Knowledge and reasoning

Vocabulario

English	Significado
propositional logic	Logic combining statements with truth values using logical connectives.
inference/ˈɪnfərəns/	Deriving conclusions from premises using a reasoning rule or model.
forward chaining	Applying rules to known facts to derive additional conclusions.
backward chaining	Starting with a goal and working backward to facts or subgoals that could support it.

English

Rules and consequences

Propositional logic: facts and rules ($P \to Q$); inference applies modus ponens. Forward chaining floods from the facts; backward chaining aims from the query — symbolic reasoning draws conclusions the data never saw.

{exercise:uni-cs1302-rules}

Práctica

Forward chaining starts from —

Dificultad 1/5 · 100 monedas + un pequeño bono en el primer intento de hoy

English

F1 Storm; F2 Weekend; R1 Storm → Delayed; R2 Weekend → HeavyTraffic; R3 HeavyTraffic → Delayed; R4 Delayed → RefundRisk. Forward chaining: wave one derives Delayed and HeavyTraffic, wave two RefundRisk.
Backward chain for RefundRisk: goal ← Delayed (R4) ← Storm (R1) ← fact: proved in three steps, R2/R3 never fire — goal-directed search.

{exercise:uni-cs1302-kb}

Práctica

The course KB derives RefundRisk in — waves

Dificultad 1/5 · 100 monedas + un pequeño bono en el primer intento de hoy

English

Every step is modus ponens on assumed rules, so derivations cannot invent falsehood; completeness (every consequence reachable) is the harder property.
To prove $Q$ by refutation: assume $\neg Q$, derive the empty clause by resolution — the machinery behind SAT solvers. The converse error ($P \to Q$ read as $Q \to P$) is the classic trap.

{exercise:uni-cs1302-sound}

Práctica

Modus ponens makes inference —

Dificultad 1/5 · 100 monedas + un pequeño bono en el primer intento de hoy