Typically, a component uses the

source

property to identify where it should obtain input. For example, a

GroupSerializer

can use the property to identify an occurrence that it should serialize.

It is also possible to use the property to identify where the component should store output. For example, suppose that a Parser has already created 10 occurrences of an XML element. After the occurrences have been created, a

Group

anchor assigns an attribute in one occurrence of the element. The

Group

can use the

source

property to identify the occurrence.