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Read "Service-Oriented Architecture Concepts, Technology, and Design" by Thomas Erl available from Rakuten Kobo. Sign up today and get $5 off your first. its successful implementation. Service-Oriented Architecture. Concepts, Technology, and Design. About the Author. THOmAS Erl is the world's top-selling SOA. "Service Oriented Architecture is a hot, but often misunderstood topic in IT today. Thomas articulately describes the concepts, specifications, and standards.

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Oriented Architecture (SOA) Concepts, Technology, And Design - Ebook download as In Service-Oriented Architecture: Concepts, Technology, and Design, .. dedicated to nailing down a clear definition of what SOA actually is and is not. state of eBusiness technology by building upon the proprietary- free Internet. “Service-Oriented Architecture: Concepts, Technology, and Design”. By Thomas Erl, . The application of service-orientation principles to processing logic results in .. broken down into a series of services, each responsible for executing a. Service-Oriented Architecture: Concepts, Technology, and Design URL: http://

Thomas articulately describes the concepts, specifications, and standards behind service orientation and Web Services. For enterprises adopting SOA, there is detailed advice for service-oriented analysis, planning, and design. This book is a must read! Understanding the right approach to analyzing, designing, and developing service-oriented solutions is critical. Thomas has done a great job of demystifying SOA in practical terms with his book. Through clarifying the principles and nuances of this space, the author provides a comprehensive treatment of critical key aspects of SOA from analysis and planning to standards ranging from WS-specifications to BPEL. I'll be recommending this book to both clients and peers who are planning on embracing SOA principles.

This is to prevent overlap with Service-Oriented Architecture: What this book does not cover While issues relating to integration and interoperability are referenced and discussed throughout this book. The Field Guide is dedicated to matters of integration and explores numerous service-oriented integration architectures. The step-by-step instructions provided focus on building and orchestrating service endpointsnot the underlying component logic.

XML Schema. As part of this exercise. Parts I. Over individual case study examples are interspersed throughout the chapters to provide constant real-life reference points that further demonstrate key topics. These sections help cut through some of the confusion surrounding SOA and set the groundwork for the many SOA-related topics we discuss in subsequent chapters.

Some serious thought was given to organization so that this book would be easy to read. Let's now take a closer look at what's covered in the remaining chapters. To further clarify what SOA is not.

We accomplish this by first studying the core characteristics of what constitutes a fundamental or "primitive SOA. Case studies are introduced in Chapter 2.

A common thread across all parts of the book is the consistent use of case studies. How this book is organized The next 17 chapters contain a mountain of information. Content was finally divided into the following primary parts: Thanks We then move on to identifying and explaining the key benefits behind adopting SOA.

Most notably. We begin with a brief historical account of XML and Web services and discuss how these now established technologies have shaped SOA and are. The ongoing activity of standards organizations and contributing vendors that are further extending the breadth of the SOA platform. Although these benefits are discussed throughout this book. We subsequently dig up the roots of service-orientation by describing each of the following traditional platforms for the purpose of contrasting them with SOA: Organizations and software vendors involved with developing contemporary SOA specifications and products are discussed.

This part of the chapter is rounded out by a preliminary comparison of service-orientation and object-orientation. Past architectural platforms from which SOA has evolved and inherited traits and qualities. Understanding these "worst practices" is important not only to avoiding a whole lot of problems.

Part II: We begin with a review of the fundamental mechanics behind the Web services communications framework.

Note that this chapter introduces a new feature of the book called In Plain English. The following parts of contemporary SOA are explored: Message exchange patterns Activities Coordination Atomic transactions Business activities Orchestration.

Topics covered include the following: Even though all sections in this chapter are supplemented with examples that are part of our continuing case studies. This chapter now explains how these characteristics are fulfilled by first-generation Web services technologies.

The standardized messaging format provided by SOAP is discussed. In Chapter 3 we formally defined the characteristics of primitive SOA. The following topics are covered: The sequence of these topics is intentional.

Thanks Choreography. Advanced Messaging. This chapter introduces a view of the enterprise referenced throughout subsequent parts of this book. We then move on to a detailed review of the eight most common principles of service-orientation. We then go on to discuss how SOA promotes service-orientation throughout both of these domains.

This fosters SOA throughout the enterprise and facilitates the realization of many important benefits. In these sections we discover how some principles support or rely on others. We first examine the primary influences that are shaping and broadening the reach of SOA. Thanks WS-Eventing. The subsequent section provides a mini-study of how common object-orientation OO principles relate to or influence the service-orientation principles we just discussed. After explaining the principles of service-orientation.

Part III: We then move on to defining an approach to designing SOA in support of these characteristics wherein a series of specialized service layers abstract key parts of generic and application-specific logic.

The respective languages of the first five specifications in the above list are explained later in Chapter We then study which of these influences are responsible for realizing certain characteristics. Key among these are service-oriented business modeling and organizational agility.

The chapter concludes with an important revelation. It is these principles that form the basis for SOA and shape and standardize the individual services from which SOA is comprised. We begin this process with an examination of the core components of the Web services framework and then illustrate how these are positioned and augmented within SOA. Service Layers Chapter 9 Advanced service-orientation issues are addressed in this chapter. Through deduction we end up with a list of contemporary SOA characteristics that require explicit design effort.

Principles of Service-Orientation Chapter 8 We now turn our attention to the fundamental principles of service-orientation. Each is explained individually and each is accompanied by a case study example. We continue this exercise by examining how the components of an SOA inter-relate. Also as with the previous chapter. This is an important piece of knowledge. As with Chapter 6. These principles are then revisited as we explore how they inter-relate. This then tells us which of the service-orientation principles are provided automatically by the mere use of Web services and which require explicit effort to realize.

This is an interesting analysis for those familiar with object-orientation. These chapters establish crucial concepts that form the basis for service and architecture-level design approaches described in later chapters. Part IV: Building SOA Planning and Analysis All of the previous chapters provide a knowledge of concepts and theory that can now be applied to the real world.

The last of these steps is a service modeling process that is described in Chapter This chapter now takes the first step of applying this knowledge by establishing the service-oriented analysis phase.

These phases are then assembled into the following three SOA delivery strategies: Top-down strategy Bottom-up strategy Agile strategy The pros and cons of each are contrasted. These next two chapters structure an SOA delivery project around the creation of a contemporary SOA and then supply detailed guidance as to how business and application logic can be defined and modeled into service candidates.

This chapter then examines what constitutes a business-centric SOA. The following three service layers are defined at this stage: Application service layer Business service layer Orchestration service layer These layers establish the basis for a series of standardized services that are discussed and further explained in subsequent chapters.

For the most part. Service-Oriented AnalysisPart I: Introduction Chapter 11 At this point we have covered fundamental and advanced concepts relating to SOA. It explains the key benefits of investing in the creation of business service layers and highlights the various ways business services can be derived from existing business models.

The overall objectives of service-oriented analysis are defined. Numerous technology tutorials are supplied to help understand the code examples used throughout these chapters. This approach breaks down and labels units of logic.

This important part of building SOA allows us to create service candidates that become a primary input for the ultimate SOA design we finalize as part of the service-oriented design processes described in upcoming chapters.

Following the process description are a dozen service modeling guidelines. The remaining steps consist of the following individual design processes: Entity-centric business service design Application service design Task-centric business service design Service-oriented business process design Step-by-step descriptions for each of these design processes are provided in Chapters 15 and Part V: Our service modeling process is supplemented with detailed case study examples that demonstrate the execution of individual process steps.

This part concludes with an overview of what constitutes an SOA technology platform. We now prepare to move our service candidates into service-oriented design.

Service-Oriented DesignPart I: Introduction Chapter 13 This chapter continues where we left off when we completed the service-oriented analysis phase. These exercises will result in the creation of WSDL definitions that implement service candidates which originated from the service-oriented analysis process.

The first step is an SOA composition exercise that helps identify the architectural boundary of our planned solution this step is detailed in Chapter Service Modeling Chapter 12 We now embark on a twelve-step analysis process wherein we apply service-orientation to an existing business workflow and derive business and application service candidates. A WS-BPEL process definition is created as part of the case study examples to orchestrate services that were modeled and designed in previous chapters.

Service Design Chapter 15 This chapter. As part of this procedure. Before we get into the service-oriented business process design. Business Process Design Chapter 16 Step-by-step instructions for building a service-oriented business process are provided in this chapter.

This chapter ends with a discussion of service interface modeling approaches. This important chapter is then concluded with a set of service design guidelines applicable to the previously described processes. SOA Composition Guidelines Chapter 14 Chapter 14 kicks off the service-oriented design process by providing guidance for composing a service-oriented architecture based on known functional requirements and technical limitations.

The following design processes are described: Entity-centric business service design Application service design Task-centric business service design Each process description is supplemented with extensive case study examples that demonstrate the application of individual process steps in real-world scenarios.

Each of these sections begins with a high-level introduction of the respective platforms and then continues to revisit the following aspects of SOA established in earlier chapters: Conclusion Appendix A Appendix A acts as a bookend to the case study storylines that began inChapter 2.

The individual parts that comprise the development and runtime environments required to build and host a service-oriented solution are explained.

The original objectives established at the beginning of the book are revisited to ensure that all have been met. This is followed by two identically structured sections that supply an overview of SOA support provided by the J2EE and. The progress of each organization is reviewed. Key elements and constructs for the following specifications are covered: Service Models Reference Appendix B.

While this is done intentionally to improve clarity. This appendix provides a quick reference table for all of the service models described in this book. This happens most often when some of the larger URLs are used for namespace references. These summaries are provided to allow readers to confirm that a given subject matter was fully understood. Code examples On several occasions code used in this book contains examples with long lines.

To avoid these lines from wrapping. If you are trying out any of these examples. Conventions Summary of Key Points Each primary section within a chapter ends with a summary that recaps and highlights the main topics or conclusions covered.

Figures This book contains over diagrams. I am interested in your feedback. Additional information 1. For more information. Contact the Author To contact me directly. Any experiences you'd like to share or suggestions you may have as to how I can continue to improve this book would be much appreciated. Case Studies 2. Chapter 2. The second.. Though purely fictional. Due to the distinctive nature of modern-day service-oriented architectures.

This chapter provides background information for two separate organizations.

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The first is RailCo Ltd. Though treated as separate case studies. Style characteristics To more easily identify these examples. Appendix A concludes this book by ending the storylines of both case studies and exploring the results of the organizations' respective transitions to SOA.

This essentially establishes these two organizations as constant real-world reference points. Relationship to abstract content For those of you not interested in learning with case studies. This book has been designed so that the supplementary technology tutorials include descriptions of all of the language elements used in the case study code samples. They are provided only to further assist in communicating the purpose and meaning behind the concepts.

How case studies are used This book weaves approximately examples relating to these case studies throughout all subsequent chapters. None of the abstract descriptions reference or rely on the examples. These code samples are used to demonstrate many of the technologies discussed..

Below is an example. Any portion of the book beyond Chapter 2 that discusses our case studies will contain a light gray background. Note that there are three samples in Chapter 17 that introduce elements from languages that are not explained to demonstrate an aspect of a container element that is explained..

Code samples The chapters that comprise Part V: Feel free to bypass shaded areas or perhaps only reference them when you need further elaboration on a given subject. Automation solutions RailCo's automated environment consists of the following applications: A two-tier client-server system governing all accounting and inventory control transactions.

Receipt and submission of these documents typically initiates corresponding inventory receiving and order shipping processes. Business goals and obstacles Profit margins have been noticeably declining over the past year. Though its primary line of business is product resale.

Two administrative clerks manually feed this solution with standard transaction document data primarily incoming and outgoing purchase orders and invoices. A contact management system in which customer and business partner profile information is stored and maintained. RailCo also has a small group of specialized technicians that are hired out locally for installations and repairs.

A recent review revealed that the overhead associated with RailCo's. Users range from managers to administrative assistants and accounting personnel. History Established in the early 90s. The narrowed business focus resulted in increased opportunities. Custom development tasks have typically been outsourced to local consulting firms.

This simple application consists of a database fronted by Web-based data entry and reporting user-interfaces. It started out as a brokerage for various railway wholesalers. Technical infrastructure Five employees and one manager are dedicated to full-time IT duties. RailCo ships air brake parts internationally. Its top priority is to participate in online transactions with TLS. A further unpleasant revelation was that RailCo's primary client.

The design of this solution. RailCo must upgrade its automation environment as soon as possible.

Service Oriented Architecture (SOA) Concepts, Technology, And Design

By that point RailCo runs into some limitations and decides to re-evaluate its environment in consideration of establishing an SOA. Clients have been switching to a competitor providing the same products in a more efficient manner and at a lower cost.

Transit Line Systems. RailCo's initial set of Web services. To remain competitive and minimize losses. This new requirement ends up also affecting the design of its SOA. They have subsequently been able to reduce the staff required for processing orders. These services are explained and referenced as we progress through chapters discussing Web services technology. It is looking to overhaul its technical environment to better respond to new business trends and automation requirements.

RailCo realizes that it must also seek new clients to make up for the lost sales to TLS. Figure 2. RailCo has already hurried to build a pair of Web services Figure 2.

Before our storyline begins. RailCo is a company with outdated technology automating inefficient business processes. Further investigation led to the discovery that this competitor has implemented an extension to their existing accounting system. Chapter 5 explains how services play both requestor and provider roles. It is important not to view this service as just a Web service client program. It begins to perform more of a provider role in later chapters where it evolves along with RailCo's SOA.

Individual legacy systems are typically isolated in separate environments. An economic downturn sent this company to the brink of liquidation until TLS stepped in.. Though only generic parts can be produced by the factory. Though its primary line of business is providing private transit. Parts manufacturing for other industries. A tourism branch that partners with airlines and hotels. TLS formed a partnership with Sampson Steel.

Over the course of approximately ten years. While Sampson Steel continues to service its existing clientele. Sampson Steel Corp. History TLS existed as a mid-sized corporation centered around a single private railway for several years.

The overall technical infrastructure is mixed. A maintenance and repair branch that outsources TLS service technicians to public transit sectors.

Thanks 2. TLS is a prominent corporation in the private transit sector. Mainframes have their own space. TLS enjoyed a successful period of expansion during which it established two further private railways in separate cities.

More contemporary eBusiness solutions are hosted in a clustered server environment. It employs over 1. TLS made a series of corporate acquisitions. Not only has the maintenance of automation solutions become unreasonably expensive.

The identity and structure of the company has been altered numerous times. This is the B2B system to which RailCo and many other vendors connect to conduct transactions online.

The primary motivation behind this decision is a desperate need to introduce enterprise-wide standardization and increase organizational agility. It replaced TLS's original accounting package during its expansion period. TLS has built its first service-oriented solution already Figure 2. The services that comprise this solution are introduced in Chapter 5. The information collected by this program is later manually entered into the accounts receivable module of the accounting system. A third-party time tracking system used by some employees that are outsourced by TLS to record the time they spend at client sites.

However inPart V. Tired of having to continually invest in a non-functional technical environment. The cost of business automation has skyrocketed.

As the storyline begins. Its IT department has had to deal with a volatile business model and regular additions to its supported set of technologies and automation solutions. Business goals and obstacles TLS is a corporation that has undergone a great deal of change over the past decade.

The product vendor is relatively progressive and has offered a set of Web service adapters that plug into different modules of the overall system. Automation solutions Following is the subset of TLS's inventory of legacy systems that we will be referencing in case study examples: A distributed enterprise accounting solution.

This solution is partially custom developed but relies mostly on out-of-the-box accounting features. TLS's technical environment therefore is riddled with custom developed applications and third-party products that were never intended to work together. It provides sophisticated Web front-ends for intranet and remote access but also offers some desktop tools for analysis and reporting.

This shifts our focus to a new set of services. IT directors decided to adopt SOA as the standard architecture to be used for new applications and as the founding principle to unite existing legacy systems. Much of this book is therefore focused on realizing SOA through and applying service-orientation principles to Web services technology.

Perhaps one day Web services will be supplanted by a superior platform even more capable of bringing the world closer to pure service-orientation. For now. How case studies are used: After we cover the fundamental parts of a primitive SOA. Thanks Chapter 3. Introducing SOA 3. How services encapsulate logic To retain their independence. It is already full of service-oriented businesses. Fundamental SOA Because the term "service-oriented" has existed for some time.

It makes sense for a business community not to be served by a single business outlet providing all services. Individual companies are service-oriented in that each provides a distinct service that can be used by multiple consumers.

Units of logic are still required to conform to a set of principles that allow them to evolve independently. A service-oriented analogy Let's take your average cosmopolitan city. What distinguishes the service-oriented approach to separating concerns is the manner in which it achieves separation.

When coupled with "architecture. Within SOA. What this means is that logic required to solve a large problem can be better constructed. By decomposing the community into specialized. Although we want to allow outlets to interact and leverage each other's services.

It is an established and generic theory that can be used to address a variety of problems. These conventions standardize key aspects of each business for the benefit of the consumers without significantly imposing on the individual business's ability to exercise self-governance.

By empowering businesses to self-govern their individual services. This context can be specific to a business task. One constant through its existence has been that it represents a distinct approach for separating concerns.

What is it then that makes service-oriented separation so different? Much of this book is dedicated to answering that question. Though we encourage independence within our business outlets.

Each of these pieces addresses a concern or a specific part of the problem. Distributing automation logic into separate units is nothing new.

Even in a distributed business community. This approach transcends technology and automation solutions. As shown in Figure 3. A service can even encapsulate the entire process logic. In this case. In the latter two cases. The logic is decomposed into a series of steps that execute in predefined sequences according to business rules and runtime conditions.

Figure 3. To do so. For example. This process is comprised of logic that dictates the actions performed by the solution. For services to use the logic they encapsulate they can participate in the execution of business activities.

Services can encapsulate varying amounts of logic. Thanks The concern addressed by a service can be small or large. To that effect. A communications framework capable of preserving their loosely coupled relationship is therefore required. One such framework is messaging. That is why we require messages to exist as "independent units of communication. This awareness is achieved through the use of service descriptions. How services communicate After a service sends a message on its way.

A service description in its most basic format establishes the name of the service and the data expected and returned by the service. F Figure 3. How services relate Within SOA. Because it has access to service B's service description. The manner in which services use service descriptions results in a relationship classified as loosely coupled. A message existing as an independent unit of communication. For services to interact and accomplish something meaningful. What distinguishes ours is how its three core components services.

Service-orientation principles address design issues. This is where service-orientation comes in. How services are designed Much like object-orientation.

Thanks Services that provide service descriptions and communicate via messages form a basic architecture.

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So far. Discoverability Services are designed to be outwardly descriptive so that they can be found and assessed via available discovery mechanisms. Composability Collections of services can be coordinated and assembled to form composite services. The individual principles of service-orientation are fully explained later in this book.

Autonomy Services have control over the logic they encapsulate. Abstraction Beyond what is described in the service contract. How services are built As we mentioned earlier. Statelessness Services minimize retaining information specific to an activity. For the purpose of providing a preliminary introduction. The Web services technology set offers us such a platform. The application of service-orientation principles to processing logic results in standardized service-oriented processing logic.

All forms of SOA we explore from here on are based on and extend this primitive model. When a solution is comprised of units of service-oriented processing logic.

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Loose coupling Services maintain a relationship that minimizes dependencies and only requires that they retain an awareness of each other. All major vendor platforms currently support the creation of service-oriented solutions.

Service contract Services adhere to a communications agreement. Some of the extensions we discuss are attainable today through the application of advanced design techniques. Reusability Logic is divided into services with the intention of promoting reuse. It is labeled as such because it represents a baseline technology architecture that is supported by current major vendor platforms.

With a knowledge of the components that comprise our basic architecture and a set of design principles we can use to shape and standardize these components. The ability for business automation logic to be partitioned into units so as to properly represent services. The ability for these units of logic to be relatively independent of each other so as to support the requirement for them to participate in different compositions.

If multiple services are used. Case Study RailCo's accounting solution exists as a two-tier client-server application. The ability for these units of logic to communicate with each other in such a manner that their respective independence is preserved. This process was originally modeled using standard workflow logic and then implemented as part of a packaged solution.

Within a service-oriented business model. The details of this application are described in the next chapter. For instance. The fundamental characteristics of service encapsulation. This sub-process may already exist as part of a separate Customer Contact Reporting Process. Enter Customer Purchase Order Create Customer Order The completion of each task involves a series of steps that constitute a business process.

To implement such a model. Within the application. Our primitive SOA model represents a mainstream variation of SOA based solely on Web services and common service-orientation principles. Throughout the remainder of this book.

Contemporary SOA fosters inherent reusability. Contemporary SOA promotes federation. Chapters 6 and 7 explain how the evolving landscape of Web services specifications addresses typical quality of service QoS requirements. Common characteristics of contemporary SOA Numerous recent and ongoing industry trends and developments have shaped the real world look of SOA. Contemporary SOA increases quality of service.

Contemporary SOA is still maturing. Contemporary SOA is a building block. Contemporary SOA promotes loose coupling throughout the enterprise. Contemporary SOA is an evolution. Contemporary SOA fosters intrinsic interoperability. Contemporary SOA is based on open standards. Note the absence of traditional architectural qualities such as "secure.

Major software vendors are continually conceiving new Web services specifications and building increasingly powerful XML and Web services support into current technology platforms. Its founding principles remain. Contemporary SOA promotes discovery. Contemporary SOA is fundamentally autonomous. These have been grouped into the "Contemporary SOA increases quality of service" characteristic.

Contemporary SOA promotes organizational agility. Contemporary SOA supports vendor diversity. Contemporary SOA promotes architectural composability. Contemporary SOA builds upon the primitive SOA model by leveraging industry and technology advancements to further its original ideals. Though the required implementation technology can vary. Contemporary SOA is an achievable ideal. Contemporary SOA is at the core of the service-oriented computing platform.

Contemporary SOA supports a service-oriented business modeling paradigm. Contemporary SOA implements layers of abstraction. The result is an extended variation of service-oriented architecture we refer to as contemporary SOA. Contemporary SOA emphasizes extensibility. Contemporary SOA is at the core of the service-oriented computing platform Before we get into the actual meaning behind contemporary SOA.

The ability for tasks to be carried out in a secure manner. With SOA. Contemporary SOA represents an architecture that promotes service-orientation through the use of Web services. For lack of a better term. As we step through the following sections we elaborate on each of the characteristics in our list and discuss their overall meaning to SOA. Past terms used to identify distinct application computing platforms were often suffixed with the word "architecture" when the architecture was actually being referenced.

Along those same lines. Perhaps the best way to view it is that if a product. Contemporary SOA increases quality of service There is a definite need to bring SOA to a point where it can implement enterprise-level functionality as safely and reliably as the more established distributed architectures already do. Transactional capabilities to protect the integrity of specific business tasks with a guarantee that should the task fail. Many argue that the manner in which SOA is used to qualify products.

This relates to common quality of service requirements.

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Allowing tasks to be carried out reliably so that message delivery or notification of failed delivery can be guaranteed. Performance requirements to ensure that the overhead imposed by SOAP message and XML content processing does not inhibit the execution of a task. Because the acronym already represents the word "architecture" we are unfortunately subjected to statements that can be confusing. The terms "client-server" or "n-tier. In doing so. This is further realized through message-level autonomy where messages passed between services are sufficiently intelligence-heavy that they can control the manner in which they are processed by recipient services.

The use of SOAP. Contemporary SOA is fundamentally autonomous The service-orientation principle of autonomy requires that individual services be as independent and self-contained as possible with respect to the control they maintain over their underlying logic. Contemporary SOA is based on open standards Perhaps the most significant characteristic of Web services is the fact that data exchange is governed by open standards.

Later we explain how by creating service abstraction layers. This establishes a level of autonomy that can cross solution boundaries. An SOA limits the role of proprietary technology to the implementation and hosting of the application logic encapsulated by a service. Standard open technologies are used within and outside of solution boundaries. Thanks 3. Contemporary SOAs fully leverage and reinforce this open.

After a message is sent from one Web service to another it travels via a set of protocols that is globally standardized and accepted. The use of an open. SOA builds upon and expands this principle by promoting the concept of autonomy throughout solution environments and the enterprise.

The opportunity for inter-service communication is therefore always an option. Applications comprised of autonomous services. SOA supports and encourages the advertisement and discovery of services throughout the enterprise and beyond. In fact. Organizations can certainly continue building solutions with existing development tools and server products.

Web services were more often employed to facilitate point-to-point solutions. When utilized within traditional distributed architectures.

Disparate technology platforms do not prevent service-oriented solutions from interoperating. This may have to do with the fact that not enough Web services were actually built to warrant a registry. A serious SOA will likely rely on some form of service registry or directory to manage service descriptions Figure 3.

Contemporary SOA supports vendor diversity The open communications framework explained in the previous section not only has significant implications for bridging much of the heterogeneity within and between corporations. This option is made possible by the open technology provided by the Web services framework and is made more attainable through the standardization and principles introduced by SOA. When properly standardized. Fostering this characteristic can significantly alleviate the cost and effort of fulfilling future cross-application integration requirements.

Regardless of whether an application actually has immediate integration requirements. Contemporary SOA fosters intrinsic interoperability Further leveraging and supporting the required usage of open standards.

Thanks Figure 3. Registries enable a mechanism for the discovery of services. When building an SOA application from the ground up. Intrinsically interoperable services enable unforeseen integration opportunities. One of the most attractive aspects of this architecture is its ability to introduce unity across previously non-federated environments.

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The modular nature of these specifications allows an SOA to be composed of only the functional. Contemporary SOA promotes architectural composability Composability is a deep-rooted characteristic of SOA that can be realized on different levels.

Contemporary SOA promotes federation Establishing SOA within an enterprise does not necessarily require that you replace what you already have. As previously mentioned. A business process can therefore be broken down into a series of services.

Services enable standardized federation of disparate legacy systems.

SOA supports the automation of flexible and highly adaptive business processes. While Web services enable federation. SOA promotes this cause by establishing and standardizing the ability to encapsulate legacy and non-legacy application logic and by exposing it via a common.

What provides this flexibility is the fact that second-generation Web services specifications are being designed specifically to leverage the SOAP messaging model.

Different solutions can be composed of different extensions and can continue to interoperate as long as they support the common extensions required. Individual specifications consist of modular extensions that provide one or more specific features.

Thanks building blocks it requires. Collections of services that form service compositions can themselves be reused by larger compositions. In other words. The emphasis placed by SOA on the creation of services that are agnostic to both the business processes and the automation solutions that utilize them leads to an environment in which reuse is naturally realized as a side benefit to delivering services for a given project.

This represents both composable services. Inherent reuse accommodates unforeseen reuse opportunities. When service logic is properly partitioned via an appropriate level of interface granularity. SOA encourages you to think beyond immediate. Extensible services can expand functionality with minimal impact.

Contemporary SOA emphasizes extensibility When expressing encapsulated functionality through a service description. We therefore spend a significant portion of this book exploring the service-oriented business modeling paradigm.

Because the loosely coupled relationship fostered among all services minimizes inter-service dependencies. Contemporary SOA represents an open. A collection layer of services encapsulating business process logic. Extending entire solutions can be accomplished by adding services or by merging with other service-oriented applications which also. BPM models. Partitioning business logic into services that can then be composed has significant implications as to how business processes can be modeled Figure 3.

Thanks Extensibility is also a characteristic that is promoted throughout SOA as a whole. This is an area of SOA that is not yet widely accepted or understood. Analysts can leverage these features by incorporating an extent of service-orientation into business processes for implementation through SOAs.

Time to revisit our original definition to add a few adjectives that represent the characteristics we've covered. By implementing standardized service abstraction layers. Typical SOAs can introduce layers of abstraction by positioning services as the sole access points to a variety of resources and processing logic. The result is an environment that can better accommodate business and technology-related changea quality known as organizational agility.

Through the implementation of service layers that abstract business and application logic. Thanks One of the characteristics that tends to evolve naturally through the application of service-oriented design principles is that of abstraction.

