Abstraction applied to variables.Ahigher level of data abstraction
uses fewer variables, fewer values for those variables, and simpler data types.
data state. The part of the state that does not determine control flow. Contrast to
control state.
dead state. A state from which an accepting state cannot be reached. A system that
reaches a dead state experiences a liveness failure. Dead states indicate deadlocks
or livelocks.
deadlock. A liveness failure where a program stops executing because it reaches a
state where no actions are enabled.
Appendices 319
decrementing action weight. In a certain kind of strategy, a number associated
with an action that determines its probability of selection. The weight is initially
assigned to some value and decremented each time the action is executed.
De Morgan??™s Law. Describes how to negate expressions involving and and or: !(p
&& q) == !p || !q.
defect. Incorrect code or missing code that can cause a failure. Also called a fault
or a bug.
delegate. In C#, a type whose instances are methods. In an asynchronous stepper,
the observer is assigned to a delegate.
dependent feature. A feature with no state variables of its own. Dependent features
are often used for scenario control.
derived state. Methods or properties that query the state but do not change it.
design. A description of how a system or program is built up from parts and how
the parts communicate.
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