(4) Problem of Semantics: Syntax vs. Meaning

• Computation is great at syntax and grammar
  • All X are Y
• Take the following syllogisms
  • All dogs are mammals
  • All cats are bipeds
  • All Lady Gagas are cats
• Logical syntax does not necessarily take into consideration meaning
  • 'The sum of the angles of a triangle is equal to the color red'
  • While grammatically correct this makes no sense

(5) Adding Meaning to HTML

• HTML describes structures in a very general way
  • HTML elements describe logical page structures such as headings, lists, tables, …
  • useful for dynamic and adaptive page rendering, but not for understanding contents
• Good HTML may have more information available
  • classes in HTML elements may represent underlying concepts (CSS may use this)
  • HTML containers (e.g. lists) may represent aggregation of some basic information items
• Very good HTML
  • standard class names and some guidelines for using them
  • some rules for using combinations of particular class names

(6) Plain HTML

<div>
  <h1>Spoon, Deerhunter, and Micachu and the Shapes at The Fox Theater</h1>
  <p>Tuesday 13 April 2010 at 7:30pm</p>
  <div>
    <div>The Fox Theater</div>
    <div>
      1807 Telegraph Avenue<br/>
      Oakland, CA 94612
    </div>
    <div>(510) 302-2277</div>
  </div>
</div>

(7) Good HTML

<div class="event">
  <h1 class="title">Spoon, Deerhunter, and Micachu and the Shapes at The Fox Theater</h1>
  <p class="when">Tuesday 13 April 2010 at 7:30pm</p>
  <div class="where">
    <div class="venue">The Fox Theater</div>
    <div class="address">
      <div class="street-address">1807 Telegraph Avenue</div>
      <span class="city">Oakland</span>, 
      <span class="state">CA</span>
      <span class="zip">94612</span>
    </div>
    <div class="phone">(510) 302-2277</div>
  </div>
</div>

(8) Very Good HTML: Microformats

<div class="vevent">
  <h1 class="summary">Spoon, Deerhunter, and Micachu and the Shapes at The Fox Theater</h1>
  <p class="date">
    <abbr title="20100413T1930Z" class="dtstart">Tuesday 13 April 2010</abbr> 
    at <span>7:30pm</span>
  </p>
  <div class="location vcard">
    <div class="fn org">The Fox Theater</div>
    <div class="adr">
      <div class="street-address">1807 Telegraph Avenue</div>
      <span class="locality">Oakland</span>, 
      <abbr class="region" title="California">CA</abbr> 
      <span class="postal-code">94612</span>
    </div>
    <div class="tel">(510) 302-2277</div>
  </div>
</div>

(9) Microformats

• A microformat is an agreed-upon set of names for HTML element classes, and rules for using them
• Microformats don't add anything new to HTML: they're a way of using HTML
• Microformats are good for small, commonly encountered bits of data
  • Calendar events [http://microformats.org/wiki/hcalendar], contact info [http://microformats.org/wiki/hcard], licensing info [http://microformats.org/wiki/rel-license], etc.
  • nofollow [Web Search; nofollow (1)] is a microformat too
• Creating new microformats involves reaching consensus in the microformat community
  • This takes time and effort, so there are lots of "draft" microformats and few actually in use
  • Only the most common kinds of data get standardized

(10) Very Good HTML: RDFa

<div class="vevent">
  <h1 class="summary">
    <span about="http://dbpedia.org/resource/Spoon_%28band%29"
          typeof="http://purl.org/ontology/mo/MusicGroup">
    <span property="http://xmlns.com/foaf/0.1/name">Spoon</span></span>, 
    <span about="http://dbpedia.org/resource/Deerhunter"
          typeof="http://purl.org/ontology/mo/MusicGroup">
      <span property="http://xmlns.com/foaf/0.1/name">Deerhunter</span></span>, 
    and 
    <span about="http://dbpedia.org/resource/Micachu"
          typeof="http://purl.org/ontology/mo/MusicArtist">
      <span property="http://xmlns.com/foaf/0.1/name">Michachu</span></span>, 
    and the Shapes at The Fox Theater
  </h1>
  <p class="date">
    <abbr title="20100413T1930Z" class="dtstart">Tuesday 13 April 2010</abbr> 
    at <span>7:30pm</span>
  </p>
  <div class="location vcard">
    <div class="fn org">The Fox Theater</div>
    <div class="adr">
      <div class="street-address">1807 Telegraph Avenue</div>
      <span class="locality">Oakland</span>, 
      <abbr class="region" title="California">CA</abbr> 
      <span class="postal-code">94612</span>
    </div>
    <div class="tel">(510) 302-2277</div>
  </div>
</div>

