Using Formal Methods. A practical comparison between Z/EVES and PVS

This paper consists of a review and comparison between Z/EVES and PVS--two tools designed for analyzing formal specifications. Z/EVES is a tool for analyzing specifications written in Z. PVS is a general theorem prover for a language that consists of higher order logic together with set theory. The review has its focus on the possibility to use these tools in an industrial context. The plan for the review was to get acquainted with the tools on a general level and then to use them to partially validate a formal specification of requirements for the safety function of railway signaling systems. The conclusion is that PVS is clearly superior to Z/EVES. PVS has such a good performance that it can be recommended for industrial use in the area of formal methods. Concerning Z/EVES, its applicability seems more restricted

Efficient Refinement Checking in VCC

We propose a methodology for carrying out refinement proofs across declarative abstract models and concrete implementations in C, using the VCC verification tool. The main idea is to first perform a systematic translation from the top-level abstract model to a ghost implementation in VCC. Subsequent refinement proofs between successively refined abstract models and between abstract and concrete implementations are carried out in VCC. We propose an efficient technique to carry out these refinement checks in VCC. We illustrate our methodology with a case study in which we verify a simplified C implementation of an RTOS scheduler, with respect to its abstract Z specification. Overall, our methodology leads to efficient and automatic refinement proofs for complex systems that would typically be beyond the capability of tools such as Z/Eves or Rodin

Exploiting Full-duplex Receivers for Achieving Secret Communications in Multiuser MISO Networks

We consider a broadcast channel, in which a multi-antenna transmitter (Alice) sends $K$ confidential information signals to $K$ legitimate users (Bobs) in the presence of $L$ eavesdroppers (Eves). Alice uses MIMO precoding to generate the information signals along with her own (Tx-based) friendly jamming. Interference at each Bob is removed by MIMO zero-forcing. This, however, leaves a "vulnerability region" around each Bob, which can be exploited by a nearby Eve. We address this problem by augmenting Tx-based friendly jamming (TxFJ) with Rx-based friendly jamming (RxFJ), generated by each Bob. Specifically, each Bob uses self-interference suppression (SIS) to transmit a friendly jamming signal while simultaneously receiving an information signal over the same channel. We minimize the powers allocated to the information, TxFJ, and RxFJ signals under given guarantees on the individual secrecy rate for each Bob. The problem is solved for the cases when the eavesdropper's channel state information is known/unknown. Simulations show the effectiveness of the proposed solution. Furthermore, we discuss how to schedule transmissions when the rate requirements need to be satisfied on average rather than instantaneously. Under special cases, a scheduling algorithm that serves only the strongest receivers is shown to outperform the one that schedules all receivers.Comment: IEEE Transactions on Communication

Efficient Refinement Checking in VCC

We propose a methodology for carrying out refinement proofs across declarative abstract models and concrete implementations in C, using the VCC verification tool. The main idea is to first perform a systematic translation from the top-level abstract model to a ghost implementation in VCC. Subsequent refinement proofs between successively refined abstract models and between abstract and concrete implementations are carried out in VCC. We propose an efficient technique to carry out these refinement checks in VCC. We illustrate our methodology with a case study in which we verify a simplified C implementation of an RTOS scheduler, with respect to its abstract Z specification. Overall, our methodology leads to efficient and automatic refinement proofs for complex systems that would typically be beyond the capability of tools such as Z/Eves or Rodin

An integration of uml use case diagram and activity diagram with Z language for formalization of library management system

Unified Modeling Language (UML) is the effective standard for modeling object-oriented software systems. However, the ambiguity of semantics and the absence of consistency among UML diagrams lead to lack of precisely defining the requirements of a system. On the other hand, formal methods are techniques and tools use the mathematical notations, and they involve the precise syntax and semantics of the unambiguous software requirements specification. It applied in early stages of Software Development Life Cycle (SDLC). Therefore, an integrated between UML specification and formal specification is required to reduce the requirements' ambiguity and error, and to improve the quality and security of software systems. This paper proposes an approach involves the combining UML use-case diagram and activity diagrams with Z language for formalization of Library Management System (LMS). The focus of this paper is on consistency between the UML diagrams to Z Schema, and then verified by using the Z / EVEs tool

The Effects of Environmental Prompts on Stair Usage

Experts have advocated exercise with little success, and have turned to encouraging physical activity by incorporating it into daily activities such as taking the stairs over elevators. Much literature exists suggesting that environmental prompts can encourage the use of stairs and literature has established that some messages may be more effective than others. This study aimed to assess the effects of selected signage prompts on stair usage. Methods: Stair and elevator use were monitored in three, two-story buildings. One building served as a control, while a fitness message was placed in another building, and the final building received a weight control message. Observations took place twice per week for the seven weeks of the study. Results: Predictors of stair usage included age (