A system engineering methodology integrating performance evaluation and formal specification

Various methods are used to describe communication protocols. The search for suitable description methods for communication protocols in the 1980s yielded a broad range of approaches out of which some fundamental methods have crystallized. These methods constitute the basis of the semantic models of the various formal description techniques. Therefore we first consider the most important description methods in this chapter before we turn to the formal description techniques. From these, finite state machines, Petri nets, process calculi, and temporal logics have crystallized as the most important and most common ones. Apart from these methods, other approaches were also investigated, such as the use of grammars, data flow languages, and functional languages. They did not receive wider attention because they were not applied to real-life protocols. The use of high-level programming languages was considered likewise. Programming languages support the algorithmic description of protocol procedures as well as the generation of prototypes, but they usually do not possess a formally defined semantics. In addition, programming languages are primarily implementation languages and not specification languages. They often yield descriptions which are close to an implementation. For that reason, high-level programming languages are not used for protocol description. Many formal description techniques, however, use programming language features.

We propose a methodology that intends to reuse formal specification effort to build a performance modeling. The methodology starts abstracting the relevant features of a real system in a formal specification. Then, we enhance the specification with performance information (quality of service, workload, processing design). At that point, we map the enhanced formal representation in a performance modeling that preserves the formal properties. Thereupon, we implement this modeling in a performance evaluation environment. We develop the methodology for the SDL and Estelle standardized formal techniques. Ultimately, we illustrate the methodology by an example: the transport control protocol (TCP). Finally, we simulate the achieved executable, varying evaluation conditions.

This paper describes a research result on automatic generation of abstract test cases from INAP protocol in formal specifications by using and applying many existing related algorithms and techniques such as the testing framework, rural Chinese postman tour and UTO (Unique Input Output) sequence concepts. We use the I/OFSM (Input/Output Finite State Machine) generated from SDL specifications and a characterizing sequence, called Unique Input/Output (UIO) sequence, is defined for the I/O FSM. The UIO sequence is combined with the concept of rural Chinese postman tour, without reliable reset capability, to obtain an optimal test sequence. To develop this method, first of all, we establish a framework leading to formal testing methodology which can be used to assess the conformance of an IUT (Implementation Under Test) to the behaviours specified in an I/OFSM which is equivalent to corresponding FDT (Formal Description Technique) specification. By this framework, we present a methodology for automatic test generation from FDT specifications. A prototype of the proposed framework has been built with special attention to real application in order to generate the executable test cases in an automatic way.

This paper describes the application of Real-Time Maude to the formal modeling, simulation, and model checking analysis of the NORM multicast protocol standard being developed by the Internet Engineering Task Force. Because of its size and sophistication, real-time features, and the need to model and analyze subcomponents of NORM both in isolation and in combination, NORM poses a set of challenging problems for its formal specification and analysis. Our formal modeling and analysis efforts made us aware of ambiguities, inconsistencies, and cases of under-specification in the informal specification of NORM. Our work indicates that formal methods can successfully be applied by non-experts during the development of advanced Internet protocol standards.

Computer networks are large and complex systems. The use of natural language to design and analyse communications protocols will lead to ambiguous representations. This inadequacy of the natural language gives rise to the many recent research works on formal description techniques (FDTs). FDTs are methods to define the behaviour of an information processing system in a language with formal syntax and semantics. FDT has been chosen as a basis for the design of protocol converter. A survey of existing widely accepted FDTs is presented. From this survey, a selection is made for an appropriate FDT to be used as the basis for future research work on FDT-based protocol converter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The chapter presents a description of a novel modelling language called Alvis defined for the design of concurrent especially real-time systems. Alvis combines the advantages of formal methods and practical modelling languages. Based on CCS and XCCS process algebras, Alvis utilizes flexible graphical modelling of interconnections among agents and a high level programming language used for the description of agents behaviour. Each agent in a model can use rule-based systems to support its decisions. A small set of language statements and graphical concepts make Alvis easy to learn and use. The possibility of a formal model verification, makes Alvis a formal modelling language. Alvis modelling environment creates in parallel a model of the considered system and a labelled transition system (LTS graph) that is its formal representation. The LTS graph can be formally verified with the CADP toolbox. A survey of main Alvis features from practical point of view, is given in the chapter.

