- A concept is a fundamental unit of meaning.
- A concept is a unitary mental representation.
- A concept is an atomic unit of thought.
Are 1., 2. and 3. equivalent?
What is 'abstract thought'? Is it the same as: thought about what are referred to above as abstract things? Is this still thought of the sort that takes place in human brains? If yes, what sort of technology does the author of this sentence have in mind? If no, what sort of thought is it, that does not take place in human brains?
If concepts are mental representations, as according to 1., or units of thought, as according to 2., how -- leaving aside complex brain surgery -- could concepts be captured or shared or manipulated? How could concepts thus conceived (i.e. as creatures of human mental activity) play a role in computational interoperability?
Does this mean that the concepts which are the atomic units of thought -- the concepts, presumably, with which human thinkers operate when they have thoughts -- are to be replaced by other, standardized, concepts when Code Systems are introduced? If so, where do these new standardized concepts live? Are they still 'units of thought'? And if so, who or what is the thinker who is having the relevant thoughts?
Our thoughts, or mental representations, are to be standardized by Code Systems. What does this mean? What is the end-result of such standardization? Concepts themselves, we are told, are representations of real or abstract things, and Code Systems provide representations of concepts. From this we can infer:
4. Code Systems provide representations of representations of real or abstract things.
But then a further problem arises; for if Code Systems provide representations of the very concepts they themselves standardize, does this mean that they provide representations of these concepts as they existed before standardization; or that they provide representations of the very concepts which they themselves have standardized? How can something be a representation of X and a standardization of X at one and the same time?
5. Meanings are associated with concepts.
According to 1. a concept is a unit of meaning. According to 5. there are meanings associated with concepts. Which is correct?
6. Symbols can stand in for meanings
What could this mean? Surely the symbols are the sorts of things that have meanings.
7. There are descriptive names which are concept representations.
This means, I think, that there are descriptive names such as 'person' or 'arm' which represent concepts. Such descriptive names, presumably, also have meanings. Are these meanings also concepts? If so, are they the same concepts as the concepts which the descriptive names represent? If not, are there some meanings of descriptive names which are concepts, and other meanings which are not concepts? And if so, how do we then tell the difference between the two?
There is an issue, here, of what is called the 'use-mention confusion', illustrated by the sentence "Swimming is healthy and has two vowels." The use-mention confusion occurs when it is not realized that "swimming" refers to swimming (and not to "swimming"), that "London" refers to London (and not to "London"), and so on.
We are told that we can put together the symbol for "arm" with the symbol for "left" in order to construct a concept representation for "left arm". Not so, however, The symbol for "arm" is '"arm"'. ("Arm" is the symbol, not for "arm", but for arm.)
[See the second comment by Spero melior below on a further problem raised by this paragraph -- which is that it suggests that the combination of the concepts arm and left would itself constitute a concept, which conflicts with HL7's own definition of concept as an atomic unit of thought.]
So that's clear, then.
1. The above continues my commentary here.
2. For an example of a set of definitions which, I believe, comes closer to the level of precision that is required, in this difficult field, see here, and especially the distinction between what are there called "levels 1, 2 and 3." For further discussion of the problems we face in understanding the meaning of the term 'concept' in computer science circles -- including arguments on behalf of the view that we should abandon this term entirely, see here.
3. For a discussion of the historical source of some of the confusions conveyed in the above document, including the delightful passage concerning "technology able to directly transmit or manipulate abstract thought", see here.
4. Update June 30, 2011: See now Grahame Grieve and Thomas Beale discussion here.