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Key words: Spatial Data Distribution, OpenGIS, Component, COM, CORBA
In this paper, we present a solution for the sharing and integration of spatial information in a distributed computing environment. The method for spatial information distribution component implementation is based on OpenGIS using platform independent component technology. We designed a basic model for the distribution of spatial information and developed a prototype for a data provider. We applied UML to the system design; used the standard specification of OpenGIS for users in various platform environments; and developed the technology of COM-CORBA interoperability.
We classify the Spatial Information Distribution Model according to the actor and internal usage to efficiently distribute the geographical information. The actor in the system is the data producer and the user of the data provider. We then designed the internal detail architecture of the system. The Spatial Information Distribution Model consists of a (Spatial Information) Distribution Server and a (Spatial Information) Distribution Basic Component.
The Distribution Basic Component supports interoperability between platforms and provides spatial information and geoprocessing services in a distributed computing environment. When a COM-based data provider, not in compliance with the OMG CORBA standard specification, provides spatial information to the user on a heterogeneous distributed computing platform, CORBA and COM interfaces must work together. We suggest the following process to use the Rowset object obtained from the COM interface regardless of heterogeneous distributed computing platform:
First, the Rowset object is transformed using the OpenGIS standard COM interface into OpenGIS CORBA's Simple Features. Next, the Simple Features are provided to the data consumer. To convert Rowset object into CORBA Simple Features, COM-CORBA inter-working is required. This should comply with OpenGIS CORBA specification.
The Distribution Basic Component is essential to distribute the spatial information. Its core function is to provide the data and services offered by the Data Provider Component, the MapBase Component, and the Application Component. These are based on Microsoft COM, and are produced by mapping between COM and CORBA interfaces. To obtain the Rowset object after accessing the data source in the Distribution Basic Component, we use the OpenGIS OGISDataProvider component. For this work, we used the standard OLE/DB Interface supported by extended OGISDataProvider, extended for OGIS. The OLE/DB interfaces used are DataSource, Session, Command, and Rowset. CORBA was used to distribute the Rowset object obtained as the result. The OpenGIS CORBA Simple Features specification was then implemented. We implement the Feature module, Geometry module, and WKB(Well-Known-Binary) to transfer the resultant Rowset object. Anyone who uses the OpenGIS standard specification can use the Spatial Information Distribution Component.