I am trying to understand the WMS service in MapServer. What I've done so far is making a complete map with a roads network some buildings and parks. Then I create an HTML template and by calling the url I get my map. My question is: is this map considered a WMS service? This confuses me because I came across this http://mapserver.org/ogc/wms_server.html that explains how to set up a WMS server and so I set it up and now I can call fot the GetCapabilities and GetMap requests. So, this confuses me. Various resources on the internet refer to a simple map as a WMS. On the other hand, the link refers to the WMS as something a bit more different. Eventually what is the difference?
An OGC Web Map Service (WMS) is any service that conforms to the (well any version of the) OGC WMS standard. The current version is WMS 1.3.0, though the previous version (WMS 1.1.1) is also widely used. Other versions exist but aren't commonly used.
At its simplest a service is deemed to be a WMS if supports two operations:
Other operations exist such as:
And when combined with the Styled Layer Descriptor (SLD) specification:
A GetCapabilities is as you say an XML response to a request like:
http://myservice/ows?service=WMS&request=GetCapabilities& ~ which should return the highest version of the WMS standard supported by your service
or a request like:
http://myservice/ows?service=WMS&request=GetCapabilities&version=1.1.1& ~ which should return a version 1.1.1 response for your service, if your service supports it...
The GetCapabilities response lets a client know all the operations supported by your service, the names of the layers, the coordinate reference system(s), and the extent, the link to metadata, feature data sets, and other datasets, the geographic extents of your layers, etc, etc.
A GetMap response is an image, it isn't just limited to gif/jpeg, the following image formats are supported in one MapServer service I know of... (as advertised in the GetCapabilities response)
<GetMap> <Format>image/png</Format> <Format>image/jpeg</Format> <Format>image/png; mode=8bit</Format> <Format>application/x-pdf</Format> <Format>image/svg+xml</Format> <Format>image/tiff</Format> <Format>application/vnd.google-earth.kml+xml</Format> <Format>application/vnd.google-earth.kmz</Format>