Transcript Semantic annotation and search of large virtual heritage collections

Semantic annotation and search of
large virtual heritage collections
Guus Schreiber
Free University Amsterdam
Overview
• A non-technical view on the Semantic Web
• Work on Semantic-Web deployment
– SKOS, RDFa
• Semantic annotation and search in virtual
collections: the E-Culture example
The Web:
resources and links
URL
Web link
URL
The Semantic Web:
typed resources and links
Painting
“Femme aux chapeau”
SFMOMA
URL
Dublin Core
ULAN
creator
Henri Matisse
Web link
URL
Principle 1: semantic annotation
• Description of
web objects with
“concepts” from
a shared
vocabulary
Principle 2: semantic search
• Search for objects
which are linked via
concepts (semantic
link)
• Use the type of
semantic link to
provide meaningful
presentation of the
search results
ape
great ape
urang-utang
orange
Principle 3: multiple vocabularies. or: the
myth of a unified vocabulary
• In large virtual collections there are always multiple
vocabularies
– In multiple languages
• Every vocabulary has its own perspective
– You can’t just merge them
• But you can use vocabularies jointly by defining a
limited set of links
– “Vocabulary alignment”
• It is surprising what you can do with just a few links
Example
“Tokugawa”
AAT style/period
Edo (Japanese period)
Tokugawa
SVCN period
Edo
SVCN is local in-house thesaurus
A link between two thesauri
RDF/OWL language constructs
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classes and individuals
subclasses
properties
subproperties
domain/range of
properties
• XML Schema datatypes
• equality, inequality
• inverse, transitive,
symmetric, functional
properties
• property constraints:
cardinality,
allValuesFrom,
someValuesFrom
• conjunction, disjunction,
negation of classes
• hasValue, enumerated
type
How useful are RDF and OWL?
• RDF: basic level of interoperability
• Some constructs of OWL are key:
– Logical characteristics of properties: symmetric,
transitive, inverse
– Identity: sameAs
• OWL pitfalls
– Bad: if it is written in OWL it is an ontology
– Worse: if it is not in OWL, then it is not an
ontology
W3C Semantic Web Deployment Working
Group
making vocabularies/thesauri/ontologies available
on the Web
• Schema for interoperable RDF/OWL
representation of vocabularies
– SKOS
• Publication guidelines:
– URI management, representation of versions
• Embedding RDF in (X)HTML pages
– RDFa
SKOS:
pattern for thesaurus modeling
• Based on ISO standard
• RDF representation
• Documentation:
http://www.w3.org/TR/swbp-skos-coreguide/
• Base class: SKOS Concept
Multi-lingual labels for concepts
Semantic relation:
broader and narrower
• No subclass semantics assumed!
Indexing a resource with a SKOS
concept
• primarySubject is
defined as
subproperty
Adding semantics
• Adding OWL statements
• Interpretations of thesaurus relations such as
narrower as subclass-of are often imprecise
(but can still be useful)
• Learning relations between thesauri is
important form of additional semantics
– Example: AAT contains styles; ULAN contains
artists, but there is no link
– Availability of this kind of alignment knowledge is
extremely useful
W3C standardization process
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Input: draft specification
Collect use cases
Derive requirements
Create issues list: requirements that cannot be
handled by the draft spec
Propose resolutions for issues
Continuously: ask for public feedback/comments
Get consensus on amended spec
Find two independent implementation for each
feature in the spec
Example issue:
relationships between lexical labels
• In draft SKOS spec lexical labels of concepts are
represented as datatype properties
• Use cases require relations between labels, e.g.
“AAT” is an acronym of “Art & Architecture
Thesaurus”
• This is a problem because literals have no URI (so
cannot be subject of an RDF property)
• Possible resolutions:
– Labels/terms as classes
– Relaxing constraints on label property
– …..
Recipes for vocabulary URIs
• Simplified rule:
– Use “hash" variant” for vocabularies that are
relatively small and require frequent access
http://www.w3.org/2004/02/skos/core#Concept
– Use “slash” variant for large vocabularies, where
you do not want always the whole vocabulary to
be retrieved
http://xmlns.com/foaf/0.1/Person
• For more information and other recipes, see:
http://www.w3.org/TR/swbp-vocab-pub/
Query for WordNet URI returns
“concept-bounded description”
RDFa: embedding RDF metadata in
an (X)HTML file
Regular HTML
HTML with RDFa
Resulting RDF statements
More information
E-Culture
demonstrator
• Part of large Dutch
knowledge-economy project
MultimediaN
• Partners: VU, CWI, UvA,
DEN,ICN
• People:
•
– Alia Amin, Lora Aroyo, Mark
van Assem, Victor de Boer,
Lynda Hardman, Michiel
Hildebrand, Laura Hollink,
Marco de Niet, Borys
Omelayenko, Marie-France van
Orsouw, Jos Taekema, Annemiek
Teesing, Anna Tordai, Jan
Wielemaker, Bob Wielinga
Artchive.com, ICN: Rijksmuseum
Amsterdam, Dutch ethnology
musea (Amsterdam, Leiden),
National Library (Bibliopolis)
Use case: painting style
Find paintings of
a similar style
KLIMT, Gustav
Portrait of Adele BlochBauer I
1907
Oil and gold on canvas
138 x 138 cm
Austrian Gallery, Vienna
How can we find this other
‘Art nouveau’ painting?
MUNCH, Edvard
The Scream
1893
Oil, tempera and pastel on
cardboard
91 x 73.5 cm
National Gallery, Oslo
Issues w.r.t. the use case
• Parse annotation to find matches with thesauri terms
– E.g. match artists to ULAN individuals
• Artists-style links
– AAT contains styles; ULAN contains artists, but there is no
link
• Learn link from corpora
• Derive it from other annotations
– Domain-specific rules/reasoning needed
• see example in SWRL doc
• Painters may have painted in multiple styles
Example enrichment
• Learning relations between art styles in AAT
and artists in ULAN through NLP of
art0historic texts
• But don’t learn things that already exist!
Culture Web demonstrator
http://e-culture.multimedian.nl
16 Nov 2006
Perspectives
• Basic Semantic Web technology is ready for
deployment
– in open knowledge-rich domains
– Important research issues: scalability, vocabulary alignment,
metadata extraction
• Web 2.0 features:
– Involving community experts in annotation
– Personalization, myArt
• Social barriers have to be overcome!
– “open door” policy
– Involvement of general public => issues of “quality”
• Importance of using open standards
– Away from custom-made flashy web sites