A SGML DTD (Document Type Definition) is a physical model of the grammar that describes the mark-up of data. When translating our conceptual E-R model to a DTD we have adopted a systematic method, designed in particular to encode most of the constraints, cardinality constraints at least. The principles of transposition from the E-R formalism into SGML are as follows:
The model expressed at conceptual level by means of the Entity-Relationship formalism is now translated to a SGML DTD that describes a possible physical format of a file containing a lexicon conformant with the model, following the transposition principles we adopted. Thus, although we do not propose a complete E-R model of the lexicon, we here propose a subset of a complete DTD that could encode the lexicon and that could include this subpart to deal with syntactic information. On its own, it is not usable, because it has to be inserted in a global representation of the lexicon. As EAGLES is producing recommendations rather than a complete and finished model, our work can be seen as an example of a possible SGML formalisation, not as a strong constraint.
To make it easier to understand a SGML DTD, we note: