From Transmodel to data file

Models may exist at different levels of abstraction. 

• Conceptual Model – A high level implementation neutral representation. A conceptual model describes the elements and relationships of a model independently of any specific implementation technology. It can be used to understand and relate different implementations using many different technologies and physical models. 
• Physical Model – A design for implementing the Conceptual model using a specific technology. A physical model maps a conceptual model into a more detailed model that assumes a specific implementation technology, subject to particular constraints of that technology. In general a physical model will have more limited semantics than a conceptual model because of the constraints of the chosen implementation language and of the need to simplify the use of a rich conceptual model for any practical implementation. A physical model is still however not usually an executable or completely finalised representation, but rather a translation tool that shows how to go from a very high level technology-independent conceptual model to a concrete implementation in a specific language. 

• Implementation Model – An implementation of the model in a specific language that supports declarative modelling constructs. An implementation model represents a physical model in the actual language constructs and types of an implementation language, such as a DDL (Data Definition Language) for a database or an XML (Extensible Markup Language)  schema for an exchange format. It is directly executable using tools or programs. NeTEx uses W3C XML schemas for this purpose, but in principle other languages could be chosen in future.