1. ?bbox= -> spatial query 
    * left, bottom, top, right. 
2. ?maxfeatures= -> maximum number of returned features. 
    * May also be limited by the datasource. 
3. ?startfeature= -> first feature should be this far into dataset 
    * Equivilant to 'offset' in database queries. 
4. ?queryable=list,of,keys -> keys which can be queried against via URL 
    * Can also be specified in the datasource configuration. 
      Datasource configuration overrides URL configuration.
5. ?key=value -> key=value attribute query
    * only keys in 'queryable' will be queried.