On the Compression of Geography Markup Language

The Geography Markup Language (GML) is a standard XMLbased language that enables the representation and easy interchange of geographic data between Geographic Information Systems (GIS). In this paper, we explored the compressibility of GML performing some empirical experiments over real GML corpus using a wide set of wellknown compressors. In particular, the main characteristics of GML are first described. Next, it is shown how these characteristics can be exploited to achieve a better compression rate on GML files. We use these ideas to design a specific parser and a strategy to compress the representation of geographic objects (their coordinates in a map). Finally, to check the correctness of our hypothesis, the same GML files are compressed by applying the new parser and coordinates encoding strategy.