porting library vocabularies to the semantic web - ifla 2010
DESCRIPTION
Presentation at IFLA 2010TRANSCRIPT
making sense of content TM
2010-08-15 Session 149
Information Technology, Cataloguing, Classification and Indexing with Knowledge Management
Porting library vocabularies to the Semantic Web, and backA win-win round trip
making sense of content TM
making sense of content TM Summary
1. Libraries and the Web have a twenty-years affair of love and hatewhich should now come of age.
2. The role of vocabularies is critical in this affair.
3. The Linked Data architecture should leverage proven heritage vocabularies instead of reinventing them.
4. Specific features of library vocabularies make them more or less portable and useful to the Semantic Web.
5. To-do list and guidelines for vocabulary audit and publication.
6. Semantic Web tools feedback : helping vocabulary management.
making sense of content TM Libraries and the Web, a love and hate story
Libraries have been around for thousands of years
The Web is barely in its twenties
Webbies has been claiming the Web was bound to become the Universal Library- Bottom line : traditional libraries are obsolete
Librarians have been claiming the Web is a mess and will never improve- Bottom line : keep using libraries for serious stuff
But they look at each other with fascination- The Web : if only we could be as efficient as libraries for classification and index- Libraries : if only we could scale at the size of the Web, and be as user-friendly
They are bound to be married at the end of the day !
making sense of content TM What is there? Everything!
In libraries- Resources (aka records) and catalogues- Authority lists (aka descriptions of « real-world entities »)- Subject headings, thesaurus, classification schemes (aka vocabularies)- Metadata linking resources to entities and subjects
On the Web- Resources (aka web pages) w/o catalogue- Real-world entities descriptions (w/o authority lists)
- Exemple : Wikipedia, Facebook
- Profusion of vocabularies, but w/o general schemes- Often called « taxonomies », handcrafted for user navigation
- More and more metadata based on RDF family of standards
Vocabularies are the missing pieces of the Semantic Web- Libraries are the natural providers!
making sense of content TM Web vs Libraries (1.0 view)
Library The Web
scope local, focused global
size manageable unknown, organic growth
content controlled unknown, organic growth
type of content controlled unknown
methods polished, proven experimental, wild
organization of content native, vocabulary-based local, quality unknown
classification native, vocabulary-based local, quality unknown
search and retrieval vocabulary-based search algorithms
making sense of content TM Attempts for organizing the Web #fail
Directories- Could not cope with the scale of Web growth- Were often built by amateurs in classification and vocabulary management- Were biased by the commercial use of the Web
Vocabularies- Open Directory categories- Wikipedia categories- Globally messy, organic growth
Metadata in html <head>- Spammed, not in sync with the content- Ignored by most search engines now
Bottom line : The Web is not and will never be a Global Library
making sense of content TM What the Web is good at
Creating representation of « things »- Wikipedia pages- Facebook pages- Pages for products, species, places …
Providing standard identifiers (URI) associated to access protocol (http)- Identity of things is encapsulated in resources URIs
Linking things together- Via http protocol, hypertext etc
Semantic Web is just an extension of the Web- Leveraging all the above features- Expliciting the semantics of URIs and descriptions- Allowing better, less ambiguous access to resources
making sense of content TM The Semantic Web in perspective
INTERNET (ca.1970)- Network of identified, connected and addressable computers
- Similar to libray infrastructure level : buildings, rooms, shelves …- Technical support : IP addresses
WEB 1.0 (ca. 1990)- Network of identified, connected and addressable resources
- Similar to library resources level : books, documents …- Technical support : URLs, http
Semantic Web (ca. 2010)- Network of identified, connected and addressable concepts
- Similar to library vocabulary level : thesaurus, classification, authority lists- Technical support : URIs, RDF, content negociation
making sense of content TM Vocabularies as Core Data
Definition of « Core Data » (Hannemann & Kett, 2010)- Stable and reliable- persistent nodes with a strict, transparent policy :
data provenance, no deletions, versioning- maintained or backed by trusted public organizations- standards based
Library Vocabularies are just that!- Or at least they should play this role
Vocabularies can be used on the Web as in libraries- Despite the difference in scope and size
Based on shared metadata standards- That’s where the Semantic Web comes in
making sense of content TM A roadmap for Semantic Web migration
Audit- Choose the vocabularies which are worth publishing- Sort out terms, concepts and things- Explicit the semantics of your specific syntactic constructs- Check the actual transitivity of your hierarchies- Figure the translation into vocabularies/ontologies popular on the Web
Make ready for publication- Package by domains- Define a strict URI policy, including versioning- Map to other vocabularies
Integration- Expose and promote your Vocabulary as a Service
- Using de-referencable URIs and SPARQL endpoints
- Use Semantic Web software for vocabulary management- To ensure native standard conformance and logical consistency
making sense of content TM Semantic audit of vocabularies ?
Publication for the Semantic Web can be a painful process
Not only technically (formats etc) but conceptually
Making semantic explicit often shows clearly where you’ve gone wrong
But it’s an healthy process anyway
Better do most of the audit before any publication on the Web
But publishing early can trigger useful Web community feedback …
making sense of content TM Which vocabularies are worth it?
