Architecture

Underlying Technology

Java/JEE Standards

Constellation is build on Java technology and exploits the most recent libraries from the Java community to build a high performance, rigourous platform. Constellation relies heavily on the most recent work being done in the Java Community Process to get early access to new advances.

Geo-informatic standards

Interoperability in the world of geogrpahic information systems rests on the norms and specifications published by several groups, notably the Internalional Organisation for Standardization (ISO) with its geographic information technical committee TC/211 and the Open Geospatial Consortium (OGC). Constellation is build around these standards to ensure the best possible interoperability.

Modular Design

The Constellation project is built of separate functional modules in order to enable the flexible assembly of these modules for different elements in a spatial data infrastructure. Constellation consists of:

• An indexing system for georeferenced data currently focused on raster data such as multi-dimensional imagery. The indexing system enables the rapid access to the appropriate part of the file system so as to efficiently extract the required portions of what are often volumnious data sets. The indexing system further enables the mosaicing and tiling of spatial and time series. We anticipate to eventually build a similar system for vector data.
• A subsystem for handling "real time" data issued from distributed sensors. This subsystem rests on the Sensor Web Enablement (SWE) group of standards published by the OGC, notably the Observation & Measurement standards. This module leverages the indexing subsystem described above which is needed for rapid access to recent data such as needed for up to date input in decisional systems.
• A metadata management subsystem based on flexible meta-model mappable to a relation data model for storage. The subsystem is sufficiently generic to handle metadata schemas from different organisations such as Dublin Core, ISO 19115, and SensorML. Eventually the subsystem will also handle the ebRIM meta-model. The subsystem exploits the Lucene indexation system which has been extended to include spatial data drawing on the GeoAPI and Geotools libraries.
• A series of Web Service modules for geospatial data based on the web service specifications published by the OGC. While Consellation plans to develop modules for all the OGC web services, the platform already offers:
  • WMS 1.1.1 and 1.3.0 (for raster data)
  • WCS 1.0 and 1.1
  • SOS 1.0