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Web Processing Service

Introduction

The Spatial Information Services Stack provides interoperable access to information utilising open standards. With the exposure of this data in a uniform manner, there is opportunity to provide value add services at request on the data. A Web Processing Service will enable the processing of requested data and deliver user requested products.

Overview

Web Processing Service detailed by the OGC provides a standardised interface for geospatial Processing services. The standard specifies rules for inputs/outputs and how clients request and expect a response from the service.

Some limitations of the WPS in comparison to other web service frameworks is the absence of state and restfulness. The standards do not specify mechanisms for authentication/authorisation etc and do not detail how state should be handled. This is up to the implementer/deployment engineer and is important since the service is stateless.

Implementation Testing

WPS Reference Material

Operations

The WPS Specification supports 3 operations which include:
  • GetCapabilities - returns service-level metadata (what the service can do)
  • DescribeProcess - a description of the process along with its inputs & outputs
  • Execute - given the required input, this operation will result in the provision of the described output

Service Discovery

Service discovery is accomplished by using one or more OGC Catalog Service (CS-W) instances. The CS-W specification allows entities to be registered so that they can later be discovered by data consumers. It is also expected that catalogs may periodically harvest information from the capabilities documents of each service they know about in order to keep that service’s attributes up to date. OGC Catalog Services allow the following information to be used for discovery:
  • Type of Processing Service
  • Operations provided by the Processing Service
OGC Catalogs may additionally enable discovery based on other parameters, such as the feature of interest, procedure/sensor, sampling rate.

Resources

Topic revision: r4 - 10 Oct 2012, BenCaradocDavies
 

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