Verification of Solid State Interlocking Programs

James, Phillip; Lawrence, Andy; Moller, Faron; Roggenbach, Markus; Seisenberger, Monika; Setzer, Anton; Kanso, Karim; Chadwick, Simon

doi:10.1007/978-3-319-05032-4_19

Cited by 25 publications

(21 citation statements)

References 12 publications

(15 reference statements)

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“…This suggests that the details of object placement at one station seldom influence the object placements at another station. Such locality of properties has been earlier exploited by other railway verification approaches, e.g., [23] or [4]. Bonacchi et al [4], in particular use locality to split model checking problems into smaller pieces, and using topology data to optimize variable ordering in BDD-based verification.…”

Section: Incremental Verificationmentioning

confidence: 99%

Efficient verification of railway infrastructure designs against standard regulations

Luteberget

Johansen

2017

Form Methods Syst Des

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In designing safety-critical infrastructures s.a. railway systems, engineers often have to deal with complex and large-scale designs. Formal methods can play an important role in helping automate various tasks. For railway designs formal methods have mainly been used to verify the safety of so-called interlockings through model checking, which deals with state change and rather complex properties, usually incurring considerable computational burden (e.g., the state-space explosion problem). In contrast, we focus on static infrastructure models, and are interested in checking requirements coming from design guidelines and regulations, as usually given by railway authorities or safety certification bodies. Our goal is to automate the tedious manual work that railway engineers do when ensuring compliance with regulations, through using software that is fast enough to do verification on-the-fly, thus being able to be included in the railway design tools, much like a compiler in an IDE. In consequence, this paper describes the integration into the railway design process of formal methods for automatically extracting railway models from the CAD railway designs and for describing relevant technical regulations and expert knowledge as properties to be checked on the models. We employ a variant of Datalog and use the standardized "railway markup language" railML as basis and exchange format for the formalization. We developed a prototype tool and integrated it in industrial railway CAD software, developed under the name RailCOMPLETE . This on-the-fly verification tool is a help for the engineer while doing the designs, and is not a replacement to other more heavy-weight software like for doing interlocking verification or capacity analysis. Our tool, through the export into railML, can be easily integrated with these other tools. We apply our tool chain in a Norwegian railway project, the upgrade of the Arna railway station.

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Section: Incremental Verificationmentioning

confidence: 99%

Efficient verification of railway infrastructure designs against standard regulations

Luteberget

Johansen

2017

Form Methods Syst Des

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“…This principle has been exploited in [22] to define domain-oriented optimisation of the variable ordering in a BDD-based verification. Locality can be used also for slicing, as suggested in [3,9,8,1]: the idea is to consider only the portion of the model that has influence on the property to be verified, by a topological selection of interested track elements (therefore closely related to the cone of influence of the property): this allows for a much more efficient verification of the single property, but comes at the price of repeating the slicing and the verification for every property, and of separately checking that verifying slices does actually imply the satisfaction of desired properties for the whole system. Nevertheless, it appears that when automated, this process can offer significant time and memory savings.…”

Section: Compositionalitymentioning

confidence: 99%

Compositional Verification of Interlocking Systems for Large Stations

Fantechi

Haxthausen

Macedo

2017

Software Engineering and Formal Methods

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Abstract. Railway interlocking systems are responsible to grant exclusive access to a route, that is a sequence of track elements, through a station or a network. Formal verification that basic safety rules regarding exclusive access to routes are satisfied by an implementation is still a challenge for networks of large size due to the exponential computation time and resources needed. Some recent attempts to address this challenge adopt a compositional approach, targeted to track layouts that are easily decomposable into sub-networks such that a route is almost fully contained in a sub-network: in this way granting the access to a route is essentially a decision local to the sub-network, and the interfaces with the rest of the network easily abstract away less interesting details related to the external world. Following up on previous work, where we defined a compositional verification method that started considering routes that overlap between sub-networks in interlocking systems governing a multi-station line, we attack the verification of large networks, which are typically those in main stations of major cities, and where routes are very intertwined and can hardly be separated into sub-networks that are independent at some degree. At this regard, we study how the division of a complex network into sub-networks, using stub elements to abstract all the routes that are common between sub-networks, may still guarantee compositionality of verification of safety properties.

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“…Locality can be used also for slicing, as suggested in (17) and (25). The idea is to consider only the portion of the model that has influence on the property to be verified, by a topological selection of interested track elements: this allows for a much more efficient verification, at the price of repeating the verification activity for each extracted slice and of showing that verifying slices does implies the satisfaction of desired properties for the whole system.…”

Section: Environment Assumptions and Slicingmentioning

confidence: 99%

Validation process for railway interlocking systems

Bonacchi

Fantechi

Bacherini

et al. 2016

Science of Computer Programming

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An interlocking system monitors the status of the objects in a railway yard, allowing or denying the movement of trains, in accordance with safety rules. The high number of complex interlocking rules that guarantee the safe movements of independent trains in a large station makes the verification of such systems a complex task, which needs to be addressed in conformance with EN50128 safety guidelines.In this paper we show how the problem has been addressed by a manufacturer at the final validation stage of production interlocking systems, by means of a model extraction procedure that creates a model of the internal behaviour, to be exercised with the planned test suites, in order to reduce the high costs of direct validation of the target system. The same extracted model is then subject to formal verification experiments, employing an iterative verification process implementing slicing and CEGAR-like techniques, defined to address the typical complexity of this application domain.

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Verification of Solid State Interlocking Programs

Cited by 25 publications

References 12 publications

Efficient verification of railway infrastructure designs against standard regulations

Efficient verification of railway infrastructure designs against standard regulations

Compositional Verification of Interlocking Systems for Large Stations

Validation process for railway interlocking systems

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