Contents E. Wilde: Microformats

2Abstract
3HTML vs. XML
4Plain HTML
5Good HTML
6Excellent HTML
7XML → HTML Stylesheet
8Graceful Degradation
9Excellent HTML
10From Information, Knowledge
11The Semantic Web Hype
12Semantic Web Layer Cake
1 Microformats
- 14Islands of Semantics
- 15Microformat Syntax
- 16Magic Names
- 17Microformats on the Web
2 Resource Description Framework (RDF)
- 19Describing Resources
- 20RDF Graphs
- 21RDF is Simple and Complex
- 22RDF Schema Graph
- 23RDF in Attributes (RDFa)
3 More Languages
- 25SPARQL
- 26Web Ontology Language (OWL)
- 27Vocabulary Taxonomy
4 Conclusions
- 29Some Questions
- 30Semantics are Important and Hard

E. Wilde: Microformats

(3) HTML vs. XML

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 [Advanced HTML; All-Purpose Elements (1)] may represent aggregation of some basic information items
Very good HTML
- some guidelines/rules/methods for understanding class names
- some model for the underlying schema (what may appear in which combination)
Excellent HTML is dynamically generated from XML
- the model is exposed as structured XML data that is available to the client
- there is a stylesheet for producing the HTML version of the XML
- but even XML does not provide semantics (it is just a structured syntax)

E. Wilde: Microformats

(5) Good HTML

<html>
   <head>
      <title>Cannondale 2007 System Six 2</title>
   </head>
   <body>
      <h1 class="bike"><span class="manufacturer">Cannondale</span> <span class="year">2007</span> <span class="model">System Six</span> <span class="type">2</span></h1>
      <ul class="components">
         <li class="component"><span class="manufacturer">Mavic</span> <span class="type">Ksyrium ES</span> wheelset</li>
         <li class="component"><span class="manufacturer">Maxxis</span> <span class="type">Xenith Hors Categorie</span> tires</li>
         <li class="component"><span class="manufacturer">Fi'zi:k</span> <span class="type">Arione Titanium</span> saddle</li>
         <li class="component"><span class="manufacturer">SRAM</span> <span class="type">Force</span> components</li>
      </ul>
      <p>Sizes: <span class="size">48cm</span>, <span class="size">50cm</span>, <span class="size">52cm</span>, <span class="size">54cm</span>, <span class="size">56cm</span>, <span class="size">58cm</span>, <span class="size">60cm</span>, <span class="size">63cm</span></p>
      <p>Dealers: </p>
      <ul>
         <li class="dealer"><span class="name">Mike's Bikes of Berkeley</span>, <span class="adr"><span class="street-address">2161 University Avenue</span>, <span class="locality">Berkeley</span>, <span class="region">CA</span> <span class="postal-code">94704</span></span>; <a href="tel:+1-510-8452453">+1-510-8452453</a></li>
      </ul>
   </body>
</html>

systemsix-good.html

E. Wilde: Microformats

(6) Excellent HTML

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="bike2html.xsl" type="text/xsl"?>
<bike manufacturer="Cannondale" year="2007">
 <model>System Six</model>
 <type>2</type>
 <sizes>
  <size unit="cm">48</size>
  <size unit="cm">50</size>
  <size unit="cm">52</size>
  <size unit="cm">54</size>
  <size unit="cm">56</size>
  <size unit="cm">58</size>
  <size unit="cm">60</size>
  <size unit="cm">63</size>
 </sizes>
 <parts>
  <wheelset manufacturer="Mavic">Ksyrium ES</wheelset>
  <tires manufacturer="Maxxis">Xenith Hors Categorie</tires>
  <saddle manufacturer="Fi'zi:k">Arione Titanium</saddle>
  <components manufacturer="SRAM">Force</components>
 </parts>
 <dealers>
  <dealer>
   <name>Mike's Bikes of Berkeley</name>
   <address>2161 University Avenue</address>
   <city>Berkeley</city>
   <zip>94704</zip>
   <state>CA</state>
   <phone>+1-510-8452453</phone>
  </dealer>
 </dealers>
</bike>

