Browse Prior Art Database

Partial Document Access Cache

IP.com Disclosure Number: IPCOM000034162D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-26
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Bainbridge, JH: AUTHOR [+2]

Abstract

This technique is a method for buffering document data for improved performance and reduced data transfer between a file-serving system and a personal computer when using partial document access methods. The technique is centered around a set of content-sensitive functions that maintain a document caching buffer in memory on the PC. When using partial document access (see the figure), all the data (text and formatting information) for a page or a set of consecutive lines is assembled on the file-serving system and sent to the personal computer for processing. The text information is served by page, and line number and the formatting information is referenced by key. Both sets of this information are stored and processed as variable length records.

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Partial Document Access Cache

This technique is a method for buffering document data for improved performance and reduced data transfer between a file-serving system and a personal computer when using partial document access methods. The technique is centered around a set of content-sensitive functions that maintain a document caching buffer in memory on the PC. When using partial document access (see the figure), all the data (text and formatting information) for a page or a set of consecutive lines is assembled on the file-serving system and sent to the personal computer for processing. The text information is served by page, and line number and the formatting information is referenced by key. Both sets of this information are stored and processed as variable length records. Using this technique, the caching code maintains information about all the document data that is in memory and tracks changes made during any processing. This code processes all reads and writes (changes) of the document data by the processing code on the personal computer. It keeps track of any changes and controls when updates to the file server are required. The document storage buffer is maintained using conventional linked list techniques. The text lines and associated formatting information are stored as variable length records. The text lines are accessed and stored sequentially by page and line number, and the formatting information is accessed and stored by key. In this implementation, only one document is accessed at a time, so no document identifying information is kept by the program. But, this support could be added by extending the current information. Free memory is also maintained using a linked list of variable length records. All unused memory is kept on a forward linked list that is sorted in memory address order. When storage for a text line or for formatting information is freed, its address is used to find where it belongs in the free list and, then, if it is contiguous with the previous free record or the next free record, it is added to this existing record. If this is not the case, it is simply inserted into the free list as a new record. The processing logic on the personal computer to maintain the caching buffer is based on keeping the currently active document page in memory so processing within a page remains fast. This is done by keeping track of the current lines on the screen and those lines marked for text operations such as copy and delete. This equates to t...