Named entities, authority files- A growing number of entities already defined in the Linked Data Cloud …
- 3.4 million « things » identified and described at dbpedia.org- Over 7 million « features »identified and described at geonames.org- http://www.freebase.com/view/people/views/person 1,687,119 entries and counting- http://www.freebase.com/view/en/victor_hugo- http://dbpedia.org/resource/Victor_Hugo
- Consider if duplicate efforts are worth it- Should you throw away our yet-another-Victor Hugo entry?- No, but link to other descriptions in the Cloud (based on http URI)
and keep existing identifiesr for retro-compatibility
Taxonomies, subject headings, classifications- That’s where library heritage is strong and the Web is weak- Such vocabularies can be structuring for the web of data as they are for libraries- Their publication should be a priority !
making sense of content TM Sort out Terms, Concepts and Things
Terms are denotations for concepts- In a given language- If possible qualified by vocabulary specialists
Concepts are specific representations of « things »- In a certain view of the world- For a specific functional purpose in mind
Things are ... just things- What users are about at the end the day (people, places, products …)
Terms, Concepts and Things should all be first-class citizens in the Semantic Web- Switching from a term-centric to a concept-centric view
- That’s what SKOS and ISO 25964 … are all about
- Does not mean that terms and terminology are out of the picture!- They simply need to be defined and managed at a different level
making sense of content TM Building on SKOS and extensions
Thing
Concept
Term
denotes
represents
owl:Thing
skos:Concept
skos-xl:Label
foaf:focus *
skos-xl:prefLabel
* Under discussion
geo:Feature
foaf:Person
time:TemporalEntity
making sense of content TM Explicit the semantics of your syntax
<http://id.loc.gov/authorities/sh00000562> a skos:Conceptskos:prefLabel ‘Environmental justice--Religious aspects--Buddhism, [Christianity, etc.]’
What does such an aggregation mean?- Has « -- » the same semantics in all subject headings in LCSH?- Is yes, which one?- Same questions for [ ]
How does this concept link to its components?- Currently it does not, although they are defined elsewhere in LCSH- http://id.loc.gov/authorities/sh97002483 : Environmental justice- http://id.loc.gov/authorities/sh00000564 : Environmental justice--Religious aspects- http://id.loc.gov/authorities/sh85017454 : Buddhism
Expliciting the link between the above concepts would definitely add value!- To do : figure out how (using flavors of skos:semanticRelation)
making sense of content TM Make sense of hierarchies
From LCSH hierarchyAuxiliary sciences of history.Civilization..Learning and Scholarship…Humanities….Philosophy…..Psychology……Attention…….Listening……..Eavesdropping………Wiretapping
Kind of semantic drift all the way down- Every local relation makes sense, globally it’s weird if transitivity applies- Bust most automatic systems will rely on transitivity as default feature
Either fix it, or specify the hierarchy is not transitive
making sense of content TM Consider how the vocabulary will be used
The Web is an open world- Whatever is not explicitly forbidden is allowed- Whereas in closed library practice, whatever is not explicitly allowed is forbidden- So be prepared to all sort of misuses if you let room for interpretation
Package by domains- Web users will be happy to integrate hundreds of concepts rather than millions- Small, focused vocabularies are more re-usable than general ones- The widest the scope, the more room for ambiguity!
Package by versions- Versioning at vocabulary level and/or at concept level (open issue)
- Should a concept keep the same URI in successive versions?- When has a concept changed enough to be replaced by a different one?
- Never delete a concept, deprecate it if necessary- Using e.g. dcterms:isReplacedBy- Concepts have a life cycle, but cool URIs don’t change
making sense of content TM Mapping to other vocabularies
A most important but still open area- Dealing with hard notions like identity, similarity, sameness …
Tools for help to alignment are emerging- See e.g. ONAGUI http://sourceforge.net/projects/onagui/- Work in progress (TAE project)
- More background in ontology mapping than vocabulary mapping
Mapping at the concept level seems to make sense- SKOS provides basic vocabulary for simple mapping- But no provision for mapping a simple concept to an aggregate- In particular no boolean operators (Actor AND Musician vs Actor OR Musician)
Alignment of « things » is a contentious area- See various debates on use and abuse of owl:sameAs
- http://events.linkeddata.org/ldow2010/papers/ldow2010_paper09.pdf
making sense of content TM Ready to publish?
Follow recommended (best) practices - See e.g. http://www.w3.org/TR/swbp-vocab-pub/
Provide usable packaging (see above, particularly if the vocabulary is large)- 500 Mo dump with one single SKOS file is not the most manageable form!
Choose and expose a clear licensing policy- Using e.g. Creative Commons license model
Make all concept URIs de-referencable- Using content negociation : one description for machines, one for humans
Publish a vocabulary description- For humans and for machines (using e.g., SIOC)
Publish your own use of the vocabulary- In metadata of your records
making sense of content TM Spread the word, join the community!
The Web is an open collaborative entreprise …
Push what you’ve done outside the library world- Join linked data and Semantic Web forums and work groups- Be ready to answer feedback
The Semantic Web will be a Social Web- Look out how your vocabulary will be adopted or not by social applications- Facebook, Twitter and the like …
And of course look out for further developments at LLD XG- http://www.w3.org/2005/Incubator/lld/
making sense of content TM Put Semantic Web software in the back-office
Publication of linked data can be done from any information system- It can be dealt as yet another publication issue …
But it’s simpler if semantic formats are dealt natively in the back-office- Supporting import/export of vocabularies in the system in standard formats
- Native RDF and SKOS integration
- Supporting semantic queries in the back-office- Supporting sanity checking, inference rules
… And making librarians natively at ease with semantic technologies!- Not the least part of it
The technology is mature, software is on the market …- Time to think about it!- So, just ask
making sense of content TM
Thanks for your attention
Questions?