Jump to Content

Calisphere and OAC Technical Information

Supported Content Types in Our Repository

DSC hosts four major types of digital content:

  • EAD and supplemental PDF collection guides
  • METS digital objects
  • UC website URLs
  • MARC collection guide and item-level records

These digital collections are managed in a single repository with two separate publicly accessible web interfaces: the OAC and Calisphere.

Content in the repository conforms to the following criteria:

  • Collection guides encoded using the Encoded Archival Description (EAD) standard should conform to the OAC Best Practice Guidelines for EAD.
  • Collection guides or item-level records encoded using the MARC21 format should conform to the UC Bibliographic Standards for Cooperative, Vendor, and Campus Backlog Cataloging (Appendix B, "Collection Level Records"). We utilize the MARC Leader 07 field to differentiate between collection guides vs. item-level records, within the context of the OAC display.
  • Digital objects are formatted using the Metadata Encoding and Transmission Standard (METS) standard, and should conform to the "Enhanced Service Level" specifications defined in the CDL Guidelines for Digital Objects.
  • Collection guides and digital objects are assigned persistent identifiers according to a naming scheme called the Archival Resource Key (ARK), to ensure long-term public access. The ARK scheme was developed at the National Library of Medicine and is currently in production use at the CDL.

Repository Search and Delivery Platform: XTF

The repository supports a CDL-developed external linkXML- and external linkXSLT-based delivery platform, packaged as the eXtensible Text Framework (XTF). The XTF system contains Java Servlets and tools that permit users to perform Web-based searching and retrieval of electronic documents. It utilizes external linkLucene indexing technology and XSLT stylesheets for generating displays.

XTF supports the search and delivery of collections that is user-friendly, flexible, and viable for the long term. XML provides a means by which the structure and meaning of a document can be specified by "tags". For example, the title of this document is: Calisphere and OAC Technical Framework <title>. Because particular document segments are identifiable by software, sophisticated searching and display becomes possible. For example, when searching, it would be possible to specify that only document headings should be searched. Also, since the document is rendered for display at the moment of request, some display decisions can be made "on-the-fly," such as providing different versions that display better based on the user's operating system and web browser.

Metadata for all objects in the repository -- regardless of format -- are mapped to the external linkDublin Core element set for generalizability and to support cross-collection discovery.

Image-based Digital Object Search and Delivery

For search and delivery of image-based digital objects, Calisphere and the OAC utilize XTF. Images featuring zoom-and-pan options comprise JPEG2000 files. They are derived from TIFF image files, when the latter are supplied by contributing institutions specifically for the purpose of providing detailed image views. The JPEG2000 files are generated and displayed using LuraTech's
external linkImage Content Server, a J2EE application that has been customized by the CDL for OAC and Calisphere.

Text-based Digital Object Search and Delivery

For search and delivery of TEI, PDF, or imaged text-based digital objects, Calisphere and the OAC utilize XTF. Text searches are limited to the full text of the documents.

TEI is an encoding standard for encoding textual documents. Like EAD, it enables Internet delivery of these texts and is based on a DTD following the rules of SGML and XML.

Collection Guide Search and Delivery

For search and delivery of EAD collection guides and MARC records, the OAC utilizes XTF. Text searches target the full text of the documents.

EAD is an encoding standard for preserving the hierarchy and designating the content of collection guides to archival holdings worldwide. It enables Internet delivery of these collection guides and also ensures their permanence by providing a stable, non-proprietary encoding format, which is maintained by the Society of American Archivists. In technical terms, EAD comprises a Document Type Definition (DTD) for encoding collection guides that is written following the syntactic rules of the SGML and XML markup languages.

OAI-PMH Data Service

Metadata for EAD collection guides and METS digital objects is available for harvesting via the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH). For more information, see our OAI-PMH Data Service documentation.

Web Accessibility Policy

Our web accessibility policy is followed for all websites that we produce, including the OAC and Calisphere.


Last updated: November 22, 2013