A design model for Open Distributed Processing systems

This paper proposes design concepts that allow the conception, understanding and development of complex technical structures for open distributed systems. The proposed concepts are related to, and partially motivated by, the present work on Open Distributed Processing (ODP). As opposed to the current ODP approach, the concepts are aimed at supporting a design trajectory with several, related abstraction levels. Simple examples are used to illustrate the proposed concepts

A model-based approach to service creation

This paper presents a model-based approach to support service creation. In this approach, services are assumed to be created from (available) software components. The creation process may involve multiple design steps in which the requested service is repeatedly decomposed into more detailed functional parts, until these parts can be mapped onto software components. A modelling language is used to express and enable analysis of the resulting designs, in particular the behaviour aspects. Methods are needed to verify the correctness of each design step. A technique called behaviour refinement is introduced to assess the conformance relation between an abstract behaviour and a more concrete (detailed) behaviour. This technique is based on the application of abstraction rules to determine the abstraction of the concrete behaviour such that the obtained abstraction can be compared to the original abstract behaviour. The application of this refinement technique throughout the creation process enforces the correctness of the created servic

Revisiting property transfer theory: English law and Chinese law compared

The relationship between a conveyance’s validity and its underlying contract has been a classic but unsettled topic for comparative private lawyers over the past three decades. This paper attempts to add positivist and normative observations drawn from property transfer theories and practices in English and Chinese law. A jurisdiction adopting an ‘intent plus’ model does not necessarily recognise a separate intent to convey distinct from the intent in the underlying contract, as exemplified by Chinese law, while a jurisdiction adopting the ‘intent alone’ model does not necessarily deny the separate intent to convey, as exemplified by English law. One advantage for a jurisdiction that takes the separatist approach is its flexibility, so that it can still choose between pure causality, pure abstraction, or context-based abstraction at a later stage. Recent developments show that English and Chinese law are moving towards this approach. As to whether flaws in the underlying contract infect the validity of the conveyance, the English position depends on vitiating factors, whereas the mainstream Chinese judgments tend to be pro-causal. Justifications favouring causality provided in the English and Chinese academia are different, though neither can stand up to scrutiny. The detecting opportunity argument submitted in this paper helps to justify abstraction

An Engineering Approach towards Action Refinement

In the abstract modelling of distributed systems we may need methods to replace abstract behaviours by more concrete behaviours which are closer to implementation mechanisms. Furthermore, we may want these methods to preserve the correctness of such a replacement. This paper introduces an approach towards action refinement in which an abstract action is replaced by a concrete activity. This approach is based on a careful consideration of the `action' and `causality relation' architectural concepts, which enable an abstract action to be replaced by many alternative concrete activities in a general way. This approach is based on the application of abstraction rules to determine whether a concrete activity conforms to an abstract action, considering the context in which the concrete activity and the abstract action are embedde

An approach to relate business and application services using ISDL

This paper presents a service-oriented design approach that allows one to relate services modelled at different levels of granularity during a design process, such as business and application services. To relate these service models we claim that a 'concept gap' and an 'abstraction gap' need to be bridged. The concept gap represents the difference between the conceptual models used to construct service models by different stakeholders involved in the design process. The abstraction gap represents the difference in abstraction level at which service models are defined. Two techniques are presented that bridge these gaps. Both techniques are based on the Interaction System Design Language (ISDL). The paper illustrates the use of both techniques through an example

What makes industries believe in formal methods

The introduction of formal methods in the design and development departments of an industrial company has far reaching and long lasting consequences. In fact it changes the whole environment of methods, tools and skills that determine the design culture of that company. A decision to replace current design practice by formal methods, therefore, appears a vital one and is not lightly taken. The past has shown that efforts to introduce formal methods in industry has faced a lot of controversy and opposition at various hierarchical levels in companies, resulting in a marginal spread of such methods. This paper revisits the requirements for formal description techniques and identifies some critical success and inhibiting factors associated with the introduction of formal methods in the industrial practice. One of the inhibiting factors is the often encountered lack of appropriateness of the formal model to express and manipulate the design concerns that determine the world of the engineer. This factor motivated our research in the area of architectural and implementation design concepts. The last two sections of this paper report on some results of this research

Advanced Design Concepts for Open Distributed Systems Development

Experience with the engineering of large scale open distributed systems has shown that their design should be specified at several well-defined levels of abstraction, in which each level aims at satisfying specific user, architectural, and implementation needs. Therefore, designers should dispose of a comprehensive design methodology, which allows them to conceive a specification at a certain abstraction level and transform this specification into a conforming specification at a lower abstraction level. The collection of these transformations should abridge the total design trajectory from initial user requirements to final implementation. The authors present and discuss some advanced design concepts that provide a basis for such a design methodolog

Counterfactual Causality from First Principles?

In this position paper we discuss three main shortcomings of existing approaches to counterfactual causality from the computer science perspective, and sketch lines of work to try and overcome these issues: (1) causality definitions should be driven by a set of precisely specified requirements rather than specific examples; (2) causality frameworks should support system dynamics; (3) causality analysis should have a well-understood behavior in presence of abstraction.Comment: In Proceedings CREST 2017, arXiv:1710.0277

On interoperability and conformance assessment in service composition

The process of composing a service from other services typically involves multiple models. These models may represent the service from distinct perspectives, e.g., to model the different roles of systems involved in the service, and at distinct abstraction levels, e.g., to model the service’s capability, interface or the orchestration that implements the service. The consistency among these models needs to be maintained in order to guarantee the correctness of the composition process. Two types of consistency relations are distinguished: interoperability, which concerns the ability of different roles to interoperate, and conformance, which concerns the correct implementation of an abstract model by a more concrete model. This paper discusses the need for and use of techniques to assess interoperability and conformance in a service composition process. The paper shows how these consistency relations can be described and analysed using concepts from the COSMO framework. Examples are presented to illustrate how interoperability and conformance can be assessed

Advances in architectural concepts to support distributed systems design

This paper presents and discusses some architectural concepts for distributed systems design. These concepts are derived from an analysis of limitations of some currently available standard design languages. We conclude that language design should be based upon the careful consideration of architectural concepts. This paper aims at supporting designers by presenting a methodological design framework in which they can reason about the design and implementation of distributed systems. The paper is also meant for language developers and formalists by presenting a collection of architectural concepts which deserve consideration for formal support