WFS has three requests:

1. GetCapabilities

2. GetFeature

3. DescribeFeatureType
   

WFS returns GML only, no images.  Also, the WFS standard does not support a time parameter, which is a serious limitation when dealing with time series.  It does support the OGC's Filter Encoding standard, which allows the client to restrict the results returned by the WFS provided that the server has been configured appropriately. But this standard is clumsy to implement as a mechanism for dealing with time series, and it's clumsy to demonstrate with a web browser. There's an example below.

GetCapabilities

• http://www.gomoos.org/cgi-bin/wfs/wfs_gomoos?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetCapabilities

 Similar to the WMS XML response.  Scroll down and search for <FeatureType><Name>gomoos_sst</Name>

 These are the list of values to use in the GetFeature request string:  TYPENAME=gomoos_sst

active_platforms	gomoos_sst	gomoos_water_temp_A01
gomoos_salinity_50m	gomoos_salinity_all_depths

New FeaturesTypes must be defined and set up for more specific queries without using Feature Encoding.
In the list above, to avoid having to deal with Filter Encodings, particular FeatureTypes are defined for particular data results.

GetFeature

All platforms sea surface temperatures at 1 meter depth:

• http://www.gomoos.org/cgi-bin/wfs/wfs_gomoos?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=gomoos_sst

All platforms salinity at 50 meter depth:

• http://www.gomoos.org/cgi-bin/wfs/wfs_gomoos?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=gomoos_salinity_50m
  

Water temp for A01 at all depths:

• http://www.gomoos.org/cgi-bin/wfs/wfs_gomoos?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=gomoos_water_temp_A01
  

Here is an example, set up as part of the Oceans Interop Experiment, that shows the use of Filter Encoding and it's complexity. This is a WFS with the filter encoding string -- with filter encoding you get a subset of all the possible features.  You can remove the filter encoding by eliminating everything in the URL including and after &Filter to get the entire set of of features.

http://sos-web.tamu.edu/sos-cgi/madis?service=wfs&request=getfeature&version=1.0.0&typename=ndbc_44029&Filter=%3CFilter%3E%3CPropertyIsEqualTo%3E%3CPropertyName%3Eobservedproperty%3C/PropertyName%3E%3CLiteral%3Esea_surface_temperature%3C/Literal%3E%3C/PropertyIsEqualTo%3E%3C/Filter%3E

DescribeFeatureType

This part of the standard tells WFS to return an XML schema document (xsd) describing the format of the GetFeature request, that is, the xsd describes the contents of the WFS response.