systemsix.xml

E. Wilde: Microformats

(7) XML → HTML Stylesheet

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:template match="/">
  <html>
   <head>
    <title>
     <xsl:value-of select="bike/@manufacturer"/>
     <xsl:text> </xsl:text>
     <xsl:value-of select="bike/@year"/>
     <xsl:text> </xsl:text>
     <xsl:value-of select="bike/model"/>
     <xsl:text> </xsl:text>
     <xsl:value-of select="bike/type"/>
    </title>
   </head>
   <body>
    <h1 class="bike">
     <span class="manufacturer">
      <xsl:value-of select="bike/@manufacturer"/>
     </span>
     <xsl:text> </xsl:text>
     <span class="year">
      <xsl:value-of select="bike/@year"/>
     </span>
     <xsl:text> </xsl:text>
     <span class="model">
      <xsl:value-of select="bike/model"/>
     </span>
     <xsl:text> </xsl:text>
     <span class="type">
      <xsl:value-of select="bike/type"/>
     </span>
    </h1>
    <ul class="components">
     <xsl:for-each select="//parts/*">
      <li class="component">
       <span class="manufacturer">
        <xsl:value-of select="@manufacturer"/>
       </span>
       <xsl:text> </xsl:text>
       <span class="type">
        <xsl:value-of select="text()"/>
       </span>
       <xsl:text> </xsl:text>
       <xsl:value-of select="local-name()"/>
      </li>
     </xsl:for-each>
    </ul>
    <p>
     <xsl:text>Sizes: </xsl:text>
     <xsl:for-each select="//size">
      <span class="size">
       <xsl:value-of select="concat(text(), @unit)"/>
      </span>
      <xsl:if test="not(position() = last())">
       <xsl:text>, </xsl:text>
      </xsl:if>
     </xsl:for-each>
    </p>
    <p>Dealers: </p>
    <ul>
     <xsl:for-each select="//dealer">
      <li class="dealer">
       <span class="name">
        <xsl:value-of select="name"/>
       </span>
       <xsl:text>, </xsl:text>
       <span class="adr">
        <span class="street-address">
         <xsl:value-of select="address"/>
        </span>
        <xsl:text>, </xsl:text>
        <span class="locality">
         <xsl:value-of select="city"/>
        </span>
        <xsl:text>, </xsl:text>
        <span class="region">
         <xsl:value-of select="state"/>
        </span>
        <xsl:text> </xsl:text>
        <span class="postal-code">
         <xsl:value-of select="zip"/>
        </span>
       </span>
       <xsl:text>; </xsl:text>
       <a href="tel:{phone}">
        <xsl:value-of select="phone"/>
       </a>
      </li>
     </xsl:for-each>
    </ul>
   </body>
  </html>
 </xsl:template>
</xsl:stylesheet>

bike2html.xsl

E. Wilde: Microformats

(8) Graceful Degradation

XML was designed as a language for Web content
- the idea was that XML documents would be delivered to the browser
- stylesheets (CSS/XSL) would take care of the client-side rendering
CSS [Cascading Style Sheets (CSS)] is good at supporting graceful degradation
- viewing an HTML page with CSS turned off most of the time works fine
XSLT is not good at supporting graceful degradation
- the browser just displays the raw XML when XSLT is not supported
Serving XML on the Web is not a good idea
- in closed scenarios (intranet applications) this is a viable solution
- in open scenarios, HTML should be served as the default representation
- alternate versions can be provided by supporting HTTP Content Negotiation [Hypertext Transfer Protocol (HTTP); HTTP Content Negotiation (1)]

E. Wilde: Microformats

(9) Excellent HTML

<html>
   <head>
      <title>Cannondale 2007 System Six 2</title>
      <link title="XML version" rel="alternate" type="application/xml" href="systemsix.xml"/>
   </head>
   <body>
      <h1 class="bike"><span class="manufacturer">Cannondale</span> <span class="year">2007</span> <span class="model">System Six</span> <span class="type">2</span></h1>
      <ul class="components">
         <li class="component"><span class="manufacturer">Mavic</span> <span class="type">Ksyrium ES</span> wheelset</li>
         <li class="component"><span class="manufacturer">Maxxis</span> <span class="type">Xenith Hors Categorie</span> tires</li>
         <li class="component"><span class="manufacturer">Fi'zi:k</span> <span class="type">Arione Titanium</span> saddle</li>
         <li class="component"><span class="manufacturer">SRAM</span> <span class="type">Force</span> components</li>
      </ul>
      <p>Sizes: <span class="size">48cm</span>, <span class="size">50cm</span>, <span class="size">52cm</span>, <span class="size">54cm</span>, <span class="size">56cm</span>, <span class="size">58cm</span>, <span class="size">60cm</span>, <span class="size">63cm</span></p>
      <p>Dealers: </p>
      <ul>
         <li class="dealer"><span class="name">Mike's Bikes of Berkeley</span>, <span class="adr"><span class="street-address">2161 University Avenue</span>, <span class="locality">Berkeley</span>, <span class="region">CA</span> <span class="postal-code">94704</span></span>; <a href="tel:+1-510-8452453">+1-510-8452453</a></li>
      </ul>
   </body>
</html>

