Electrical computers and digital processing systems: multicomput – Computer-to-computer data routing – Least weight routing
Reexamination Certificate
1996-10-21
2001-09-11
Courtenay, III, St. John (Department: 2151)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data routing
Least weight routing
Reexamination Certificate
active
06289392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a messaging system for passing messages between calling programs and called programs, and in particular to a messaging system wherein all messages are passed within a defined message block, and via a message interface.
2. Related Art
Large computer systems generally comprise a number of components, or programs which interact with each other via calls. Dividing a large computer system into a number of programs is advantageous for many reasons, for example, it enables a number of computer programmers to work on the system with some degree of independence, it allows the computer system to be modified or enhanced more easily, and it allows the programs within the system to be reused in other computer systems.
The interface between the various programs within a computer system must be defined, so that a calling program is able to call a called program. In known computer systems the interface between programs is embodied in the computer code of both the calling and the called programs, thus if one calling program within a computer system is altered so as to require a change to the interface, all other programs calling the altered program must also be altered to conform to the new interface requirements.
A system which provides an interface between applications and various computers attached to a computer network is described in European Patent Application EP-A-0 414 624.
A further problem arises when, for example due to the growth of the computer system, a program needs to be moved from the initial physical hardware e.g. a mainframe, to another physical system, the interface must be enhanced to allow this. This enhancement must be made to all calling programs still resident on the initial mainframe, in addition to those programs which have been moved to the remote physical system.
SUMMARY OF THE INVENTION
According to the present invention there is provided:
a messaging system for passing messages between calling programs and called programs, wherein all messages are passed within a defined message block and via a message interface;
the message interface having memory means for storing, for each called program, an identifier and a program interface, the message block comprising a control block, having a fixed format, and a data area having a free format, the control block comprising a first portion for carrying data entity keywords, and a second portion for carrying characteristics of data items, and the said first portion remaining unaltered when a message block is passed between the message interface and a called program or a calling program, and the said second portion is altered dependent on the destination of the message block;
and, in use, the message interface;
i) receives a message block from a calling program containing an identifier;
ii) associates the identifier with a particular called program and a particular program interface; and
iii) sends a message block to the particular called program utilizing the particular program interface.
Embodiments of the present invention, by providing a central repository of program interface details, reduce the amount of interface information that needs to be held by the programs themselves. Thus, for example, a calling program rather than communicating directly with a called program, will send an identifier within a defined message block to the message interface. The message interface will then determine for example, both the location and interface requirements of the called program. If the called program is located on the same physical machine a relatively simple communications protocol can be utilized. If the called program is however resident on a remote computer system, the message from the calling program can be packaged appropriately and transmitted via an appropriate communication protocol to the called program resident on the remote system.
Embodiments of the present invention furthermore are particularly suitable for use with data management systems, and by associating a tag with each data entity and utilizing the defined message block and message interface, ensure a high degree of modularity between calling and called programs, as will be apparent from the following description.
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Mullender et al. , “Amboeba—A Distributed Operating System for the 1990s”, CWI, the Center for Mathematics and Computer Science, pp. 1-2, May 1990.*
Reynolds et al. , “Design for a New Untyped IPC for Mach”, OSF Research Institute, DARPA and AFMC, pp. 1-2, Sep. 1993.*
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British Telecommunications PLC
Courtenay III St. John
Nixon & Vanderhye P.C.
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