Method and apparatus for updating and transmitting line-oriented data sets

• US 5,689,639 A
• Filed: 05/25/1995
• Issued: 11/18/1997
• Est. Priority Date: 10/29/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Schwarz, Siegfried
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Barot, Bharat
• Application Number:
  US08/450,054
• Time in Patent Office: 908 Days
• Field of Search: 395/200.01, 395/200.09, 395/200.03, 395/155, 395/200.18, 395/286, 395/309, 395/613, 395/614, 395/615, 341/51, 341/55, 380/25, 358/263, 358/261.1
• US Class Current: 710/73
• CPC Class Codes: G06F 3/1415 with means for detecting differences between the image stored in the host and the images displayed on the displays

Abstract

A method for the transmission of line-oriented data sets. This method employs two data set structures which keep the images of the data sets at different time stages and which are filled alternatingly with the data sets. The method allows to determine updates of the data sets and avoids re-transmission of old information. In particular, moved lines are detected in a very effective manner. As a result, high update rates with low amounts of transmitted data are achieved. The method is suitable for local terminal sessions employing text or raster graphic terminals, which have to be operated from a remote site.

Claims

1. A method for updating line-oriented data sets of characters in a receiving data processing unit with respect to timely occurring changes of said data sets in a transmitting data processing unit, comprising the steps of:

providing for each of said data processing units at least two data structures which keep the states of the data sets at different time intervals and which are filled alternatingly with the data sets;

at the transmitting data processing unit,

comparing the data sets provided in said data structures in order to locate changed and unchanged lines;

in case of changed lines, determining for the data sets of the later time interval whether said changed lines are blank lines, and if not, determining whether said changed lines are moved lines with respect to at least another line contained elsewhere in the data set of the previous time interval;

generating updated information with respect to said changed and unchanged lines;

transferring said updated information from the transmitting data processing unit to the receiving data processing unit;

receiving said updated information at the receiving data processing unit; and

applying said updated information to the data structures provided at the receiving data processing unit in order to generate updated data sets.

5. The method according to one of claims 1 to 4 wherein changed lines, if not a moved line, are encoded as new lines.

6. The method according to one of claims 1 to 4 wherein unchanged lines at the receiving site are taken from the data structure which keeps the data set of the older time interval.

7. The method according to one of claim 1 to 4 wherein said updated information for unchanged lines is provided by change flags.

8. The method according to one of claims 1 to 4 wherein the steps being performed at the transmitting site are executed by exploiting hash values.

9. The method according to claim 8, wherein hash values are formed by more than two sets of four ASCII characters or by more than two sets of 4-byte machine words.

10. The method according to claim 8, further comprising the steps of:

picking up data at a fixed position within a line and getting their attributes;

filling up one machine word with the attributes of these data; and

comparing this machine word with the line split up into machine word representation.

11. The method according to one of claims 1 to 4, wherein multiple consecutive moved lines or multiple consecutive lines with only repetitive data are encoded as a block of lines containing only repetitive data.

12. The method set forth in one of claims 1 to 4, further comprising the step of providing an additional data structure for initializing the data structures at the receiving site or for re-synchronizing the transmitting site.

13. The method according to one of claim 1 to 4, wherein the transmitted information carries sequence numbers.

15. Application of the method according to one of claims 1 to 4 to raster graphic terminals.

2. A method for updating line-oriented data sets of characters in a receiving data processing unit with respect to timely occurring changes of said data sets in a transmitting data processing unit, said method comprising the steps of:

providing for each of said data processing units at least two data structure which keep the states of the data sets at different time intervals and which are filled alternatively with the data sets;

at the transmitting data processing unit,

comparing the data sets provided in said data structures in order to locate changed and unchanged lines;

in case of changed lines, determining for the data sets of the later time interval whether said changed lines are blank lines, and if not, determining whether said changed lines are moved lines with respect to at least another line contained elsewhere in the data set of the previous time interval;

locating unchanged parts of lines at identical line positions;

locating, in the data sets of the later time interval, repetitive parts within lines;

generating update information with respect to said changed and unchanged lines or parts of lines, respectively;

transferring said update information from the transmitting data processing unit to the receiving data processing unit;

receiving the update information at the receiving data processing unit; and

applying said update information to the data structures provided at the receiving data processing unit in order to generate updated data sets.

3. A method for updating line-oriented data sets of pixel graphics in a receiving data processing unit with respect to timely occurring changes of said data sets in a transmitting data processing unit, said method comprising the steps of:

providing for each of said data processing units at least two data structures which keep the states of the data sets of pixel graphics at different time intervals and which are filled alternatively with the data sets of pixel graphics,

at the transmitting data processing unit,

comparing the data sets of pixel graphics provided in said data structures in order to locate changed and unchanged lines;

in case of changed lines, determining for the data sets of the later time interval whether said changed lines are filled with pixels having identical attributes, and if not, determining whether said changed lines are moved lines with respect to at least another line contained elsewhere in the data set of the previous time interval;

generating updated information with respect to said changed and unchanged lines;

transferring said updated information from the transmitting data processing unit to the receiving data processing unit; and

applying said updated information to the data structures provided at the receiving data processing unit in order to generate updated data sets.

4. A method for updating line-oriented data sets of pixel graphics in a receiving data processing unit with respect to timely occurring charges of said data sets in a transmitting data processing unit, said method comprising the steps of:

providing for each of said data processing units at least two data structures which keep the states of the data sets of pixel graphics at different time intervals and which are filled alternatingly with the data sets of pixel graphics,

at the transmitting data processing unit,

comparing the data sets of pixels provided in said data structures in order to locate changed and unchanged lines;

in case of changed lines, determining for the data sets of the later time interval whether said changed lines are filled with pixels having identical attributes, and if not, determining whether said changed lines are moved lines with respect to at least another line contained elsewhere in the data set of the previous time interval;

locating unchanged parts of lines at identical line positions;

locating, in the data sets of the later time interval, repetitive parts within lines;

generating update information with respect to said changed and unchanged lines;

transferring said update information from the transmitting data processing unit to the receiving data processing unit; and

applying said update information to the data structures provided at the receiving data processing unit in order to generate updated data sets.

14. Application of the method according to one of claimed 1 to 4 to text mode terminals.

16. A method for determining changes in line-oriented data sets of characters or pixel graphics in a data processing unit with respect to timely occurring changes of said data set, said method comprising the steps of:

providing, in said data processing unit, two data structures which keep the states of the data sets at different time intervals and which are filed with the data sets;

comparing the data sets provided in said data structures in order to locate changed and unchanged lines;

in case of changed lines, determining for the data sets of the later time internal whether said changed lines are blank lines, and if not, determining whether said changed lines are moved lines with respect to at least another line contained elsewhere in the data set of the previous time interval; and

generating updated information with respect to said changed and unchanged lines.

17. The method of claim 16 wherein the data processing unit includes a transmitting data processing unit.

18. The method of claim 17 further including the steps of transmitting the updated information.

19. The method of claim 18 wherein the data processing unit further includes a receiving data processing unit.

20. The method of claim 19 further including the steps of providing, in said receiving data processing units, at least two data structures which keep the states of data sets at different time intervals;

receiving, at said receiving data processing unit, the update information; and

applying said update information to the data structures provided at the receiving data processing unit in order to generate updates data sets.