(11) RDFa

• RDFa is another approach to adding meaning to HTML
• Unlike microformats, RDFa adds some new attributes to HTML
• While microformats are defined for specific kinds of data, RDFa can be used for any kind of data
  • No need for wide consensus
• But RDFa is a little more complicated to use than microformats

(12) Using Microformats & RDFa with Operator

• Operator [https://addons.mozilla.org/en-US/firefox/addon/4106] is a Firefox add-on for interacting with microformats and RDFa
• It looks for microformat and RDFa classes and attributes and does intelligent things with them
• Its functionality can be extended with user scripts
• Try it on our example [src/event-rdfa.html], or Yelp [http://www.yelp.com/biz/top-dog-berkeley], or Best Buy [http://products.semweb.bestbuy.com/y/products/9811355/]

(14) Linked Data Principles

1. Use URIs as names for things.
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information, using a standard data model.
4. Include links to other URIs, so that people can discover more things.

(15) URIs as Names

• Recall [Web Foundations (URIs & HTTP); Resources & Representations (1)] that a URI identifies an abstract resource
• This means that a URI can identify any abstract concept, not just web pages
• The Semantic Web is mainly about how to assign URIs to any concept
• DBpedia [http://dbpedia.org/] is a project creating URIs for every topic in Wikipedia
  • Spoon: http://dbpedia.org/resource/Spoon_%28band%29 [http://dbpedia.org/resource/Spoon_%28band%29]
  • Mysticism: http://dbpedia.org/resource/Mysticism [http://dbpedia.org/resource/Mysticism]
• But anyone can create URIs for concepts
  • Panthera tigris: http://lod.geospecies.org/ses/QMUrD [http://lod.geospecies.org/ses/QMUrD]
• Multiple people or groups can create URIs for the same concept
  • All the URIs for Panthera tigris [http://sameas.org/html?uri=http%3A%2F%2Flod.geospecies.org%2Fses%2FQMUrD]

(16) Semantic Web Data Model

• The standard data model defined by Semantic Web standards is called RDF
  • Stands for Resource Description Framework
• Data in RDF is just lists of statements:
  • Spoon is a music group
  • Spoon is named "Spoon"
  • Spoon has a member Britt Daniel
• A statement consists of three parts: [subject] [predicate] [object]
  • [Spoon] [is a] [music group]
  • [Spoon] [is named] ["Spoon"]
  • [Spoon] [has a member] [Britt Daniel]

(17) Semantic Web Data Model

(18) Semantic Web Data Model

(19) Linking Data Sets

(21) Enhanced Search Results

• When indexing [Web Search; Indexing (1)] web pages, search engines can parse microformats and RDFa to add details to result pages
• Instead of trying to guess at address, prices, or reviews, they can access this data directly
• Doesn't affect ranking, only the display of results
  • So there's no point in putting in fake/spam data

(22) Practical Applications

[http://search.yahoo.com/search?p=avila+boston]

(23) Practical Applications

[http://www.google.com/search?q=fillmore+new+york+concerts]

(24) Government Data

• Government data sets are a good use case for the Semantic Web
  • Government data is intended to be made available to the public
  • Publishing on the web is a great way to make data widely available
• Data sets are more useful when they can be linked and merged
• Linking and merging before publishing to some centralized place creates a bottleneck
• In theory, the Semantic Web can enable linking and merging of data sets published independently
• Theory being tested at data.gov.uk [http://data.gov.uk/]