Pragmatics

1. Pragmatics • How do we use language to communicate? • Dave Inman NLP Pragmatics

2. Outline • 1. Introduction • 2. Goals and plans • 3. Example of a "primitive plot" plan • 4. Frames and scripts • 5. A "dog" frame • 6. A "restaurant script" • 7. Presuppositions • 8. Rules of discourse • 9. Why don't these work? NLP Pragmatics

3. Introduction • This talk looks at what knowledge we use in everyday discourse, and how we might use this to help a computer understand natural language. • The kinds of knowledge we will consider here are: • Goals and plans • Frames and scripts • Presuppositions • Rules of discourse • Grice's maxims NLP Pragmatics

4. Introduction - Goals and plans • e.g. Email dialogue analysis • If we know what the goal of communication is, or the plan of the communicator, we should be able to limit the range of possible interpretations. If an email requests a meeting, the reply should accept, change or deny the request, for example. NLP Pragmatics

5. Introduction - Frames and scripts • e.g. Shank's restaurant script • If we can describe the use of language in terms of frames (like an object description) or scripts (like a film script) then we may be able to match the natural language against one of these objects, and gain a lot of default expectations NLP Pragmatics

6. Introduction - Presuppositions • "Have you stopped beating your dog." • Language often points to the unstated commonly understood information. We may be able to use inference to find out what this information is. NLP Pragmatics

7. Introduction - Rules of discourse • Grice's maxims • Here we can gain information by knowing that unless there are "funny circumstances" we tend to use language in predetermined ways. For example unless we want to deceive we tell the truth. Such rules should allow us to gain insights if the rules are followed, or to determine what the funny circumstance might be if the rules are not followed. • Why do you think this is? NLP Pragmatics

8. 2. Goals and plans • If we discover the goal of a speaker for example, it should make interpretation of their uttererances easier. • "How much is a train ticket on the 3pm to Bristol?" • "Nothing" would be inappropriate response if no 3pm train • "The next train leaves at 3:30 and costs £30" if plan of speaker is known • Once a plan is known we can fill in the gaps with defaults even if we have no information • We need "plan templates" for "primitive plots" NLP Pragmatics

9. 3. Goals and plans : primitive plots • Problems : • You get fired and need a job • Your cheque bounces and you need to find money • You dog dies and you need companionship • Success : • You ask for a raise and get it • You fix a flat tyre • You need a car so you steal one • Failure • Your marriage proposal is declined • You can't find you wallet • You can't get a bank loan • Loss / Perseverance / Hidden blessing / Mixed blessing etc NLP Pragmatics

10. 4. Goals and plans :Frames and scripts • Frames and scripts act as templates of expectation.Work by Schank and others • They have slots and values • Slots can be • Compulsory • Optional • Default • Procedures • Frames are used for concepts • Scripts are used for sequences of actions / frames NLP Pragmatics

11. 5. A "dog" frame • Make a conversation Frame NLP Pragmatics

12. 6. A "restaurant script" • Write an exam script NLP Pragmatics

13. Goals and plans • Scene 1: Entering • Customer enters restaurant • Customer looks for table • Customer decides where to sit • Customer sits down • Scene 2: Ordering • Scene 3: Eating • Scene 4: Leaving • Fill in the sections above. • Compare your results to your neighbours. • What problems do you have here? NLP Pragmatics

14. 7. Presuppositions • "Have you seen John's car?" • - we should infer that John has a car • "Was it John who stole the money?" • - we want to infer that money was stolen, NOT John stole it • - acceptable reply is "No it was Bill" • - unacceptable reply is "No it was the car" NLP Pragmatics

15. Rules of discourse – Grice’s Maxims • Be brief • Be honest • Be relevant • Be clear NLP Pragmatics

16. Rules of discourse – Grice’s Maxims • Be brief • Give as much info as needed, but not more • "Who is the President of the USA?" • "Clinton" - OK • "A guy who has a wife, 2 daughters, 3 ...called Clinton" - Too much NLP Pragmatics

17. Rules of discourse – Grice’s Maxims • Be honest • Unless we have a goal of humour, escape conviction etc • If you were a criminal would you lie to: • "Do you take sugar in your coffee?" - to a partner • "What is your annual income?" to the police NLP Pragmatics

18. Rules of discourse – Grice’s Maxims • Be relevant • "Can you pass the salt?" • is not a relevant question in most situations, so it must be a request NLP Pragmatics

19. Rules of discourse – Grice’s Maxims • Be clear • unless you have reasons / objectives not to be such as a politician, answering a student's question about exam questions NLP Pragmatics

20. 9. Why don't these work? • Goals and plans • Frames and scripts • Presuppositions • Rules of discourse • Write down 1 reason why each of these may not work. • Compare with your neighbour. NLP Pragmatics

21. 9. Why don't these work? • Goals and plans • How many plots do you need? • How do adapt one plot to make a similar but slightly different one? • How do you match an utterance against a plot? NLP Pragmatics

22. 9. Why don't these work? • Frames and scripts • How do you acquire a new script for a novel situation • (a) Create a new one - maybe we have too many • (b) Update an existing one - which one? • How do we add new knowledge to an existing script • e.g. being short changed to a restaurant script - which other scripts do we need to update? • shop /garage / cinema /theatre • what else? • How do you match an utterance against a frame / script? NLP Pragmatics

23. 9. Why don't these work? • Presuppositions • How do you deal with: • "How many students does Audrey teach?" • If she is on sabbatical leave we cannot presuppose she teaches students. • - acceptable reply is "She does not teach now" • - unacceptable reply is "None" : this is accurate but breaks rules of being relevant NLP Pragmatics

24. 9. Why don't these work? • Rules of discourse • How do we decide what is "normal" and what is a "funny circumstance" ? • How many "funny circumstances" are there? If we have enough "funny circumstances" what value are these guidelines? NLP Pragmatics

25. Conclusions • Language is like the tip of an iceberg. • Context is like the picture on the box. • How do we represent context? e.g. CYC • Can we make do with restricted domains? • Can we do NLP by example? NLP Pragmatics