singular part of speech for multi-word units and expressions?

Question

Part of speech assignment provides a pos to a word. In many pos systems this can occasionally produce errors due multi-word expressions of one form or another. When 'we' look at the text, we may see it as a compound, common sequence, set phrase or idiomatic expression etc. And we tend to see them as singular pieces. For example, frying pan, computer screen, kicked off. These are not really individual words, but singular concepts represented with spaces in them.

So the thought in my mind is whether it would make sense to assign only a single pos to some/all mwe's? Has anyone done research into such an approach? Are there any obvious grammatical flaws people can see?

Answer 1

I find the question and much of the discussion so far contaminated by confusions between language and writing and between word and phrase. "Frying pan" is a noun; it is a compound, made up of two words, "frying" and "pan", which are both nouns. It is not a noun phrase, though you might be able to find a noun phrase (e.g., the subject of a sentence) which just this noun occurring alone, but at the moment, no such example occurs to me.

The fact that "frying pan" would customarily be spelled with a space between the two nouns that make up the compound, rather than "frying-pan" or "fryingpan", has really nothing to do with its grammatical category. Why should it? The space there is just a spelling convention, not a linguistic hypothesis.

It may be part of your understanding of the term "phrase" that a phrase has more than one word. You ought to try not to carry over this understanding to grammar, because the terms "noun" and "noun phrase", as used in grammatical analysis, have nothing to do with whether a constituent has more than one word. One of the first things that has to be done in teaching modern grammar to a student who is trained in traditional grammar is to convince the student that a noun can never be the subject of sentence -- only a noun phrase can.

Now, can a multi-word constituent ever be a word, as I have claimed above for "frying pan"? Yes, and the case of word compounds is one such case. There are others. Here is a pretty clear one. A general principle of coordination is that the constituent created by combining two constituents has the same grammatical category as the constituents that were combined. Combining the verb phrases "run" and "eat sardines" with "and" gives the verb phrase "run and eat sardines", for instance. Note that I've categorized "run" as a verb phrase, even though it has just one word in it.

Now consider the perfectly ordinary sentence "The man and woman left". What category is "man and woman"? It has more than one word -- does that make it a phrase? No, it's just a noun, formed by the general rule of coordination mentioned above. Start with two nouns, connect them with "and", and you get something of that same category -- a noun. So, if we can agree that a noun is a word, clearly here is a case of a multi-word word.

Answer 2

Sorry, but for some reason I cannot comment - I've had to create an account!

jlawler
Indeed, NounPhrases cover many things, but it is also far larger in scope than what I referred to (no articles or determiners unless they are part of the "entity"). I think it also misses phrases such as "kicked off". I'm not disputing that NP is correct, it just seems slightly further along the chain than where I'm looking at at present.

hippietrail
I'm aware of the differences and volume of PoS tagsets. That doesn't negate the question though. I do agree that some of the approaches are somewhat askew. Look at how long people went before fathoming the issues regarding multi-word units.

Maybe a rephrase would be better?

If you had the choice, when processing text for PoS tagging, would you treat set phrases and obvious multi-word entities as singular "words" (regardless of the presence of hyphens/spaces)?
Would you tag "frying pan" as [Adjective Noun], or just [Noun], or an alternative noun representation ([Comp.Noun], [Noun-Comp], [Noun Comp-Adj/Nn etc.)? Does anyone know of a tagging system or approach that does or has tried this?

Thank you both for commenting. I hope I've made it a little clearer.

curiousdannii
Yes. The examples given were two-word phrases. And yes, many taggers will accurately tag them most of the time, in most cases. And yes, higher level parsers would also identify them as being adjoined.
But that is Not the question being asked. The question asked was whether it should be the case that they are tagged as a collective, rather than as individually. The question asked was whether there were any known systems that did this, or theories that covered treating MWE's as singular pieces rather than multi-part pieces. Think of it this way, they are not individual words when you read them, so why should they be tagged as such? In certain structures/context, they convey different semantics when together than individually. When that happens, they stop being separate words, and instead produce a singular entity. "Big pan" is not the same as "frying pan". "falling pan" is not the same either. Nor is "full-", "deep-", "shiny-", "old-", "ageing-" etc. Yet many of those will fit one of the patterns that "frying pan" does, depending on what PoS you assign to the first word.

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And Moderators/Admin - sorry for the answer-abuse ... but unsure how to respond considering the situation.