Semantic interoperability of distributed geo-services

The last two decades have shown a major shift from stand-alone software systems to networked ones. As with all information system domains, Geographic Information Systems (GISs) have been influenced to a large extent by recent internet developments, resulting in an increasing availability of client/server applications using distributed geo-(web-)services, such as interactive maps, route planners and gazetteers. There is an increasing need for organisations to perform on demand geo-processing tasks by integrating and reusing geo-information and geo-services from within and outside the organisation. These activities are typically performed in the context of so called Geo-information Infrastructures (GIIs). The process of integrating services is commonly referred to as service chaining. This requires that services can be easily found, and that they are executable and interoperable. Interoperability means that the services ‘understand’ each other’s messages. A major impediment is formed by the semantic heterogeneity (the differences in meaning) of geo-information and of the functionality of geo-services. Making services semantically interoperable is an important prerequisite for information sharing in today’s networked society. This involves services that rely on different knowledge domains, one of which is the geo-information domain. Within this context, the research presented in this thesis provides solutions for the computer-aided integration of distributed heterogeneous geo-information and geo-services, based on their semantics (the meaning of their content). Geo-information distinguishes from other information by its spatial relevance. Geo-services often have to deal integrally with multiple-representations of features in a spatial, temporal and thematic dimension. Geo-services are also implicitly connected by the geographic location of the features they process. This has implications for the interoperability of geo-services. For example, the validity of a service (e.g., a routeplanner) may be bound to a specific geographic area, which could imply it cannot be used in combination with services involving another validity area. On the contrary, services that seem to be incompatible due to differences in feature representation (e.g., geometry, coordinate reference system), may turn out to be useful in combination, because they contain information on the same locations. On demand geo-processing requires services and the meta-information that describes the services to be available at the time a task is being executed. Moreover,