The management of spatial and temporal constraints in GIS using pictorial interaction on the web

The paper proposes and discusses an eXtended pictorial query language (XPQL) for geographic data and its possible use on the web. This query language is mapped in Geographic Markup Language (GML 3.0), which is used for transport to the Web and storage of geographic information including spatial and non-spatial properties of such information. The XPQL algebra is described and an example of this language is given using the implemented prototype. The different phases of query resolution are also explained, as well as the method used to solve ambiguities arising from drawing the different features of the pictorial query. Particular attention is paid to queries that include temporal constraints, and the way to express these in a pictorial environment.