You can use the MRM domain to model a
wide range of messages.
You can create message models to represent a wide range of message
types, using the MRM domain with one or more optional physical formats; refer
to the related links for more details. Messages in this domain are processed
by the MRM parser.
WebSphere Message Broker uses the MRM parser
to read and write messages that belong to the MRM domain. When reading a message,
the MRM parser constructs a message tree from a bit stream. When writing a
message, the MRM parser creates a bit stream from a message tree. The MRM
parser is model-driven, and it is guided by a message dictionary, which describes
the shape of the message tree (the logical model) and the bytes or characters
in the bit stream (the physical format). A message dictionary is created automatically
from a message set when it is added to the broker archive (bar) file. The
operation of the parser depends on the physical format that you have associated
with the input or output message:
- For CWF, the parser reads a set sequence of bytes, and translates them
into the fields and values in the message tree.
- For TDS, the parser uses the Data Element Separation method to parse the
bit stream. Depending on the values that you have set for the TDS physical
format properties, this method might involve identifying delimiters, tags,
fixed length elements, patterns, and so on.
- For XML, the parser identifies the XML markup language (tags and attributes),
and creates the correct objects, modified by the values that you have set
for the XML physical format properties.
In the MRM domain, the message is considered in two parts:
- The logical message model: the piece of the message that conveys the business
data, devoid of its physical representation (how it appears in a bit stream
on the wire). The logical message model is independent of platform and the
way in which the message is constructed.
For example, if you define a
message that conveys information about a debit of an individual's bank account,
the message can be represented in different physical forms on the wire (in
XML, or a fixed structure such as a COBOL copybook). The business meaning
and data is the same in both cases; only the physical layout has changed.
- The physical representation: how the data is laid out physically on the
wire. A single logical message model might have several different ways in
which it can be represented physically.
This two-part definition can be useful because it handles situations in
which you need to connect two different systems. For example, an
application that expects data to be passed to it in the form of COBOL copybooks
needs to communicate with a system that expects data in the form of XML. Both
applications work with the same data, and you do not want to alter either
application. By routing the messages through a broker, you can use a single
logical model with multiple physical representations to provide the required
transformation.
The following samples all use the MRM parser to process messages:
You can view samples only when you use the information center
that is integrated with the Message Brokers Toolkit.