The NeTEx schema itself is a W3C XML schema, so XML technical skills are typically required to build applications to create or process data in NeTEx format. General XML skills can be used to process XML documents containing data in NeTEx format, for example, to run validators or to amend content.
At a design level, NeTEx uses a “Model Driven” approach, that is, the fundamental design is described as a high level conceptual model that tries to represent the problem domain as entities and relationships that have been identified by a set of use cases, many taken from existing systems covering the desired business scope. To understand the high level model underlying the XML schema (which is valuable for building applications) requires data modelling skills and an understanding of the UML notation. Public Transport domain knowledge will of course help (additional information available at http://transmodel-cen.eu/).