1. CSE573 Autumn 1997 1 02/20/98 Planning/Language Administrative –PS3 due 2/23 –Midterms back today –Next topic: Natural Language Processing reading Chapter 10; skip 10.8 and 10.9 Last time –extensions to the operator language conditional effects universal quantification –reading a UCPOP plan output This time –Graphplan –Natural language processing

2. CSE573 Autumn 1997 2 NLP Perspective An interesting cognitive problem –language is the most “human” communication modality, so it seems impossible to understand human intelligence without understanding how language works –Turing test looked on ability to communicate in an unrestricted natural language dialogue as the definition of intelligence An interesting practical problem: incredible extensions to usefulness of computers if problems could be solved in –speech recognition and understanding (no more phone menus!) –handwriting recognition and understanding (a PDA that actually works) –machine translation (electronic funds transfers and more complex multi- national transactions) –text recognition (intelligent information retrieval)

3. CSE573 Autumn 1997 3 The main problem Understanding language is “AI Complete” –in order to do it you have to understand every other facet of intelligence as well --- planning, reasoning about physical systems, geometrical and spatial reasoning, diagnosis, etc. etc. The history of natural language processing in AI is a process of discovering just how difficult and deep the problem is Ways to make the problem easier –work in limited domains (newspaper stories about earthquakes) –work with simpler syntax (will respond to information requests or to simple commands but cannot understand arbitrary sentences about the domain). Example: electronic funds transfers; intelligent database front-ends; Truckworld scenarios

4. CSE573 Autumn 1997 4 The usual breakdown of language processing tasks Signal understanding: translate signals (spoken speech or written characters) into some internal symbolic form. Produce phonemes or characters. Phonology: group phonemes into morphemes Morphology: group morphemes into words Syntax: parse words into phrases, phrases into sentences Semantics: connect words to objects and concepts in some internal representation language Pragmatics: infer what is desired from what is said in a sentence Discourse: constructing an argument, negotiating an agreement, (communication among agents) We are here Bottom up processing Top down processing

5. CSE573 Autumn 1997 5 Our Main Task: A Command Processor The system will parse, interpret and execute commands in a simple world –Blocksworld: “Pick up the green sphere on top of the yellow cube” “Put it down next to the red cube.” –Truckworld: “Recycle the red broken glass.” “Refuel using the fuel drum at position 7.” Parsing: is the sentence well formed? Semantic Interpretation: –does the command make sense given the current state of the world? –what do the pronouns refer to? Execution: simple call to an execution system (Macrops or behaviors)

6. CSE573 Autumn 1997 6 Our Limited Problem 12345 Arm can lift at most one object at a time Pyramid can be put on top of a block but not below Sphere cannot be put on top or below any block Actions pick up top block at current position put down block being held move to another position