Copyright © 2006 Open Geospatial Consortium – All rights reserved
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8 Geospatial Technology Platform and Components
Like most complex software applications, the extensive functionality of an Integrated Client of OGC Web Services is typically implemented as a suite of software modules that
have more or less independent although related functions. Although there is a relationship between functional categories and the software modules that implement them, the
relationship is not necessarily one to one.
By the same token, neither functionality nor the underlying software always bears a direct relationship to user interface. In this section, we describe some of the software
components that support the fundamental operations of an integrated client. In the next section, we discuss user interface.
8.1 Generic Descriptions of Client Components
The following paragraphs provide a description of modules that may be found in a client that supports a variety of OGC specifications.
8.1.1 Search and Discovery System
The ability to search for data is fundamental to Service Discovery and Binding functionality. User interface of some sort is essential to this system component; it has no
use as a hidden internal engine. Speaking schematically, the search subsystem connects at one end to an OGC search protocol client interface, such as a CS-W, Stateless Catalog, or
UDDI client. The discovery subsystem includes code capable of parsing and organizing the Capabilities Documents that come through the protocol interface, as well as analyzing
and presenting the material from the parsed data.
8.1.2 Data Selection Component
Once data sources have been presented by the Search and Discovery System, they may be selected by the user for retrieval, and subsequent display or further processing. Details of
the logical organization of selection software may be varied and are not discussed here. The selection event itself, resulting from user interaction with a GUI widget such as a
pull-down menu or selectable list, is typically mediated by the user interface library that comes with the operating system or windows support subsystem. Ultimately, control
passes to code that actually binds to a data service, retrieves the selected layers, and caches them or passes them to display or processing components within the client
application.
There are some variations on this theme. The selection software may be used to choose local as well as remote data sets. Data selection software might also connect to services
that appear to be OGC data services, but in fact are opaque interfaces to rendering or other processing services that ultimately connect to data services. The only such services
at this time are the Coverage Portrayal Service, which presents a WMS interface to the
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Copyright © 2006 Open Geospatial Consortium – All rights reserved
web, and the Data Aggregation Service, which presents remodeled WFS endpoints as an aggregated WFS.
8.1.3 Display and Navigation System
