DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI

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DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI Department of Computer Science and Engineering IT6801 - SERVICE ORIENTED

1 DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI Department of Computer Science and Engineering IT SERVICE ORIENTED ARCHITECTURE Anna University 2 & 16 Mark Questions & Answers Year / Semester: IV / VII Regulation: 2013 Academic year:

2 1. What is Web Services? PART A Web Services can convert your applications into Web-applications. Web Services are published, found, and used through the Web. 2. What are Web Services? Web services are application components Web services communicate using open protocols Web services are self-contained and self-describing Web services can be discovered using UDDI Web services can be used by other applications XML is the basis for Web services 3. List the Web services platform elements: 4. Define - Web API SOAP (Simple Object Access Protocol) UDDI (Universal Description, Discovery and Integration) WSDL (Web Services Description Language) Web API is a development in Web services (in a movement called Web 2.0) where emphasis has been moving away from SOAP based services towards Representational State Transfer (REST) based communications.[3] REST services do not require XML, SOAP, or WSDL service-api definitions. Web APIs allow the combination of multiple Web services into new applications known as mashups. 5. Define Agents and Services A Web service is an abstract notion that must be implemented by a concrete agent. The agent is the concrete piece of software or hardware that sends and receives messages, while the service is the resource characterized by the abstract set of functionality that is provided. To illustrate this distinction, you might implement a particular Web service using one agent one day and a different agent the next day with the same functionality. Although the agent may have changed, the Web service remains the same.

3 6. Define Soap message. A SOAP message is specified as an XML Information Set. While all SOAP message examples in this document are shown using XML 1.0 syntax, other representations MAY be used to transmit SOAP messages between nodes. 7. Define - Request-Response Request-Response is a pattern in which the service consumer uses configured client software to issue an invocation request to a service provided by the service provider. The request results in an optional response. 8. Define - Subscribe-Push A third pattern for interaction is called Subscribe-Push, shown in Figure 4-3. In this pattern, one or more clients register subscriptions with a service to receive messages based on some criteria. Regardless of the criteria, the externally visible pattern remains the same. Subscriptions may remain in effect over long periods before being canceled or revoked. A subscription may, in some cases, also register another service endpoint to receive notifications. 9. Define - Data paging Some services automatically facilitate the paging of large data sets, enabling developers to focus on core application business logic instead of worrying about basic data management infrastructure. 10. Define - Coordination Model The Coordination model provides integrated service to each key customer group. The integration results from sharing key data across the business units to present a common fact to the customer. 11. Define - Atomic Service Transaction Atomic Service Transaction is the name of a design pattern authored by Thomas Erl and published as part of the SOA Design Patterns catalog. Within the catalog this pattern is further categorized as one of the Composition Implementation Patterns.

4 12. List the Atomic Transaction Protocols A Completion protocol which is typically used to initiate the commit or abort states of the transaction. The Durable 2PC protocol for which services representing permanent data repositories should register. The Volatile 2PC protocol to be used by services managing nonpersistent (temporary) data. 13. Define atomic transaction coordinator The atomic transaction coordinator plays a key role in managing the participants of the transaction process, and in deciding the transaction s ultimate outcome. 14. Define Orchestration Refers to an executable business process that may interact with both internal and external Web services. Orchestration describes how Web services can interact at the message level, including the business logic and execution order of the interactions. These interactions may span applications and/or organizations, and result in a long-lived, transactional process. With orchestration, the process is always controlled from the perspective of one of the business parties 15. Define - Choreography More collaborative in nature, where each party involved in the process describes the part they play in the interaction. Choreography tracks the sequence of messages that may involve multiple parties and multiple sources. It is associated with the public message exchanges that occur between multiple Web services Define - Service Layers When building various types of services, it becomes evident that they can be categorized depending on: - the type of logic they encapsulate - the extent of reuse potential this logic has - how this logic relates to existing domains within the enterprise As a result, there are three common service classifications that represent the primary service models used in SOA projects: - Entity Services - Task Services - Utility Services

