Implementation of Smart Contracts Using Hybrid Architectures with On- and Off-Blockchain Components

Recently, decentralised (on-blockchain) platforms have emerged to complement centralised (off-blockchain) platforms for the implementation of automated, digital (smart) contracts. However, neither alternative can individually satisfy the requirements of a large class of applications. On-blockchain platforms suffer from scalability, performance, transaction costs and other limitations. Off-blockchain platforms are afflicted by drawbacks due to their dependence on single trusted third parties. We argue that in several application areas, hybrid platforms composed from the integration of on- and off-blockchain platforms are more able to support smart contracts that deliver the desired quality of service (QoS). Hybrid architectures are largely unexplored. To help cover the gap, in this paper we discuss the implementation of smart contracts on hybrid architectures. As a proof of concept, we show how a smart contract can be split and executed partially on an off-blockchain contract compliance checker and partially on the Rinkeby Ethereum network. To test the solution, we expose it to sequences of contractual operations generated mechanically by a contract validator tool.Comment: 12 pages, 7 figure

A toolkit for model checking of electronic contracts

PhD ThesisIn the business world, contracts are used to regulate business interactions between trading parties. In this context, an electronic contracting systems can be used to monitor business–to–business interactions to ensure that they comply with the rights (permissions), obligations and prohibitions stipulated in contract clauses. Such an electronic contracting system will require an executable version of the contract (e-contract) for compliance checking. It is important to be verify the correctness properties of an e- contract before deploying it for compliance checking. Model checkers are widely used for automatic verification of concurrent systems. However, such tools for e-contracts with means for expressing directly and intu- itively key concepts that appear recurrently in contracts, such as execu- tions of business operations, granting (cancellation, suspension, fulfilment, violation, etc.) of rights, obligations and prohibitions to role players are not yet available. This thesis rectifies the situation by developing a high-level e-contract verification toolkit using the Spin model checker. A formal Contractual Business-To-Business interaction (CB2B) model based on the concepts of contract compliance checking developed earlier at Newcastle university has been constructed. Further, Promela, the input language of the Spin model checker, has been extended in a manner that enables specification of contract clauses in terms of contract entities: role players, business operations, rights, obligations and prohibitions. A given contract can now be expressed using extended Promela as a set of declarations and a set of Event-Condition-Action rules. In addition, the designer can specify the correctness requirements to be verified in Linear-Temporal-Logic directly in terms of the contract entities. A notable feature is that the CB2B model automatically checks for contract independent properties: properties that must hold for all contracts. For example, at run time, a contract should not simultaneously grant a role player a right to perform an operation and also prohibit it. Thus, the toolkit hides much of the intricate details of dealing with Promela processes communicating through channels and enables a designer to build verifiable abstract models directly in terms of contract entities. The usefulness of the toolkit is demonstrated by trying out a number of contract examples used by researchers working on contract verification. The thesis also shows how the toolkit can be used for generating test cases for testing an implemented system

Using fairness to make abstractions work

Abstractions often introduce infinite traces which have no corresponding traces at the concrete level and can lead to the failure of the verification. Refinement does not always help to eliminate those traces. In this paper, we consider a timer abstraction that introduces a cyclic behaviour on abstract timers and we show how one can exclude cycles by imposing a strong fairness constraint on the abstract model. By employing the fact that the loop on the abstract timer is a self-loop, we render the strong fairness constraint into a weak fairness constraint and embed it into the verification algorithm. We implemented the algorithm in the DTSpin model checker and showed its efficiency on case studies. The same approach can be used for other data abstractions that introduce self-loops

Putting Teeth into Open Architectures: Infrastructure for Reducing the Need for Retesting

Proceedings Paper (for Acquisition Research Program)The Navy is currently implementing the open-architecture framework for developing joint interoperable systems that adapt and exploit open-system design principles and architectures. This raises concerns about how to practically achieve dependability in software-intensive systems with many possible configurations when: 1) the actual configuration of the system is subject to frequent and possibly rapid change, and 2) the environment of typical reusable subsystems is variable and unpredictable. Our preliminary investigations indicate that current methods for achieving dependability in open architectures are insufficient. Conventional methods for testing are suited for stovepipe systems and depend strongly on the assumptions that the environment of a typical system is fixed and known in detail to the quality-assurance team at test and evaluation time. This paper outlines new approaches to quality assurance and testing that are better suited for providing affordable reliability in open architectures, and explains some of the additional technical features that an Open Architecture must have in order to become a Dependable Open Architecture.Naval Postgraduate School Acquisition Research ProgramApproved for public release; distribution is unlimited

