Tuesday, February 26, 2008

The Semantic Web is not about real-world meaning

Although semantics is all about meaning and the Semantic Web is a bold attempt to layer representation of meaning onto a web of raw information, the Semantic Web is not about real-world meaning at all. Rather, the semantics and meaning of the Semantic Web is the same type of semantics that we encounter in traditional computer programming languages and relational databases.

For example, the most common example of the Semantic Web in practice, the ubiquitous RSS web feeds for blogs, are equivalent to a sequence of database records or rows with each record having a collection of fields or columns. The titles of blog posts are directly analogous to a column in a relational database. The summaries of blog posts would be another database field or column. There is a database meaning or semantics for blog post titles as discrete pieces of information, but it in no way attempts to comprehend or represent the intended human meaning of the words in the blog post title. Similarly, the bodies of blog posts would be another field or column. Even tags, where a lot of the meaning of a blog post is categorized, are analogous to records or rows in a relational database table, one per tag with an "id" to tie it to the blog post, but little or no attempt to tie the literal tag to an associated human meaning. Besides, the tags are usually assigned by the user on an ad hoc basis, with no Semantic Web verification that the body of a blog post really ties closely to the tags in terms of semantics that a person has in their mind. Yes, there is plenty of semantics and "meaning", in the traditional database sense, but not in the dictionary or encyclopedia sense of "what do you mean."

The Semantic Web does a credible job of utilizing metadata to associate meaning with data, but this is the meaning of the database world and not the meaning of the real world and real users.

This is the essence of the semantic abyss, the semantic gap between the internal meaning associated with computer data structures and the external meaning that real people keep in their minds and attempt to communicate through natural language speech, writing, music, art, and other cultural artifacts.

-- Jack Krupansky


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