物件導向軟體之架構(Object-Oriented Software Construction)探討

[서평]「Component Software」 - Beyond Object-Oriented Programming -

A new class of models, formalisms and mechanisms has recently evolved for describing concurrent and distributed computations based on the concept of ``coordination''''. The purpose of a coordination model and associated language is to provide a means of integrating a number of possibly heterogeneous components together, by interfacing with each component in such a way that the collective set forms a single application that can execute on and take advantage of parallel and distributed systems. In this chapter we initially define and present in sufficient detail the fundamental concepts of what constitutes a coordination model or language. We then go on to classify these models and languages as either ``data-driven'''' or ``control-driven'''' (also called ``process-'''' or ``task-oriented''''). Next, the main existing coordination models and languages are described in sufficient detail to let the reader appreciate their features and put them into perspective with respect to each other. The chapter ends with a discussion comparing the various models and some conclusions.

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Coordination models and languages

A super-peer is a node in a peer-to-peer network that operates both as a server to a set of clients, and as an equal in a network of super-peers. Super-peer networks strike a balance between the efficiency of centralized search, and the autonomy, load balancing and robustness to attacks provided by distributed search. Furthermore, they take advantage of the heterogeneity of capabilities (e.g., bandwidth, processing power) across peers, which recent studies have shown to be enormous. Hence, new and old P2P systems like KaZaA and Gnutella are adopting super-peers in their design. Despite their growing popularity, the behavior of super-peer networks is not well understood. For example, what are the potential drawbacks of super-peer networks? How can super-peers be made more reliable? How many clients should a super-peer take on to maximize efficiency? we examine super-peer networks in detail, gaming an understanding of their fundamental characteristics and performance tradeoffs. We also present practical guidelines and a general procedure for the design of an efficient super-peer network.

Designing an Super-Peer Network

All one needs to know about fog computing and related edge computing paradigms: A complete survey

Service-oriented computing strongly supports the development of future distributed business applications through the use of (web) services. Due to the heterogeneous and evolving nature of business processes, service adaptation is necessary in order to overcome mismatches between the interacting parties. Our long-term objective is to develop a general methodology for service adaptation capable of suitably overcoming semantic and behaviour mismatches in view of business process integration within and across organisational boundaries. In this paper, we show how to adapt a service in order to fulfil a client query requesting a service with certain inputs and outputs. The proposed technique relies on inspecting service execution traces and it generates a service contract tailored to the client needs. Service contracts include a description of the service behaviour (expressed by a YAWL workflow) as well as an (ontology-annotated) signature.

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Service adaptation through trace inspection

The paper proposes a theoretical study of coordination languages. A language that embodies the essential features of coordination languages is considered. The language includes Linda's asynchronous communication primitives, as well as several composition operators. Computations in this language are described by means of an operational semantics, reporting the whole traces of executions. The non-compositionality of this intuitive operational semantics motivates the design of a compositional and fully abstract denotational semantics, can be exploited for studying program equivalence in this setting.

Modeling Coordination via Asynchronous Communication

Available component-oriented platforms address software interoperability only at the signature level, while they do not provide suitable mechanisms for adapting components with mismatching interaction behaviour. This paper presents a methodology for automatically developing adaptors capable of solving behaviour mismatches between heterogeneous components. These adaptors are generated from abstract specifications of the intended connection between the components, by taking into account both signature interfaces and component behaviours.

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Dynamically Adapting the Behaviour of Software Components

Advances in pervasive technology have made it possible to consider large-scale application types that potentially span heterogeneous organizations, technologies, and device types. This class of application will have a multilayer architecture, where each layer is likely to use languages and technologies appropriate to its own concerns. An example application is a geographically large-scale crisis management system. Typically, such applications are required to dynamically adapt their behavior based on current circumstances, with adaptations potentially affecting all layers of the application. The complexities involved in dynamically adapting multilayer applications will significantly benefit from formal approaches to its specification.This article presents a new methodology for flexible, multilayer application adaptation, with layer-specific adaptation solution templates bound to application mismatches that are organized into hierarchical taxonomies. Templates can be linked either through direct invocations or through adaptation events, supporting flexible cross-layer adaptation. The methodology illustrates the use of different formalisms for different elements of its specification. In particular, we combine semiformal metamodeling techniques for the system model specification with formal Petri nets, which are used to capture template matchmaking using reachability analysis. This work demonstrates how existing formalisms can be used for the specification of a generic adaptation model for pervasive applications.

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A formalized, taxonomy-driven approach to cross-layer application adaptation

We present the open reference architecture of the SeaClouds solution It aims at enabling a seamless adaptive multi-cloud management of complex applications by supporting the distribution, monitoring and reconfiguration of app modules over heterogeneous cloud providers

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Antonio Brogi

Papers

Service adaptation through trace inspection

Modeling Coordination via Asynchronous Communication

Dynamically Adapting the Behaviour of Software Components

A formalized, taxonomy-driven approach to cross-layer application adaptation

SeaClouds: An Open Reference Architecture for Multi-cloud Governance