A new dialect of SOFL-Syntax formal semantics and tool support

Structured Object Orientated Formal Language (SOFL) is a formal method design methodology that combines data flows diagrams and predicates in order to describe processes that can be refined. This methodology creates a very versatile method of describing a system, which system properties can be proven rigorously. Data flows are grouped by ports that define from which data flows data can be consumed or on which flows data can be generated. For predicates, Logic of Partial Functions (LFP) are used; and an undefined element that is also used to indicate if a data flows do not contain any data. Over time SOFL “evolved organically” and a number of features were added: usability was the main consideration for a feature being added. For a formal language to be useful there must be no uncertainty of a specific design’s meaning. With SOFL, there is a possible contradiction between the requirement that a process's precondition must be true when the process fire, and the fire rules. This contradiction is due to the use of LPF. Semantics (the meaning) of SOFL was not always updated to keep track of the changes made to SOFL which resulted in an outdated and incomplete semantic. The incompleteness of the semantics is a significant factor motivating the work done in this dissertation. In this dissertation, a dialect of SOFL is created to define a semantic. Not all the elements of SOFL are added in order that a simpler semantic can be defined. Elements that were removed include: LPF, Classes, and Non-deterministic broadcast nodes. Semantics of the dialect is created by a two-step process: firstly, an intuitive understanding of the dialect is created, and secondly, both static and dynamic semantics are defined by means of translations. A translation is a mapping from the dialect to a formal language that describes a certain aspect of the dialect. Static semantics defines the meaning of the elements that are “fixed” in their state: SMT-LIB is used as the target language to describe the static semantics of the dialect. Dynamic semantics describes how an element in a design changes over time: the process algebra mCRL2 is used as the formal language which describes the dynamic behaviour of the dialect. The SMT-Solver Z3 and tools included in mCLR2 are used to analyse the translation of the dialect. Use of these tools allows properties that are necessary for a design to have a well defined meaning, to be proven. Properties that can be proven include: a process can fire, a process can fire an infinite number of times, and a predicate that described a property. An Eclipse plug-in is created so that translation is not required to be done manually. After a design is translated the tools Z3 and mCRL2 are run using script files and the results of the analysis are displayed on the screen. The desired properties could be proven but for a moderate size design, but as the size of the design increased the analysis of the translation could not be completed due to computational problem. Usability of the tool can be improved by not only using a textual representation of a design, but also visual representations as in SOFL. As a result, properties that are necessary for a design to have a well-defined meaning, can be proven using these tools.Dissertation (MSc)--University of Pretoria, 2018.Computer ScienceMScUnrestricte

Automated Visualization of Input / Output for Processes in SOFL Formal Specifications

While formal specification is regarded as an effective means to capture accurate requirements and design, validation of the specifications remains a challenge. Specification animation has been proposed to tackle the challenge, but lacking an effective representation of the input / output data in the animation can considerably limit the understanding of the animation by clients. In this paper, we put forward a tool supported technique for visualization of the input / output data of processes in SOFL formal specifications. After discussing the motives of our work, we describe how data of each kind of data type available in the SOFL language can be visualized to facilitate the representation and understanding of input / output data. We also present a supporting tool for the technique and a case study to demonstrate the usability and effectiveness of our proposed technique

