Social Meaning on the Web: From Wittgenstein To Search Engines

Harry Halpin, <H.Halpin@ed.ac.uk>
<harry@w3.org>

Textorized Parthenon

Social Meaning on the Web: From Wittgenstein To Search Engines

Links Join Across Different Sources of Information

 Links between column headings

Verb/predicate/Property using same URIs

Beyond Ontologies: Social Semantics for the Semantic Web

The Problem

The Semantic Web uses URIs not just to refer to web-pages, but to things.

For the Semantic Web to work, there must be agreement from decentralized agents on what "things" a URI refers to.

Thesis

How can we determine what a good URI is? Can it be determined from the kinds of acts found in the associated description of it?

We're going to have use an interdisciplinary approach from two rarely connected fields: philosophy and the World Wide Web.

The Identity Crisis

Infamous argument between Pat Hayes and Tim Berners-Lee.

Social Meaning and RDF: "the meaning of an RDF document includes the social meaning, the formal meaning, and the social meaning of the formal entailments" so that "when an RDF graph is asserted in the Web, its publisher is saying something about their view of the world" and "such an assertion should be understood to carry the same social import and responsibilities as an assertion in any other format" RDF Concepts and Abstract Syntax Draft

Berners-Lee said "a single meaning is given to each URI" which is summarized by the slogan that a URI "identifies one thing."

Hayes retorted that "I'm not saying that the `unique identification' condition is an unattainable ideal: I'm saying that it doesn't make sense, that it isn't true, and that it could not possibly be true. I'm saying that it is crazy" since it goes against the "basic results in 20th century linguistic semantics"

Two positions

  1. Logicist Position: the meaning of a URI is given by whatever model(s) satisfy the formal semantics of the Semantic Web "the Semantic Web languages would operate exactly unchanged if the identifiers in them were not URIs at all, and if the Web did not exist" (Hayes, In Defense of Ambiguity).
  2. Corresponds to Russell's descriptivist theory of reference.
  3. Direct Reference position: the meaning of a URI is whatever was intended by the owner
    1. The position held by Berners-Lee, seems to make sense trivially on the hypertext Web (a URI identifies the web-page it accesses!)
    2. Corresponds to Kripke's causual theory of reference.

Russell's Descriptivist Theory of Names

Names are shorthand for logical expressions - so the name "Eiffel Tower" includes a host of facts about it such as "in Paris" and "completed in 1889". Bertrand Russell

Patches of sense-data known through direct acquaintance allow one to ground the atoms of logical statements or create descriptions that can form the basis for names.

The priority of reference over sense

We are also assuming the real world (as opposed to any logical idealization of it) is divided neatly into individuals (Strawson).

But how can we deal with referents in the past, or imaginary referents?

Kripke's Causal Theory of Names

A name refers to same referent in all possible worlds and is so independent of any logical description.

A name can be transmitted through time via historical and causal chains, with a name being given its original referent through a process Kripke calls baptism. Saul Kripke

A URI is given its meaning by a baptism by its owner, such as registering a domain name.

The Identity Crisis in Practice

Question:Is there too many or no URIs for things?

Answer: : Sample the Semantic Web using a query log

Data Set: Microsoft Live Search Query Logs

Too Many URIs

There are too many URIs for the same thing probably...

An average of 1,339 URIs (S.D. 8,000) returned per query

That's a lot, but most may obviously be URIs that just mention the term...

Saul Kripke

Top Entities and Concepts

Number of Searches (RDF Hits) Entity:
  1. 7311 (99) david blaine
  2. 2997 (134) jessica alba
  3. 2100 (16723) nick
  4. 1280 (178) michael hayden
  5. 1098 (10) marcus vick
  6. 1092 (199) keith urban
  7. 1015 (43) lane bryant
  8. 990 (55) desmond dekker
  9. 922 (312) jennifer white
  10. 900 (100) clay aiken
  11. 883 (359) bill cosby
    Concepts:
  1. 11383 (10767) weather
  2. 10321 (7777) dictionary
  3. 3675 (434333) people
  4. 3217 (189115) music
  5. 3117 (7196) monster
  6. 2192 (1444) autism
  7. 1468 (149436) map
  8. 1198 (17562) travel
  9. 1191 (12067) pregnancy
  10. 1104 (82074) news

