Polyscheme
John Laird
February 21, 2008
Major Observations
• Polyscheme is a FRAMEWORK not an architecture
– Explicitly does not commit to specific primitives for knowledge representation
and processing
– Provides a control structure to integrate together processing modules for a
given system/agent
• Integration is at the level of individual common functions
– Instead of Soar’s PSCM functions (elaborate, proposal, evaluate, select, apply)
– Polyscheme seems to have more varied functions and oriented around what is
reasoned about (time, causality, events) instead of action.
– Emphasizes multiple algorithms as opposed to multiple sources of knowledge
– Attempts to have interaction between modules for individual steps
– Segregates knowledge based on implementation medium
• Similar to Soar, but not based on sources of knowledge from learning.
• Soar has a fixed set of modules and has tighter integration of those modules
– But does not provide a means to easily integrate new modules
– Soar does not provide parallel integration – rules – impasses – memories …
Claims 1-3
1. Cognitive substrate hypothesis: “a relatively small set of
properly integrated data structures and algorithms can
underlie the whole range of cognition required for humanlevel intelligence.”
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Computational problems that need to be solved: “… reasoning
about temporal intervals, causal relations, identities between
objects and events, ontologies, beliefs, and desires.”
“… reasoning about time, space, part-hood, categories,
causation, uncertainty, belief, and desire.”
“The cognitive substrate hypothesis suggests that once a set of
computational mechanisms, in other words, a cognitive
substrate, that solves the problems of human-level AI for this
set of problems is constructed, achieving the rest of humanlevel AI will be a relatively easy problem.”
Claims 2
1.
2.
“Identifying and implementing a cognitive substrate will accelerate
progress toward human-level intelligence.”
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“Creating intelligent systems for new domains is accelerated.”
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“It took very little extra work to design a parser once the structural dualities
between syntax and physical law were found. No new algorithms need to be
designed, thus making the procedural profusion problem less severe.”
“As work with Polyscheme illustrates, these approaches enable
great progress in solving the integration problems associated with
implementing a cognitive substrate.”
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“…the problem of achieving human-level AI is reduced and
simplified.”
– “Instead of needing enormous databases of knowledge and hundreds or
thousands of algorithms to achieve human-level intelligence,
researchers can focus on solving the problems of human-level AI for a
relatively small (but still difficult) set of problems knowing that other
domains can be addressed by mapping them onto a substrate.”
Claims 3
• Systems built using Polyscheme demonstrate
that algorithmic hybrids implemented using a
focus of attention can (1) exhibit more
characteristics of intelligence than individual
computational methods alone and (2) deal with
problems that have formerly been beyond the
reach of synthetic computational intelligence.”
Theoretical Picture
Individual and
Hybrid Algorithms
Stochastic
Simulation
]Forward Inference
Subgoaling
Simulate Alternate Worlds
Identity Matching]
[store information, offer
opinion, forward inference,
request information (subgoal)
identity, represent alternative
worlds]
Multiple
Implementations
Neural Networks
Forward Rule
Changing (?)
Ontologies
Cognitive substrate = “…
reasoning about time, space,
part-hood, categories,
causation, uncertainty, belief,
and desire.”
Focus of attention fuses results of specialists’ inferences together and a set of attentioncontrolling strategies shape flow of computation.
specialists
Search
Common Functions
Key Ideas in Implementation
•
Specialists
– Implementations of specific methods/algorithms
– Appear to be no constraint on how implemented.
– “Polyscheme modules can have arbitrarily large, varied and persistent memories …”
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Communication between specialists
– Propositional language
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“Specialists must be able to translate back and forth into this language in order to inform other specialists of
their inferences and receive knowledge from other specialists.”
Focus of Attention
– A proposition that all specialists focus on.
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Behave is a sequence of “attention fixations” (involving all specialists) called
“focus traces”.
“When an algorithm performs a common function on a proposition, we say it
attends to or fixes its attention on this proposition.”
No fixed control structure
– But seems you “implement” one through controlling attention fixation.
•
Execution of specialists are interleaved (serial and parallel) to process focus of
attention.
Polyscheme Control Loop
• Do forever:
– A = FM.getNextFocus().
– For all pairs of specialists (S1, S2)
• S1.store (P, S2.opinionOn(A))
– For all S
• S.modifyFM(A)
Evaluation
• What about
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Computational resources required
Bounded execution – guaranteed reactivity
Required knowledge to generate/control behavior
Types of knowledge that can be used to
generate/control behavior
Reliability
Ease of modification (and debugging)
Expressiveness
Learnability