| Architecture |
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The organizational structure and operating environment of
the CGDI, including the relationships between its parts, and
the principles and guidelines governing their design and evolution
over time.
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| Application |
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A program that performs a specific function directly for
a user. Applications can make use of CGDI services.
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| Client |
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A software component or an application
that accesses a service.
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| Component |
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Software that packages the client or
server implementation of a service
and can provide the realization of a set of interfaces.
A component consists of software code (source, binary or executable)
or other equivalents such as scripts or command files.
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| Conceptual Architecture |
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An overview of the services, data,
technology and institutional environment of CGDI. It describes,
in general terms, both what the CGDI will include, and how
it will operate.
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| Core Service |
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A service that is critical to the
ongoing operations of the CGDI. The Service
Registry Service is an example of a core service. It is
used to keep track of where CGDI services can be found, so
if this service were unavailable, client applications would
not be able to locate the services required in order to complete
a task.
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| Coverage |
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A continuous representation of a portion of the earth's surface.
A coverage may be a collection of features (like a vector
dataset) or it may be a raster or gridded surface representing
one or more attributes.
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| Event |
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An occurrence of interest to users or developers of the CGDI.
Events can be things such as the adjustment of a feature in
a framework data layer, a flood
in the Red River basin, or the release of a new specification
for a CGDI service.
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| Framework Data |
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The set of geospatial data
that provides the reference framework for all other CGDI compliant
geodata. See the CGDI
Framework Data Definition.
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| Geodata |
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Georeferenced spatial data such as a road network or a satellite
image. Geodata explicitly describes the spatial extent of
a set of features or describes a measurable surface. It includes
both geospatial data and geolinked
data.
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| Geolinked Data |
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Geodata that is referenced to an identified
set of geographic features without including the spatial description
of those features. Geolinked data is normally attribute data
in tabular data (such as population counts) that refers to
a known framework (such as provinces), where the elements
(the provinces) are refered to by their unique identifier
(such as the province name). Geolinked data refers to all
attribute data that is not directly attached and bundled with
the geographic coordinates to which it applies.
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| Geospatial Data |
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Geodata with explicit geographic positioning
information included, such as a road network from a GIS, or
a georeferenced satellite image. Geospatial data may include
attribute data that describes the features found in the dataset.
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| Interface |
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The named set of related
operations that structures how a client
interacts with a server. The state and
functionality of the underlying component
is hidden, and is only made externally accessible through its
interface (i.e. the interface is the only "public" or "visible"
part of the component). The same interface
may be provided by several components
and used by many components or applications.
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| Master System |
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A primary system that is mirrored
to other identical systems, so as to
ensure that an important information or services
can be accessed in an identical fashion from multiple sites.
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| Operation |
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An interaction between a client and
a server, resulting in a transfer of
information or an action. An operation can be either an interrogation
(i.e. request-response) or an announcement (i.e. notification).
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| Primary System |
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A system that provides a core
service and thus is critical to the operations of the
CGDI. Although a primary system may not be mirrored to other
sites, or even the most popular implementation
of a particular service, they are publicly
identified and funded to ensure that core
services are implemented on at least one system.
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| Reference Architecture |
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A technical blueprint that identifies and defines the services
that comprise the CGDI, and specifies the interfaces
to those services.
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| Registry |
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A listing of the individual datasets, services,
or other things made available by an organization to users
of the CGDI. There are two kinds of registries:
Type Registry: A listing of the different types (classes)
of objects, such as services, components,
or events, which are recognized by CGDI
services or applications.
Instance Registry: A listing of the individual services,
components, datasets, or other things
that comprise the CGDI or are relevant to its users. Instance
registries are used to identify, locate, and describe individual
instances.
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| Server |
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(a) A software component that delivers
a service.
(b) A physical implementation of such a component,
that provides the realization of its operations.
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| Service |
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A collection of operations, accessible
through one or more interfaces, that
allows a user to evoke a behavior of value to that user. A
service is delivered by a server.
A "service instance" is another name for a server
(b) .
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| Site |
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A location (e.g. URL) at which a system
is accessed.
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| System |
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Servers and data organized to accomplish
one or more services. A system may
be accessible at more than one site.
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