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Semantic Interoperability of Geographic Information


Sumit Sen
Institute for Geoinformatics (IFGI), Robert-Koch-Str. 26-28, 48149 Münster, Germany
Email: sumitsen@uni-muenster.de

Geographic Information (GI) is characterized by cross domain applicability and the eco-nomic value of such information is linked to the wider usage of such information. With increas-ing efforts to provide GI data and processing through web based services, it has become essen-tial to have a closer look at the term interoperability, its various forms and the notion of seman-tic interoperability in particular. Recent research focus on these issues has helped to outline some major challenges of semantic interoperability of GI and approaches to solve these.

1. GI usage and Information communities
Users of GI come from different domains and are ever expanding. Traditionally such in-formation resided locally with the users and human interfacing provided the means to usage across domains. Such user domains could be at various levels ranging from industry verticals, cultural-linguistic communities or even departments in the same organization. Such domains can be characterized by the term information communities [1].

Access and usage of GI has undergone radical change in the last decade with a higher emphasis on co-operation and interchange for enterprise decision making and management. This does not just include geospatial data but also geospatial processing (i.e., query and analysis tasks pertaining to geospatial data). This has not only lead to efforts on format and interface standardi-zation efforts but also generated data sharing infrastructures such as Spatial Data Infrastructures (SDIs) and move towards open technology based architectures (OGC). All this can be argued to be interrelated to the trend of increased integration of the information communities.

It is also important to note that information communities enshrine their identity in the way it uses the GI. These may include the GI data components used, the processing that is ap-plied on such data components and the combinations of these. Thus while the cadastral mapping agency usually creates and maintains the land parcel maps, the utilities agencies create and main-tain the utility data in reference to the base map. Power or sewerage utilities can only refer to the base map and not alter it. Beyond this level one can also see how within a power utility company the operations department is allowed to create or alter the utility network data. Departments such as safety or marketing are only able to view this data besides make specialized analysis.

The view of information communities about GI data and processing also varies and this can be easily seen from the granularity at which the data is used. The notion of granularity can be explained on the basis of how people understand geospatial entities as constituted of other geo-spatial entities. For example the marketing department of the power utility company may visual-ize a building or apartment as a customer point the operations department would consider it as a region with access points (say the main switch, meter etc). It is more interesting to note that people belonging to two different information communities at the same time are able to switch between such granularity levels. The dual role of such people imbibes the mapping of what we call semantics of the GI between domains. The important point that can be noted in this example is that human services are employed to ensure information exchange and hence interoperability in some sense. Such human resources who have experience across domains are crucial for or-ganizations and cross department appointments or transfers are intentionally resorted to. This is applicable to non geographic information as well. However one can understand the scale of this problem when we discuss information access across diverse communities that access and share GI in SDIs.

Given such a situation, information communities increasingly look towards technologies to provide access to information. An infrastructure and syntax to provide access to information can be considered the base requirement before one could even start. SDIs and open architectures promoted by XML based data interchange can be considered to such starting steps. We discuss such steps towards what we can claim as interoperability in the next section.