CDL Common Framework

The CDL Common Framework is an open, services-oriented technical architecture that provides an integrating framework for services related to digital libraries. As a layered architecture it aims to separate front-end tools from back-end services from underlying data storage so that different components can be reused in multiple applications, reducing the time and money it takes to develop and maintain code.  The Common Framework also supports easy integration of local and third party tools and services through a plug-in approach.  It is available through both machine (i.e. web services) and human interfaces.

The Common Framework is built on open standards such as:

• Metadata Encoding & Transmission Standard (METS)
• Archival Resource Keys (ARKs) for persistent identifiers
• Extensible Markup Language (XML)
• Java programming language

Services include:

• (Available) Ingest, Indexing, Access (basic), Administration and Account Management
• (In development) Search and Browse, Capture (for defining web crawls, harvests and other content gathering mechanisms), Rights Management, Collection Management, Metasearch

CDL-developed plug-in solutions include:

• (Available) NOID (Nice Opaque Identifier for persistent ARK generation) and XTF (eXtensible Text Framework) for text indexing, searching and browsing)
• (In Development) Metadata Normalization and Enrichment

Third-party plug-in solutions include:

• (Current) JHOVE (for object validation and technical metadata generation)
• (Current) Storage Resource Broker (for archival storage of bitstreams)
• (Current) MySQL (for metadata and administrative data storage)
• (In progress) Heritrix (for web crawling)
• (In progress) MetaLib (for metasearch)

Although Common Framework applications are intended to be self-service for digital librarians, CDL initially provides assistance in the form of guidelines, tools, and consultation.  One key guideline is the CDL Guidelines for Digital Objects, which defines the range of accepted digital content.

The Common Framework is designed to support a range of digital library models including archival (where objects are stored locally), metadata-only (where only metadata is stored locally) and portal (where no data is stored locally).  It has been used to develop UC's Digital Preservation Repository (archival model) and will be used in the American West and Metasearching Infrastructure projects (metadata-only and portal models, respectively). 

As new applications and services are envisioned and added, the Common Framework can absorb them by either aggregating existing tools and services or making modest enhancements to modular tools and services—it will not be necessary to completely reconceptualize or create entirely new tools and services for new projects.

CDL Director of Technology Peter Brantley’s talk on Deploying Services, Not Libraries given at DEFF, Denmark’s Electronic Research Library 26-27 September 2005, provides a deeper overview of the rationale behind the Common Framework.