Many applications, in areas such as land use, traffic management and location aware services, involve the storage, analysis and sharing of spatio-temporal data. The need to represent such data in a way that eases sharing across applications, has led to the development of the Geography Markup Language (GML), which provides a rich collection of constructs for representing spatial and associated aspatial data as XML documents. However, although there are a growing number of applications and tools that make use of GML, there are surprisingly few experience reports on the representation of data from existing applications or models using GML constructs. This paper provides one such report, describing the use of GML as an exchange format for the Tripod spatio-historical database. This in turn involves identifying mappings between Tripod and GML constructs, and the development of a generic architecture for carrying out such mappings. The experience demonstrates that even though GML provides rich modelling facilities, the development of mappings from pre-existing models can be challenging, as related constructs often provide semantically distinct capabilities. © 2007 The Authors. Journal compilation © 2007 Blackwell Publishing Ltd.