I am writing a software specification and I got confused with the data dictionaries section. is it a full detail of the interfaces and stored models ( like of a database ) or a just a second step of analyzing the projects's models ( a more detailed text version of the models explained before ) ?
A Data Dictionary is a set of information describing the contents, format, and structure of a database and the relationship between its elements, used to control access to and manipulation of the database.
Data dictionaries can also describe the format, type and purpose of data that is transferred between systems or modules, e.g. the JSON that flows between your web server and your user's mobile devices.
On the other hand, a Class Diagram describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the relationships among objects.
So data dictionaries are metadata for your data, class diagrams are metadata for your code. The reason there seems to be some overlap is because classes often model data.