Open Geospatial Consortium, Inc. OpenGIS ® Web Map Service Version 1.1.1
The purpose of this memo is to nominate the OpenGIS® Web Map Service Implementation Specification (WMS) for adoption as a NASA ESDS community standard for disseminating views of raster and vector data (“maps”) via the World Wide Web. WMS uses HTTP and defines several operations that allow a client to discover the functions a server is capable of providing, request a specific ”map”, and, optionally, request information about individual features shown on a map.
This nomination is for version 1.1.1 of the WMS specification. Future installations of WMS should consider use of the most recent version.
The OpenGIS ® Web Map Service Version 1.1.1 is an approved standard recommended for use in NASA Earth Science Data Systems in June 2007.
NASA Earth Science Community Recommendations for Use
WMS 1.1.1 is a mature specification. It was published in January, 2002 as an update to the original WMS 1.0 specification adopted by the Open Geospatial Consortium in April, 2000. There is a newer version, WMS 1.3, that is the topic of an Technical Note (ESDS-RFC-005) approved by the SPG. WMS 1.1.1 has many different client and server implementations. Some implementations are embodied in open source (MapServer, GeoServer, among others) and some are embodied in products sold commercially (ESRI, MapInfo, and others). WMS 1.1.1 has been deployed in a wide variety of settings - many US Government agencies, foreign government agencies, university and research organizations, and commercial organizations have operating WMS 1.1.1 servers. The TWG review centered on NASA implementations and the review comments regarding those implementations can be seen on the SPG web site.
Based on the TWG review results, WMS 1.1.1's identified weaknesses could best be described as (a) not having enough features and (b) not being applicable for all aspects of Earth Science visualization. There were no specific deficiencies found in the specification itself. Thus, potential users of WMS 1.1.1 are encouraged to make note of the next two sections on Applicability and Limitations.
WMS 1.1.1 is by and large a visualization specification. Thus it is applicable to the problem of generating renderings of georeferenced data and delivering those renderings to client applications. By virtue of the rendering request parameters, renderings made by independent and unassociated servers can be overlaid, yielding the ability to provide visual fusion of georeferenced data. WMS 1.1.1 does also provide the ability to request results in non-visual formats, and this ability can be put to good use by application designers. However, it is advisable to use WMS 1.1.1 in concert with other data delivery protocols when there is a need for sophisticated, non-rendered data transport.
System designers seem to often attempt to employ WMS 1.1.1 in ways that it was not designed o be used, particularly as a data transport mechanism. WMS 1.1.1 also has developed a reputation for being a "slow" protocol when employed in very high performance applications. This tends to be a result of the specific implementations chosen rather than a limitation of the specification itself, however it is a common complaint. Techniques such as pre-rendering or caching can significantly improve the performance of WMS 1.1.1 based applications without needing to change the protocol itself.
Overall, WMS 1.1.1 is a widely implemented and widely deployed specification that provides a standard way of performing a specific set of tasks. The ESDS-RFC-006 TWG thus recommends its endorsement by the SPG as an Earth Science Data Systems Standard.
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