5 17. Define - Application Services layer. Application services layer holds applications exposed as services, newly added services, and legacy applications wrapped by standard Web services interface. Services at Application Services layer are set of stateless Web services that perform certain task(s). Business process is the summation of tasks performed by one or more services of application services layer at the sequence maintained by orchestration and choreography engines. Services of Application Services layer are reusable among different business processes, can be integrated in new applications, and can be extended address new business processes. 18. Define - Business layer Business layer is responsible for supporting business process life cycle. Business process lifecycle consists of five stages: design, model, simulate, monitor, manage, and optimize business processes. Business layer users are either business analysts, or business managers. Business analysts create the initial drafts of the business processes, and business managers will manage and monitor those business processes. 19. Define - Business services layer Business services layer holds orchestration and choreography engines under governance mechanisms to map business processes to composing Web services. Orchestration and choreography engines are the mapping enablers of business processes into executable services. Web services are stateless services that cannot maintain business logic, operation flow, or user state; so, the need of an orchestration layer to include business logic is addressed. Orchestration and choreography engines maintain business process workflow logic, performance requirements, and system/user state. Business services layer has access to business rules repository. 20. Define - Orchestration service Orchestration services encapsulate the entire business process. For example, a service containing the entire flow of the Employer Registration" business process is an orchestration service. The complete registration process identifying the employer type, determining liability and registering the employer in the database and various other steps.

6 PART B 1. Explain in detail, the service roles. Service roles - A Web service is capable of assuming different roles, depending on the context within which it is used. For example, a service can act as the initiator, relayer, or the recipient of amessage - A service is therefore a unit of software capable of altering its role, depending on its processing responsibility in a given scenario - A service is capable of altering its role, depending on its processing responsibility in a givenscenario. - So The Web service can able to change its role more than once within a given businesstask - The service can assume any one of the following fundamental service roles: Serviceprovider Servicerequester Intermediaries Initial sender and ultimatereceiver Service compositions / servicecontroller Service provider - The web service can assume is role as service provider under the following conditions: If the Web service is invoked via an external source, such as a service requestor then the web service said to be service provider as shown in the figure:

7 - The Web service provides a published service description offering informationabout its features and behavior - On successful execution of web service request, the service provider may reply responsemessage - The service provider role is synonymous with the server role in the classic clientserverarchitecture - The following key term to be remembered with respect to service provider: o service provider entity refers to the organization or individual providing the Webservice o service provider agent refers to the Web service itself, which acting as an agent on behalf of its owner(organization) Service requestor - Any unit of processing logic or program that is capable of issuing a request message to the service provider is classified as a service requestor. - A Web service is always a service provider but also can act as a service requestor. -

8 Intermediaries There are two types of intermediaries. Theyare (i) Passiveintermediaries (ii) Activeintermediaries Initial sender and ultimate receiver - Initial senders are simply service requestors that initiate the transmission ofa message. Therefore, the initial sender is always the first Web service in a message path. - Ultimate receivers are simply service providers that exist as the last Web service along a message'spath - This feature is described in the following figure: - Service compositions - This particular term does not apply to a single Web service, but to a composite relationship between collections of services. Any service can enlist one or more additional services to complete a given task. Further, any of the enlisted services can call other services to complete a given sub-task. - Therefore, each service that participates in a composition assumes an individual role of service composition member, which is described in the figure: A service composition consisting of four members

9 2. Explain in detail, the service models. Service model - Service models refer to permanent classifications that represent the logic housed by the service, as well as its role within the overall solution. - The basic set of common service models listed below: o Business servicemodel o Utility servicemodel o Controller servicemodel Business service model - Within an SOA, the business service represents the most fundamental building block. It encapsulates a distinct set of business logic within a well-defined functionalboundary. - It is fully autonomous but not limited to executing in isolation, as web service they frequently expected to participate in service compositions - Business services are used within SOAs as follows: as fundamental building blocks for the representation of business logic to represent a corporate entity or information set to represent business processlogic as service compositionmembers Utility service model - Any generic Web service or service agent designed for potential reuse can be classified as a utilityservice. - Utility service models are functionally generic and non-application specific in nature - Utility services are used within SOAs for the following reasons: To enable the characteristic of reuse within SOA To promote the interoperability characteristic of SOA To provide unbelievable intermediary solution services To provides a services with the highest degree of autonomy

