Degreeswhen

Degreeswhen is a formalism used in knowledge representation and temporal reasoning to attach a time-stamped degree of truth to propositions. It represents each assertion with a pair (d, t), where d is a confidence level in [0,1] and t is a point in a temporal domain, allowing belief strength to reflect its recency.

In this framework, a degreeswhen value DW(p) = (d, t) expresses that the proposition p holds with truth degree d at time t. The approach extends fuzzy logic by incorporating time, enabling the modeling of dynamic knowledge states. Operators generalize fuzzy connectives to include temporal aspects; for example, conjunction may use the minimum of the truth degrees and assign the time of the latest operand, while negation flips the degree to 1 − d and may preserve or shift the timestamp depending on the chosen semantics.

History and usage: The idea of attaching time to graded truth values emerged in the early 2010s within discussions of dynamic knowledge representation and uncertainty. The term degreeswhen has appeared in several papers to describe the dual-parameter form, though specific operational choices vary by author and application.

Applications: Degreeswhen is used in temporal databases, sensor data fusion, and belief revision systems where both confidence and recency influence decisions. It supports scenarios where outdated high-confidence information should yield to newer, lower-confidence observations, or where recent high-confidence data dominates earlier inputs.

See also: fuzzy logic; temporal logic; probabilistic logic; dynamic epistemic logic.