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Meta-data of message control information Disclosure Number: IPCOM000031415D
Original Publication Date: 2004-Sep-24
Included in the Prior Art Database: 2004-Sep-24
Document File: 2 page(s) / 43K

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This article describes the association of meta-control information (or meta-data) with the control data associated with a message. This meta-data allows the control data associated with a message to be easily extended and correctly handled even by applications that do not understand all of the control data.

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Meta-data of message control information

In messaging products, such as IBM's WebSphere* MQ, the data contained within a message is supplemented by controlling information that describes how the data should be processed (e.g. the MQMD structure). One such piece of control information might be, for example, the message data's persistence; whether the data should be logged, so that it is recoverable should a system failure occur when processing the message. WebSphere MQ and Java** Message Service (JMS) messages each contain control information. This article will be described in WebSphere MQ terms but it applies to other messaging systems.

    Whenever the message is processed, each 'application' processing the message must decide how the message's control information should be processed (retained, changed or discarded) e.g. persistence usually remains unchanged with a message throughout its lifetime and typically any reply to a persistent message is sent as a persistent message. The persistence may also apply to reports generated on behalf of the original message.

    In order for the control information to be correctly processed by each application and the data treated appropriately, every application must understand all of the control information. If an application puts a message requesting that the data should be persistent, there is no way this request can be honoured if a processing application does not even understand the concept of message persistence. The processing application would have to take one of two choices - ignore the control information it doesn't understand, potentially processing the message in error, or stop processing the message. The inability to inform processing applications of which of the choices is the appropriate one for each piece of control information makes it very difficult to create new control information and not cause messages to be processed incorrectly.

    As well as being supplemented by control information, a message is permitted to contain meta-data relating to its control information which describe the nature of the control information. This meta-data can describe, for example, whether the control information should be propagated when a message is forwarded, or whether it should be discarded. The meta-data describes whether a message should be rejected by an application if it doesn't understand a piece of control information, or whether a message can be accepted even if the control information is not understood. The meta-data describes whether a piece of control information can be changed or whether it is read-only.

    Messages with control information and ass...