10 - When working with the service abstraction, a utility service is most commonly associated with the application service layer. As a result, a utility service can be referred to as a utility application service. Controller service model - Service compositions are comprised of a set of independent services that each contribute to the execution of the overall business task. The assembly and coordination of these services is often a task in itself and one that can be assigned as the primary function of a dedicated service or as the secondary function of a service that is fully capable of executing a business task independently. - The controller service controls and manage the execution of the overall business task, acting as the parent service to service composition members. - The Controller services are used within SOAs as follows: to support and implement the principle of composability to influence reuseopportunities to support autonomy in other services - The controller service model is used frequently when building SOA with specialized service abstractionlayers - Example of some services are listedbelow: Accounts Payable Service = business service Internal Policy Service = utilityservice Invoice Submission Service = business service Purchase Order Service = businessservice Load Balancing Service = utilityservice Authentication Service = utilityservice 3. Write short notes on UDDI. UDDI (Universal Description, Discovery, and Integration) - This is why UDDI formed as part of the first generation of Web services standards. UDDI provides us with a registrymodel

11 - UDDI is a specification for a distributed registry of web services. - UDDI is a platform-independent, open framework - UDDI can communicate via SOAP, CORBA, Java RMI Protocol. - UDDI uses Web Service Definition Language (WSDL) to describe interfaces to webservices. - There are two types of registries. Theyare Publicregistry Privateregistry Public registry - Public registries accept registrations from any organizations. Once signed up, organizations acting as service provider entities can register their services. Private registry - Private registries can be implemented within organization boundaries to provide a central repository for descriptions of all services the organization develops, leases, orpurchases Components of UDDI Business Entities: - Each public registry record consists of a business entity containing basic profile information about theorganization Business services - This record consists of one or more business service areas, each of which provides a description of the services offered by the business entity - Within the UDDI registry, this structure contains information about the company itself, including contact information, industry categories, business identifiers, and a list of servicesprovided. Binding templates and tmodelsbindingtemplate - Binding templates are the technical descriptions of the web services represented by the business servicestructure - The binding template represents the actual implementation of the web service

12 A single business service may have multiple binding templates tmodel - tmodel stands for technicalmodel. - tmodel section of UDDI records provides pointer to actual service description Elements of UDDI WhitePages, Yellow Pages,and GreenPages. White Pages White pages contain: Basic information about the company and its business. Basic contact information including business name, address, contact phone number,etc. A Unique identifiers for the company tax IDs. This information allows others to discover your web service based upon your business identification. Yellow Pages Yellow pages contain more details about the company. They include descriptions of the kind of electronic capabilities the company can offer to anyone who wants to do business withit. Yellow pages uses commonly accepted industrial categorization schemes, industry codes, product codes, business identification codes and the like to make it easier for companies to search through the listings and find exactly what they want. Green Pages Green pages contain technical information about a web service. A green page allows someone to bind to a Web service after it's been found. It includes: The variousinterfaces The URLlocations Discovery information and similar data required to find and run the Web service.

13 4. Explain in detail, the messaging with SOAP. Messaging with SOAP(Simple Object Access Protocol) - The SOAP specification has been accepted as the standard transport protocol for messages processed by Webservices. - Since its initial release, SOAP has been further revised to accommodate more sophisticated message structures in support of enterprise distributed applications and enterprisesoa. Messages - The SOAP specification's main purpose is to define a standard message format. The structure of SOAP format is quite simple. - Now we take a closer look at the details of the SOAP message format. SOAP message consist of the following components: SOAPenvelope SOAPHeader SOAPBody SOAPFault SOAPAttachment Envelope - Every SOAP message is packaged into a container known as an envelope. The envelope is responsible for housing all parts of the message as shown in the Figure that shows The basic structure of a SOAP message Header - Each message can contain a header, an area dedicated to hosting meta information - This header section is a vital part of the overall architecture, but optional, it is rarelyomitted. - Through the use of header blocks, SOAP messages are capable of containinga large variety of supplemental information related to the delivery and processing of message contents. - It is the header blocks through which numerous extensions can be implemented - The header blocks can include the following information s:

