What is the Semantic Web

by Liam McDermott, 29 March 2007 - 7:29pm

‘Semantic Web’ is a term often used by Web professionals, luckily it's not a buzz-word yet, but is a term everyone involved in the Web should know and understand. This article aims to explain the Semantic Web in plain English.

What the Term Semantic Web Means

The Semantic Web is a project started by the Web's inventor Sir Tim Berners-Lee. The purpose is to make the Web more easily readable for machines, the advantage is software—such as search engines—will be better able to convert human requests for information into meaningful results.

The Oxford English dictionary defines semantics as:

adjective relating to meaning in language or logic.

Semantics relates to meanings, i.e. the meaning of words in language. Therefore the Semantic Web are Web sites that describe their own contents (in a format easily understood by software).

More technical information on the Semantic Web project are available on the W3C Web site

How it Affects People Who Work on the Web

At this point all the average Web professional must do is structure their documents correctly. This means using headings (h1, h2, h3 etc), paragraphs, lists, tables etc. in their semantically correct places. Headings for headings, lists for lists and tables for tabular data. Sounds simple, but many get it wrong, for example this is incorrect:

<p class="heading"><strong>Here is a Heading</strong></p>
<p class="heading">Here is a Lesser Heading</p>

This is not semantically correct markup; using the paragraph tag for a heading is confusing for a machine, in fact it will just be treated as a paragraph. The correct markup in this situation is:

<h1>Here is a Heading</h1>
<h2>Here is a Lesser Heading</h2>

The second example will mean far more to a machine, even if CSS is used to format these two examples similarly when opened with a Web Browser. Software such as the Google spider is known to understand headings and weight the text within them as being of higher importance to the meaning of the document than a paragraph^[1].

There is much more to the Semantic Web than just structuring a document correctly, RDF (Resource Description Framework) has led to the development of many tools for a self-describing Web. This is largely of interest to developers, whereas designers will reap the rewards of RDF-enabled applications. Examples of common RDF applications include: