Only identical complex type to identical complex type is supported. This includes message-to-message if the messages are identical.
WebSphere Business Integration Message Broker supports field-to-field mappings between any combination of message fields (not including local groups) and database columns with one exception: database column to database column mappings are not supported because they do not involve messages. WebSphere Business Integration Message Broker also supports structure-to-structure mappings between complex types of exactly the same type at any level of the message.
The mapping structure for databases has one level of nesting (columns in a table), whereas message fields have arbitrary levels of nesting. Direct database-to-database mapping is not supported.
In the creation of field-to-field mappings, a field is an element in a message structure (not a local group or the message structure itself) or a database column (not a table). Mappings can be made between a message field and another message field or a database column field, and between a database column field and a message field. For example, in database-to-message mapping, a one-to-one mapping involves the first value in the selected column being assigned to the target message element; in many-to-one mapping, the result of the scalar operation performed on the first values of the selected column is assigned to the target message element.
You can create structure-to-structure mappings between equivalent messages (that is, messages having exactly the same XSD complex type). In a bottom-up approach, field mappings are created. You can select the parent messages and create a mapping between them, provided the messages are of identical XSD complex types. Structure level mappings are not created automatically. In a top-down approach, you can create the mapping between the parent messages and the subordinate mappings later. A simple example of this is to map the input to the output message without any alterations. In this example, the top level mapping is sufficient.
One case in which this is useful is to pass message headers through without any alterations. A scenario where top-down mapping is useful is when a message needs to be modified only partially. For example, only five fields in a message with more than 400 fields. In this case, the top-level mapping can be made from the message to itself to indicate that all fields are identical. To change the way that the five fields are modified, create five explicit mappings that specify the desired behavior for those fields. This means that you do not have to specify 395 mappings where things are identical and five where something is different.
These topics describe the various mapping types.