This feature serves as the head of a substitution group for program features that contain properties about the design and specifications for a collection of planned activities and observations associated with a project. These include properties that define the planning and specifications for both exploration efforts and construction activities.
Database handle for the object. It is of XML type ID, so is constrained to beunique in the XML document within which it occurs. An external identifier for the object inthe form of a URI may be constructed using standard XML and XPointer methods. This is doneby concatenating the URI for the document, a fragment separator, and the value of the idattribute.