Given any of the syntactic conventions described here, you can follow any of the available positional or semantic conventions. In practice, however, promoters of each syntactic convention typically also promote at least particular positional conventions. In evaluating syntactic conventions, it is important to remember that data modeling has two audiences. The first is the user community, that uses the models and their descriptions to verify that the analysts in fact understand their environment and their requirements. The second audience is the set of systems designers, who use the business rules implied by the models as the basis for their design of computer systems.
Different techniques are better for one audience or the other.
Models used by analysts must be clear and easy to read. This often means that these models may describe less than the full extent of detail available. First and foremost, they must be accessible by a non-technical viewer. Models for designers, on the other hand must be as complete and rigorous as possible, expressing as much as possible. The evaluation, then, will be based both on the technical completeness of each technique and on its readability.