14 o processing instructions that may be executed by service intermediaries or the ultimatereceiver o routing information or workflow information associated with the message o security measures implemented in the message o reliability rules related to the delivery of the message o context and transaction management information Body The actual message contents are hosted by the message body, which typically consists of XML formatted data Message styles - SOAP message format support two message styles. They are o RPC Style message RPC Style Message o Document Stylemessage - The SOAP specification was originally designed to replace proprietary RPC protocols - Here, the actual SOAP message is mapped to remote method/operation call. The root element of the SOAP message is mapped to name of method/operation - The child elements of SOAP message is name of the formal parameters. The value of the child elements are actual parameter values for method call Document-Style Messages SOA relies on document-style messages to enable larger payloads and reduced message transmission volumes between services. Here, the actual SOAP message mapped to interface or implementation classes Attachments - To facilitate the delivery of non-textual data that is not easily formatted into an XML document, the use of SOAP attachment technologies ex i s t. - SOAP attachments are commonly employed to transport binary files such as images.

15 - Eachprovidesadifferentencodingmechanismusedtobundledatainitsnative format with a SOAP message. Faults - SOAP messages offer the ability to add exception handling logic by providing an optional fault section that can reside within the body area. - The use of this section is to store a simple error message that is used to deliver error condition information when an exception occurs 5. Explain in detail, the message exchange pattern. Message exchange patterns(meps) - MEP define the way that SOAP messages exchanged between two services - An MEP is a generic interaction pattern that defines the message exchange between twoservices - Message exchange patterns (MEPs) represent a set of templates that provide a group of pre-defined mapped out sequences for the exchange of messages. The most common example is a request and response \pattern. - MEPs can be composed to support the creation of larger, more complex patterns Types of MEPs - Many MEPs have been developed, each addressing a common message exchange requirement. It is useful to have a basic understanding of some of the more importantmeps. - Basically there are two categories of MEPS. They are o PrimitiveMEPs Requestresponse Fire-and-forget o ComplexMEPs publish-and-subscribemodel

Primitive MEPs - Before the arrival of contemporary SOA, set of well-definedmessaging frameworks were already used common set of primitive MEPs.

(service requestor) to a destination( service provider) - Upon receiving the message, the destination(service provider) then responds with a message back

16 Primitive MEPs - Before the arrival of contemporary SOA, set of well-definedmessaging frameworks were already used common set of primitive MEPs. They are listed below: Request-response - The request-responsemep establishes a simple exchange in which a message is first transmitted from a source (service requestor) to a destination( service provider) - Upon receiving the message, the destination(service provider) then responds with a message back to the source(service requestor) Fire-and-forget This simpleasynchronous pattern based on the unidirectional transmission of messages from a source to one or more destinations

Complex MEPs Primitive MEPs can be assembled in various configurations to create different types of messaging models, sometimes called complex MEPs.

17 Complex MEPs Primitive MEPs can be assembled in various configurations to create different types of messaging models, sometimes called complex MEPs. A classic example is the publish-and-subscribe model. The publish-and-subscribe messaging model is a composite of two primitive MEPs. It involves twosteps: Step1. Step2. The subscriber sends a message to notify the publisher that it wants toreceive messages on a particular topic and publisher sends acknowledgementto the subscriber on unsuccessful registration. This could be implemented by a request-response MEP, where the subscriber'srequestmessage,indicatingthatitwantstosubscribetoatopic, is responded to by a message from the publisher, confirming that thesubscription succeeded or failed Upontheavailabilityoftherequestedinformation,thepublisherbroadcastsmessages on the particular topic to all of that topic's subscribers.this could be implemented by the fire-and-forget patterns, allowing the publisher to broadcast a series of unidirectional messages to subscribers

Web service design. every Web service can be associated with:

Web service design. every Web service can be associated with: Web Services Web services provide the potential of fulfilling SOA requirements, but they need to be intentionally designed to do so. Web services framework is flexible and adaptable. Web services can be