On the Purpose of Event-B Proof Obligations

Well-Definedness is important for many formal methods. In B and Event-B it ensures that certain kinds of errors (e.g., division by 0) cannot appear and that proof rules based on two-valued logic are sound. For validation tools such as ProB, well-definedness is important for constraint solving. B and Event-B establish well-definedness by generating dedicated proof obligations (POs). Unfortunately, the standard provers are not always very good at discharging them. In this paper, we present a new integrated technique to simultaneously generate and discharge well-definedness POs. The implementation contains a dedicated rule-based prover written in Prolog supporting B, Event-B and extensions thereof for data validation. We show that the generation and discharging is significantly faster than existing implementations in rodin and Atelier-B and that a large number of POs are automatically discharged. The POs are fine-grained enough to provide precise source code feedback, and allow inspection of problematic POs within various editors.

TLA + is a formal specification language that is based on ZF set theory and the Temporal Logic of Actions TLA. The TLA + proof system tlaps assists users in deductively verifying safety properties of TLA + specifications. tlaps is built around a proof manager, which interprets the TLA + proof language, generates corresponding proof obligations, and passes them to backend verifiers. In this paper we present a new backend for use with SMT solvers that supports elementary set theory, functions, arithmetic, tuples, and records. Type information required by the solvers is provided by a typing discipline for TLA + proof obligations, which helps us disambiguate the translation of expressions of (untyped) TLA + , while ensuring its soundness. Preliminary results show that the backend can help to significantly increase the degree of automation of certain interactive proofs.KeywordsFunction SymbolProof ObligationType InferenceInput LanguageType AssignmentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Robots are found in most, if not all, modern production facilities and they increasingly enter other domains, e.g., health care. Robots participate in complex processes and often need to cooperate with other robots to fulfill their goals. They must react to a variety of events, both external, e.g., user inputs, and internal, i.e., actions of other components or robots in the system. Designing such a system, in particular developing the software for the robots contained in it, is a difficult and error-prone task. We developed a formal scenario-based modeling method which supports engineers in this task. Using short, intuitive scenarios engineers can express requirements, desired behavior, and assumptions made about the system’s environment. These models can be created early in the design process and enable simulation as well as an automated formal analysis of the system and its components. Scenario-based models can drive the execution at runtime or can be used to generate executable code, e.g., programmable logic controller code. In this paper we describe how to use our scenario-based approach to not only improve the quality of a system through formal methods, but also how to reduce the manual implementation effort by generating executable PLC code.

Combining decision procedures by (model-)equality propagation

The B Method is a full spectrum formal software development method that covers the software process from specification to implementation. The method uses state machines, defined using logic and set theory with a notation similar to that of Z, that export operations. The method supports a notion of refinement and implementation, which is based on the notion of refinement in the refinement calculus with the exception that there is no distinction between procedural and data refinement. The B Toolkit is a configuration tool that manages developments under the B Method, generating proof obligations and supporting tools for the discharge of those proof obligations. There is also support for the generation of documentation, and for the browsing of developments.

Formally verifying functional and security properties of a large-scale production operating system is highly desirable. However, it is challenging as such OSes are often written in multiple source languages that have no formal semantics - a prerequisite for formal reasoning. To avoid expensive formalization of the semantics of multiple high-level source languages, we present a lightweight and rigorous verification toolchain that verifies OS code at the binary level, targeting ARM machines. To reason about ARM instructions, we first translate the ARM Specification Language that describes the semantics of the ARMv8 ISA into the PVS7 theorem prover and verify the translation. We leverage the radare2 reverse engineering tool to decode ARM binaries into PVS7 and verify the translation. Our translation verification methodology is a lightweight formal validation technique that generates large-scale instruction emulation test lemmas whose proof obligations are automatically discharged. To demonstrate our verification methodology, we apply the technique on two OSes: Google's Zircon and a subset of Linux. We extract a set of 370 functions from these OSes, translate them into PVS7, and verify the correctness of the translation by automatically discharging hundreds of thousands of proof obligations and tests. This took 27.5 person-months to develop.

