A group is a list of elements that defines how those elements can appear in a message.
Groups can be ordered (sequence or orderedSet) unordered (all or unorderedSet), or selective (choice or message). 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 that 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 that 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 modelled. Wildcard elements can be included to allow unmodelled 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 that 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 have a name, and are displayed using the group's composition by the message definition editor.
In XML Schema, a group can have its composition set to sequence, all, or choice.
The message model also allows other compositions: orderedSet, unorderedSet, and message. For more information, see Schema extensions in the message model.
Content validation determines how strictly the content of the group should be validated. See MRM content validation for more details.
The Content validation property does not affect validation in the XMLNSC domain. Validation in these domains follows the rules of XML Schema 1.0.