Towards a repository – independent implementation of Digital Object Prototypes K. Saidis 1, G. Pyrounakis 2 1 Department of Informatics And Telecommunications 2 Libraries Computer Center University of Athens 10 th European Conference on Research and Advanced Technology for Digital Libraries DORSDL Workshop

September 21, Alicante, Spain2 Digital Material Model Store Preserve Search Retrieve Describe Publish Share Relate Validate

September 21, Alicante, Spain3 In a … manner User-friendly Effective Inexpensive Uniform Flexible Correct [Add your own]

September 21, Alicante, Spain4 Complex, isn’t it? Can we make it any simpler?

September 21, Alicante, Spain5 A real-life example Pergamos: University of Athens DL Demo (in beta phase): Cataloging Demo will be also available Contact:

September 21, Alicante, Spain6 Requirements Build an integrated web-based DL Small development team Mostly digitized material, requiring detailed cataloging Catalogers & digitizers without technical background Simplify and speed up cataloging & object input

September 21, Alicante, Spain7 Pergamos Material Handwritten Notebooks Historical Archive Theatrical Programmes Medical Images Papyri Byzantine Music Manuscripts Research Papers and Dissertations Press Articles

September 21, Alicante, Spain8 We wanted to… Treat digital material variations in a uniform manner

September 21, Alicante, Spain9 But… Current DL systems focus on how DOs are encoded & stored… Which parts constitute each object and how each part should behave is not effectively handled In other terms, it is hard to make DOs behave according to the nature imposed by their underlying “real- world” objects

September 21, Alicante, Spain10 Nature? Essence? Type? “Types arise informally in any domain to categorize objects according to their usage and behavior. The classification of objects in terms of the purposes for which they are used eventually results in a more or less well-defined type system… Sets of objects with uniform behavior may be named and are referred to as types.” L. Cardelli, P. Wegner, On Understanding Types, Data Abstraction and Polymorphism Computing Surveys, Vol 17 n. 4, pp , December 1985

September 21, Alicante, Spain11 We argue Lack of DO types leads to manual resolution of DO variations: Catalogers Developers Designers Users The DL system should resolve DO typing issues automatically

September 21, Alicante, Spain12 Digital Object Prototypes First realization of DO types, introduced in last year’s ECDL A DOP is a DO Type specification that provides a detailed definition of a DO’s constituent parts: metadata, files, relationships and behaviors DOs automatically conform to their respective DOP

September 21, Alicante, Spain13 DOPs Implementation DOPs draw on the notions of the OO model to implement DO types All objects have a type Objects honor encapsulation Inheritance (under development) DOs are conceived as instances of their respective prototype Stored DOs are treated as serializations of DO instances

September 21, Alicante, Spain14 A DO Instance

September 21, Alicante, Spain15 Instantiation / Serialization

September 21, Alicante, Spain16 DOPs Power Provide the means to generate user- defined types of digital objects Allow the inexpensive addition of new types of digital material (no custom coding required) Enable high level services to treat digital material variations in a uniform manner

September 21, Alicante, Spain17 DOPs 3-tier DL Architecture Composition Semantics Storage

September 21, Alicante, Spain18 What’s next dops4j: DOPs Open Source release Pergamos DOPs implementation is tightly coupled to FEDORA Re-engineering that focuses on making DOPs operate independently of the underlying repository Inexpensive DO type conformance for all

September 21, Alicante, Spain19 The concept Pluggable, Configurable Approach Developers use the DOPs API to implement DL services Repository implementers provide repository-specific implementations of the DOStorage interface

September 21, Alicante, Spain20 Visualization DO Repository DOStorage Interface DO Dictionary DL services DOPS API

September 21, Alicante, Spain21 Scenario 1 dops4j

September 21, Alicante, Spain22 Scenario 2 dops4j DO Repository

September 21, Alicante, Spain23 Scenario 3 dops4j Repository-independent Type-conscious DL Services

September 21, Alicante, Spain24 Benefits The DOPs framework will become a reusable, configurable component Easier to switch repositories Easier to add DO type conformance in many DL application contexts: Centralized, P2P, Distributed, Service-based Advance interoperability capabilities of repositories

September 21, Alicante, Spain25 Thank you dops4j release in October (hopefully) Contact: Questions?