Undergraduate students often find the process of collating research results and producing structured written text from this difficult. Research suggests that those with a writing strategy and those who leverage visual modelling techniques to structure their research or writing had an advantage over those who did not. There are strong parallels here with the field of software engineering in terms of established processes and the use of visual models. We hypothesise that undergraduate computing students will adopt Mind Maps (a visual modelling technique) as a tool in their writing process. To explore this, we conducted first a survey to better understand students' attitudes towards academic research and also a practical intervention, involving mind-mapping their research proposals prior to writing their literature reviews and full research proposal.Our investigation indicates that mind maps can serve as effective intermediary tools for organizing concepts and structuring academic writing, with parallels observed between their use and formal modeling methods such as UML diagrams. Survey and intervention data demonstrated that students who engaged in mind-mapping prior to drafting research proposals exhibited measurable improvements in literature density and overall proposal quality, though participation was voluntary and potentially biased toward more motivated students. Nevertheless, because improvements were assessed against individual baselines rather than cohort-wide performance, the results substantiate the pedagogical value of mind mapping as a research-support strategy.

Cognitive network is a new approach to solve self-management of complex heterogeneous network, and its model and analysis method are key problems to be solved. a formal modeling and analysis method for cognitive network is proposed based on stochastic process algebra. Firstly, basic concept of PEPA is introduced. then system behaviors are abstracted combining with cognitive essence, and formal models for cognitive network are constructed from the angles of macroscopic operating states and internal services with PEPA respectively. on the basis, quantitative analysis method is discussed. the proposed modeling and analysis method has the features logical accuracy, which can apply in any phases and direct the designation of cognitive network.

Correct-by-Construction Approach for Formal Verification of IoT Architecture

This paper aims at presenting a formal modeling and verification method of a cross-layer technique to building an efficient P2P unstructured overlay over MANET underlays. Peer-to-Peer (P2P) overlays are formed dynamically to create a virtual network on top of an underlying physical network such as the Internet. P2P overlay networks can also be deployed over Mobile Ad hoc Networks (MANET) to address content discovery issues. However, deploying P2P systems straight over MANET do not exhibit satisfactory performance. Bandwidth limitation, limited resources and node mobility are some of the key constraints. The rational behind our proposal is to take advantage of MANET underlay to select and maintain physically nearest and fresh P2P neighbors. The combination of elementary strategies makes our overlay building likely- matches the MANET underlay, thereby, leading to efficient paths between P2P neighbors and reduction of network overhead. The formal modeling consists in capturing the behavior of wireless nodes and the medium using the input language of the UPPAAL model checker, that is a network of communicating timed automata. Last, we proceed with the checking of some safety and liveness properties by means of this tool, such as deadlock-freedom.

The home automation controls the electronic devices remotely and automatically with the help of context aware behaviour. Context awareness is the process where data from various sensors and input from user or user action must be interpreted and corresponding commands to actuators must be generated. This context aware automation and decision support process is done with the help of adaptive rules which is defined for the automatic behaviour of devices in the smart home environment. The consistent behaviour of the devices in the smart environment will capture the customer satisfaction. This work describes the process of checking the consistent behaviour of the context aware system in smart home environment using formal modelling and verification method. We have discussed a mechanism to check the consistent behaviour of the adaptive mechanism of smart home environment. The result ensures the consistent behaviour of the context aware system in the smart environment.

The article deals with development of a doctrinal system of effectiveness standards for the investigation of corruption crimes. The study used a number of philosophical, general scientific and specific methods of gaining scientific knowledge, including: dialectical method, hermeneutic method, method of systemic and structural analysis, methods of analysis and synthesis, functional method, formal legal method and modeling method. It is proposed to define the investigation effectiveness as the feature of pre-trial investigation, which is characterized by the ability to achieve the tasks envisioned in Art. 2 of the CPC of Ukraine (Law No. 4651-VI, 2012) and can be assessed by checking the number of objectively necessary procedural actions and the effectiveness of making intermediate and final procedural decisions. It is emphasized that the general standards of investigation effectiveness, formulated by the case law of the ECHR, are partially taken into account in Art. 2 of the CPC of Ukraine (Law No. 4651-VI, 2012) through stating the need of investigation being efficient, complete and impartial. The authors formulate scientific approaches to determining the main criteria for the effectiveness of pre-trial investigation of corruption crimes.

Using induction and rewriting to verify and complete parameterized specifications

Distributing the Workload in a Lazy Theorem-Prover

This paper introduces a new technique for the verification of interactive systems. It first presents the use of a model oriented formal method for specifying interactive systems, i.e. the B method. Then, it suggests formally based solutions which allow solving difficulties that are inherent to interactive systems specification, like reachability, observability or reliability. Our claim is that this model-oriented technique that uses proof obligations can be used together with model checking techniques, where automatic proofs of properties can be performed.KeywordsModel oriented notationB methodspecification refinementinteraction properties verificationspecification of interactive system.