S.C. Shapiro 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 |

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

S.C. Shapiro Uses of Time by 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 Cassie A Computational Cognitive Agent Based on SNePS –Logic-based –Network-based –Knowledge representation, reasoning, and acting.

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

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

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

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

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

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

S.C. Shapiro Movement of Time v.1 t1 t2! beforeafter t3! beforeafter NOW

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

S.C. Shapiro Movement of Time with Pacemaker NOW COUNTn hom 0 KL PML t1 t2 q ! beforeafter time duration !

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

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

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

S.C. Shapiro 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 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 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 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 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 NOW-MTF 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 Maximal Temporal Frame based on *NOW

S.C. Shapiro Moving NOW with MTF NOW

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

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

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

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

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