or report); multiple views may be opened in this manner. In response to receiving one or more modifications to information stored in the database, the system employs incremental queries to maintain the "liveness" of the views. In particular, each registered view is notified of the modification (i.e., specific modified data records) and undertakes to apply the user-specified criteria for the particular view only against the modification. Here, the system determines for each view whether the modified data records should be added to the view (if such records now meet the user-supplied criteria for that particular view) or removed from the view (if such records no longer meet the user-supplied criteria for that particular view), without testing whether other records meet the user-specified criteria (i.e., without having to re-execute the query). In this fashion, the system maintains "live" views of the data so that all views reflects at all times the state of the underlying information or data, but without having to re-execute entire queries that initially gave rise to the views.

Claims

1. In a database system, said system having a database providing a storage mechanism for storing user-supplied information on a storage device as at least one database table, each database table comprising a plurality of data records, said user-supplied information being modified over time, a method for providing a "live" view of said database, the method comprising:

(a) receiving a request for displaying a view of said database on an output device, said view comprising portions of said user-supplied information rendered on said output device, which portions are selected from said at least one database table based on a set of user-supplied criteria, wherein the set of user-supplied criteria is such that at least some of said data records do not satisfy the set of user-supplied criteria;

(b) registering said view with said database and thereafter displaying said view;

(c) receiving at least one modification to said user-supplied information stored on said storage device, by storing a modification to at least one data record of said at least one database table; and

(d) updating said view by;

(i) notifying the view of which particular at least one data record of said at least one database table was modified,

(ii) if said modification stored to at least one data record affects portions of said user-supplied information rendered on said output device for the view, ceasing display of the affected portions from the view if the affected portions no longer meet the set of user-supplied criteria for the view, and

(iii) if said modification stored to at least one data record creates portions of said user-supplied information not currently displayed in the view, adding the created portions to the view if the created portions now meet the set of user-supplied criteria;

substeps d(ii) and d(iii) being performed with reference to said modification stored to at least one data record without testing whether other data records in said database meet the view'"'"'s set of user-supplied criteria.

2. The method of claim 1, wherein each said data record comprises a plurality of data fields, and wherein said set of user-supplied criteria comprises at least one condition which must be satisfied by data stored in said data fields.

3. The method of claim 1, wherein step (b) includes:

registering a view by storing an identifier of the view in a document list for said database, so that said document list lists an identifier for each view opened on said database.

4. The method of claim 1, wherein said at least one codification comprises a selected one of inserting a new data record, deleting an existing data record, and changing content of information stored in an existing data record.

5. The method of claim 1, further comprising:

repeating steps (c) and (d) for a plurality of modifications, whereby said view at all times the correct state of data stored in said database.

6. The method of claim 1, wherein said view includes a view of a view, nested to an arbitrary depth.

7. The method of claim 1, wherein:

steps (b) and (c) Are repeated to establish and register a plurality of views;

each view includes a tree structure storing data pointers to particular ones of the data records stored in the database;

a data record is removed from a view by deleting its corresponding data pointer stored in the tree for the view; and

a data record is added to a view by storing its corresponding data pointer in the tree for the view.

8. An improved database system comprising:

a computer having a storage device for storing user-supplied information in a database, said database comprising a plurality of data records;

an output device;

means for requesting a view of said database, said view being a representation of information in said data records, said view including a view constraint for selecting certain portions of said user-supplied information to be rendered on said output device while rejecting other portions of said user-supplied information;

means for rendering on said output device said portions of said user-supplied information according to said view constraint;

input means for modifying said user-supplied information stored on said storage device, by storing a modification to at least one of the data records stored on said storage device; and

incremental maintenance means, responsive to said modification, for updating said view based on whether said modification changes that portion of said user-supplied information that satisfies said view constraint after said modification, said updating including adding portions of said user-supplied information to said view or portions of said user-supplied information data records from said view, based on whether such data records satisfy said view constraint for said view, said updating being performed without testing records other than said at least one of said data records that was modified to determine whether the other records satisfy said view constraint.

9. The system of claim 8, wherein said view constraint comprises a user-specified condition for filtering out undesired ones of the data records from view.

