digital object prototypes

Digital Object Prototypes

An Effective Realization of Digital Object Types

K. Saidis1, G. Pyrounakis2, M. Nikolaidou2, A. Delis1

1Department of Informatics And Telecommunications2Libraries Computer Center

University of Athens

10th European Conference on Research and Advanced Technology for Digital Libraries

September 18, 2006 - Alicante, Spain 2

Outline The problem:

Develop an integrated web-based DL that manages diverse & heterogeneous digital material in a unified manner

Our proposed solution: Digital Object Prototypes – an effective

realization of Digital Object (DO) types DOPs Overview Discussion


Pergamos: Un. of Athens DL Over 1 million objects originating

from 8 disparate collections Heterogeneous, digitised material

requiring detailed cataloguing Motivation

Simplify & speed up cataloguing Decrease development time Avoid custom coding for handling

variations of digital material


Digital Objects Human generated artifacts

comprised of 4 components: metadata, digital content, relationships

& behaviors Several ways to encode them: METS,

FOXML, RDF, MPEG-21 Diverse kinds of material are

represented using variations of DO components


The problem DOs (e.g. books, papers, photos etc)

should be treated in a manner that reflects the nature of the underlying “real-world” objects

DL systems do not capture, express or use the nature of DOs effectively: DL users are forced to deal with each object’s idiosyncrasies manually


Digital Object Prototypes Introduced in last year’s ECDL A Digital Object Prototype (DOP) is a

DO Type specification, providing a detailed definition of a DO’s constituent parts: metadata, files, relationships and behaviors

With the use of DOPs, high level services can handle DO component variations in a uniform manner


DOPs Contd. DOPs provide the means to generate

user-defined types of digital objects DO type conformance: DOs

automatically conform to their respective DOP

Inexpensive to add new types of digital material or modify existing ones (no custom coding required)


DOPs Contd. 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 3-tier DL ArchitectureComposition of DO behaviors

DO Typing & Instantiation

Storage


A DOP specifies Metadata element sets File types / conversions / batch

ingestions Permitted relationships Private & Public behaviors


Behaviors Encapsulation: Private & Public

behaviors Private behaviors are executed by

the DO instance “behind the scenes” (the object itself triggers selected functionality)

Public behaviors are exposed to clients (clients trigger selected functionality)


Metadata Specification DOPs specify:

the metadata element sets used by all objects of this type

the individual elements (fields) that constitute each set

possible mappings among elements of these sets


Metadata Specification II Automatic loading / serialization of

metadata sets Behavioral characteristics of

metadata elements: isMandatory, isHidden, isRepeatable, defaultValue, validation

facilitate services to adjust to the object’s requirements

Mappings are automatically applied by the DO instance


Files Specification DOPs specify:

The permitted files and their allowed formats

The information required to convert files from one format to another

Batch file ingestion / automatic DO creation process for each file


Example Historical Archive’s Senate Session

Proceedings > Folders > Sessions > Pages

What is a Page DO: A digital image stored in various

formats (e.g. high quality TIFF, web quality JPEG, thumbnail)

What is a Session DO: A complex DO, consisting of Page DOs

and session proceedings metadata


Example Contd. Automatic file conversions

Page DOs automatically generate the two derivate formats from the high quality image

Batch Content Ingestion / DO Creation Session DOs generate Page DOs from

zip files containing high quality images


Session DOP


Page DOP


Relationships DOPs specify:

The structural relationships the objects are allowed to participate in (e.g. child-of, or is-parent-of)

Whether the objects are allowed to reference other entities, either internal (residing in the same DL) or external ones


DOPs and Collections DOPs “live” in the context of a

collection (collection pertinent scope)

Collections are represented in terms of “special-purpose” DOs

Collections may contain other collections (hierarchical namespace)

The Digital Library is the collection of all collections


Pergamos Collections & DOPs Collection Sub collections DOPsdl theatre, papyri,

medical, folklore, histarch

-

dl.theatre - album, photo

dl.papyri papyrus

dl.medical - image

dl.folklore - notebook, chapter, page

dl.histarch senate -

dl.histarch.senate procs -

dl.histarch.senate.procs - folder, session, page


A hierarchy of DO instances


dl.histarch.* DOPsDOP Metadata Files Relationsfolder - Qualified DC

- EAD-like- EAD to DC mappings

none -contains session or page

session -Qualified DC-EAD-like-EAD to DC mappings

zip -contains page

page none -HQ image-Web image-Thumbnail


dl.folklore.* DOPsDOP Metadata Files Relationsnotebook - Qualified DC none -contains chapter

or page

chapter -Qualified DC zip -contains page

page none -HQ image-Web image-Thumbnail


dl.papyri.* DOPsDOP Metadata Files Relationspapyrus Qualified DC -Original Image

-Processed image-Web image-Thumbnail

none


dl.theatre.* DOPsDOP Metadata Files Relationsalbum -Custom

(theatrical play metadata)-DC-Custom to DC mappings

none contains photo

photo Qualified DC -Original Image-Web image-Thumbnail

none


Summary We argue that digital objects do have

types (they fall into categories with uniform characteristics and behavior)

First realization of DO Type conformance: DOs honor the specifications residing in their DOP automatically

Effective management of diverse digital material: the DL system interprets DO types, not the user


Future Work Implementation of DOPs inheritance

(reuse: new types can be derived from existing ones)

Offline DOP validation process Make DOPs operate independently

of the underlying repository Open source release of the DOPs

framework


Thank you Questions?

Email: [email protected] DOPs in action: Pergamos demo

tomorrow (Poster #17)

digital object prototypes

Documents

digital content

new types of digital

typesall objects

nature of dos

objects requirementsmappings

digitised material

use of dops

diverse kinds of material