The content in IRs tends to be freely available to anyone with access to the Internet, although there are sometimes access restrictions or embargos placed on material. In order to promote long-term access, most IRs offer persistent URLs—that is, Web addresses that do not change—using Handles (http://www.handle.net/), Archival Resource Keys (ARK)
(http://www.cdlib.org/inside/diglib/ark/), or other services. Institutional repositories also are likely to be optimized for crawling by Web spiders from search engines like Google; “splash” pages of the information describing material (metadata) are crawled as well as the content itself. Most IRs expose their metadata for harvesting via the Open Archives Initiative Protocol for Metadata Harvesting (OAI PMH) (http://www.openarchives.org/). The OAI PMH facilitates an integrated search with content from other institutional repositories (as well as any other service exposing metadata
via the OAI PMH) via a service like OAIster (http://www.oaister.org/). Many offer RSS feeds and other services that further the dissemination of the material held in the repository. All of these efforts serve the purpose of maximizing the discovery of and access to the content contained in the repository, as well as the promotion of the institution as a whole.