This is the current procedure for loading data from DAS servers. Currently,

this only works on two DAS servers

 (it no longer works for Ensembl):

UCSC = http://genome.cse.ucsc.edu/cgi-bin/das/dsn

Ensembl = http://www.ensembl.org/das/dsn

http://genome.cse.ucsc.edu/cgi-bin/das/dsn
http://www.ensembl.org/das/dsn

- initialize server:
for each DSN element {
   for each "SOURCE" element {
      sourceid = get "id" attribute from SOURCE element
   }
   master = first "MAPMASTER" element of DSN element
   masterURL = get text from master element
   version key = end (after last /) of masterURL
   one source object (=version) per version key
   add sourceid to source object.
}
this creates a collection of source objects (versions)

- select species/version
issue a types query = server name -/dsn suffix + <versionid> + "/types" :
http://genome.cse.ucsc.edu/cgi-bin/das/<id>/types
for each TYPE element {
   typeid = get "id" attribute from TYPE element
   featureURL = server name -/dsn suffix + <versionid> + "/features?type=" + <typeid>
   add features map entry, key = typeid, value = featureURL
}


h1. Proposal for using the DAS registry to find data.
It is possible to use the DAS registry to find data on DAS servers,
the problem is that all DAS servers can be set up differently, they
all follow different rules or different DAS versions, some don't follow
all the protocol rules, and some are not maintained.
DAS is a protocol, and it has different versions. The spec for the
latest version (1.6) is at:
http://www.biodas.org/documents/spec-1.6.html

the registry itself is at:
http://www.dasregistry.org

So, for example, if we want to find servers for H_sapiens_Feb_2009,

we can use the query:
http://www.dasregistry.org/das/sources?organism=9606&capability=features&version=37

and parse the results.