10. The system of claim 8, wherein said view constraint comprises a Boolean expression which is applied to information stored in each database record for determining whether that record meets the view constraint.

11. The system of claim 8, further comprising:

means for requesting a view of said view, the view of said view including an additional view constraint for further narrowing selection of certain ones of said data records for view.

12. The system of claim 8, wherein said incremental maintenance means includes:

registration means for registering all views dependent upon said database; and

notification means for notifying all views dependent upon said database of a change to information stored in said database.

13. In a computer system, a method for maintaining "live" views of a database, said database having a storage mechanism for storing on a storage device a plurality of data records having user-supplied information, the method comprising:

(a) opening a plurality of views on the database, each view being a representation, separate from said mechanism for storing, of a respective portion of said user-supplied information, which portion is selected from the database based on a respective view constraint for the view, wherein each view constraint is such that at least some of said data records do not satisfy that view constraint;

(b) registering with the database each view so opened in step (a), so that all views dependent on the database are known to the system at all times;

(c) receiving user input which specifies modification to said user-supplied information stored on said storage device;

(d) in response to said user input, storing a modification to at least one of the data records of the database;

(e) notifying each view that a particular record of the database has changed; and

(f) for each view, updating the view based on whether said modification to said particular record changed the portion of said user-supplied information that meets the view constraint for that view after said modification, said updating including adding information from said particular record to that view or removing information from said particular record from that view, based on whether said particular record satisfies the view constraint for that view, said updating being performed without testing records other than said particular record to determine whether the other records meet the view constraint for that view.

14. The method of claim 13, wherein each record of the database is uniquely identified by a key value, and wherein step (d) includes notifying each view of the key value for said particular record that has changed.

15. The method of claim 13, wherein each data record is uniquely identified by a record number, and wherein step (d) includes notifying each view of the record number for said particular record that has changed.

16. The method of claim 13, further comprising:

opening a view of a view, said view of a view showing information from certain data records selected from a previous view, said previous view selecting information from certain records from the database according to a particular view constraint.

17. The method of claim 13, further comprising:

(g) receiving user input which causes a change to an existing view constraint; and

(h) for each view dependent on said existing view constraint, updating the view so that only information from data records now satisfying the view constraint is included in the view.

18. In a database system, said system having a database with a mechanism for storing user-supplied information in a plurality of data records on a storage device, said information being modified over time, a method for providing a "live" view of said database, the method comprising:

(a) receiving a request for first and second views of said database, each of said views being a representation, separate from said mechanism for storing, of information from a respective set of data records selected from said database based on a respective set of user-supplied criteria, said respective sets of user-supplied criteria for said first and second views being different, resulting in said respective sets of data records being different for said first and second data views;

(b) registering said first and second views with said database and thereafter displaying at least one of said first and second views;

(c) receiving a modification to a particular data record of said database stored on said storage device, wherein

(i) prior to said receiving said modification, information from said particular data record meets said first view'"'"'s set of user-supplied criteria but does not meet said second view'"'"'s set of user-supplied criteria, and

(ii) after said receiving said modification, said information from said particular data record does not meet said first view'"'"'s set of user-supplied criteria but does meet said second view'"'"'s set of user-supplied criteria;

(d) updating said first view by;

(i) notifying said first view of which particular data record of said database was modified, and

(ii) since said information from said particular data record was present in said first view prior to the modification, but no longer meets said first view'"'"'s set of user-supplied criteria, removing said information from said particular data record from said first view; and

(e) updating said second view by;

(i) notifying said second view of which particular data record of said database was modified, and

(ii) since said information from said particular data record was not present in said second view prior to the modification, but after the modification meets said second view'"'"'s set of user-supplied criteria, adding said information from said particular data record to the said second view;

substeps d(ii) and e(ii) being performed with reference to the information from said particular data record without testing whether information from other records in said database, which other records have not been modified, meet said first view'"'"'s set of user-supplied criteria or said second view'"'"'s set of user-supplied criteria.

19. The method of claim 18, wherein:

each view includes a tree structure storing data pointers to particular ones of the data records stored in the database;

a data record is removed from a view by deleting its corresponding data pointer stored in the tree for the view; and

a data record is added to a view by storing its corresponding data pointer in the tree for the view.