systemsix-excellent.html

E. Wilde: Microformats

(10) From Information, Knowledge

XML is often said to be self-describing
- many people think this is the same as self-explanatory
- the catch is what exactly it is you refer to by describing
Database data cannot live without a database
- database data is simply content, the structure is provided by a DBMS
- XML documents have their structure encoded within them
- compared to database data, XML in fact is self-describing
What is the gap between self-describing and self-explanatory?
- it is impossible to find out how the document could be modified
- there are no semantics associated with structure or content
- so self-describing means, you can guess a lot, but you maybe wrong

E. Wilde: Microformats

(11) The Semantic Web Hype

1965, H. A. Simon: machines will be capable, within twenty years, of doing any work a man can do [http://en.wikipedia.org/wiki/Artificial_intelligence#_note-11]
1967, Marvin Minsky: Within a generation [ … ] the problem of creating artificial intelligence will substantially be solved. [http://en.wikipedia.org/wiki/Artificial_intelligence#_note-12]

How to get past the limitations of HTML?
- a machine-friendly Web must make Web resources machine-processable
- XML solved the problem on the syntax level
- how could the problem be solved on the level of semantics?
As in the 1970's, description logic was declared as being the solution
- there was a need for the Web to move towards semantics
- there was a community of AI researchers with a long history
- the Semantic Web was born and is currently repeating AI history

Microformats

Outline (Microformats)

Microformats [4]
Resource Description Framework (RDF) [5]
More Languages [3]
Conclusions [2]

Microformats E. Wilde: Microformats

(14) Islands of Semantics

Microformats solve very specific problems in a very specific way
- encoding address information on a Web page
- encoding a location of something represented by a Web resource
Microformats can be compared to tagging
- a very simple mechanism with a minimal barrier-to-entry
- little flexibility in adapting the mechanism to slightly other uses
- often underspecified and interpretation implementation-dependent
- no unified rules across different platforms which makes processing hard
- nice and easy to start with, but questionable for robust long-term solutions
Currently there are about 10 reasonably popular microformats
- calendar entries, addresses, licenses, outlines, geolocation, resumes, social networking, … [http://microformats.org/wiki/Main_Page]

Microformats E. Wilde: Microformats

(15) Microformat Syntax

HTML has some underspecified and underused elements
- dfn, code, samp, kbd, var, cite, abbr, acronym
- they can be reused and augmented with additional information
HTML allows non-HTML content in HTML pages
- unknown elements and attributes must be ignored
HTML allows class attributes to carry semantics
HTML has a head which contains page metadata
- for example, the link element specifies connections to other resources

Microformats E. Wilde: Microformats

(16) Magic Names

A syntax defines where and how to embed information
- what is embedded and how well is it defined semantically?
- is there an underlying model for specifying dependencies?
- how many assumptions does it take to implement a microformat?
Names are never self-explanatory, they always represent concepts
- nothing can remove the burden of defining a conceptual model
- if this is not done, models evolve and there will be more than one
Microformats and tagging share the same folklore
- define simple things and good things will happen
- this works by supporting a quickly growing ecosystem of diverging semantics
- semantics are most useful when they are well-defined
- loose semantics also have some utility

Microformats E. Wilde: Microformats

(17) Microformats on the Web

Easy to embed for generated content
- some of the very basic formats may even appear in browsers one day
- combining well-designed URIs with document relationships is better than every site map
Hard to rely on for applications that need dependable semantics
- useful as a hint and as a starting point
- microformats are not a good idea for complex information management tasks
Use as foundation for representing common concepts
- when formatting addresses, use adr [http://microformats.org/wiki/adr] class names
- for structured documents use XOXO [http://microformats.org/wiki/xoxo]

Resource Description Framework (RDF)

Outline (Resource Description Framework (RDF))

Microformats [4]
Resource Description Framework (RDF) [5]
More Languages [3]
Conclusions [2]