Application logic created with proprietary technology can be abstracted through a dedicated service layer. Contemporary SOA promotes loose coupling throughout the enterprise As we've established.

Each end only requires an awareness of the other. When applied through proper design. Services only require an awareness of each other. Within an organization where service-orientation principles are applied to both business modeling and technical design.

The only remaining concern is the functionality offered via the service interfaces. Contemporary SOA promotes organizational agility Whether the result of an internal reorganization. Thanks [View full size image] 3. The more dependencies that exist between these two parts of an enterprise. A loosely coupled relationship between business and application technology allows each end to more efficiently respond to changes in the other. Change in an organization's business logic can impact the application technology that automates it.

SOA offers the potential to increase organizational agility Figure 3. By leveraging service business representation. Change in an organization's application technology infrastructure can impact the business logic automated by this technology. Organizational agility is perhaps the most significant benefit that can be realized with contemporary SOA.

When viewed in the context of SOE. Change imposed on any of these environments is more easily facilitated for the same reasonsa loosely coupled state between services representing either ends of the communication channel. What this all boils down to is that an individual service-oriented application can. Contemporary SOA is a building block A service-oriented application architecture will likely be one of several within an organization committed to SOA as the standard architectural platform.

In responding to business model-level changes. SOAs can be augmented to change the nature of their automation. Other benefits realized through the standardization of SOA also contribute to minimizing dependencies and increasing overall responsiveness to change: As companies adopt SOA during this evolution. Further supporting this prediction is the evolving state of the technology set that is emerging to realize enterprise-level SOAs.

It is similar to previous platforms in that it preserves the successful characteristics of its predecessors and builds upon them with distinct design patterns and a new technology set. Even though SOA is being positioned as the next standard application computing platform.

Contemporary SOA is an evolution SOA defines an architecture that is related to but still distinct from its predecessors. Standards organizations and major software vendors have produced many specifications to address a variety of supplementary extensions. An SOA consists of services within services within services.

The reality is that the process of transitioning to this state demands an enormous amount of effort. It differs from traditional client-server and distributed environments in that it is heavily influenced by the concepts and principles associated with service-orientation and Web services.

Despite the fact that Web services are being used to implement a great deal of application functionality. SOA supports and promotes reuse. This past set of characteristics has further broadened our definition. These changes foster service-orientation in support of a service-oriented enterprise.

If you needed to provide an accurate definition of SOA today. This book provides a series of. Every technical environment will undergo changes during such a migration. When SOA platforms and tools reach an adequate level of maturity. These and other established design principles that are commonplace in traditional distributed environments are still very much a part of SOA.

Contemporary SOA is an achievable ideal A standardized enterprise-wide adoption of SOA is a state to which many organizations would like to fast-forward.

This will likely result in countless hybrid architectures. Let's append the definition with the following: SOA can establish an abstraction of business logic and technology that may introduce changes to business process modeling and technical architecture. As mentioned earlier.

SOA is a form of technology architecture that adheres to the principles of service-orientation. By trimming these items. The first start-to-finish, step-by-step guide to modeling and designing SOA. Using Service-Oriented Architecture SOA , enterprises can deliver high-value business services more rapidly and effectively, and gain unprecedented flexibility and value from existing IT infrastructure.

In Service-Oriented Architecture: Concepts, Technology, and Design, the author of 's best-selling SOA book presents the first end-to-end-tutorial for modeling and designing successful service-oriented architectures from the ground up. Writing in plain English, Thomas Erl provides step-by-step process descriptions for analyzing and designing any service or service-oriented business process definition.

Get A Copy. Hardcover , pages. More Details Other Editions 8. Friend Reviews. To see what your friends thought of this book, please sign up. To ask other readers questions about Service-Oriented Architecture , please sign up.

Be the first to ask a question about Service-Oriented Architecture. Lists with This Book. This book is not yet featured on Listopia. Community Reviews. Showing Rating details. Sort order. Sep 23, Arunkumar Goge rated it really liked it Recommended to Arunkumar by: I found it in Library. This book is simply awesome. The author cover the basics of SOA in detail with real time use cases and block diagrams, which makes me more interesting.

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