Special capabilities are offered by some data sources to provide additional functionality, such as TimeSeriesBrowse.  
TimeSeriesBrowse is where the data 
    source can construct URIs to read any time span. 
Caching is used when it's convenient for data sources to read in several data sets at once, and 
    clients should query to see if other datasets have been loaded already.  
Updating allows the data source to ask clients to come back and ask for a new 
    version of the data sets.