The Is Available At element refinement could be used to describe the relationship between:

• a physical item and a repository that holds the item;
• a collection of physical items and a repository that holds the collecton;
• a collection of digital items and a Web site that provides access to the items;
• a collection of metadata records and a Z39.50 target that provides access to those records

The provision of access to an information resource is distinct from that information resource itself, and the two entities may be described as separate resources in distinct DC metadata descriptions. A single information resource may be available through multiple services. However, it is critical to be able to describe the relationship between these two resources. Having discovered an information resource, a user requires information on how to obtain access to it.

Resource Identifier, Dublin Core Metadata Element Set, v1.1 [dc:identifier]
http://purl.org/dc/elements/1.1/identifier

Definition: An unambiguous reference to the resource within a given context.

Recommended best practice is to identify the resource by means of a string or number conforming to a formal identification system. Example formal identification systems include the Uniform Resource Identifier (URI) (including the Uniform Resource Locator (URL)), the Digital Object Identifier (DOI) and the International Standard Book Number (ISBN).

A URL is an accepted and widely used value for dc:identifier. A URL is

a type of URI that identifies a resource via a representation of its primary access mechanism (e.g., its network "location"), rather than by some other attributes it may have.
http://www.w3.org/TR/uri-clarification/

However it remains the case that a URL is a URI and, used as a value of dc:identifier, it is still simply an identifier of a resource. It may identify a location or service because any type of resource (including a location or service) can be identified by a URI (including a URL) and described by a DC metadata description. However, it is not an inherent property of a URL that it identifies a location or service.

By contrast, the value of the isAvailableAt property is a resource that provides access to the described resource.

The Metadata Object Description Schema (MODS), version 3.0, includes an XML element

• <location> with "sub-elements":

  • <physicalLocation>
  • <url>

  The MODS User Guide has not yet been updated to describe these version 3.0 sub-elements.

  For version 2.0, the location element is described:

  "location" identifies the institution or repository holding the resource or from which it is available. It may be expressed as text or as a code with the authority attribute used to designate the source of the code. <location> may include specific information to locate a resource within a collection, such as subcollection, or shelf number or it may just contain the name or code of an institution/repository.

  <location> is equivalent to MARC 21 field 852 subfields $a, $b, $j, and $e. If information equivalent to these subfields is included, it is given in a string and is not parsed. Fuller holdings information may be included in the MODS <extension> element using an established XML holdings schema.

These are XML elements, not RDF properties. The proposed term would be used to capture information recorded in both of the sub-elements of MODS 3.0.

The UK e-Government Metadata Standard (eGMS) includes a metadata element:

• Location

  Definition: The physical location of the resource.

  Purpose: Enables the physical form of the resource to be found.

  Notes: Location will mainly be used for items held in a physical format, e.g. paper files.
  
  This is especially relevant for items listed in a metadatabase (a catalogue containing the metadata of resources but not the resources themselves). Metadatabases may refer to items not available in electronic format. It will also be valuable for electronic resources stored on physical media, e.g. magnetic tapes or CD-ROMs.

The eGMS Location element describes the relationship between a resource and its physical location. It is not used for the description of digital resources.

The Australian Government Locator System (AGLS) includes an element:

• Availability

  Definition: How the resource can be obtained or contact information for obtaining the resource.

  Comment: The Availability element is primarily used for non-electronic resources to provide information on how to obtain physical access to the resource.

The AGLS Availability element is used for the description of offline resources and (physical) services. In the description of a physical resource, it is used to describe a service that provides access to that physical resource; in the description of a service, it is used to describe the access conditions that apply to the service. It does not appear to be used for the description of digital resources.

The New Zealand Government Locator System (NZGLS) includes an element:

• Availability

  Definition: How the resource can be obtained or contact information.

  Purpose: The Availability element is mostly used for services and non-electronic resources, to provide information for searchers about physical access to the resource.

The NZGLS Availability element is used for the description of non-electronic resources and (physical) services. In the description of a physical resource, it is used to describe a service that provides access to that physical resource; in the description of a service, it is used to describe the access conditions that apply to the service. It does not appear to be used for the description of digital resources.

The term is proposed by the Dublin Core Collection Description Working Group. One of the primary aims of the WG is the development of a Dublin Core Application Profile (DCAP) for collection-level description, i.e. for the description of a collection as a resource, rather than the description of the individual items that make up that collection.

Records of the activity of the WG are available in the mailing list archives.

The current draft of the Collection Description Application Profile is available at http://www.ukoln.ac.uk/metadata/dcmi/collection-application-profile/