Named Model Groups

These do for Elements what named Attribute groups do for Attributes. However, I have yet to see very many grounds for using them. In most cases, things are grouped together for a semantic reason. Putting them together as children under a parent Element explicitly shows their association when used in an instance document. Named model groups let you reuse groups of Elements in schema declarations, but they have no visibility in instance documents. You can't differentiate something that is part of a named model group from a sibling that isn't. When implemented in an organized fashion, deriving complex types by extension generally tends to meet most people's needs.