Metadata - Abstracts and Keywords

Animations are interesting by themselves, but the real value comes when more information is available about the purpose and content of what's being seen. This information is called "Metadata", or data about the data (the animation in this case). For the SVS Image Server, there are a number of different kinds of metadata that can be accessed. These include

Let's go back and look more closely at the information about the African Fires layer in the Capabilities XML. The beginning of the information about the layer looks like this

<Layer opaque="0" noSubsets="1" fixedWidth="1024" fixedHeight="1024">
  <Name>2890_17402</Name>
  <Title>African Fires during 2002 (1024x1024 Animation)</Title>
  <Abstract>
    This animation shows fire activity in Africa from January 1, 2002 to 
    December 31, 2002.  The fires are shown as tiny particles with each 
    particle depicting the geographic region in which fire was detected.  
    The color of a particle represents the number of days since a sizable 
    amount of fire was detected in that region, with red representing less 
    than 20 days, orange representing 20 to 40 days, yellow representing 
    40 to 60 days, and gray to black representing more than 60 days.  
    This data was measured by the MODIS instrument on the Terra satellite.  
    MODIS detects fires by measuring the brightness temperature of a region 
    in several frequency bands and looking for "hot spots" 
    where this temperature is greater than the surrounding region.
  </Abstract>

This time we see the full abstract. The abstract contains enough information to clearly describe what it is you are seeing when you look at the animation. The abstract gives you a frame of reference to understand the animation.

Following the abstract is a keyword list, e.g.,

  <KeywordList>
    <Keyword>Africa</Keyword>
    <Keyword vocabulary="DLESE">Atmospheric science</Keyword>
    <Keyword>Fires</Keyword>
    <Keyword vocabulary="DLESE">Forestry</Keyword>
    <Keyword vocabulary="DLESE">Natural hazards</Keyword>
    <Keyword vocabulary="GCMD">EARTH SCIENCE:Agriculture:
      Forest Science:Forest Fire Science</Keyword>
    <Keyword vocabulary="GCMD">EARTH SCIENCE:Biosphere:
      Ecological Dynamics:Fire Occurrence</Keyword>
    <Keyword vocabulary="GCMD">EARTH SCIENCE:Human Dimensions:
      Natural Hazards:Fires</Keyword>
    <Keyword vocabulary="GCMD">Location:Africa</Keyword>
  </KeywordList>

The keywords define some of the subject areas under which the animation might fall. Since the keyword lists are part of the Capabilities XML, it is up to the client to use the lists in some way. The WMS specification does not include the capability for a client to request a list of animations from the server based on a keyword search.

Note: Some of the keywords have a "vocabulary" attribute. This allows a very strict categorization of the animations based on a well-defined keyword list. The SVS currently uses keyword vocabularies from the Digital Library for Earth System Education and the Global Change Master Directory. However, the vocabulary attribute was introduced in WMS 1.3.0 and is not available in WMS 1.1.1.

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