Current programming languages and programming models make it easy to create software and hardware systems that fulfill an intended function but also leave such systems open to unintended function and vulnerabilities. Software engineering and code hygiene may make systems incrementally safer, but do not produce the wholesale change necessary for secure systems from the outset. Yet there exists an approach with impressive results: We cite recent examples showing that formal methods, coupled with formally informed digital design, have produced objectively more robust code even beyond the properties directly proven. Though discovery of zero-day vulnerabilities is almost always a surprise and powerful tools like semantic fuzzers can cover a larger search space of vulnerabilities than a developer can conceive of, formal models seem to produce robustness of a higher qualitative order than traditionally developed digital systems. Because the claim is necessarily a qualitative one, we illustrate similar results with an idealized programming language in the form of Boolean networks where we have control of parameters related to stability and adaptability. We argue that verifiability with formal methods is an instance of broader design constraints that promote robustness. We draw analogies to real-world programming models and languages that can be mathematically reasoned about in contrast to ones that are essentially undecidable.

With the application of formal description techniques (FDTs) in the communication protocol area since the mid 1980s, avenues have been opened up to allow a system to be analyzed early in the specification phase. Quantitative measures on its maintainability can then be extracted from such a formal specification, so that we can develop easily maintainable communication software systems and further reduce the increasingly high cost of software maintenance. This paper describes some maintainability metrics for a communication protocol specified in Estelle.

The paper presents our experience using the formal description technique Estelle for the protocol development cycle in the area of real time industrial communication systems. As a real world application, the PROFIBUS parts FMS and DP of the European fieldbus standard were completely implemented using formal models. These implementations are successfully used in industrial applications and embedded systems. Our development method, results, and experiences during the development process are discussed. A closed, tool based method is the overall aim concerning the development life cycle to support the requirement definition as well as the implementation of the product code with final testing. To meet these needs, our approach defines some assumptions and constraints using the syntactic and semantic model of the specification language Estelle, aspects of the modelling process concerning the architecture, handling data abstraction and encapsulation of the specification language vs. real time data flow in the product code implementation, synchronous vs. asynchronous communications to local interfaces (e.g. physical layer or partly data link layer ASIC) and dealing with special local events like timeouts and interrupts in the specification and in the real time execution environment. The paper discusses advantages and also critical points using the formal way of the protocol development cycle. In theory, it is quite clear that formal description techniques enhance quality. Therefore, we discuss this approach from the user's point of view.

Specifications of a simplified transport protocol using different formal description techniques

To be formal a method must have a systematic and repeatable process for verifying the consequences of a specification. Verifications can be manual, partially mechanized, or fully mechanized. Formal representations can be tabular, graphical, notational, expressed in a formal (programming) language, or any combination thereof. Barriers to adoption and reasons for adoption are discussed. The examples presented show successful commercial as well as safety critical applications and show that formal specifications can be understood by users. >

This paper proposes a new methodology for system engineering. It provides an integrated approach covering formal specification and performance evaluation. Therefore it associates the advantages of formal techniques that allow formal proof and automatic implementation with the benefits of performance evaluation. The basic idea is to abstract the relevant features of the system in the formal specification (structure, functional description), enhance it with relevant information for performance modeling (quality of service, operating load, processing architecture and processing constraints), and map them into a performance evaluation environment. In this paper, we develop the suitable extensions for the formal language SDL and apply them to an example: Transmission Control Protocol (TCP).

A survey is presented of the evolution of performance modeling and of current trends in distributed systems. Also outlined is a proposal for integrated functional specification, time representation, and performance analysis. The author discusses two main trends, namely, a drastic change in modeling methodology and gradual changes to more formal model description techniques. The combination of process algebra and performance analysis assures constructivity. This means a systematic technique for the structured design of complex systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Many critical control systems are developed using formal methods. When software applied to such systems is developed, the employment of formal methods in the software requirements specification and verification will provide increased assurance for such applications. Earlier error of overlooked requirement specification can be detected using formal specification method. Also the testing and full verification to examine all reachable states using model checking to undertake formal verification are able to be completed. In this paper, we proposed an eclectic approach to incorporate Z(Zed) formal language and ‘Statemate MAGNUM’ which is formal method tools using Statechart. Also we applied the proposed method to safety-critical railway signaling systems for the formal requirement specification and analyzed the specification results.

Nowadays, there exist web sites that allow users to retrieve and install software in an easy way. The performance of these sites may be poor if they are used in wireless networks; the reason is the inadequate use of the net resources that they need. If these kinds of systems are designed using mobile agent technology the previous problem might be avoided. In this paper, we present a comparison between the performance of a software retrieval system especially designed to be used in a wireless network and the performance of a software retrieval system similar to the well-known Tucows.com web site. In order to compare performance, we make use of a software performance process enriched with formal techniques. The process has as important features that it uses UML as a design notation and it uses stochastic Petri nets as formal model. Petri nets provide a formal semantics for the system and a performance model.