1. Introduction

The World Wide Web is built upon the notion of atomic units of information called resources that are identified with URIs such as http://www.openarchives.org/ore/0.2/toc (this page). In addition to these atomic units, aggregations of resources are often units of information in their own right.  Examples of these aggregations are:

• A simple unordered set, or bag, of resources, such as a collection of favorite images from various Web sites.
• A multi-page, HTML document where the pages are linked together by hyperlinks that provide "previous page" and "next page" access.
• Information available from "social networking" sites, such as flickr, YouTube, and myspace.  Information in flickr, for example, consists of an entry page, a single Resource, that links to comments or annotations (each existing as a separate Resource), and  an image in  multiple sizes and resolutions, each also existing as a separate Resource.
• A scholarly publication stored in an ePrint repository such as arXiv or in a DSpace, ePrints, or Fedora repository.  Such a publication may appear on the Web as multiple resources, each with an individual URI.  The set of resources typically consists of a human readable "splash page", that links to the body of the publication in multiple formats such as LaTeX, PDF, and HTML.  In addition, the publication may have citation links to other publications, each existing as one or more resources.
• An overlay journal issue that aggregates multiple scholarly publications as described above, each located in their origin repository, into an issue.  Issues may be recursively aggregated themselves into volumes, and then into the journal itself.
• A semantically-linked group of cellular images - each available as a Resource resident in repositories from research laboratories, museums, libraries, and the like - in the manner implemented in the ImageWeb Project.
• Published scientific results such as those envisioned by [Lynch CTWatch] that, in addition to the features of the scholarly publication described above, incorporate data plus the tools to visualize and analyze that data.

A mechanism to associate identities with these aggregations and describe them in a machine-readable manner would make them visible to Web agents, both humans and machines.  This could be useful for a number of applications and contexts.  For example:

• Crawler-based search engines could use such descriptions to index information and provide search results sets at the granularity of the aggregations rather than their individual parts.
• Browsers could leverage them to provide users with navigation aids for the aggregated resources, in the same manner that machine-readable site maps provide navigation clues for crawlers.
• Other automated agents such as preservation systems could use these descriptions as guides to understand a "whole document" and determine the best preservation strategy.
• Systems that mine and analyze networked information for citation analysis/bibliometrics could achieve better accuracy with knowledge of aggregation structure contained in these descriptions.
• These machine-readable descriptions could provide the foundation for advanced scholarly communication systems that allow the flexible reuse and refactoring of rich scholarly artifacts and their components [Value Chains]. 

2. User Guide

There are several User Guide documents intended to provided implementers with the information and guidance that they need to use the ORE Specifications. An introduction to the ORE Model, and how to create Resource Maps conforming to, it is given in the ORE User Guide - Resource Map Overview. The ORE User Guide - Resource Map Implementation in Atom gives practical details and advice on how to create Resource Maps in the Atom format.

The ORE User Guide - Resource Map Discovery introduces and describes a number of mechanisms for the discovery of Resource Maps by automated agents and browsers.

3. Specifications

The OAI-ORE specifications are based around the ORE Model which is described in details in ORE Specification - Abstract Data Model. The ORE Model introduces the Resource Map that makes it possible to associate an identity with aggregations of resources and make assertions about their structure and semantics.

The ORE Model makes use of a number of terms from existing Semantic Web vocabularies and introduces a small number of new terms particular to the model. These are described in ORE Specification - Vocabulary.

The primary serialization format for Resource Maps is a profile of Atom and is described in ORE Specification - Resource Map Profile of Atom. However, because the ORE Model is expressed in RDF, Resource Maps may also be serialized in any format capable of serializing RDF. A GRDDL crosswalk from Atom XML to RDF/XML is provided and we anticipate that later releases of these specifications will describe other serializations.

4. Additional Resources

Addition resources that are also described in the ORE Specification - Resource Map Profile of Atom are the Validator for ORE Resource Maps in Atom, Schematron Schema for the Resource Map Profile and the GRDDL crosswalk from Atom XML to RDF/XML.

The ORE logo used at the top right of this page is available in a number of different sizes and in a form better suited for use as a small icon. These are described on the ORE Logos page.

The namespace used by ORE specific elements listed in the Vocabulary is described in an RDF namespace document http://www.openarchives.org/ore/terms/.

5. References

[Lynch CTWatch]

The Shape of the Scientific Article in The Developing Cyberinfrastructure, C. Lynch, CTWatch Quarterly, August 2007.

[Value Chains]

An Interoperable Fabric for Scholarly Value Chains, H. Van de Sompel, C. Lagoze, J. Bekaert, X. Liu, S. Payette, S. Warner, D-Lib Magazine, 12(10), October 2006.