This is the top level entry document into the DATEX II specification set. The document describes the way that modelling is handled in DATEX II, especially focusing on the data model aspects. Data modelling in DATEX II takes a formal, metamodel-based approach that allows the process of generating the transfer syntax to be implemented in software. A tool that creates an XML schema from the DATEX II data model based on this methodology is available from this website.
The methodology also caters for user generated model extensions, which can be created either in a constrained but backwards compatible way (so called "level B" extension), or as completely new model parts ("level C") which provide more flexibility for the price of losing compatibility to the standard model (referred to as "level A"). A feature that is actually more related to the tool than to the methodology itself - but that is also briefly described in the Methodology document - is the possibility to deselect optional features during XML schema generation, which allows for application/service specific Profiles, which are fully upwards compatible to the full schema.