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Endowing Agents with a Personal Sense of Time

Endowing Agents with a Personal Sense of Time. Haythem O. Ismail & Stuart C. Shapiro Department of Computer Science and Engineering and Center for Cognitive Science State University of New York at Buffalo {hismail | shapiro}@cse.buffalo.edu. Outline. Introduction Subjective Time

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Endowing Agents with a Personal Sense of Time

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  1. Endowing Agents with a Personal Sense of Time Haythem O. Ismail & Stuart C. Shapiro Department of Computer Science and Engineering and Center for Cognitive Science State University of New York at Buffalo {hismail | shapiro}@cse.buffalo.edu S.C. Shapiro

  2. Outline • Introduction • Subjective Time • Time and Bodily Knowledge • Time and External States • Summary S.C. Shapiro

  3. Uses of Timeby a Cognitive Agent • Reason about time • Talk about time • Reason and act in time • Decide to act in timely fashion • Remember acts and when done • Sense current states • Be informed of current states • Be informed of past/future states • Understand & generate NL with correct tense & aspect. S.C. Shapiro

  4. Cassie • A Computational Cognitive Agent • Based on SNePS • Logic-based • Network-based • Knowledge representation, reasoning, and acting. S.C. Shapiro

  5. Embodied Cassie • A Cognitive Robot • Hardware • or Software-Simulated • Separate, but aligned • Body • Mind. S.C. Shapiro

  6. GLAIR Architecture Grounded Layered Architecture with Integrated Reasoning Knowledge Level NL SNePS Perceptuo-Motor Level Sensory-Actuator Level Vision Sonar Motion Proprioception S.C. Shapiro

  7. green find robot Symbol Grounding: Alignment lex lex classhead classmod class ! member lex B6 action object “Find the green robot.” S.C. Shapiro

  8. Outline • Introduction • Subjective Time • Time and Bodily Knowledge • Time and External States • Summary S.C. Shapiro

  9. Deictic Center • <I, YOU, NOW> • Variables whose values are SNePS terms • Aspects of embodiedness • *I: SNePS term representing Cassie • *YOU: person Cassie is talking with • *NOW: current time. S.C. Shapiro

  10. Subjective Time • NOW contains SNePS term representing current time. • NOW moves when Cassie acts or perceives a change of state. S.C. Shapiro

  11. find Representation of Time before after before after ! ! ! ????????????? state time agent act B1 action object B6 I lex NOW S.C. Shapiro

  12. before after before after ! t2 ! t3 NOW NOW NOW Movement of Time v.1 t1 S.C. Shapiro

  13. The Pacemaker • PML process periodically increments variable COUNT. • *COUNT = some PML integer. • Reset to 0 when NOW moves. • Provides bodily “feel” of passing time. S.C. Shapiro

  14. Quantizing Time Cannot conceptualize fine distinctions in time intervals. So quantize, e.g. into half orders of magnitude (Hobbs, 2000). S.C. Shapiro

  15. ! duration time before after ! Movement of Time with Pacemaker q t1 t2 KL PML hom COUNT n NOW 0 S.C. Shapiro

  16. Outline • Introduction • Subjective Time • Time and Bodily Knowledge • Time and External States • Summary S.C. Shapiro

  17. Modality Variables • Similar to Deictic Center. • E.g.: VISION, AUDITION, WHEELS, ARMS • *VISION = Holds(Lookat(Cassie, Stu), t3) • if vision currently occupied by looking at Stu • t3 denotes the time during which Cassie will be looking at Stu • *NOW is during t3 • Set at PML when bodily state starts/ceases. • One state may occupy multiple modalities. S.C. Shapiro

  18. Knowing What You’re Doing • When NOW moves • For each modality variable v • s.t. *v = Holds(s, t) • Make *NOW a subinterval of t • So the agent believes it is now doing everything it is, in fact, doing. S.C. Shapiro

  19. When you stop • When state s ceases • For each modality variable vi • s.t. *vi = Holds(s, ti) • Set vi to nil • Move NOW • Believe each ti is before *NOW. S.C. Shapiro

  20. When you start • When state s starts • For each modality v that s occupies • set v to Holds(s, ti) • Move NOW. S.C. Shapiro

  21. Outline • Introduction • Subjective Time • Time and Bodily Knowledge • Time and External States • Summary S.C. Shapiro

  22. The Problem of the Fleeting Now How can you reason about “now” if it never stands still? S.C. Shapiro

  23. Motivating Joke 9:30:00 AM (Door-to-Door Salesman): May I interest you in a brush? 9:30:02 AM (Homeowner): Not now. 9:30:03 AM (Salesman): Now? S.C. Shapiro

  24. Fleeting Now Example 1 9:15:00: If the walk light is on now, cross the street. = If the walk light is on at 9:15:00, cross the street. 9:15:01: Turn to look at walk light. 9:15:02: The walk light is on at 9:15:02. Should you cross the street? Yes, but why? S.C. Shapiro

  25. Fleeting Now Example 2 12:15:00: “Is John having lunch now?” 12:15:02: Agent walks to John’s office. 12:17:00: Agent sees John at his desk, eating. 12:19:00: Agent reports “yes”. Appropriate granularity. S.C. Shapiro

  26. Fleeting Now Example 3 12:15:00: “Is John having lunch now?” Agent knows John is at home without a phone. Agent contemplates driving to John’s home. Don’t bother---inappropriate granularity. S.C. Shapiro

  27. The Vagueness of “now” I’m now giving a talk. I’m now teaching a course. I’m now visiting Houston. I’m now living in Buffalo. The agent is now walking to John’s office. The agent is now seeing if John is eating lunch. Multiple now’s at different granularities. S.C. Shapiro

  28. NOW-MTF Maximal Temporal Frame based on *NOW NOW Semi-lattice of times, all of which contain *NOW, any of which could be meant by “now” Finite---only conceptualized times of conceptualized states S.C. Shapiro

  29. Moving NOW with MTF NOW S.C. Shapiro

  30. Typical Durations “If the walk light is on now, cross the street.” Relevant duration is typical duration of walk lights. “Is John having lunch now?” Relevant duration is typical duration of lunch. Use quantized typical durations when updating NOW-MTFs. S.C. Shapiro

  31. Using Appropriate Granularity Lunch time Lunch? Lunch! NOW Yes! S.C. Shapiro

  32. Outline • Introduction • Subjective Time • Time and Bodily Knowledge • Time and External States • Summary S.C. Shapiro

  33. Summary • Distinguish body & mind, but align them. • Body (PML): • What people and things look like. • Primitive and routine actions. • Time intervals. • Pacemaker: Feel for elapsing time. • Deictic Center variables. • Modality variables. • Mind: • Conceptualized people, things, actions, times, states. S.C. Shapiro

  34. When Inquire about States Put them into MTF According to their typical duration. S.C. Shapiro

  35. When NOW Moves • Use Pacemaker to measure old NOW. • Include current actions in MTF. • Include other states according to their typical durations. S.C. Shapiro

  36. For More Information http://www.cse.buffalo.edu/sneps/ S.C. Shapiro

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