パターンに基づく要求仕様の形式化方法及び支援ツールに関する研究

Despite the effectiveness of requirements formalization in producing accurate requirements documentation and deepening the developers\u27 understanding of the envisioned systems, this technique can hardly be accepted by software industry mainly because it requires mathematical sophistication and considerable experience in using formal notations, which remains a challenge to many practitioners. Many methods and tools have been proposed to deal with the problem by providing general guidance or automatic support in transforming informal requirements into formal specifications. However, they fail to accomplish the task when encountering incompleteness and ambiguities in the informal requirements. To handle this challenge, this thesis describes a pattern-based approach to facilitating the formalization of requirements. In this approach, a specification pattern system is pre-defined to guide requirements formalization where each pattern provides a specific solution for formalizing one kind of function into a formal specification. All of the patterns are classified and organized into a hierarchical structure according to the functions they can be used for formalization. The distinct characteristic of our approach is that all of the patterns are stored on computer as knowledge for creating effective guidance to facilitate the developer in requirements formalization; they are "understood" only by the computer but transparent to the developer. Based on the pattern system, a method that guides the requirements formalization process by applying the pattern system is described. To facilitate the understanding of the guidance produced by the pattern system and the utilization and maintenance of the pattern knowledge, a method for representing the pattern system is proposed where attribute tree and HFSM are adopted. These two notations are used to represent different parts of the pattern knowledge. The method for applying the pattern knowledge represented in the two notations is given. We also describe a prototype tool that supports the pattern-based approach. The tool derives necessary functional details of the intended requirement through interactions with the developer and generates a formal specification according to the obtained information. Two experiments on the tool supported approach are presented to demonstrate the effectiveness of the approach.博士(理学)法政大学 (Hosei University

Automatic Transformation from SOFL Formal Specifications to Programs for Software Verification and Testing

Abstract— The Structured Object-oriented Formal Language (SOFL) method is developed to overcome the disadvantages of existing formal methods and provide effective techniques for writing formal specifications and carrying out verification and testing. Although it has been applied to system modeling and design in practical and research projects, SOFL has not been widely applied to the industrial software development systems because of the lack of efficient tool support. Aiming at improving the existing SOFL supporting tool and solving the problem that the formal specifications cannot be directly executed, this paper firstly analyzes the relationship between the structures of SOFL formal specifications and C# programs, and then designs and implements the transforming classes for module transformations and data type transformations. Finally, a test is performed to ensure the reliability and validity of the implemented software system. Keywords— SOFL; Formal specifications; Automatic transformations; Programs

Security Requirements Specification and Tracing within Topological Functioning Model

Specification and traceability of security requirements is still a challenge since modeling and analysis of security aspects of systems require additional efforts at the very beginning of software development. The topological functioning model is a formal mathematical model that can be used as a reference model for functional and non-functional requirements of the system. It can also serve as a reference model for security requirements. The purpose of this study is to determine the approach to how security requirements can be specified and traced using the topological functioning model. This article demonstrates the suggested approach and explains its potential benefits and limitations

Integrating Functional and Security Requirements Analysis using SOFL for Software Security Assurance

Formal methods have been applied to define requirements for safety and/or security critical software systems in some industrial sectors, but the challenge is the lack of a systematic way to take security issues into account in specifying the functional behaviors. In this paper, we propose a formal approach to expressing and explicitly interweaving security and functional requirements. With this approach, the functional behaviors of the system are precisely specified using the Structured Object Oriented Formal Language (SOFL), the security rules are systematically explored, and the result is properly incorporated into the functional specification as constraints. The resultant specification then defines the system functionality that implies the conformance to the security rules. Such a specification can be used as a firm foundation for implementation and testing of the implementation. We discuss the principle of interweaving security rules with functional specifications and present a case study to demonstrate the feasibility of our approac

Petri Nets as Semantic Domain for Diagram Notations

AbstractThis paper summarizes the work carried out by the authors during the last years. It proposes an approach for defining extensible and flexible formal interpreters for diagram notations based on high-level timed Petri nets.The approach defines interpreters by means of two sets of rules. The first set specifies the correspondences between the elements of the diagram notation and those of the semantic domain (Petri nets); the second set transforms events and states of the semantic domain into visual annotations on the elements of the diagram notation. The feasibility of the approach is demonstrated through MetaEnv, a prototype tool that allows users to implement special-purpose interpreters

A Software Tool to Support Scenario-Based Formal Specification for Error Prevention

