Web Services Based on SOA: Concepts, Technology, Design by Thomas Erl MIS 181.9: Service Oriented Architecture 2 nd Semester,

Web Services ► web-based applications that use open, XML-based standards and transport protocols to exchange data with clients

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

How does it work? ► The basic Web services platform is XML + HTTP. ► XML provides a language which can be used between different platforms and programming languages and still express complex messages and functions. ► The HTTP protocol is the most used Internet protocol.

Web services model Web Service Provider Web Service Registry Web Service Client publish bind/invoke find

Web Services ► Technology Framework ► Includes one or more of the following: ► Architectures ► Technologies ► Concepts ► Models ► Sub-frameworks

Web Services Framework ► Characterized by ► Web services, service descriptions, messages ► Communications agreement (service description) based on WSDL ► Messaging framework using SOAP ► Service description registration and discovery architecture using UDDI

Web services platform elements ► SOAP (Simple Object Access Protocol) ► UDDI (Universal Description, Discovery and Integration) ► WSDL (Web Services Description Language)

Web services platform elements UDDI WSDL SOAP XML Service Discovery and Publication Service Description XML based messaging Data level description

Why use web services? ► Interoperability has Highest Priority ► Web Services take Web-applications to the Next Level ► Web Services have Two Types of Uses ► Reusable application-components. ► Connect existing software.

What is SOAP? ► stands for Simple Object Access Protocol ► an XML-based protocol to let applications exchange information over HTTP ► a protocol for accessing a Web Service

What is SOAP? ► a communication protocol ► a format for sending messages ► designed to communicate via Internet ► platform independent ► language independent ► based on XML ► simple and extensible ► SOAP allows you to get around firewalls ► SOAP is a W3C standard

What is WSDL? ► an XML-based language for locating and describing Web services ► stands for Web Services Description Language ► based on XML ► used to describe Web services ► used to locate Web services ► a W3C standard

What is UDDI? ► a directory service where companies can register and search for Web services ► stands for Universal Description, Discovery and Integration ► a directory for storing information about web services ► a directory of web service interfaces described by WSDL ► communicates via SOAP ► built into the Microsoft.NET platform

Web Services Design Concepts ► Web service can have two classifications ► Temporary based on roles assumed during runtime ► Permanent based on application logic it provides

Web Service Roles ► Web service can assume different roles depending on context of usage ► Message Initiator ► Message Relayer ► Message Recipient ► Agnostic services

Service Roles ► Service Provider ► Recipient of the request message ► Service Requestor ► Any unit of processing logic capable of issuing a request message ► Searches for provider by reviewing Service Descriptions ► Web Service is always a provider but can also be a requestor

Other roles ► Intermediaries ► Service composition member

Intermediaries ► Web services communications is based on use of messaging paths ► Vs. point-to-point communication ► message sent by a requester can be processed by multiple intermediate routing and processing agents before received by ultimate destination ► Intermediaries: web services that route and process a message ► After initially sent ► Before target destination

Service Composition Member ► Any service can enlist one or more additional services to complete a given task ► Any of the enlisted services can call other services to complete a given sub-task

Service Models ► Application logic classification ► Business-related roles within a solution ► Business service model ► Utility service model ► Controller service model

Business Service Model ► Most fundamental building block within SOA ► Encapsulates distinct set of business logic

Utility Service Model ► Any generic service designed for potential reuse ► Used in SOA as: ► Services that are reused ► Solution-agnostic intermediary services ► Services with highest degree of autonomy ► Most commonly associated with the application service layer

Controller Service Model ► Assembles and coordinates service compositions ► Used in SOA ► To support and implement principle of composability ► To leverage reuse opportunities ► There can be master controller and sub- controller services

Service Descriptions ► WSDL used to define service descriptions ► Required to accompany any web service ► Service requestor uses WSDL of a service provider to ensure that messages sent is understood and accepted

Service endpoints ► WSDL describes the point of contact for a service provider ► Provides definition of endpoint interface ► So requestor can know how to structure request message ► Establishes the physical location (address) of the service

WSDL Definition ► Abstract Definition ► Interface characteristics ► Technology Independent ► portType/interface ► operation ► Represents a specific action performed by a service ► Similar to public method ► message

WSDL Definition ► Concrete Description ► Binding ► Technology transport ► E.g. SOAP ► Port/endpoint ► Physical address

SOAP ► Header ► Meta information on how data will be delivered and processed ► Allows SOAP messages to be independent ► Sample instructions ► Processing ► Routing/workflow ► Security ► Body ► XML formatted data

Service Description Advertisement and Discovery ► UDDI ► One standard for structuring registries that keep track of service descriptions ► Registries can be searched manually or automatically thru an API ► Public Registries ► Accept registration from any organizations ► Private Registries ► Can be implemented within an organization

UDDI Registry Records Components ► Business entities ► For public registry records ► Profile of business entity ► Services offered by the entity ► Binding information ► Can be an address of a web site ► Can be a pointer to actual service descriptions