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Issues in Temporal and Causal Inference Pei Wang Temple University, USA Patrick Hammer Graz University of Technology, Austria
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Predication and Explanation Make conclusions about the future and the past based on past experience. Causal inference: Drawing a conclusion about a causal connection based on the conditions of the occurrence of an effect Causal relation: Relating a cause event to an effect event.
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Classical Causality The classical notion of causality is that every event E has a unique cause C, which explains why E happened, and can predict its happing in the future. Formal models of causality: Logical implication, e.g., C E Conditional probability, e.g., P(E|C)
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Limitations of Classical Models Insufficient knowledge: It is difficult, to find the “true cause” of an event. Insufficient resources: It is difficult to consider all candidate causes. The criteria of “causality” are domain- dependent Causal beliefs are revisable.
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NARS as a Reasoning System Non-Axiomatic Reasoning System: a language for representation a semantics of the language a set of inference rules a memory structure a control mechanism
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NARS as an AGI System “Intelligence”: the capability of a system to adapt to its environment and to work with insufficient knowledge and resources Assumption of Insufficient Knowledge and Resources (AIKR): To rely on finite processing capacity To work in real time To be open to unexpected tasks
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Fundamental Issues/Properties Under AIKR, the system cannot guarantee absolute correctness or optimality anymore. Validity and rationality become relative to the available knowledge and resources. (Related: Strive for simplicity, partial descriptions, coexisting interpretations, forgetting)
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Knowledge Representation Term names a concept, e.g., bird Compound Term is composed from other terms, e.g., ([yellow] ∩ bird) Inheritance (→ ) is a relation representing the substitutability of one term by another one, e.g., {Tweety} → ([yellow] ∩ bird) $x → raven $x → [black]
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Truth-Value Definition The truth-value of a statement is a pair of real numbers in [0, 1], and measures the evidential support to S P f, c Total evidence: w = w + +w - Frequency: f = w + /w Confidence: c = w / (w +1)
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Temporal Knowledge An event is a statement whose truth- value has a duration A term can name a concept with temporal meaning, e.g., today A compound term can specify the temporal order among components e.g., $x → [leaving] / $x → [gone]
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Temporal Inference Temporal inference in NARS processes the logical factor and the temporal factor in parallel Classical (Pavlovian) conditioning can be processed as temporal inference
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Classical Conditioning The observation of a → c followed by a → u can be generalized by induction into $x → c / $x → u Repeated observations can strengthen the belief by increasing its confidence New observation of b → c may lead to anticipation b → u
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Classical Conditioning (cont.) Unrealized anticipation generates negative evidence for the belief The abduction rule takes the belief and an observation of d → u to produce the conclusion that d → c may have occurred Whenever there are conflicting conclusions, the choice rule compares truth-value and simplicity
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Conclusion Prediction and explanation can be carried out without a well-defined “causal relation” Causal relation is learned, revisable, subjective, and domain-dependent It is still possible to distinguish causality from correlation, enabling condition, and so on
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