A Spatio-Temporal Query Language for a data model based on XML

The recent emergence of eXtensible Markup Languge (XML) as a new standard for data representation and exchange on the World-Wide Web has drawn considerable attention in the Geographic Information Systems (GIS) world. OCG (OpenGIS Consortium) is contributing with a XML specification to the representation of geographic information (called GML Geographical Markup Language). GML allows the exchange of geographical information in the Web. In addition, using XML to represent this type of information can benefit the interoperability between different architectures of GIS. In this case, we need a query language to retrieve and analyse information from this data structure. In this paper, a query language for a spatio-temporal model based on XML is shown (STQ). The model uses a subset of the spatio-temporal model called STML that has been developed in our research group. The query language has a familiar select-from-where syntax and is based on SQL (Structured Query Language). STQ includes a set of spatial operators (overlap, cross, etc), and set of temporal operators (previous, next, etc). In addition, STQ includes traditional operators (=,>, <,...) for non-spatial information. The result of a query is another XML document. Since integration of XML in Web environments is easily achieved, STQ may be easily used to query geographical information on the Web.