Formal specification can be an error-prone process for complex systems and how to efficiently write correct specifications is still a challenge for practitioners in industry. This paper presents a software tool to support the scenario-based formal specification approach developed in the SOFL formal engineering method. Using the tool, some suggestion of the further contents of the specification may be automatically predicated to facilitate the user in completing the specification. To improve the readability of the formal specification, the tool can also automatically translate the textual format of the specification into a comprehensible tabular format. Both of these functions can be helpful to prevent errors during the construction of the specification. We discuss each of the functions by first presenting its principle and then illustrating it with examples. We present a case study to show how the tool supports the scenario-based specification approach. Finally, we conclude the paper and suggest topics for future research

A Formal Engineering Approach for Interweaving Functional and Security Requirements of RESTful Web APIs

RESTful Web API adoption has become ubiquitous with the proliferation of REST APIs in almost all domains with modern web applications embracing the micro-service architecture. This vibrant and expanding adoption of APIs, has made an increasing amount of data to be funneled through systems which require proper access management to ensure that web assets are secured. A RESTful API provides data using the HTTP protocol over the network, interacting with databases and other services and must preserve its security properties. Currently, practitioners are facing two major challenges for developing high quality secure RESTful APIs. One, REST is not a protocol. Instead, it is a set of guidelines that define how web resources can be designed and accessed over HTTP endpoints. There are a set of guidelines which stipulate how related resources should be structured using hierarchical URIs as well as how specific well-defined actions on those resources should be represented using different HTTP verbs. Whereas security has always been critical in the design of RESTful APIs, there are no clear formal models utilizing a secure-by-design approach that interweaves both the functional and security requirements. The other challenge is how to effectively utilize a model driven approach for constructing precise requirements and design specifications so that the security of a RESTFul API is considered as a concern that transcends across functionality rather than individual isolated operations.This thesis proposes a novel technique that encourages a model driven approach to specifying and verifying APIs functional and security requirements with the practical formal method SOFL (Structured-Object-Oriented Formal Language). Our proposed approach provides a generic 6 step model driven approach for designing security aware APIs by utilizing concepts of domain models, domain primitives, Ecore metamodel and SOFL. The first step involves generating a flat file with APIs resource listings. In this step, we extract resource definitions from an input RESTful API documentation written in RAML using an existing RAML parser. The output of this step is a flat file representing API resources as defined in the RAML input file. This step is fully automated. The second step involves automatic construction of an API resource graph that will work as a blue print for creating the target API domain model. The input for this step is the flat file generated from step 1 and the output is a directed graph (digraph) of API resource. We leverage on an algorithm which we created that takes a list of lists of API resource nodes and the defined API root resource node as an input, and constructs a digraph highlighting all the API resources as an output. In step 3, we use the generated digraph as a guide to manually define the API’s initial domain model as the target output with an aggregate root corresponding to the root node of the input digraph and the rest of the nodes corresponding to domain model entities. In actual sense, the generated digraph in step 2 is a barebone representation of the target domain model, but what is missing in the domain model at this stage in the distinction between containment and reference relationship between entities. The resulting domain model describes the entire ecosystem of the modeled API in the form of Domain Driven Design Concepts of aggregates, aggregate root, entities, entity relationships, value objects and aggregate boundaries. The fourth step, which takes our newly defined domain model as input, involves a threat modeling process using Attack Defense Trees (ADTrees) to identify potential security vulnerabilities in our API domain model and their countermeasures. aCountermeasures that can enforce secure constructs on the attributes and behavior of their associated domain entities are modeled as domain primitives. Domain primitives are distilled versions of value objects with proper invariants. These invariants enforce security constraints on the behavior of their associated entities in our API domain model. The output of this step is a complete refined domain model with additional security invariants from the threat modeling process defined as domain primitives in the refined domain model. This fourth step achieves our first interweaving of functional and security requirements in an implicit manner. The fifth step involves creating an Ecore metamodel that describes the structure of our API domain model. In this step, we rely on the refined domain model as input and create an Ecore metamodel that our refined domain model corresponds to, as an output. Specifically, this step encompasses structural modeling of our target RESTful API. The structural model describes the possible resource types, their attributes, and relations as well