This is the UCSC DAS server.

The DAS specification is at:
    http://www.biodas.org/documents/spec.html

DAS alignment extension:
    http://www.dasregistry.org/spec_1.53E.jsp


Issues with UCSC server:
   - assignment of category and method is a hard-coded heuristic and
     essentially broken.

General DAS issues:
   - spec doesn't define how specifying both type and category filter show
     behave.
