Distributed database system having a center system with a link file and a method for retrieving data from same

• US 5,634,048 A
• Filed: 03/13/1995
• Issued: 05/27/1997
• Est. Priority Date: 09/14/1989
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Matsumoto, Tohru, Ryu, Tadamitsu, Takahara, Toshio, Mogi, Yoshio, Hirono, Shingo, Tomita, Masao, Fukatsu, Takanori, Ohshiro, Takashi, Kakehi, Gen
• Primary Examiner(s): Amsbury, Wayne
• Assistant Examiner(s): Loomis, John C.
• Application Number:
  US08/402,725
• Time in Patent Office: 806 Days
• Field of Search: 395/200.03, 395/200.09, 395/600, 395/650, 395/700
• US Class Current: 1/1
• CPC Class Codes: G06F 16/22 Indexing; Data structures therefor; Storage structures

Abstract

A data retrieval method and apparatus in a distributed database system. Data is retrieved from a distributed database quickly with a minimum load on each terminal. A contents file is provided in each terminal, and a link file is provided in a center system to coordinate access to the distributed data in each terminal.

Claims

1. A data retrieval method in a distributed database system comprising the steps of:

(a) associating commands defining attributes of database data with at least one keyword in each of a plurality of terminals connected to a center system;

(b) managing command names to which keywords are assigned in units of keywords in each of the terminals in dependence upon a keyword contents file in each of the terminals;

(c) managing in the center system a terminal number of terminals in which keywords are registered in units of keywords in dependence upon a keyword link file in the center system; and

(d) retrieving data in one of the terminals when a keyword is specified by locating a command name associated with a specified keyword in dependence upon one of a keyword contents file and a command name associated with a specified keyword located in the keyword contents file in the terminal specified by the terminal number located using the keyword link file.

2. A data retrieval method in a distributed database system as recited in claim 1, further comprising the step of:

(e) registering data in the database with a display screen.

3. A data retrieval method in a distributed database system as recited in claim 1, further comprising the steps of:

(e) managing command names associated with keywords in each of the terminals in dependence upon the keyword link file, in addition to terminal numbers; and

(f) retrieving data in one of the terminals by locating the command name associated with a specified keyword by one of;

(i) using the keyword contents file thereof; and

(ii) locating the command name assigned to the terminal number located using the keyword link file in the center system.

4. A data retrieval method in a distributed database system as recited in claim 1, further comprising the steps of:

(e) managing item numbers paired with keywords in each of the terminals in dependence upon the keyword contents file, and transmitting match link data indicating matches between keywords by item number; and

(f) locating the command names associated with other keywords linked by the match link data when one of the terminals specifies a keyword.

5. A data retrieval method in a distributed database system as recited in claim 4, further comprising the steps of:

(f) managing match link data in each of the terminals in dependence upon the keyword link file; and

(g) locating the terminal numbers and command names associated with other keywords linked by the match link data when a keyword specified by one of the terminals is transmitted to the center system.

6. A data retrieval method in a distributed database system as recited in claim 4, further comprising the step of:

(f) preparing temporarily in the keyword contents index file of each of the terminals item numbers paired with keywords before the keyword contents file is created.

7. A data retrieval method in a distributed database system as recited in claim 1, further comprising the steps of:

(e) managing item numbers paired with keywords in each of the terminals in dependence upon the keyword contents file and link data linking data with a next record using the item number when the number of commands for a keyword exceeds a number that can be held in one record of the keyword contents file; and

(f) locating the command name associated with a keyword specified by a terminal and other command names linked by the link data.

8. A data retrieval method in a distributed database system as recited in claim 7 further comprising the steps of:

(g) managing link data in a keyword link file; and

(h) locating the terminal number and command name associated with a keyword specified by a terminal, and other command names linked by the link data.

9. A data retrieval method in a distributed database system as recited in claim 7, further comprising the steps of:

(g) managing first characters of keywords and associated item numbers in a keyword contents index management file, and managing keywords based on the item numbers of the management file in a keyword contents index file; and

(h) sorting the keyword contents file in a specified character order using the management file to create the contents index file.

10. A data retrieval method in a distributed database system as recited in claim 1, further comprising the step of:

(e) selecting one of the terminals declared as a temporary center as the center system.

11. A distributed database system, comprising:

a plurality of terminals, more than one having distributed individual databases and each having a contents file, said contents file being adapted to store a correspondence between command names and keywords in units of keywords;

a public network, connecting said plurality of terminals; and

a center system having a link file which is adapted to allow management of information for locating those of said terminals in which a given keyword is registered, each of said plurality of terminals accessing said center system when a given keyword is requested and the given keyword is not registered at that terminal.

12. A distributed database system as recited in claim 11, wherein the contents file comprises:

a keyword contents index management file which stores first characters of keywords and relates said characters of keywords to start item numbers of the first characters;

a keyword contents index file which stores keywords according to detailed item numbers based on the start item numbers of the first characters; and

a keyword contents file which stores keywords and related command names.

13. A distributed database system as recited in claim 12, wherein said link file and the contents file have a common configuration.

14. A distributed database system as recited in claim 12, wherein:

the keyword contents file comprises a plurality of records each containing a predetermined number of command names and when a predetermined number of command names is exceeded for a specified keyword, link data with a next record is registered in a record with the specified keyword.

15. A distributed database system as recited in claim 12, wherein the keyword contents file comprises a plurality of records, and when other keywords are related to a single keyword, match link data for establishing a link with the record having the keyword is stored in a record with the related keyword.

16. A distributed database system as recited in claim 11, wherein each of said terminals has a flag indicating whether data stored therein can be registered externally, and storage of said data is administered to said center system in dependence upon the flag.

17. A distributed database system as recited in claim 11, wherein said center system has a data contents file to allow for managing revision of data.