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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 - PowerPoint PPT Presentation
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cse@buff
alo
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 | shapiro}@cse.buffalo.edu
S.C. Shapiro
cse@buff
alo
Outline
• Introduction
• Subjective Time
• Time and Bodily Knowledge
• Time and External States
• Summary
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
Cassie
• A Computational Cognitive Agent
• Based on SNePS– Logic-based– Network-based– Knowledge representation, reasoning, and acting.
S.C. Shapiro
cse@buff
alo
Embodied Cassie
• A Cognitive Robot– Hardware– or Software-Simulated
• Separate, but aligned– Body– Mind.
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
Symbol Grounding: Alignmentrobot
green
!
lex lexclassmod classhead
member
class
find lex
actionobject
“Find the green robot.”
B6
S.C. Shapiro
cse@buff
alo
Outline
• Introduction
• Subjective Time
• Time and Bodily Knowledge
• Time and External States
• Summary
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
Subjective Time
• NOW contains SNePS term representing current time.
• NOW moves when Cassie acts or perceives a change of state.
S.C. Shapiro
cse@buff
alo
B6
Representation of Time
find
lex
action object
B1
!
agentact
state time
NOW
!!before after before after
?????????????
I
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
Quantizing Time
Cannot conceptualize fine distinctions in time intervals.
So quantize, e.g. into half orders of magnitude (Hobbs, 2000).
S.C. Shapiro
cse@buff
alo
Movement of Time with Pacemaker
NOW COUNT n
hom
0
KL
PML
t1 t2q
!before after
time duration!
S.C. Shapiro
cse@buff
alo
Outline
• Introduction
• Subjective Time
• Time and Bodily Knowledge
• Time and External States
• Summary
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
Outline
• Introduction
• Subjective Time
• Time and Bodily Knowledge
• Time and External States
• Summary
S.C. Shapiro
cse@buff
alo
The Problem of the Fleeting Now
How can you reason about “now”
if it never stands still?
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
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
cse@buff
alo
Outline
• Introduction
• Subjective Time
• Time and Bodily Knowledge
• Time and External States
• Summary
S.C. Shapiro
cse@buff
alo
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
cse@buff
alo
When Inquire about States
Put them into MTF
According to their typical duration.
S.C. Shapiro
cse@buff
alo
When NOW Moves
• Use Pacemaker to measure old NOW.• Include current actions in MTF.
• Include other states according to their typical durations.