as their interface and representations. The sixth and the final step involves behavioral modeling. The input for this step is an Ecore metamodel from step 5 and the output is formal security aware RESTful API specifications in SOFL language. Our goal here is to define RESTful API behaviors that consist of actions corresponding to their respective HTTP verbs i.e., GET, POST, PUT, DELETE and PATCH. For example, CreateAction creates a new resource, an UpdateAction provides the capability to change the value of attributes and ReturnAction allows for response definition including the Representation and all metadata. To achieve behavioral modelling, we transform our API methods into SOFL processes. We take advantage of the expressive nature of SOFL processes to define our modeled API behaviors. We achieve the interweaving of functional and security requirements by injecting boolean formulas in post condition of SOFL processes. To verify whether the interweaved functional and security requirements implement all expected functions correctly and satisfy the desired security constraints, we can optionally perform specification testing. Since implicit specifications do not indicate algorithms for implementation but are rather expressed with predicate expressions involving pre and post conditions for any given specification, we can substitute all the variables involved a process with concrete values of their types with results and evaluate their results in the form of truth values true or false. When conducting specification testing, we apply SOFL process animation technique to obtain the set of concrete values of output variables for each process functional scenario. We analyse test results by comparing the evaluation results with an analysis criteria. An analysis criteria is a predicate expression representing the properties to be verified. If the evaluation results are consistent with the predicate expression, the analysis show consistency between the process specification and its associated requirement. We generate the test cases for both input and output variables based on the user requirements. The test cases generated are usually based on test targets which are predicate expressions, such as the pre and post conditions of a process. when testing for conformance of a process specification to its associated service operation, we only need to observe the execution results of the process by providing concrete input values to all of its functional scenarios and analyze their defining conditions relative to user requirements. We present an empirical case study for validating the practicality and usability of our model driven formal engineering approach by applying it in developing a Salon Booking System. A total of 32 services covering functionalities provided by the Salon Booking System API were developed. We defined process specifications for the API services with their respective security requirements. The security requirements were injected in the threat modeling and behavioral modeling phase of our approach. We test for the interweaving of functional and security requirements in the specifications generated by our approach by conducting tests relative to original RAML specifications. Failed tests were exhibited in cases where injected security measure like requirement of an object level access control is not respected i.e., object level access control is not checked. Our generated SOFL specification correctly rejects such case by returning an appropriate error message while the original RAML specification incorrectly dictates to accept such request, because it is not aware of such measure. We further demonstrate a technique for generating SOFL specifications from a domain model via model to text transformation. The model to text transformation technique semi-automates the generation of SOFL formal specification in step 6 of our proposed approach. The technique allows for isolation of dynamic and static sections of the generated specifications. This enables our technique to have the capability of preserving the static sections of the target specifications while updating the dynamic sections in response to the changes of the underlying domain model representing the RESTful API in design. Specifically, our contribution is provision of a systemic model driven formal engineering approach for design and development of secure RESTful web APIs. The proposed approach offers a six-step methodology covering both structural and behavioral modelling of APIs with a focus on security. The most distinguished merit of the model to text transformation is the utilization of the API’s domain model as well as a metamodel that the domain model corresponds to as the foundation for generation of formal SOFL specifications that is a representation of API’s functional and security requirements.博士(理学)法政大学 (Hosei University

A Review of Software Reliability Testing Techniques

In the era of intelligent systems, the safety and reliability of software have received more attention. Software reliability testing is a significant method to ensure reliability, safety and quality of software. The intelligent software technology has not only offered new opportunities but also posed challenges to software reliability technology. The focus of this paper is to explore the software reliability testing technology under the impact of intelligent software technology. In this study, the basic theories of traditional software and intelligent software reliability testing were investigated via related previous works, and a general software reliability testing framework was established. Then, the technologies of software reliability testing were analyzed, including reliability modeling, test case generation, reliability evaluation, testing criteria and testing methods. Finally, the challenges and opportunities of software reliability testing technology were discussed at the end of this paper