The Specification Language TLA+

Merz, Stephan

doi:10.1007/978-3-540-74107-7_8

Cited by 30 publications

(12 citation statements)

References 39 publications

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“…KerA + is a subset of TLA + Ð except for the three operators discussed above Ð and the meaning of the operators coincides with the description in the book by [Lamport 2002]. Denotational semantics of TLA + in first-order logic is given by [Merz 2008]. In Sections 6ś10, we give a brief description of each KerA + operator along with the semantics for finite structures in terms of rewriting rules.…”

Section: Kera+: the Kernel Language Of Tla+ Expressionsmentioning

confidence: 94%

TLA+ model checking made symbolic

Konnov

Kukovec²,

Tran³

2019

Proc. ACM Program. Lang.

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TLA + is a language for formal specification of all kinds of computer systems. System designers use this language to specify concurrent, distributed, and fault-tolerant protocols, which are traditionally presented in pseudo-code. TLA + is extremely concise yet expressive: The language primitives include Booleans, integers, functions, tuples, records, sequences, and sets thereof, which can be also nested. This is probably why the only model checker for TLA + (called TLC) relies on explicit enumeration of values and states. In this paper, we present APALACHE Ð a first symbolic model checker for TLA +. Like TLC, it assumes that all specification parameters are fixed and all states are finite structures. Unlike TLC, APALACHE translates the underlying transition relation into quantifier-free SMT constraints, which allows us to exploit the power of SMT solvers. Designing this translation is the central challenge that we address in this paper. Our experiments show that APALACHE outperforms TLC on examples with large state spaces. CCS Concepts: • Theory of computation → Logic and verification; • Software and its engineering → Model checking; Specification languages.

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Section: Kera+: the Kernel Language Of Tla+ Expressionsmentioning

confidence: 94%

TLA+ model checking made symbolic

Konnov

Kukovec²,

Tran³

2019

Proc. ACM Program. Lang.

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“…Transition formulas in TLA + are first-order terms and formulas with flexible variables (unprimed and primed ones). We give the necessary definitions of TLA + semantics, whereas details can be found in [19]. An interpretation I defines a universe |I| of values and interprets each function symbol by a function and each predicate symbol by a relation.…”

Section: Soundness Of Our Approachmentioning

confidence: 99%

Extracting symbolic transitions from TLA+ specifications

Kukovec

Tran

Konnov

2020

Science of Computer Programming

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In TLA + , a system specification is written as a logical formula that restricts the system behavior. As a logic, TLA + does not have assignments and other imperative statements that are used by model checkers to compute the successor states of a system state. Model checkers compute successors either explicitly-by evaluating program statementsor symbolically-by translating program statements to an SMT formula and checking its satisfiability. To efficiently enumerate the successors, TLA's model checker TLC introduces side effects. For instance, an equality x = e is interpreted as an assignment of e to the yet unbound variable x. Inspired by TLC, we introduce an automatic technique for discovering expressions in TLA + formulas such as x = e and x ∈ {e1,. .. , e k } that can be provably used as assignments. In contrast to TLC, our technique does not explicitly evaluate expressions, but it reduces the problem of finding assignments to the satisfiability of an SMT formula. Hence, we give a way to slice a TLA + formula in symbolic transitions, which can be used as an input to a symbolic model checker. Our prototype implementation successfully extracts symbolic transitions from a few TLA + benchmarks.

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“…Starting in the early 1990s and encouraged by successful experiments with TLP [21], a prototype proof system for TLA based on the Larch Prover, Lamport developed the specification language TLA + . The language is described in the book Specifying Systems [43]; the Hyperbook and Lamport's video series [46,48] provide excellent tutorial introductions, whereas the description of TLA + in [56] focuses on the semantics of the language. TLA + is based on a variant of Zermelo-Fraenkel set theory with choice (ZFC) for describing the data manipulated by an algorithm.…”

Section: Overall Design Of Tla +mentioning

confidence: 99%