VDM-RT State Types Sample Clauses

VDM-RT State Types. We describe the types needed to describe the state of a VDM-RT model, in terms of CPUs, threads, busses, statements, objects, message and so on. The majority of the types are adapted from [28] but modified for ▇▇▇▇▇▇▇▇/HOL, for example by the replacement of union types with disjoint unions and algebraic datatypes. Moreover the names of primitives and types differ slightly and we have made a number of simplifications. Datatypes not directly relevant for the semantics (such as patterns) are omitted from the presentation, though present in the Isabelle theories. We also specify some basic types like VDMValue and VDMExpr, and functions like the VDM-SL typing relation x :v t that are omitted. A number of identifier types are also defined, including: • cla-id – class identifier • obj-id – object identifier • op-id – operation identifier • fun-id – function identifier • thr-id – thread identifier • bus-id – bus identifier • var-id – variable identifier We first describe bindings Σ, that are partial functions mapping variables identifiers to VDM values. They are used widely in the semantics to represent state spaces, let definitions, and the result of executing pattern matches. type-synonym Σ = var-id - VDMValue Next we defined pending updates to a state, which are partial mappings from object identifiers to bindings. Each write within an object does not update the global CPU state until specific synchronisation times. Until then, they are stored in a pending buffer. type-synonym Pending = obj-id - Σ An assignment associated variable identifier, or object and variable identifier, with an expres- sion. record Assignment = × asntarget :: var-id + (obj-id var-id) asnexp :: VDMExpr record CallContext = ccpending :: Pending ccstate :: Σ ccpost :: VDMExpr option type-synonym Definition = var-id ∗ VDMExpr The statement type specifies all the different kind of statements that can be constructed in VDM-RT. = Skip A null statement | | | × × × AsyncCall (name: (obj-id op-id) + (cpu-id obj-id op-id)) (args: VDMExpr list) Asychronous call, consisting of a method identifier and arguments × × × | × SyncCall (ctarget: (var-id + (cpu-id thr-id)) option) (name: (obj-id op-id) + (cpu-id obj-id op-id)) (args: VDMExpr list) Sychronous call | × Cases (exp: VDMExpr) (cases: (Pattern Stm) list) Stm option Case statement | Cycles (cycles: VDMExpr) (body: Stm) Cycles statement | DurOrPDur (durOf : DurOrPDur) Either a duration statement or a (semantic) partial duration statement | ForIndex ...
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