Many guidelines for safety-critical industries such as aeronautics, medical devices, and railway communications, specify that traceability must be used to demonstrate that a rigorous process has been followed and to provide evidence that the system is safe for use. In practice, there is a gap between what is prescribed by guidelines and what is implemented in practice, making it difficult for organizations and certifiers to fully evaluate the safety of the software system. In this paper we present an approach, which parses a guideline to extract a Traceability Model depicting software artifact types and their prescribed traces. It then analyzes the traceability data within a project to identify areas of traceability failure. Missing traceability paths, redundant and/or inconsistent data, and other problems are highlighted. We used our approach to evaluate the traceability of seven safety-critical software systems and found that none of the evaluated projects contained traceability that fully conformed to its relevant guidelines.

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Mind the gap: assessing the conformance of software traceability to relevant guidelines

Requirements should specify expectations on a software system and testing should ensure these expectations are met. Thus, to enable high product quality and efficient development it is crucial that requirements and testing activities and information are aligned. A lot of research has been done in the respective fields Requirements Engineering and Testing but there is a lack of summaries of the current state of the art on how to link the two. This study presents a systematic mapping of the alignment of specification and testing of functional or nonfunctional requirements in order to identify useful approaches and needs for future research. In particular we focus on results relevant for nonfunctional requirements but since only a few studies was found on alignment in total we also cover the ones on functional requirements. The map summarizes the 35 relevant papers found and discuss them within six major sub categories with model-based testing and traceability being the ones with most prior results.

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Alignment of Requirements Specification and Testing: A Systematic Mapping Study

In this paper, we describe a novel unsupervised approach for detecting, classifying, and tracing non-functional software requirements (NFRs). The proposed approach exploits the textual semantics of software functional requirements (FRs) to infer potential quality constraints enforced in the system. In particular, we conduct a systematic analysis of a series of word similarity methods and clustering techniques to generate semantically cohesive clusters of FR words. These clusters are classified into various categories of NFRs based on their semantic similarity to basic NFR labels. Discovered NFRs are then traced to their implementation in the solution space based on their textual semantic similarity to source code artifacts. Three software systems are used to conduct the experimental analysis in this paper. The results show that methods that exploit massive sources of textual human knowledge are more accurate in capturing and modeling the notion of similarity between FR words in a software system. Results also show that hierarchical clustering algorithms are more capable of generating thematic word clusters than partitioning clustering techniques. In terms of performance, our analysis indicates that the proposed approach can discover, classify, and trace NFRs with accuracy levels that can be adequate for practical applications.

Detecting, classifying, and tracing non-functional software requirements

[Context and motivation] Safety critical software systems pervade almost every facet of our lives. We rely on them for safe air and automative travel, healthcare diagnosis and treatment, power generation and distribution, factory robotics, and advanced assistance systems for special-needs consumers. [Question/Problem] Delivering demonstrably safe systems is difficult, so certification and regulatory agencies routinely require full life-cycle traceability to assist in evaluating them. In practice, however, the traceability links provided by software producers are often incomplete, inaccurate, and ineffective for demonstrating software safety. Also, there has been insufficient integration of formal method artifacts into such traceability. [Principal ideas/results] To address these weaknesses we propose a family of reusable traceability queries that serve as a blueprint for traceability in safety critical systems. In particular we present queries that consider formal artifacts, designed to help demonstrate that: 1) identified hazards are addressed in the safety-related requirements, and 2) the safety-related requirements are realized in the implemented system. We model these traceability queries using the Visual Trace Modeling Language, which has been shown to be more intuitive than the defacto SQL standard. [Contribution] Practitioners building safety critical systems can use these trace queries to make their traceability efforts more complete, accurate and effective. This, in turn, can assist in building safer software systems and in demonstrating their adequate handling of hazards.

https://patrickmaeder.de/pdf/REFSQ12_huangEtAl_TraceQueriesInHighAssuranceSystems.pdf

Trace queries for safety requirements in high assurance systems

Designing a secure system has always been a difficult exercise. In practice, much of the focus for designers and developers has been on delivering a working system in the first place. Security concerns have long been considered only in retrospect, especially after serious flaws are discovered. On the contrary, safety issues are commonly taken into account from the very first development phases. However, the size, heterogeneity, and communication features of modern embedded systems make it compelling to develop an appropriate engineering methodology to more explicitly define security objectives and threats. All this complexity also makes it compelling to verify that requirements are consistent with and satisfied by a candidate design before any commitment to a particular implementation.
This paper introduces SysML-Sec, a new SysML environment that makes it possible for security experts to intervene at all methodological stages, as well as to assess the impact of security over safety. Safety and security requirements are first captured within extended SysML Requirement diagrams. Attacks are organized within Parametric diagrams, where assets are represented with blocks. Since assets in embedded system are composed of functional and architectural elements of the system, requirements are linked to as- sets, and subsequently attacks, in a partitioning stage. The partitioning phase includes a functional description, a description of the hardware architecture, and a mapping stage in which functions and communications between functions are to be mapped over hardware components. Once partitioned, software-implemented functions are designed with communicating blocks and state machines. Executable code can then be generated from design diagrams.
An automotive embedded application, developed with industrial partners in the scope of the FP7 European project EVITA, illustrates the relevance of SysML-Sec. This use case was modeled with the open-source tool TTool, which supports SysML-Sec as well as safety/security simulation and formal proof.

/pdf/sysml-sec-a-sysml-environment-for-the-design-and-development-1oj5ii3xse.pdf

SysML-sec: A sysML environment for the design and development of secure embedded systems

Safety engineering analysis is a mandatory stage in the design of critical embedded automotive systems. The derivation of safety requirements and their verification require establishing traceability links between requirements and the different artifacts involved in the design flow. This paper presents the different steps of a method for expressing non functional requirements (safety, timing, hardware, performance) and ensuring their validation and their traceability over a design flow for automotive system design based on the conjoint use of EAST-ADL2 and MARTE languages and supported in an Eclipse platform. A specific meta-model for requirements modeling and traceability is used. The methodology is illustrated on an industrial knock-control system characterized by strict safety and temporal constraints

Requirement traceability in safety critical systems

Automotive software systems are characterized by increasing complexity, tougher safety requirements and ever-tighter timing constraints. Recent industrial experience has indicated that timing verification and validation can help improving overall system quality and avoid costly design errors. In this paper, we discuss some crucial capabilities that need to be pro-vided by scheduling analysis tools to enable accurate timing analysis for automotive applications. We evaluate the extent to which two open-source analysis tools, MAST and Cheddar, meet these needs.

Arnaud Albinet

Papers

Requirement traceability in safety critical systems

Requirements and solutions for timing analysis of automotive systems