USGIN DRAFT SPECIFICATIONS FOR GEOSCIENCE RESOURCE METADATA AND IDENTIFIERS

Over the course of the last year, the USGIN project has drafted specifications for use of ISO 19115/19/39 metadata, recommendations for simple metadata content, and a proposal for a URI scheme to identify resources using resolvable http URI’s (see http://lab.usgin.org/usgin-profiles). One of the key components of a federated data system is a catalog in which resources can be registered and described by data providers for discovery by users. The metadata offered by the catalog must provide sufficient content to guide search engines to locate requested resources, to describe the resource content, provenance, and quality so users can determine if the resource will serve for intended usage, and finally to enable the user to obtain or access the resource. As client software becomes more sophisticated, it is increasingly important that instructions for resource access are formalized so that clients can use the metadata to automatically access the resource. A variety of metadata standards have been published, as well as an OpenGeospatial Consortium specification for a Catalog Service for the Web (CSW 2.0.2) that defines a protocol for querying metadata catalogs. In order to achieve an operational federated catalog system, the USGIN project has been working on specifications to reduce the heterogeneity of ‘standard’ metadata and service implementations such that a single client can search against different catalogs.

For the meaning of an identifier to be discovered in a distributed information system, there must be a dereferencing mechanism that yields a description of the identified thing. A USGIN proposal for minting of http URIs explicitly distinguishes the dereferencing host from the name authority, recognizing that these may be decoupled. One of the objectives of this URI scheme is to define a syntax that makes clear the distinction between an identifier for a non-information resource, information resource, and specific representation resource. Another design criterion is that the http URIs should be dereferenceable using web server resource path conventions, in order to make implementation of dereferencing as simple as possible. The ABNF syntax can be summarized as: ginURI = "http:" "//" uriHost “/” URIscheme “/” nameAuthority “/” resourcePath [“/” resourceSpecificString] [( “/” / “/” representationPart )]