A Service-Oriented Computing Platform: An Architecture Case Study

A Service-Oriented Computing Platform: An Architecture Case Study

Michael Sobolewski (United States Air Force Research Laboratory, USA & Polish-Japanese Institute of Information Technology, Poland)
DOI: 10.4018/978-1-4666-6178-3.ch010
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Abstract

In Service-Driven Computing, the client-server architecture describes the relationship of cooperating programs in a distributed application. The providers of a resource or service execute workloads submitted by service requestors. Web service, Grid, and Cloud Computing technologies are based on the client-server architecture. A true service-oriented architecture describes everything, anywhere, anytime as a service. This chapter presents the SORCER (Service-ORiented Computing EnviRonment) platform, which provides service-oriented modeling or programming or both (mogramming) environments within its operating system that runs front-end service-oriented mograms and dynamically manages corresponding federations of local and remote service providers. The architecture of SORCER is described with the focus on service-oriented mogramming, service context-awareness, and its operating system managing everything as a service type. A case study report illustrates how SORCER is used for a conceptual design of the next generation of efficient supersonic air vehicles.
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Introduction

From the very beginning of networked computing, the desire has existed to develop protocols and methods that facilitate the ability of people and automatic processes across different computers to share resources and information among computing nodes in an optimized way. As ARPANET (Postel et al., 1981) began through the involvement of the NSF (Lynch et al., 1992; Postel & Reynolds, 1987) to evolve into the Internet for general use, the steady stream of ideas became a flood of techniques to submit, control, and schedule workloads across distributed systems (Lee, 1992).

The term “metacomputing” (Metacomputing, n.d.) was coined around 1987 by NCSA Director, Larry Smarr. The metacomputer is, simply put, a collection of computers held together by state-of-the-art technology and balanced so that, to the individual user, it looks and acts like a single computer. The constituent parts of the resulting metacomputer could be housed locally, or distributed between buildings, and even continents. Globally distributed service-oriented (SO) computing systems are metacomputing systems.

The latest in client-server ideas are the Grid (Foster et al., 2001) and Cloud (Linthicum, 2009), intended to be used by a wide variety of different users in a non-hierarchical manner to provide access to powerful aggregates of resources and services. Grids and Clouds, in the ideal, are intended to be accessed for computation, data storage and distribution, and visualization and display, among other applications, without undue regard for the specific nature of the hardware and underlying operating systems on the resources on which these jobs (executable codes) are carried out. While a Grid is focused on computing resource utilization, Clouds are focused on platform virtualization in computer networks. In general, Grid and Cloud Computing is client-server model that abstract the details of the server away by requesting a service (resource), and not a specific server (machine). However, both terms are vague from the point of view of service-oriented (SO) architectures and related programming models. In those cases the architecture refers usually to a form of API-based, client-server middleware-managing services and clients written in general-purpose software languages with no front-end SO layer. It means that at the back-end, each time a new service (code) has to be developed; it must be deployed at the server by software developers and later accessed by the end users in their applications via the middleware API. In these systems there is no front-end option that allows the end user to create at runtime complex service collaborations directly from existing services in the network.

As we reach adolescence in the information era, we are facing the dawn of the service era, an era that will be marked not by PCs, workstations, and servers, but by computational capability that is embedded in all things around us exposing ubiquitous services. A service is the work performed in which a service provider (one that serves) exerts acquired abilities to execute a computation. Service providers just consume services and provide services from and to each other respectively. Applications are increasingly moving to the network - self aware, autonomic networks that are always fully functional. The service providers implement instructions of the virtual service processor (metaprocessor). In a true SO system everything anytime anywhere is a service by the analogy to an object-oriented system where everything is an object. Therefore for each service there is a corresponding local or remote service provider and all service providers are treated by the SO platform in a uniform way.

Key Terms in this Chapter

SORCER: A Service-ORiented Computing EnviRonment (SORCER) is a SOOA based computing platform, which provides federated service-oriented environment within its operating system that runs front-end services (exertions) and dynamically manages corresponding federations of local and remote service providers.

SPOA: A Service-protocol-oriented Architecture is SOA with a wire protocol between a service proxy used by the requestor and its service provider that is predefined and final, for example IIOP, JRMP, or SOAP protocol.

Client-Server Architecture: The client-server architecture is a distributed architecture that separates a service requestor (client) from a provider of service or resource (server).

Service Federation: A service federation is a runtime collection of all service providers needed to actualize service collaboration expressed by an exertion.

Exertion: An exertion is a service-oriented process expression functioning as a proxy to a corresponding service federation created at runtime. A task exertion (or simply a task) is an elementary service provided by a single service provider. A job exertion (or simply a job) is a service composition that represents a hierarchically organized collaborative service federation (workflow). A block exertion is a concatenation of exertions having common block scope for control flow. An exertlet is a corresponding object proxy for the exertion. A netlet is a corresponding interpreted script for the exertion.

Service: A service is the work performed in which a service provider (one that serves) exerts acquired abilities to execute a computation.

Computing Platform: A computing platform allows software to run on the computer and requires a processor, operating system, and mogramming environment with related runtime libraries and user agents.

Mogramming: Mogramming is programming or modeling or both.

EOP: Exertion-oriented programming (EOP) is a programming paradigm that represents concepts as “services proxies”, called exertions, that have hierarchically organized data contexts (attributes that describe the service data), control contexts (attributes that describe the service control strategy), and signatures to associated service providers. The associated providers collaborate according to control strategies imposed by control contexts to process data contexts of the service federation created at runtime.

SOOA: A Service-object-oriented Architecture is SOA with the communication based on remote message passing with the ability to pass data using any wire protocol that can be chosen by a remote object (provider) to satisfy efficient communication with its requestors. In SOOA a proxy object used by the requestor, for example in Jini ERI, is created, registered, and owned by the provider.

Service Proxy: A service proxy, in its most general form, is a service functioning as an interface to another service. The proxy could interface to anything: a network connection, a large object in memory, a file, or a service provider that is expensive or impossible to duplicate like a server or federation of servers.

SOA: A Service-oriented Architecture (SOA) is a software architecture using loosely coupled service providers that introduces a service registry, the third component to client-server architecture. The registry allows finding service providers in the network.

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