Content area
Composition of time and space in a unified data framework results into spatio-temporal databases. Spatiotemporal Database Management Systems (STDBMS) are able to process, manage and analyze spatiotemporal data. HERMES provides spatio-temporal functionality to Oracle 10g Object-Relational Database Management System (ORDBMS). It introduces time-varying geometries that change their position and/or extend in space and time dimension either discretely or continuously, extending PL/SQL, the data definition and manipulation language of Oracle 10g, with spatio-temporal semantics. Currently, its main use is for representing moving objects (cars, trucks, people etc.) trajectories.
The problem of geospatial data interoperability has been an issue throughout the Geographic Information Systems (GIS) industry for a long time. The Open GIS Consortium (OCG) developed an eXtensible Markup Language based standard, Geography Markup Language (GML) with the intension to overcome this issue. GML is the standard for transport and storage of geographic information for those who need spatial and temporal sharing. GML, being a subset of XML, separates the content from presentation. Making maps from GML data involves a transformation of GML data into a display format that can be interpreted by viewer software. Keyhole Markup Language (KML) is an XML-based formatting standard that can be used to visualize GML data, using projection engines. The transformation of GML data into KML can be accomplished using an eXtensible Stylesheet Language Transformation (XSLT) stylesheet together with an XSLT processor. The XSLT stylesheet is an XML-based document that describes how data in a GML document is transformed into graphic elements in the KML document. By using different stylesheets, the same GML dataset can be visualized differently. In the same way, different datasets having a homogenous schema can use the same stylesheet. The possibility to use the same stylesheet for visualizing different datasets could be very useful in geographic data visualization.
This thesis is focused on two domains;
Ιn designing and implementing a wrapper for transforming raw HERMES‟s data into GML entities and process specialized GML queries sent to the database and
Transforming these GML results into KML files for visualization purposes, via third-party projection engines.