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About Web Services

The W3C defines a Web service generally as a software system designed to support interoperable machine-to-machine interaction over a network. This is generally done over a machine processable format like Web Service Description Language (WSDL). Other systems interact with the Web service in a manner prescribed by its description using Simple Object Access Protocol (SOAP) messages, typically conveyed using https.

In layman's terms, think of web services as a standardized way of integrating Web-based applications using the eXtensible Markup Language (XML), Simple Object Access Protocol (SOAP), WSDL and UDDI open standards over an Internet protocol backbone.

XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the services available and Universal Description, Discovery and Integration (UDDI) lists what services are available.

MDL's Role in Web Services

Web Services can be broken down into two higher level classifications (Discovery Services and Data/Retrieval Services)

Discovery Services are those services that associate a particular web service (i.e. WCS, WFS, WMS) with a particular dataset and exposes the endpoint to that service. Generally speaking, there are two types of discovery Services:

  • Registry/Repository (Reg/Rep)
  • Catalog Service on the Web (CSW)

Data/Retrieval Services are those service (i.e. WCS, WFS, WMS, WPS) that allow a consumer to find additional information about the data (e.g. projection, areal coverage, dimensions, availability of data, etc) tied to the service, and then allow consumers the ability to retrieve as much or as little data as they want. One particular service (Web Processing Service (WPS)) allows a consumer to manipulate data associated with the backend web services (WCS, WFS, WMS) and retrieve the resulting data by executing the WPS script. Note, the aforementioned services “WCS, WFS, WMS, WPS” are all Open Geospatial Consortium (OGC) compliant. The NDFD Web Service that returns data in DWML is not, and is currently transitioning over to the OGC compliant NDFD Web Service that returns data in TSML. Finally, the MetOcean Application Profile represents a forward way of thinking about the WCS, and the coverages it disseminates, in a new way.

Discovery Services