arXiv subjects

Noemi Passing

Publications and source records attributed to Noemi Passing.

7 recordsLinked to original sources

arXiv2023

Synthesizing Dominant Strategies for Liveness (Full Version)

Reactive synthesis automatically derives a strategy that satisfies a given specification. However, requiring a strategy to meet the specification in every situation is, in many cases, too hard of a requirement. Particularly in compositional synthesis of distributed systems, individual winning strategies for the processes often do not exist. Remorsefree dominance, a weaker notion than winning, accounts for such situations: dominant strategies are only required to be as good as any alternative strategy, i.e., they are allowed to violate the specification if no other strategy would have satisfied it in the same situation. The composition of dominant strategies is only guaranteed to be dominant for safety properties, though; preventing the use of dominance in compositional synthesis for liveness specifications. Yet, safety properties are often not expressive enough. In this paper, we thus introduce a new winning condition for strategies, called delay-dominance, that overcomes this weakness of remorsefree~dominance: we show that it is compositional for many safety and liveness specifications, enabling a compositional synthesis algorithm based on delay-dominance for general specifications. Furthermore, we introduce an automaton construction for recognizing delay-dominant strategies and prove its soundness and completeness. The resulting automaton is of single-exponential size in the squared length of the specification and can immediately be used for safraless synthesis procedures. Thus, synthesis of delay-dominant strategies is, as synthesis of winning strategies, in 2EXPTIME.

cs.LO↗

arXiv2022

Compositional Synthesis of Modular Systems (Full Version)

Given the advances in reactive synthesis, it is a natural next step to consider more complex multi-process systems. Distributed synthesis, however, is not yet scalable. Compositional approaches can be a game changer. Here, the challenge is to decompose a given specification of the global system behavior into requirements on the individual processes. In this paper, we introduce a compositional synthesis algorithm that, for each process, constructs, in addition to the implementation, a certificate that captures the necessary interface between the processes. The certificates then allow for constructing separate requirements for the individual processes. By bounding the size of the certificates, we can bias the synthesis procedure towards solutions that are desirable in the sense that the assumptions between the processes are small. Our experimental results show that our approach is much faster than standard methods for distributed synthesis as long as reasonably small certificates exist.

cs.LO↗

arXiv2022

Reactive Synthesis of Smart Contract Control Flows

Smart contracts are small but highly error-prone programs that implement agreements between multiple parties. We present a reactive synthesis approach for the automatic construction of smart contract state machines. Towards this end, we extend temporal stream logic (TSL) with universally quantified parameters over infinite domains. Parameterized TSL is a convenient logic to specify the temporal control flow, i.e., the correct order of transactions, as well as the data flow of the contract's fields. We develop a two-step approach that 1) synthesizes a finite representation of the - in general - infinite-state system and 2) splits the system into a compact hierarchical architecture that enables the implementation of the state machine in Solidity. We implement the approach in our prototype tool SCSynt, which - within seconds - automatically constructs Solidity code that realizes the specified control flow.

cs.LO↗

arXiv2022

Temporal Stream Logic modulo Theories (Full Version)

Temporal stream logic (TSL) extends LTL with updates and predicates over arbitrary function terms. This allows for specifying data-intensive systems for which LTL is not expressive enough. In the semantics of TSL, functions and predicates are left uninterpreted. In this paper, we extend TSL with first-order theories, enabling us to specify systems using interpreted functions and predicates such as incrementation or equality. We investigate the satisfiability problem of TSL modulo the standard underlying theory of uninterpreted functions as well as with respect to Presburger arithmetic and the theory of equality: For all three theories, TSL satisfiability is highly undecidable. Nevertheless, we identify three fragments of TSL for which the satisfiability problem is (semi-)decidable in the theory of uninterpreted functions. Despite the high undecidability, we present an algorithm - which is not guaranteed to terminate - for checking the satisfiability of a TSL formula in the theory of uninterpreted functions and evaluate it: It scales well and is able to validate assumptions in a real-world system design.

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arXiv2021

Specification Decomposition for Reactive Synthesis

Reactive synthesis is the task of automatically deriving a correct implementation from a specification. It is a promising technique for the development of verified programs and hardware. Despite recent advances in terms of algorithms and tools, however, reactive synthesis is still not practical when the specified systems reach a certain bound in size and complexity. In this paper, we present a sound and complete modular synthesis algorithm that automatically decomposes the specification into smaller subspecifications. For them, independent synthesis tasks are performed, significantly reducing the complexity of the individual tasks. Our decomposition algorithm guarantees that the subspecifications are independent in the sense that completely separate synthesis tasks can be performed for them. Moreover, the composition of the resulting implementations is guaranteed to satisfy the original specification. Our algorithm is a preprocessing technique that can be applied to a wide range of synthesis tools. We evaluate our approach with state-of-the-art synthesis tools on established benchmarks: The runtime decreases significantly when synthesizing implementations modularly.

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arXiv2020

Verified Rust Monitors for Lola Specifications

The safety of cyber-physical systems rests on the correctness of their monitoring mechanisms. This is problematic if the specification of the monitor is implemented manually or interpreted by unreliable software. We present a verifying compiler that translates specifications given in the stream-based monitoring language Lola to implementations in Rust. The generated code contains verification annotations that enable the Viper toolkit to automatically prove functional correctness, absence of memory faults, and guaranteed termination. The compiler parallelizes the evaluation of different streams in the monitor based on a dependency analysis of the specification. We present encouraging experimental results obtained with monitor specifications found in the literature. For every specification, our approach was able to either produce a correctness proof or to uncover errors in the specification.

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arXiv2020

Dependency-based Compositional Synthesis (Full Version)

Despite many recent advances, reactive synthesis is still not really a practical technique. The grand challenge is to scale from small transition systems, where synthesis performs well, to complex multi-component designs. Compositional methods, such as the construction of dominant strategies for individual components, reduce the complexity significantly, but are usually not applicable without extensively rewriting the specification. In this paper, we present a refinement of compositional synthesis that does not require such an intervention. Our algorithm decomposes the system into a sequence of components, such that every component has a strategy that is dominant, i.e., performs at least as good as any possible alternative, provided that the preceding components follow their (already synthesized) strategies. The decomposition of the system is based on a dependency analysis, for which we provide semantic and syntactic techniques. We establish the soundness and completeness of the approach and report on encouraging experimental results.

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