Towards a repository – independent implementation of D igital O bject Prototypes

Towards a repository – independent

implementation of Digital Object Prototypes

K. Saidis1, G. Pyrounakis2

1Department of Informatics And Telecommunications2Libraries Computer Center

University of Athens

10th European Conference on Research and Advanced Technology for Digital LibrariesDORSDL Workshop

September 21, 2006 - Alicante, Spain 2

Digital Material Model Store Preserve Search Retrieve Describe Publish Share Relate Validate


In a … manner User-friendly Effective Inexpensive Uniform Flexible Correct [Add your own]


Complex, isn’t it?

Can we make it any simpler?


A real-life example Pergamos: University of Athens DL

Demo (in beta phase): http://homer.lib.uoa.gr:8080/dl

Cataloging Demo will be also available Contact: [email protected]


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


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


We wanted to…

Treat digital material variations in a uniform manner


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


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 PolymorphismComputing Surveys, Vol 17 n. 4, pp 471-522, December 1985


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


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


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


A DO Instance


Instantiation / Serialization


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


DOPs 3-tier DL ArchitectureComposition

Semantics

Storage


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


The concept Pluggable, Configurable Approach Developers use the DOPs API to

implement DL services Repository implementers provide

repository-specific implementations of the DOStorage interface


Visualization

DO Repository

DOStorage Interface

DO Dictionary

DL services

DOPS API


Scenario 1

dops4j


Scenario 2

dops4j

DO Repository


Scenario 3

dops4j

Repository-independentType-conscious

DL Services


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


Thank you dops4j release in October (hopefully) Contact: [email protected] Questions?

Documents

Towards a repository – independent implementation of D igital O bject Prototypes