Calisphere and OAC Technical Framework

All image- and text-based digital objects delivered through Calisphere and the OAC are stored and managed within the CDL's METS-based access repository, and conform to the repository's requirements. Metadata for all objects -- regardless of format -- are mapped to the Dublin Core element set for generalizability and to support cross-collection discovery.

The OAC hosts finding aids encoded using the Encoded Archival Description (EAD, Version 2002 Document Type Definition) format, contributed by participating institutions. In addition, it hosts digital content described within those finding aids, including images and texts (texts are encoded in the Text Encoding Initiative (TEI) format).

Calisphere and the OAC are based on a CDL-developed XML- and XSLT-based infrastructure. It 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: <title>Calisphere and OAC Technical Information<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.

This infrastructure provides a full range of services for researchers, scholars, teachers, and readers, including searching across different kinds of content and full text searching within specific kinds of content.

Image-based digital object search and delivery

For search and delivery of image metadata, Calisphere and the OAC utilize the CDL-developed XTF system.

Text-based digital object search and delivery

For search and delivery of TEI-encoded texts, Calisphere and the OAC utilize the CDL-developed XTF system. 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.

Finding aid search and delivery

For search and delivery of EAD finding aids, the OAC utilizes the CDL-developed eXtensible Text Framework (XTF) system. The XTF system consists of Java Servlets and tools that permit users to perform Web-based searching and retrieval of electronic documents. It utilizes Lucene indexing technology and XSLT stylesheets for generating displays. Text searches are limited to the full text of the documents.

EAD is an encoding standard for preserving the hierarchy and designating the content of finding aids to archival holdings worldwide. It enables Internet delivery of these finding aids 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 finding aids that is written following the syntactic rules of the SGML and XML markup languages.