Contract specification for compliance checking of business interactions

PhD ThesisIn the business world, contracts are used to regulate business interactions between trading parties. When business transactions are conducted over an electronic channel, electronic forms of contracts are needed; and because of the additional capabilities of an electronic means, their function can be extended to include compliance checking for the interactions of the parties, and enforcement of contractual clauses when needed. A contract is assumed to be a document that stipulates a list of clauses stating rights, obligations and prohibitions, and their associated constraints, that business partners are expected to honour. Compliance checking is taken to mean checking if business operations executed by business partners match with their rights, obligations and prohibitions as stipulated in the contract. We intend enforcement as making sure that business operations match the rights, obligations, and prohibitions of the parties, possibly compensating for deviations from expected behaviour. In traditional business interactions, compliance checking and enforcement are carried out man- ually. With electronic business interactions, such tasks can ideally be automated. This requires a model for the process of checking contract compliance, and an electronic language for the speci ca- tion of the actual contract. The rst main contribution of this thesis is such a model. The EROP model (from Events, Rights, Obligations and Prohibitions), composed of an ontology and an architecture, observes the interactions between the business partners, forms an interpretation of their outcome from a neutral perspective and checks their contractual compliance by matching executed operations with their sets of rights, obligations, and prohibitions, and reacting accordingly to them. Implementations of the EROP ontology and of an experimental prototype of the architecture are also presented. The second main contribution of this thesis is the EROP language, designed to specify contractual compliance, and to regulate execution of business operations through the manipulation of the sets of rights, obligations and prohibitions of the business partners. The EROP language is rule-based and event-driven, and, in a similar fashion to contracts in natural language, contractual clauses are expressed as business rules, conditional statements associating events and conditions to lists of actions altering the rights, obligations and prohibitions of the participants. The practicality of the approach taken with the EROP language is evaluated presenting a larger, complete scenario and a number of smaller ones taken from comparable work. Notes on the translation of the EROP language to one on a lower level of abstraction that relies on the implementation of the EROP ontology are also presented. The Appendix presents a formal grammar for the language.UK EPSRC e-Science Pilot Project: "GOLD (Grid-based Information Models to Support the Rapid Innovation of High Value Added Chemicals)

Can the Application of the Visual Programme Tool Dynamo Assist in Streamlining Current COBie Requirements for Design Professionals

information exchange (COBie) is still a misunderstood and miscommunicated topic. Despite the free distribution of supporting information, many errors remain in its practical application. This study explores strengthening COBie design practices, reducing computational expense by data automation and streamlining the workflow process without the need for designer’s total immersion into COBie theory. Synergies between Autodesk Revit and Dynamo BIM were the chosen software utilised to achieve such a goal. A literature review is first employed to provide a current overview from academic and industry sources, with the principles of design science the chosen methodology in the development, implementation and evaluation of a solution orientated research strategy. Data was gathered via questionnaires from eight Mechanical, Electrical and Plumbing (MEP) engineering firms in Ireland who currently have a demand for COBie design deliverables. This paper reports a general lack of awareness for the open source COBie Testing software tool and a misconception as to exact COBie for Design deliverables. Results indicate considerable time saving across separate projects for six COBie parameters identified for streamlining due to inefficient workflows. Testing COBie data was fully verified in accordance with the international standard NBIMS v3 using the COBie Quality Control Reporter, making it compliant for Facilities Management software use

Contract representation for validation and run time monitoring

PhD ThesisOrganisations are increasingly using the Internet to offer their own services and to utilise the services of others. This naturally leads to resource sharing across organisational boundaries. Nevertheless, organisations will require their interactions with other organisations to be strictly controlled. In the paper-based world, business interactions, information exchange and sharing have been conducted under the control of contracts that the organisations sign. The world of electronic business needs to emulate electronic equivalents of the contract based business management practices. This thesis examines how a 'conventional' contract can be converted into its electronic equivalent and how it can be used for controlling business interactions taking place through computer messages. To implement a contract electronically, a conventional text contract needs to be described in a mathematically precise notation so that the description can be subjected to rigorous analysis and freed from the ambiguities that the original humanoriented text is likely to contain. Furthermore, a suitable run time infrastructure is required for monitoring the executable version of the contract. To address these issues, this thesis describes how standard conventional contracts can be converted into Finite State Machines (FSMs). It is illustrated how to map the rights and obligations extracted from the clauses of the contract into the states, transition and output functions, and input and output symbols of a FSM. The thesis then goes on to develop a list of correctness properties that a typical executable business contract should satisfy. A contract model should be validated against safety properties, which specify situations that the contract must not get into (such as deadlocks, unreachable states .... etc), and liveness properties, which detail qualities that would be desirable for the contract to contain (responsiveness, accessibility .... etc). The FSM description can then be subjected to model checking. This is demonstrated with the aid of examples using the Promela language and the Spin validator. Subsequently, the FSM representation can be used to ensure that the clauses stipulated in the contract are observed when the contract is executed. The requirements of a suitable run time infrastructure for monitoring contract compliance are discussed and a prototype middleware implementation is presented.UK Engineering and Physical Sciences Research Council (EPSRC)

FLACOS’08 Workshop proceedings

The 2nd Workshop on Formal Languages and Analysis of Contract-Oriented Software (FLACOS’08) is held in Malta. The aim of the workshop is to bring together researchers and practitioners working on language-based solutions to contract-oriented software development. The workshop is partially funded by the Nordunet3 project “COSoDIS” (Contract-Oriented Software Development for Internet Services) and it attracted 25 participants. The program consists of 4 regular papers and 10 invited participant presentations