Interoperability:
Where the irresistible force of
flexibility meets the immovable
object of standardization.
DRH Conference 2003
Chris Turner
Leaders Project UCL SLAIS
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Conflicting needs
• Flexibility in encoding
– Wide range of source materials
– Existing practices
• Standardisation
– Reusability
– Support
– Sustainability
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Interoperability
‘to be interoperable, one should actively be engaged in the
ongoing process of ensuring that the systems, procedures
and culture of an organisation are managed in such a way
as to maximise opportunities for exchange and re-use of
information, whether internally or externally’
Miller, Paul. ‘Interoperability. What is it and Why should I want it?’,
Aridane, Issue 24 (21 June 2000)
http://www.ariadne.ac.uk/issue24/interoperability/intro.html
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6 Aspects of Interoperability
•
•
•
•
•
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Technical
Semantic
Political/Human
Inter-community
Legal
Informational
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Technical
Interoperability
• the ‘plumbing’, or what goes on out of
sight to make documents accessible.
– http
– tcp/ip
– etc
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Semantic
Interoperability
• Works on different levels and enables us to
understand and transform documents
– Syntactic level
• XML rules for well-formedness provide a standardized
structure for files
– Semantic level
• Common convention for naming parts of a document –
DTD/Schema
– Structural level
• Determines how parts of a file relate to each other – the
content models described by a DTD/Schema
– Content level
• What does the document actually say. E.g. Index terms for
searching, and lists of descriptors
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Interoperability of TEI and EAD
documents
• they can be moved between computers and
accessed between computers
• being XML they have a recognized syntactic
structure
• they use common tag libraries, and thus have
consistency of naming.
• the content models of the DTDs offer commonly
defined structures
• the DTDs offer some pre-defined attribute
values.
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Flexibility of TEI/EAD
• A goal of EAD is to make archival resources
from many institutions accessible to users. To
achieve this goal, EAD must accommodate a
wide range of internationally divergent
descriptive practices (EAD Working Group,
2002).
• It is important to remember...[that] many -perhaps most -- serious TEI applications have
found it necessary to build their own
customization of the full scheme in some way
(Burnard, 2000).
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Consequence
No two documents created in EAD or TEI
need have the same structural or content
markup.
– Limits possibilities for data exchange and reusability
– Makes consistent search and retrieval and
presentation of results difficult
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Solution approach
• Determined by project aims
– ‘Document-centric’ – focus is on retrieval and
presentation of TEI encoded transcripts and
images
• EAD used for metadata to facilitate search and
retrieval
• EAC used for contextual information
– Reusability of files
– Hospitality to existing files?
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Contextual presentation
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Metadata in EAD file
item description in Leaders-EAD
to harvest index terms and description from
EAD documents
resulting index document
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Controlled terms for searching
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TEI - descriptive markup
• Pizza Chef approach helpful
• Wide range of formats of archival
documents
• Descriptive/procedural distinction
• But just one DTD.
• Modify stylesheets
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Examples
Example EAC document
Example TEI document
Application example
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TEI DTD modification
TEI for Archives DTD
Abbreviations entity file
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Re-use through Web Services
• Standardisation of encoding makes
possible standardised application
functions.
• Application functions described by WSDL
(Web Services Description Language) file
• Means application developers can
incorporate LEADERS functions into their
own applications.
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Conclusions
• Trade-offs
– EAD: stricter control vs loss of hospitality to
legacy data and variation in existing practices.
– TEI: a single DTD but hospitality to a
potentially wide range of source materials vs
less reusability of stylesheets.
• Paradox
– More standardisation of encoding vs more
flexibility in terms of interoperability.
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