1 Background - mountain.PROJECTS

PETRI PELLIKKA AND KARI KAJUUTTI (ED)The OMEGA Data Server and the CatalogThe purpose of the Data Server is to store data, and to present a network interface to clients toutilize the storage. Furthermore, care has been taken to be as flexible as possible with regardsto what types of data to store.Each Data Server represents on named Dataset, and is connected to one database instance tostore the data in. The unit of storage is named a Feature, but in OMEGA the term Product isconsidered synonymous. All Features are collected into named Feature Collections. TheFigure 39 below shows the general storage data model in GIN.The GIN storage model is designed with flexibility in mind. As the Figure 38 indicates, eachfeature is more or less a collection of Properties. Furthermore each Property is a representedas a name-value pair, where the value could be one of several types: Integer, Float, String,BLOB or Geometry. OMEGA Features typically contains several meta properties of typeFloat, String or Double, and some properties of type BLOB like shape-files or jpeg-files. TheFigure 38 also shows that the Features are contained within certain named FeatureCollection. Thus the Feature Collection act as a file or folder construct to group certainrelated OMEGA Features into.Figure 38. The GIN storage model.The services offered by the Data Server are presented as a CORBA Networked API, definedin the CORBA IDL language. Through this API clients can list Feature Collections present,create new ones, manipulate metadata at various levels, write new Features to the server,search for according to Filter Encoding Specification by OGC (Open GIS Consortium, s.a.)and reading existing Features. There are also certain methods for controlling user access.55