Detecting actions within text

Question

I'm looking for a way to computationally find any actionable clauses within a body of text. Ideally there is a library I could use that I just give a body of text and it spits out the actions that it finds. Next best, would be if there is an algorithm described somewhere that does this which I could try to implement. I don't know much about NLP, but here is what I've found/thought/tried so far.

Most actions occur in imperative sentences, so detecting whether a sentence is imperative or not could help. I'm not sure how best to detect this, but one idea that was given to me was to use the Stanford parser and look for any instances of nsubj. If none are found, then this would be considered an action. Just from some testing I did with some sample sentences, I found that some sentences that I consider actions contain instances of nsubj. Are there more rules I could possibly add to this to improve the precision? I also have no clue how this will fare in terms of recall rate either. Are there any other completely different approaches you could recommend?

Some example sentences that I would like to detect as actions:

Please pass on the enclosed instructions to your teams who are interested.

In the above example, it finds nsubj(interested-12, who-10).

Can you prepare a Powerpoint presentation for 3pm today?

In the above example, it finds nsubj(prepare-3, you-2).

Remember to pick up some milk at the store.

This doesn't contain nsubj.

Answer 1

The area of research you want to look at is local grammars (an approach developed in the late 1990s). It's been used for identifying things like commands, definitions, etc. in text. The idea is that certain functional areas can be identified through certain construction patterns and keywords based on their distribution in a corpus. These patterns constitute a sort of island of regularity (a local grammar) and can be spotted in the text.

Here is an example of their application and here's some more background.

I think the linguistic community outside NLP and corpus studies should pay more attention to local grammars because they have the potential to reveal aspects of how humans deal with complex patterns in texts.

Answer 2

I think that what you're looking at is a task that resembles intent determination. I would peruse some literature on that topic. For instance, it might be good to approach this as a classification task for verb phrases (is the verb phrase an action item or not?). It seems to me that the heuristic, parser-based approach has some problems and the solution is definitely not as trivial as looking for nsubj. You've already found some problematic cases, and there are many more.

The reason your "action" sentence "Please pass on the enclosed instructions to your teams who are interested" contains an nsubj is that it contains a subordinate clause, the relative clause indicated by "who". In the case of the example, if you treat the clauses separately, you'll find that you do indeed have an action item in the clause that doesn't contain nsubj

[Please pass on the enclosed instructions to your teams] who are interested.
(Action item exists in the selected clause)

Please pass on the enclosed instructions to your [teams who are interested].
(Action item doesn't exist in the selected clause)

It seems to me that a more problematic case would concern e.g. modals:

I should eat a sandwich
I think you should eat a sandwich
Please pass on the enclosed instructions to your teams who must attend the meeting.

I would argue that each of these three examples contains the action phrases you're trying to find (and in case of the third sentence, it could contain two such phrases). Each meets your criteria for being a "To do" list type of item. However, each of them contains nsubj.

Furthermore, the Stanford parser gives you an nsubj in this case of what might look like a definite action item:

Do an assignment

You get nsubj(do-1, assignment-3)