
<!-- ais_database.dtd 

     This DTD describes how information about AIS resources is stored. The
     simple XML file described here is meant to be used for both client-side
     AIS implementations as well as by the AIS server. Each entry in the
     database has either one primary data source URL or a regular expression
     that describes a group of URLs and one or more ancillary resource URLs.
     An acillary resource may also have a rule associated with it; by default
     the overwrite rule will be assumed.

     In this DTD I used attributes liberally because they make for text that
     is both easier to read and write. Using an attribute for the ancillary
     resource rule also provides a way to make sure that only one of three
     choices will be used. -->

<!-- Use "http://xml.opendap.org/ais" to validate Databases encoded in XML -->
<!ELEMENT ais (entry*)>
<!ATTLIST ais version CDATA #FIXED "1.2"
		      xmlns CDATA #IMPLIED>

<!ELEMENT entry (primary, ancillary+)>

<!ELEMENT primary EMPTY>
<!ATTLIST primary url CDATA #IMPLIED
                  regexp CDATA #IMPLIED>

<!-- Note that the 'url' attribute can be either an http, https, file, et c.
     URL *or* it may be a plain filename. A relative filename will be 
     interpreted relative to current working directory of the program reading
     the AIS database. -->
<!ELEMENT ancillary EMPTY>
<!ATTLIST ancillary url CDATA #REQUIRED
                    rule (overwrite | replace | fallback) "overwrite">

<!--

$Log: ais_database.dtd,v $
Revision 1.3  2005/05/23 16:44:36  jimg
Added xmlns attribute to element AIS. Bumped up the version to 1.2.

Revision 1.2  2005/05/20 21:39:59  jimg
Changed from the bogus #OPTIONAL TO THE CORRECT #IMPLIED
attribute default.

Revision 1.1  2005/05/20 21:24:04  jimg
Moved from libdap module.

Revision 1.4  2003/12/08 18:02:30  edavis
Merge release-3-4 into trunk

Revision 1.3  2003/03/12 01:07:34  jimg
Added regular expressions to the AIS subsystem. In an AIS database (XML)
it is now possible to list a regular expression in place of an explicit
URL. The AIS will try to match this Regexp against candidate URLs and
return the ancillary resources for all those that succeed.

Revision 1.2  2003/02/25 05:37:42  jimg
Added version attribute to ais element. Fixed rule attribute of ancillary
element. Added a note about the somewhat bogus meaning of ancillary's url
attribute.


-->