Browse Prior Art Database

Minimizing Data Stream for Text Data

IP.com Disclosure Number: IPCOM000048078D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Paradine, C: AUTHOR

Abstract

This article describes a technique for contracting a text data stream that is transmitted to and from two locations.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

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Minimizing Data Stream for Text Data

This article describes a technique for contracting a text data stream that is transmitted to and from two locations.

A commonly occurring situation is for two components of a system to need to communicate with each other passing text data across a network link. Use of this link may be costly, and may be a critical factor in the total system performance. The volume of data that flows on this link affects both line costs and system performance, and so it will often be sound economics to spend local effort on reducing this data stream.

A typical pair of components is a 'host' computer and a display terminal, upon which a human operator will read the text and possibly modify it, for subsequent update in the host's database.

Existing field-oriented displays reduce the volume of transmitted data by only transmitting modified fields. The fields which are modified are identified by their position in the display buffer. This form of identification is not satisfactory for text data, i.e., memos, letters, etc., because the layout of the text data is the display's buffer may be chosen and completely controlled by the display, and unknown to the host computer. Instead the modified data must be identified incrementally.

The substance of this article is that:

Modifications can be adequately and efficiently

described in terms of deletions, insertions and

modifications of numbers of characters (or letters).

The capabilities of the sender can limit the optimization

of a particular transmission without sacrificing the

preciseness of the transmission.

A typical situation is that the 'host' computer transmits some part of a text document to a 'terminal'. (For the first transmission it needs to do this in full). On the display terminal an operator views the segment and modifies it in some way, e.g., by alteration of particular words, addition of new sections, and deletion of others. The terminal now requires to transmit the content of the changes back to the host, but does not need to send back the bulk of the segment received, where this has not changed, since it is assumed that the host has remembered the original.

If the document being viewed is in fact a draft of a memo, then the most common change applied with normally be to correct 'typos', e.g., omitted characters, or transposed characters. In this environment the savings in data stream can be very great indeed. Four control codes (or structured fields) are defined each with a qualifying count, N, i.e.:
1. UNCHANGED-CHARACTERS (N)
2. DELETED-CHARACTERS (N)
3. MODIFIED-CHARACTERS (N)character-string)
4. INSERTED-CHARACTERS (N,character-string)

MODIFIED is equivalent to DELETED followed by INSERTED with the same

1

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value of N.

Although described here in terms of long words, the transmitted control codes for 'UNCHANGED-CHARACTERS', etc., would only be one or two charac...