accomplished by expanding one or more operations from a high level collaboration into distinct lower level services, one for each operation.
An instance of a service may be associated with a specific instance of a dataset, or it may be a service that can be used to operate on multiple, unspecified datasets. The first case is
referred to as a tightly coupled data and service. The second case is referred to as loosely coupled service. Service operations can be associated with data classes data
type or with instances data set.
5.2.3 OWS service framework
The OWS Service Framework OSF identifies services, interfaces and exchange protocols that can be utilized by any application. OpenGIS Services are implementations
of services that conform to OpenGIS Implementation Specifications. Compliant applications, called OpenGIS Applications, can then plug into the framework to join
the operational environment.
By building applications to common interfaces, each application can be built without a- priori or run-time dependencies on other applications or services. Applications and
services can be added, modified, or replaced without impacting other applications. In addition, operational workflows can be changed on-the-fly, allowing rapid response to
time-critical situations. This loosely coupled, standards-based approach to development results in very agile systems—systems that can be flexibly adapted to changing
requirements and technologies
User Interfaces Client Applications
OWS Clients OWS Context
Web Portals
OWS Clients OWS Context
User Interfaces Client Applications
OWS Clients OWS Context
Web Portals
OWS Clients OWS Context
Business Processes
Data, Service, Style, Feature
Registries
CSW
Portrayal Services
WMS, FPS, CPS
Processing Services
WCTS, WPS
Workflow Services
WNS, BPEL Business Processes
Data, Service, Style, Feature
Registries
CSW
Data, Service, Style, Feature
Registries
CSW
Portrayal Services
WMS, FPS, CPS
Portrayal Services
WMS, FPS, CPS
Processing Services
WCTS, WPS
Processing Services
WCTS, WPS
Workflow Services
WNS, BPEL
Data Access
Data Services
WMS, WFS, WCS
Sensor Web
SOS, SPS, SAS
OpenLS
Tracking
Digital Rights Management
GeoDRM Data Access
Data Services
WMS, WFS, WCS
Data Services
WMS, WFS, WCS
Sensor Web
SOS, SPS, SAS
Sensor Web
SOS, SPS, SAS
OpenLS
Tracking
OpenLS
Tracking
Digital Rights Management
GeoDRM
Digital Rights Management
GeoDRM
Figure 3 - OWS Service Framework
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Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved.
5.2.4 Publish-find-bind
The OWS Service Framework is based on the publishfindbind pattern shown in Figure 4. This pattern enables dynamic binding between service providers and requestors.
Dynamic binding is an essential capability for distributed environments where operational needs, sites and applications are frequently changing.
2. Find
0. Code
1. Publish
3. Bind
C t l
Servic Service
Servic
Develope
4. Chain
Figure 4 - PublishFindBind Pattern
In Figure 4, there are three essential roles:
- Service provider: publishes services to a broker registry and delivers services to service requestors.
- Service requestor: performs service discovery operations on the service broker to find the service providers it needs and then accesses service providers for provision of the
desired service.
- Service broker: helps service providers and service requestors to find each other by acting as a registry or clearinghouse of services.
As shown, there are three essential kinds of operations performed by services:
- Publish: used to advertise data and services to a broker such as registry, catalog or clearinghouse. A service provider contacts the service broker to publish or unpublish a
service. A service provider typically publishes to the broker metadata describing its capabilities and network address.
- Find: used by service requestors to locate specific service types or instances. Service requestors describe the kinds of services they’re looking for to the broker and the broker
responds by delivering the results that match the request. Service requestors typically use metadata published to the broker to find service providers of interest.
Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved.
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