The TransXML GML Experiment
Paul Scarponcini-BENTLEY SYSTEMS INC
The objectives of the TransXML project are to develop standard public domain XML schemas for the exchange of transportation data, as well as a framework for the development, validation, dissemination, and extension of current and future schemas. Though initially targeted at four business areas, the long term vision is for a comprehensive, cohesive set of schemas that span the entire transportation facility life cycle of planning, design, construction, operations, and maintenance..
In order to insure an interoperable set of schemas, a common framework was desired for prescribing how the overly flexible XML language would be employed. The Geography Mark-Up Language (GML) was selected for evaluation. This was problematic since many of the initial schemas focus on engineering design and construction and GML originated in the geospatial domain. Because of the enterprise-wide view of TransXML, the feature-based approach of GML appeared promising if its apparent complexity could be overcome.
A sample problem was created involving design/construction pay items. A UML Class Diagram was developed to establish the precise requirements for data content and structure. Parallel XML and GML schema definitions and instance documents were then created and compared. GML proved to be advantageous in providing structure and consistency to the schema without undue overhead or geospatial bias. As a result, GML was selected as the framework for TransXML.