|
|
|
E-Biz-Leveraging the Web
|
A Virtual GIS
Geospatial Services
A Virtual GIS is defined here as one in which the functions that would be found in a
monolithic GIS application are implemented as a collection of Web Services that can be
chained together by the end-user in a way that fulfills the business process. The International
Standards Organization [ISO19119, 2001] identifies six classes of generic information
technology services of particular importance for geographic information. The following
identifies what might be considered the basic services that are needed in a virtual GIS:
-
Human Interaction Services are services for management of user interfaces,
graphics, multimedia, and for presentation of compound documents. Two useful
services for working with geospatial data are:
- Geospatial viewer – Client service that allows a user to view one or more
feature collections or coverages. This viewer allows a user to interact with
map data, e.g., displaying, overlaying and querying.
- Geospatial symbol editor – Client service that allows a human to select and
manage symbol libraries.
- Model/Information Management Services are services for management of the
development, manipulation, and storage of metadata, conceptual schemas, and
datasets. Two useful services for working with geospatial data are:
- Feature access service – Service that provides a client access to and
management of a feature store.
- Map access service – Service that provides a client access to geospatial
graphics, i.e., pictures of geospatial data.
- Workflow/Task Services are services for support of specific tasks or work-related
activities conducted by humans. Three useful services for working with geospatial
data are:
- Chain definition service – Service to define a chain and to enable it to be
executed by the workflow enactment service.
- Workflow enactment service – Service that interprets the chain and controls
the instantiation of services and sequencing of activities.
- Subscription service – Service to allow clients to register for notification
about events. Events are defined by a service that performs an activity
resulting in an event. Events are catalogued by the subscription service.
Clients identify events of interest. When an event occurs, the subscription
service sends notification to all clients who have registered an interest in the
event.
- Processing Services are services that perform large-scale computations involving
substantial amounts of data. A processing service does not include capabilities for
providing persistent storage of data or transfer of data over networks. There are eight
useful processing services for working with geospatial data, they are:
- Positioning service – Service provided by a position-providing device to use,
obtain and unambiguously interpret position information, and determines
whether the results meet the requirements of the use.
- Route determination service – Service to determine the optimal path
between two specified points based on the input parameters and properties
contained in the Feature Collection. May also determine the measured
distance between two points along a specified path based on the properties
supported in the Feature Collection. Further may determine the length of time
it takes to follow a route through the geospatial data in the Feature Collection.
- Coordinate conversion service – Service to change coordinates from one
coordinate system to another that is related to the same datum. Coordinate
conversion services include map projection services.
- Coordinate transformation service – Service to change coordinates from a
coordinate reference system based on one datum to a coordinate reference
system based on a second datum.
- Dimension measurement service – Service to compute dimensions of objects
visible in an image or other geospatial data.
- Geoparsing service – Service to scan text messages and text documents for
location-based references, such as place names, addresses, postal codes, etc.,
in preparation for passage to a geocoding service.
- Geocoding service – Service to augment location-based text (or graphic)
references with geospatial coordinates (or some other spatial reference), e.g.
gazetteer, address matching, feature geocoding.
- Proximity analysis service – Given a position or geographic feature, find all
resources with a given set of attributes that are located within an analyst-specified
distance of the position or feature.
- Communication Services are services for encoding and transfer of data across
communications networks. Three useful services for working with geospatial data
are:
- Encoding service – Service that provides implementation of an encoding rule
and provides an interface to encoding or decoding functionality.
- Transfer service – Service that provides implementation of one or more
transfer protocols, which allows data transfer between distributed information
systems over off-line or on-line communication media.
- Geospatial format conversion service – Service that converts from one
geospatial data format to another.
- System Management Services are services for the management of system
components, applications, and networks. These services also include management of
user accounts and user access privileges. Two useful services for working with
geospatial data are:
- Authorization and authentication services – Services in the information
technology infrastructure that supports multi-institutional operation restricting
access and manipulation of feature collections based upon the verified identity
of the requesting client.
- License management services – Services to allow authorized use of network
services based on licenses granted to a client.
The following describes how some of these services that make up the virtual GIS can be used
in conjunction with one or more web registry services to provide some useful location-based
services that might be used by someone through a mobile device, such as a cell phone.
|
|
|
|
