A
schema identifier is an optional identifier that can be inserted into SMF files. Because the SMF model does not predefine any particular
attributes, tools that consume SMF files cannot know ahead of time if the file they have just loaded will actually contain the attributes that they are expecting. A
schema identifier effectively provides a concrete name for a set of attributes so that tools that process SMF files can perform validation of attributes based on the identifier. It is somewhat analogous to XML namespace declarations; The author of a particular document inserts an XML namespace identifier into their document, and validation tools use this identifier to locate schema definitions against which the document is then validated.