What is the unit of meaning?

Superficially, that is the question: What is the unit of meaning? But, that one question is part of a bundle of questions, including (but not limited to):

1. What is the unit of knowledge?
2. What is the unit of semantics?
3. What is the unit of meaning?
4. What is the unit of communications?
5. What is the unit of expression?
6. What is the unit of thought?
7. What is the unit of facts?
8. What is the unit of reasoning?
9. What is the unit of objectivity?
10. What is the unit of subjectivity?
11. What is the unit of context?
12. What is a unit in a holistic system?

In natural language the obvious choices for a unit are word, sentence, phrase, and morpheme. I would lean towards word or term or sometimes phrase, but at least when it comes to foreign language translation, anything less than a sentence is questionable for capturing meaning. Sure, we can look a word up in a dictionary, but frequently we find that a word will have multiple senses and the context of a phrase, clause, or sentence is needed to decipher which sense is appropriate. Maybe this simply means that word are still an appropriate unit, but that context is needed as well, much in the way that pieces of wood and nails can be units for building, but tools such as a saw and a hammer and a plan are needed to make sense of the units.

In the Semantic Web, we have units such as URI and literals, but it is the statement or triple as a unit of expression that seems the most useful focus. Or maybe not. An RDF statement is somewhat analogous to a natural language statement. A URI or literal string is comparable to a natural language word. The same literal can be used in multiple RDF statements, with a multiplicity of senses, each suggested by the resource and predicate of the RDF statement which contains it.

For now, I would suggest that the word is the natural unit of meaning in natural language, and the URI is the natural unit of meaning in the Semantic Web.

One related question that concerns me: The Semantic Web does not seem to have the concept of sense for URIs that we have in a natural language dictionary. Hmmm...

Language, natural or otherwise, is used to convey meaning from one party to another. Meaning and knowledge exist primarily in the minds of the parties who are communicating. Actual words and sentences or expressions in natural language are knowledge artifacts rather than the actual knowledge and meaning itself. As carefully as we may try, analysis of natural language text can only approximate whatever meaning was intended by the initiator of the expression. So, in some sense, deciding on the unit for natural language text does not necessarily tell us the unit for meaning and knowledge in the human mind. Nonetheless, we need to start somewhere and the knowledge artifacts of natural language are a rich trove to start with.

I'll stop there for now. More thought is needed.

-- Jack Krupansky