scope:

The present document specifies a library of basic building blocks and a set of rules by which they may be combined in order to describe a digital transmission equipment. The library comprises the functional building blocks needed to specify completely the generic functional structure of the European digital transmission hierarchy. In order to be compliant with the present document, equipment needs to be describable as an interconnection of a subset of these functional blocks contained within the present document. The interconnections of these blocks should obey the combination rules given.