Whose Got the Data: Entities and Concepts

Top 10 Domain Names: Entities

  1. 76706 dbpedia.org
  2. 2992 www4.wiwiss.fuberlin.de
  3. 2848 en.wikipedia.org
  4. 1264 upload.wikimedia.org
  5. 940 www.liveinternet.ru
  6. 928 www.w3.org
  7. 668 de.wikipedia.org
  8. 630 fr.wikipedia.org
  9. 491 ontoworld.org
  10. 389 sv.wikipedia.org

Top 10 Domain Names: Concepts

  1. 18919 dbpedia.org
  2. 3032 www.w3.org
  3. 694 www.cyc.com
  4. 554 bio2rdf.org
  5. 299 truesense.net
  6. 243 www4.wiwiss.fuberlin.de
  7. 171 ontoworld.org
  8. 143 en.wikipedia.org
  9. 132 www.liveinternet.ru
  10. 97 semanticweb.org

Frege and Meaning

Frege, the father of logic, posits that the actual thing in the world is the referent, and a name is a symbol that identifies a referent(s). The sense is the mode of presentation, a type of public, objective(?), knowledge about that private concept among a shared community. The third party of sense (meaning) mediates the reference relationship.Gottlieb Frege

The priority of meaning over reference

Example:Hesperus has a sense ("the morning star") different from that of Phosphorus ("the evening star"), yet both have the same referent, the planet Venus.

As formalized in logic, meaning is taken to be given by interpretations that define the truth conditions of the statement.

Ambiguity is built in: The web of logical statements is the bearer of meaning, and whatever satisfies the sense of the statement could be a referent.

A Wittegensteinian Theory of Names

Also could be considered Neo-Fregean, as the Fregean "sense" is the "objective" sense shared in a language. The Semantic Web is just a language that allows co-ordinated action. Ludwig Wittgenstein

The amount of co-ordination needed does not need full agreement, but only the minimal agreement needed to get the task at hand completed.

How can we boot-straps URIs for things and re-use these URIs in a way that people will actually use?

Answer: Use a paradigm average Web users are familiar with, such as a search paradigm.

Referent via Serach

referent

An Algorithm

  1. Given a term, retrieve a set of web-pages (Using Yahoo!).
  2. Given a term, retrieve a set of Semantic Web URIs and all triples (facts) associated with them (Using Falcon-S).
  3. Human searches through web-sites.
  4. For each web-page the human clicks on, strip out HTML and reduce to words.
    1. Extract all text and typed data from each RDF fact
    2. Decompose RDF into "a bag of words" with lemmatization and removal of words from end of URI.
    3. match converted RDF to HTML using information retrieval text.
  5. pick the URI with the best ranking score given by IR techniques.

Relevance Feedback

Have a human judge actually figure out what web-pages are relevant, and then use those to feed back and expand the query, in order to re-rank the results.

Experiment: Had 200 queries from previous work, retrieved top 10 hypertext Web (Yahoo!) results and top 10 (FALCON-S) results each judged by 3 judges for relevancy. Fliess's Kappa=0.5724$ (p < .05, 95% Confidence interval [0.5678,0.5771]), indicating the rejection of the null hypothesis and moderate agreement. referent

Results

referent

Results of Querying the Hypertext Web

referent

Results of Querying the Semantic Web

Finding Right IR Technique and Parameters

referent

Average Precision Scores for Vector-space Model Parameters: Relevance Feedback From Hypertext to Semantic Web

Finding the Right URI is now Acceptable!

referent

Summary of Best Average Precision Scores: Relevance Feedback From Hypertext to Semantic Web

Run it in reverse!

Now apply relevance feedback from Semantic Web search engines to the hypertext Web! referent

Average Precision Scores for Language Model Parameters: Relevance Feedback From Hypertext to Semantic Web

The Semantic Web can help Hypertext Search

referent

Summary of Best Average Precision Scores: Relevance Feedback From Semantic Web to Hypertext

Conclusions

Is this a unified picture?

Thesis: Finding and giving meaning to URIs on the Semantic Web can be built out of the social semantics implicitly given by the searching behavior of ordinary users.

Wrapping Up

Any questions?