A group is a list of elements which defines how those elements can appear in a message.
Groups can be ordered (sequence) unordered (all) or selective (choice). Groups define the composition and content validation of a set of type members.
Groups can be used for any of the following purposes:
A complex type can refer to a global group which completely defines its content. (If it does not, the content of the complex type is defined by an anonymous local group, which is hidden within the Message Definition Editor.)
Two or more complex types can refer to the same global group if they both contain the same subset of elements.
You might have a complex type which is a sequence of three members, but the second member is a choice of two elements. To model this, a group with composition set to choice can be inserted as the second member of the sequence.
Groups can contain complex elements, simple elements, wildcard elements and groups.
By combining these components, the structure of any message can be modeled. Wildcard elements can be included to allow unmodeled elements to appear, thus making the message model robust and flexible.
Groups can be global or local.
A global group can be used in more than one place in the message model. It represents a structure which appears in more than one place in the message model. A global group must be given a unique name by which it can be referenced.
A local group is defined in one position within one group, and is not available for reuse elsewhere in the message model. Local groups do not need to be named.
In XML Schema, a group can have its composition set to sequence, all or choice.
The message model also allows other compositions, in order to remain compatible with earlier versions of the product. For further information, see Schema extensions in the message model.
The Content validation property is only applied when the domain is MRM or IDOC, and when validation is enabled.
Content validation determines how strictly the content of the group should be validated. See MRM content validation for further details.
The Content validation property does not affect validation in the XMLNSC domain.