Some maintainability metrics for a communication protocol specified in Estelle

The situation of telecommunications systems is rapidly evolving towards a state characterized by the presence of a multitude of services integrated in a single network structure. In order to ease their integration, it is important to provide an unambiguous description of the organization, of the functionality, and of the relationships existing among services. Since it is not possible to completely foresee the situation of services in the future, the description should be modular, so that the task of adding new services to an existing environment is simplified. Formal description techniques are languages designed to handle such descriptions. Their goal is to produce correct and unambiguous specifications, understanding and modeling the system and the domain within which it operates. Their input is a set of required statements and a conceptual overview of the system. Their output is a formal representation that captures the functional behavior. On the other hand, the throughput of physical networks is constantly growing, reaching the order of Gbit/s. In the meantime, services needing high throughput, like multimedia conferencing systems are being designed, creating a need for flexible, high performance communication systems. An important feature of new high speed services is their increased need for guarantees. Therefore, the use of powerful performance modeling techniques becomes of prime importance. Their goal is to obtain some notion of how the system will perform under a given set of conditions. Performance evaluation theorists have long been using system specifications to make a heuristic model of the system and then an analysis of the model. When system specifications exist, the question arises whether a more direct path to performance analysis can be found. Our scope is to provide a methodology that fully and consistently integrates formal specification and performance evaluation. A problem is that many of the bottlenecks and impediments to smooth data flow have to do with implementation issues not directly dealt within the system specification itself. Therefore, prior to generating a performance model, the formal specification should be enhanced with the relevant non-functional information. It is essential to assure a smooth specification of the non-functional information. Thus, it is necessary to consistently add this information to the formal specification. Besides, the extended formal method should focus on conserving the semantics of the original one, and on providing a coherent extension of the semantics and syntax for the new concepts. Since all relevant required information is integrated within the formal extended representation, we provide a mapping technique that translates the extended formal representation into a performance modeling conserving the properties of the formal model. In parallel to the development of a performance model, the formal model can be validated and verified, and their implementation can be tested for conformance towards the original formal model. Finally, the performance modelling is implemented in a programming language, and then simulated. The results from simulation can be reused as inputs for the optimization of the formal specification (functional optimization) or the extended formal model (design optimization). To sum up, the goal of this work is to: Define extensions to current formal methods that allow to enhance the formal specification with performance modeling related information. Develop a method to translate the extended formal specification into a performance modeling. Develop rules and guidelines to automatically implement the performance modeling for the purpose of a performance evaluation (we use the commercial tool Opnet). Develop a consistent and coherent methodology for the integration of performance modeling and formal specification.

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>

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.

In the healthcare industry, software quality plays a crucial role as it is used in almost all systems used for medical intervention. If the quality of healthcare software is not considered, it can potentially have a negative effect and may create catastrophic situations for the patient’s health and can seriously affect the organisation’s reputation. Maintainability is a key component of software quality, making up 80% of the total cost of the software development life cycle cost. Software maintainability can be assessed using metrics that are stored in a centralised location. Software maintainability metrics and related data are crucial. If attackers alter this data, it affects the overall quality of healthcare software. In order to solve this issue, we adapted blockchain-based storage, which offers the advantages of decentralisation, immutability, and transparency and is a promising solution. We used Storj, a blockchain-based decentralised file system, to secure the maintainability metrics and related data. According to the results, the maintainability metrics data stored in the blockchain-based decentralised file storage is more secure, redundant, and cost-effective than centralised storage.

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.

Software maintainability is often estimated by software developers and experts at the design phase to reduce maintenance efforts of software products. It is believed that the maintainability metrics help in throwing some light on the maintenance efforts of a software system. This paper studies the effectiveness of metrics of two maintainability components, namely modifiability and understandability in assessing maintenance efforts at the early design phase. To perform the empirical study, first of all, modifiability and understandability are estimated using certain design level metrics. A dataset of 776 class hierarchies from 20 different Java open source projects is considered with 12 different design level metrics as the independent variables and modifiability and understandability metrics as the dependent variables. Homogeneous as well as heterogeneous ensembles of MLR, MLP, ANN, and M5P methods are employed to predict maintainability of class hierarchies using design level metric dataset and the metric dataset of the two maintainability metrics. The concept of ROC curve for regression, ROC space and AOC introduced recently by Hernandez-Orallo (Pattern Recogn 46:3395–3411, 2013) is used to determine the under/overestimation of individual models and their ensembles. It is concluded that most of the methods underestimate software maintainability that may lead to higher maintenance cost at a later stage and may also adversely affect the reputation of software companies. While modifiability is mostly underestimated, nothing could be concluded for understandability. The study is validated with the help of two available real datasets QUES and UIMS containing records of actual maintenance efforts and design level metrics dataset. These studies suggest that the definition of software modifiability metric needs a review.

