Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data streaming
Reexamination Certificate
1999-12-17
2003-04-29
Powell, Mark (Department: 2142)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data streaming
C709S219000, C709S227000
Reexamination Certificate
active
06557043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of computer programming, and more particularly to a system, method, and computer program product for using the 3270 data stream architecture to communicate structured document content (such as content created in the Extensible Markup Language, or “XML”).
2. Description of the Related Art
One of the challenges facing information services professionals today is the difficulty of bridging legacy mainframe host data to modern applications and their PC-based user interfaces. Most legacy host applications present their data in text-based user interfaces designed for use on specific, obsolete character-based terminals. The legacy applications were written with this character-based terminal presentation space as the only interface format in which the host data output is created, and in which host data input is expected. (“Presentation space” is a term used abstractly to refer to the collection of information that together comprises the information to be displayed on a screen, as well as the control data that conveys how and where that information is to represented.)
A typical character-based terminal is the IBM Model 3270. (IBM is a registered trademark of the International Business Machines Corporation.) This terminal model was designed to display information in a matrix of characters, where the matrix consisted of 24 rows each having 80 columns. When programs were written expecting this display format, programmers would specify placement of information on the screen using specific row and column locations. Information formatted for this display is sent as a “data stream” to the mechanism in the display hardware that is responsible for actually displaying the screen contents. The phrase “data stream” refers to the fact that the data is sent as a linear string, or stream, of characters. This stream of characters contains both the actual textual information to be displayed on the screen, as well as information specifying where and how the text is to be displayed. “Where” consists of the row and column where the text is to begin, and “how” consists of a limited number of presentation attributes such as what color to use when displaying that text, the color of the background, etc. While the Model 3270 is a specific type of IBM display hardware, data formatted for any display having similar characteristics became a de facto standard format referred to as a “3270 data stream”.
Data processing systems, methods, and computer program products that use the 3270 data stream architecture have been widely used for decades. The 3270 data stream architecture has been so widely used that systems and applications using the 3270 data stream architecture are often referred to as “legacy” systems and “legacy” applications.
The 3270 data stream architecture is used to communicate between a primary logical unit and a secondary logical unit using the LU2 protocol. The primary and secondary logical units may be mainframe computers, midrange computers, personal computers, terminals, workstations, or one or more computer programs that execute on one or more of the these devices. The 3270 data stream architecture is described in many publications, including “IBM 3270 Information Display System Data stream Programmer's Reference”, IBM Publication Number GA23-0059-06 (1981), which is hereby incorporated herein by reference.
As shown in
FIG. 1
, a data processing system
100
includes a primary logical unit
110
and a secondary logical unit
120
that communicate with each other over a network
130
using the 3270 data stream. The primary logical unit
110
may also be referred to as a host or server, and the secondary logical unit
120
may be referred to as a terminal, workstation, emulator, or client. As will be obvious to one of skill in the art, although
FIG. 1
illustrates a simple data processing system
100
including one primary logical unit, one secondary logical unit
120
, and a simple network connection
130
, the 3270 data stream architecture is generally used to communicate among many primary logical units and secondary logical units using complex network environments. An example of a more typical data processing system using 3270 data stream architecture may be found in U.S. Pat. No. 5,649,101, entitled “System and Method for Improving 3270 Data Stream Performance by Reducing Transmission Traffic”, the disclosure of which is hereby incorporated herein by reference.
The 3270 data stream architecture was designed well before many of the recent advances in computing, such as the definition of markup languages including XML for representing structured document content. XML is a standardized formatting notation, created for structured document interchange on the World Wide Web (hereinafter, “Web”). XML is a tag language, where specially-designated constructs referred to as “tags” are used to delimit (or “mark up”) information. In the general case, a tag is a keyword that identifies what the data is which is associated with the tag, and is typically composed of a character string enclosed in special characters. “Special characters” means characters other than letters and numbers, which are defined and reserved for use with tags. Special characters are used so that a parser processing the data stream will recognize that this a tag. A tag is normally inserted preceding its associated data: a corresponding tag may also be inserted following the data, to clearly identify where that data ends. As an example of using tags, the syntax “<email>” could be used as a tag to indicate that the character string appearing in the data stream after this tag is to be treated as an e-mail address; the syntax “</email>” would then be inserted after the character string, to delimit where the e-mail character string ends.
The syntax of XML is extensible, providing users the capability to define their own tags. XML is based on the Standard Generalized Markup Language (“SGML”), which is an international standard for specifying document structure. XML is a simplified version of SGML, tailored to Web document content. (Refer to ISO 8879, “Standard Generalized Markup Language (SGML)”, (1986) for more information on SGML. Refer to “Extensible Markup Language (XML), W3C Recommendation Feb. 10, 1998” which is available on the World Wide Web at http://www.w3.org/TR/1998/REC-xml-19980210, for more information on XML.)
XML is widely accepted in the computer industry for defining the semantics (that is, by specifying meaningful tags) and content of the data encoded in a file. The extensible, user-defined tags enable the user to easily define a data model, which may change from one file to another. When an application generates the tags (and corresponding data) for a file according to a particular data model and transmits that file to another application that also understands this data model, the XML notation functions as a conduit, enabling a smooth transfer of information from one application to the other. By parsing the tags of the data model from the received file, the receiving application can re-create the information for rendering (i.e. display, printing, or other processing, as the generating application intended it).
Other popular markup languages include the HyperText Markup Language (“HTML”), Wireless Application Protocol Binary XML (“WBXML”), MathML, and VoiceXML. Each of these languages is adapted for the needs of a particular environment. HTML, for example, is adapted for general use with documents in the Web environment, and WBXML is adapted for document presentation on wireless computing devices.
It is anticipated that the interchange of documents created using a markup language will continue to increase in popularity as distributed computing becomes more pervasive in society. It would be desirable to rewrite legacy applications to receive and deliver data using the structured format defined by these modern markup languages, in order to make the application's functionality available to users having a wide sp
Blair Douglas
Doubet Marcia L.
Powell Mark
Ray-Yarletts Jeanine S.
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