1. Introduction
A Content Interoperability Framework
Summary
Making Digital Library Content Interoperable
L. Candela D. Castelli C. Thanos
Istituto di Scienza e Tecnologie dell’Informazione “A. Faedo” – CNR, Pisa - Italy
name.surname@isti.cnr.it
6th Italian Research Conference on Digital Libraries
Padua, Italy, 28-29 January 2010
L. Candela et al. Making Digital Library Content Interoperable

2. Introduction
A Content Interoperability Framework
Summary
Outline
1 Introduction
Motivations
2 A Content Interoperability Framework
Digital Library Content Modeling
Levels of Content Interoperability
Content Reconciliation Approaches
L. Candela et al. Making Digital Library Content Interoperable

3. Introduction
A Content Interoperability Framework Motivations
Summary
Developing Today’s Digital Libraries
e-Science scenarios (person-centric, multidisciplinary and
co-operative) face novel challenges
highly-evolving requirements
large scale resources and players distribution
heterogeneity
. . . making standard development approaches often too
“expensive” (and not sustainable)
“from-scratch” development of ad-hoc solutions
HW investment (even if intermittently needed)
The “magic” formula to reduce costs is
sharing & reuse ⇒ interoperability
L. Candela et al. Making Digital Library Content Interoperable

4. Introduction
A Content Interoperability Framework Motivations
Summary
Developing Today’s Digital Libraries
e-Science scenarios (person-centric, multidisciplinary and
co-operative) face novel challenges
highly-evolving requirements
large scale resources and players distribution
heterogeneity
. . . making standard development approaches often too
“expensive” (and not sustainable)
“from-scratch” development of ad-hoc solutions
HW investment (even if intermittently needed)
The “magic” formula to reduce costs is
sharing & reuse ⇒ interoperability
L. Candela et al. Making Digital Library Content Interoperable

5. Introduction
A Content Interoperability Framework Motivations
Summary
Developing Today’s Digital Libraries
e-Science scenarios (person-centric, multidisciplinary and
co-operative) face novel challenges
highly-evolving requirements
large scale resources and players distribution
heterogeneity
. . . making standard development approaches often too
“expensive” (and not sustainable)
“from-scratch” development of ad-hoc solutions
HW investment (even if intermittently needed)
The “magic” formula to reduce costs is
sharing & reuse ⇒ interoperability
L. Candela et al. Making Digital Library Content Interoperable

6. Introduction
A Content Interoperability Framework Motivations
Summary
Interoperability?
Although it is a known issue, it is still a vague and
confusing concept
“The ability of two or more systems or components to
exchange information and to use the information that has
been exchanged” (IEEE, 1990)
“Interoperability is the capability to communicate, execute
programs, or transfer data among various functional units in
a manner that requires the user to have little or no
knowledge of the unique characteristics of those units.”
(ISO/IEC 2382 Information Technology Vocabulary)
“Ability for a system to communicate with another system
and to use the functionality of the other system” (Vernadat,
1996)
L. Candela et al. Making Digital Library Content Interoperable

7. Introduction
A Content Interoperability Framework Motivations
Summary
Thoughts on Interoperability and Approaches
Is it difficult?
yes it is, it is (almost) impossible
Is it about content/functionality?
it is about content, functionality, user, policy, quality and
architecture, it is about (almost) everything
What kind of job is?
dirty but critical
broad but partitionable
complex but fun
will never be solved but must be solved even approximately
The DL.org Coordination Action and its approach
focused working groups (one for each RM Domain)
portfolio of best practices and pattern (Cookbook)
L. Candela et al. Making Digital Library Content Interoperable

8. Introduction
A Content Interoperability Framework Motivations
Summary
Thoughts on Interoperability and Approaches
Is it difficult?
yes it is, it is (almost) impossible
Is it about content/functionality?
it is about content, functionality, user, policy, quality and
architecture, it is about (almost) everything
What kind of job is?
dirty but critical
broad but partitionable
complex but fun
will never be solved but must be solved even approximately
The DL.org Coordination Action and its approach
focused working groups (one for each RM Domain)
portfolio of best practices and pattern (Cookbook)
L. Candela et al. Making Digital Library Content Interoperable

9. Introduction
A Content Interoperability Framework Motivations
Summary
Thoughts on Interoperability and Approaches
Is it difficult?
yes it is, it is (almost) impossible
Is it about content/functionality?
it is about content, functionality, user, policy, quality and
architecture, it is about (almost) everything
What kind of job is?
dirty but critical
broad but partitionable
complex but fun
will never be solved but must be solved even approximately
The DL.org Coordination Action and its approach
focused working groups (one for each RM Domain)
portfolio of best practices and pattern (Cookbook)
L. Candela et al. Making Digital Library Content Interoperable

10. Introduction
A Content Interoperability Framework Motivations
Summary
Thoughts on Interoperability and Approaches
Is it difficult?
yes it is, it is (almost) impossible
Is it about content/functionality?
it is about content, functionality, user, policy, quality and
architecture, it is about (almost) everything
What kind of job is?
dirty but critical
broad but partitionable
complex but fun
will never be solved but must be solved even approximately
The DL.org Coordination Action and its approach
focused working groups (one for each RM Domain)
portfolio of best practices and pattern (Cookbook)
L. Candela et al. Making Digital Library Content Interoperable

11. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
A Framework for Modeling [Content] Interoperability
Interoperability scenario:
Two [software] systems are willing to “share” an
information object
provider is the owner of the information object
consumer is interested in “using” that information object
Sharing requires a common understanding of some
information object features
Sharing requires communication between provider and
consumer
Interoperability scenario features:
resource model, i.e. the properties of a resource
interoperability level, i.e. the level of “completeness”
reconciliation function, i.e. the “how-to” remove the
heterogeneity
benchmark, i.e. the “quality” of the reconciliation function
L. Candela et al. Making Digital Library Content Interoperable

12. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Identifier
The token bound to an Information Object that
distinguished it from others within a certain scope
should be persistent and actionable
Interoperability is necessary for the purpose of referring
the target Information Object in various contexts
There are several standards, e.g. Uniform Resource Name
(URN), digital object identifier (DOI), persistent URL
(PURL), the Handle system and the Archival Resource Key
(ARK)
L. Candela et al. Making Digital Library Content Interoperable

13. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Format
The structural (and sometimes operational) properties of
the Information Objects
formal and intentional characterization of all the Information
Objects having such a “type” or “data model”
Interoperability is necessary for the purpose of enabling
the consumer of the objects to safely and/or efficiently
execute operations over it based on the structural
“assumptions” declared by its format
rigid data models, e.g. DSpace, Greenstone, Eprints, vs
flexible data models, e.g. Fedora, OAI-ORE
L. Candela et al. Making Digital Library Content Interoperable

14. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Metadata
It is is any structured information that describes, explains,
locates, or otherwise makes it easier to retrieve, use, or
manage an information
broad in scope, the majority of content interoperability
issues risks to be here
Interoperability is necessary for the purpose of enabling
the consumer of the object to gather / be informed on
some characteristics of the Information Object the
partaking systems are willing to interoperate
There are several schemas, e.g. Dublin Core,
MAchine-Readable Cataloging (MARC), Metadata
Encoding and Transmission Standard (METS), Metadata
Object Description Schema (MODS), ISO 19115, usually
encoded in XML
application specific schema and application profile
L. Candela et al. Making Digital Library Content Interoperable

15. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Quality
It is a kind of meta-property as it describes various
“characteristics” of Information Object properties and
sub-properties
quality dimensions or parameters can refer either to the
extension of data, i.e. to data values, or to their intension,
i.e. to their schema/format
Interoperability is necessary for the purpose of enabling
the consumer to exploit every kind of Information Object in
a conscious manner
Very close to Metadata
L. Candela et al. Making Digital Library Content Interoperable

16. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Protection
It includes security, i.e. protection against accidental or
intentional disclosure, integrity, i.e. ensuring that the
content remains an accurate reflection, and privacy, i.e.
when, how, and to what extent the content is transmitted
Interoperability is necessary for the purpose of enabling
the consumer to be aware of the policies governing the
Information Object
Very close to Metadata (specific languages XACML)
L. Candela et al. Making Digital Library Content Interoperable

17. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Context
It is the set of all “setting” information that can be used to
characterize the relation between the Information Object
and the “external world” surrounding it
Interoperability is necessary for the purpose of enabling
the consumer of the Information Object to behave as a
context-aware system
Very close to Metadata
L. Candela et al. Making Digital Library Content Interoperable

18. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Information Object Provenance
It is a description of the origin and/or of the descendant
line of data (a.k.a. lineage)
Interoperability is necessary for the purpose of enabling
the consumer of the Information Object to be aware of the
history leading to its current stage and thus to perform
exploitation actions that take this knowledge into account
Several model, e.g. OPM, usually encoded in XML
L. Candela et al. Making Digital Library Content Interoperable

19. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
[Content] Interoperability Levels
Model (its properties) understanding might occur at different
levels:
Technical/Basic, providing the consumer with a superficial
uniformity of the provider IO characteristic which enables
accessing it
Syntactic, ensuring that the abstract syntax of “target” IO
characteristic is understandable by the consumer
Semantic, ensuring that the precise meaning of “target” IO
feature is understandable by the consumer
Operational, ensuring the effective use of the “target” IO by
the recipient in order to perform a specific task
Secure, ensuring secure object “exchanges” between the
involved systems
L. Candela et al. Making Digital Library Content Interoperable

20. Introduction Digital Library Content Modeling
A Content Interoperability Framework Levels of Content Interoperability
Summary Content Reconciliation Approaches
Reconciliation Functions
Standard-based approaches
the oldest one!
very effective if agreed, autonomy infringement
Families of standards
multiple standards, negotiation
alleviates the autonomy infringement
Mediator-based approaches
interoperability machinery outside participants
strong in supporting autonomy
Specification-based / profile-based
no prior arrangement, dynamic binding
support autonomy, requires standard / agreement
Blending Solutions
L. Candela et al. Making Digital Library Content Interoperable

21. Introduction
A Content Interoperability Framework
Summary
Summary
Content Interoperability is a multi-faceted and multi-layered
problem
no single solution to this problem
Content Interoperability framework
captures in a systematic way these facets
categorises existing approaches
The work continue . . .
state-of-the-art survey, cookbook
L. Candela et al. Making Digital Library Content Interoperable

22. Introduction
A Content Interoperability Framework
Summary
Summary
Content Interoperability is a multi-faceted and multi-layered
problem
no single solution to this problem
Content Interoperability framework
captures in a systematic way these facets
categorises existing approaches
The work continue . . .
state-of-the-art survey, cookbook
More information http://www.dlorg.eu
L. Candela et al. Making Digital Library Content Interoperable