Specifications of a simplified transport protocol using different formal description techniques

Formal methods (FM) are mathematically-based techniques that provide a rigorous basis for software development: the application of FMs makes it possible to achieve provable correctness and reliability in the various steps of system design and implementation. This article is a tutorial presentation of formal methods and description techniques that address modeling and analysis of distributed systems and concurrent processes in telecommunications and protocol engineering. The aim of the article is to introduce to non-practitioners the main formal methods for communication protocols. For each method, a synthetic description of its textual or graphical syntax is provided. Also, the modeling capabilities and the basic communication features are pointed out by the application of the method to a common case study, a simple retransmission protocol. The tutorial description is completed by examples of recent applications of FMs to the specification and analysis of transmission and signaling protocols in industrial and research projects, which describe the methods' application domain and offer selected references for further readings.

Agents in multiagent systems need to interact in order to exchange information, cooperate or coordinate. This interaction is frequently done through interaction protocols based on distributed system communication protocols. Communication protocols are not directly used due to many differences between agents and objects or processes such as autonomy and interaction [23] [28]. Designers use formal description techniques to represent their protocols. These formal description techniques are either those coming from distributed systems or those specifically tailored to agents. In the last category, Agent UML [24] is certainly one of the most known. This paper presents Agent UML sequence diagrams and addresses several new stereotypes.

: In 1989, Estelle was approved as one of two ISO International Standard Formal Description Techniques (FDT) for the formal specification of computer communication protocols. Based on communicating extended finite state machines (CEFSM), Estelle has a formal, mathematical, implementation-independent semantics. It is an expressive, well-defined, well-structured language that is capable of specifying distributed, concurrent information processing systems in a complete, consistent, concise and unambiguous manner. Over the past 3 years with the support of ARO and US Army CECOM, the PI has derived a number of results in the areas: Extensions and enhancements of Estelle; Protocol Visualization, and Automatic Test Case Generation. These results described herein.

Formal Description Techniques (FDT), such as LOTOS or SDL are at the base of a technology for the specification and the validation of telecommunication systems. Due to the availability of commercial tools, these formalisms are now being widely used in the industrial community. Alternatively, a number of quite effcient verification tools have been developed by the research community. But, most of these tools are based on simple ad hoc formalisms and the gap between them and real fdt restricts their use at industrial scale.This context motivated the development of an intermediate representation called if which is presented in the paper. if has a simple syntactic structure, but allows to express in a convenient way most useful concepts needed for the specification of timed asynchronous systems. The benefits of using if are multiples. First, it is general enough to handle significant subsets of most fdts, and in particular a translation from sdl to if is already implemented. Being built upon a mathematically sound model (extended timed automata) it allows to properly evaluate different semantics for fdts, in particular with respect to time considerations. Finally, if can serve as a basis for interconnecting various tools into a unified validation framework. Several levels of if program representations are already available via well defined apis and allow to connect tools ranging from static analyzers to model-checkers.keywordsasynchronytimed systemstimed automatamodel-checkingstatic analysis

A communication protocol is first presented as a set of rules that determine the behaviour of a communication system in terms of the exchange of messages between communication entities. Then a protocol is also described as an artificial language which specifies this behaviour. The concepts of the abstract and the transfer syntax of protocol messages are explained and the importance of the rules for the behaviour of protocol entities is emphasised. The difference between informal and formal specification is explained, and the importance of the formal description techniques to assure nonambiguous specifications is emphasised. The basic techniques for informal and formal specification are presented. The difference between the functionality specifications that are based on the finite state machine model, and those which are based on process algebras, is pointed out. Then some of the most important formal languages are overviewed: ACT ONE and ASN.1 for message specification, SDL, Estelle and LOTOS for protocol specification, and also UML, MSC and TTCN for communication protocols design. The chapter contains five figures.

We apply formal description techniques (FDT) to model, compose and give operational meaning to the class of reactive systems representing manufacturing enterprises. The enterprise pursues its activities by means of resources and processes that execute concurrently on the resources, subject to internal (resource) and external (market) constraints. Some modelling techniques are familiar for reactive systems, other are specific to this domain: modelling management decisions, product transfer during one-to-one (one supplier one consumer) synchronisation, marketing and many-to-one (many suppliers one consumer) synchronisation. The paper is a novel application of FDTs, also a contribution to the semantics of enterprise engineering.

Protocol conversion is one of the very important research areas in protocol engineering. It is an effective approach to provide interconnectivity and interoperability between two different protocols. A protocol converter is a very complex piece of software, and its design must be precise and complete to provide the expected conversions. Formal description techniques (FDTs), which have formal syntax and semantics, are useful tools for its design. In this paper, we present a survey of existing and widely adopted FDTs, which has been made in view of the requirements of protocol converter design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

: The formal description technique (FDT) Estelle (ISO 9074) was used for the advanced design and development of communication protocols. In particular, two protocols were studied: (1) Partial Order Connection POC (RFC1693), and (2) MIL-STD 188-220: Interoperability Standard for Digital Message Transfer Device Subsystems. POC has been used as the basis of two systems: REMDOR for Remote Multimedia Document Retrieval, and NETCICATS for Network Conscious Image Compression and Transmission. The Estelle specifications of MIL-STD 188-220 were approved as an official component of the MIL-STD in January 1998.