Digital repository interoperability: design, implementation and deployment of the ecl protocol and connecting middleware

This paper describes the design and implementation of the eduSource Communication Layer (ECL) protocol. ECL is one outcome of a pan-Canadian project called eduSource Canada to build an open network of interoperable digital repositories. The design goal was to achieve a highly flexible, easy-to-use, and platform independent communication layer protocol that allows new and existing repositories to communicate and share resources across a network. ECL conforms to IMS Digital Repository Interoperability (DRI) specifications and supports four main functions: search/expose, submit/store, gather/expose and request/deliver. The ECL protocol builds on the latest standards and is flexible with respect to metadata schemas and repository contents. To support easy adoption of the protocol we provide middleware components for connecting existing systems. The ECL is currently used in the eduSource network, and we have begun work bridging with other interoperable initiatives such as Open Knowledge Initiative (OKI). Based on our experience, ECL is truly flexible and easy to use.