Ontology based chaining of distributed geographic information systems

For the last decade, Geographic Information Systems (GIS) have provided planners and geo scientists with tools to analyse, maintain and present geo spatial information (information that is, in one way or the other, referenced to the earth surface). In the early days of GIS, its software systems were sold as monolithic systems. As the software became more mature, the systems were offered as modules containing a module with basic functionality and a variety of plug-in modules with extended functions. Main software producers came to realise that specific users who wanted to customise their systems needed a development environment with smaller system building blocks (components). Today, a product like ESRI’s ArcObjects provides the software elements to create an entire GIS. However these building blocks in themselves do not provide executable GIS analysis capabilities, they have to be assembled by a programmer. Unfortunately, these ‘GIS objects’ are of little use to the common GIS end-users whose interest is to apply certain common GIS processing functions to give solution to their geographic problems. GIS applications can be characterised by the wide variety of datasets (themes and data structure) and the often complex, but reusable operation-data chains. Many GIS applications, in particular in environments that require ad hoc queries, can greatly benefit from the use of interoperable components. To enable on demand component chaining we need data components and software components that are well defined and well described in terms of functionality, together with a user interface that facilitates the user-interpretation of these descriptions. Component-based applications have been around for some time, but their deployment in GIS is still in its infancy. This can be explained by the fact that GISs have to deal with complex (spatial) data types and software manufacturers tightly couple their functional parts with internal data structures. 2. Supporting data-operation connectivity, a multi-layer approach