Introduction to the Semantic Web

The Semantic Web

Tim Berners-Lee’s description

The Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation. The first steps in weaving the Semantic Web into the structure of the existing Web are already under way. In the near future, these developments will usher in significant new functionality as machines become much better able to process and “understand” the data that they merely display at present.

Berners-Lee et al. 2001. The Semantic Web. Scientific American

The Semantic Web

My definition

A vision of the WWW whereby it is made easier for software agents to process information that automates tasks that used to be mostly performed by people manually interacting with the Web; also, it allows software agents to perform tasks that cannot be done by people but can be achieved by exploiting the Web more automatically.

The Semantic Web

• Automating tasks with the Web can be done by:
  • Making more powerful intelligent software agent on the client side. This is part of Artificial Intelligence.
  • Making a more intelligible Web: better standards, better practices, on both client and server sides. This is what the Semantic Web is about.

What we do with the Web?

• In the beginning (early 90s): read/share (mostly textual) documents
• Mid to late 90s: read/share multimedia content
• Late 90s to early 2000s: eCommerce
• Early 2000s: write/share/interact socially
• Now: do things, work, take decisions, create

Our use of the Web evolved...

• A Web of documents (for some people)
• A Web of multi-media documents (for most people)
• A Social Web (for all people)
• A Web of applications (for people and some machines)
• A Web of data (for some people and many machines)
• A Web of things (for machines)
• A Semantic Web (for people and machines)

Using the Web, find…

• …how many European people won a Physics Nobel prize in the 20th century
• …price, duration of warrantee, and technical features of at least 20 phone models that cost less than €300 and are not of Apple brand
• …man-made structures taller than 300 m that were completed in a country that was a kingdom

How a machine knows?

• Understanding people’s documents (text, image, sound, video) is too difficult for a machine (at the moment)
• Machines understand formal languages (programming languages, data formats, etc.)
• Make knowledge accessible to, and processable by machines in a formal language

Accessible and processable knowledge

• Web site owners can provide (part of the) knowledge in a formal language
• Web site consumers (esp. software agents) can embed processors for this language
• Requires a format for exchange of formal knowledge
• Requires specification of how the language is processed
• As a simpler starting point, we can start with a common data model
• A prerequisite for a Semantic Web is a Web of Data

The Web of Data

• A vision of the Web as a world-wide distributed database
• Can we query the Web as a database?

What if we could ask who are the widows of murdered American presidents? like this:

    SELECT ?widow
    FROM WorldWideWeb
    WHERE
      (?widow marriedTo ?person) AND
      (?person isPresidentOf UnitedStates) AND
      (?person killedBy ?someKiller)

The Web of Data

• A vision of the Web as a world-wide distributed database
• Can we query the Web as a database?

How many Nobel Prizes per continent?

    SELECT COUNT(?prize)
    FROM WorldWideWeb
    WHERE
      (?scientist wasAwarded NobelPrize) AND
      (?scientist countryOfOrigin ?country) AND
      (?country partOf ?continent)
    GROUP BY ?continent

Structured data

Structured data

Interlinked data

Interlinked data

lacentrale:AB-234-CD priceInEuros 6300

Interlinked data

lacentrale:AB-234-CD priceInEuros 6300
lacentrale:AB-234-CD model vw:Golf4

Interlinked data

Automate deductions

Automate deductions

Today session

• Introduce the Semantic Web
• Present the Resource Description Framework (RDF)
• Explore existing RDF data online
• Train yourselves in graph-based data modelling