Sunday, February 15, 2009

Tracking the evolution of meaning

Even the dictionary is not completely static and engraved in stone. In addition to the appearance of new words, old words can take on new meanings and cease to necessarily connote old meanings. Over time, the editors of dictionaries try to track the evolution of the meanings of words and phrases in both written and spoken language. Even when the dictionary is quite clear and most people solidly recognize the "official" meaning of a word, there will always be outliers, renegades, and revolutionaries (evolutionaries?) who insist on redefining words to have meanings of their own choice or "context." Dictionary editors do a fairly good job of tracking and reporting the evolution of meanings of words. Enter the Semantic Web.

The Semantic Web is not about natural language per se, but there is an intention to represent or at least indicate real-world concepts using URI resources and inferences.

There was an interesting email thread on the W3C Semantic Web email list triggered by an email from Jeremy J. Carroll, Chief Product Architect at TopQuadrant with the subject line "live meaning and dead languages." Jeremy opined that:

In terms of meaning on the web, I see that the web as a place where the life world is produced, by active extensions of our linguistic apparatus. I hence have an aversion to techniques and technologies that somehow pretend that meaning on the web, and in particular the semantic web, should or could be made static and somehow lifeless. So, I have difficulty seeing the meaning of any URI as univocal or fixed or even particularly well-defined. This leads to some hesitation concerning systems of definitions and axioms built on top of such univocity.

I think this worry becomes more so as axioms and systems of axioms become more complicated. (I just about see similarities between OWL2 and the Shorter Latin Primer I had at high school).

A term which is too tightly nailed down in its relationship to other terms has been dug into an early grave. Having fixed its meaning, as our world moves on, the term will become useless.

The trick, in natural language, is that the meaning of terms is somewhat loose, and moves with the times, while still having some limits.
This looseness of definition gives rise to some misunderstandings (aka interoperability failures), but not too many, we hope.

So I wonder, as some people try to describe some part of their world with great precision, using the latest and greatest formal techniques, just how long that way of describing the world will last. Maybe there is a role in such precision in allowing us to be clear about differences of opinion --- but it doesn't seem to me to be a good foundation for building knowledge.

He tells us that his thoughts were in part inspired by his recent reading of the book Emptiness & Brightness by Don Cupitt, from which he quotes:

By language, I mean the dance of signs, the continuous process of symbolic exchange between people, the humming communication network of which the human life world consists. I mean also to invoke the vast strange and multi-dimensional world of linguistic mean-ing -- and I am hyphenating mean-ing, like be-ing, because <em>mean-ing is a process too</em>. We need to make this point because for so long European intellectuals studied only dead languages -- Latin, Greek and Hebrew -- and failed to grasp the way the transactions of life are carried out and the life world is produced and formed by the <em>motion</em> of living language.

The book is (of course) available at Amazon:

There ensued a long discussion on the email list, including this issue of the distinction or disparity of the Semantic Web and natural language. This unresolved aspect of the Semantic Web will continue to haunt the practical application of the Semantic Web until somebody comes up with a model to transcend "Web" meaning and human meaning. Meanwhile, practitioners will continue to invent all manner of contrived methods for pretending that the vast gap between the two does not exist.

My immediate reaction to Jeremy's original email, sent directly to him, was:

That is why the Semantic Web is based on URIs rather than "keywords" -- as "meaning" evolves over time, people can simply construct new URIs representing the same natural language text but with the new "meaning." Sure, there is always the problem of misuse of URI when the associated natural language text "matches" but the meaning is not aligned with the real world context, but that is always going to be true in any language system, natural or non-natural. Over time, people can gradually detect "meaning misalignment" (or even "suspected meaning misalignment") and add knowledge of the perceived misalignment, so that the perceived strength of any inferences can be reduced to reflect the ambiguity of any inferred meaning.

In summary, we have two big problems here: 1) representing real-world meaning in the Semantic Web, and 2) tracking evolution of real-world meaning in the Semantic Web.

There are at least four distinct forms of variation in meaning that need to be tracked:

  1. Meaning evolves over time, either to take the meaning in a different direction or simply to refine or expand the existing direction.
  2. Difference camps or contexts have distinct interpretations.
  3. Different individuals interpret and use terms or concepts differently.
  4. Obsolete terms and concepts which have been superseded with distinct, newer terms and concepts.

-- Jack Krupansky


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