Web-Services Goals of this chapter –Provide an overview on most recent technologies –Illustrate the importance of XML –Allow students to understand the.

Web-Services

• Goals of this chapter– Provide an overview on most recent

technologies– Illustrate the importance of XML– Allow students to understand the

interconnections of the technologies– Allow students to see interconnections with

web-based architectures– Allow students to estimate future development

Web Services

• What Is an XML Web Service?• XML Web services are the fundamental building blocks

in the move to distributed computing on the Internet. • Open standards and the focus on communication and

collaboration among people and applications have created an environment where XML Web services are becoming the platform for application integration.

• Applications are constructed using multiple XML Web services from various sources that work together regardless of where they reside or how they were implemented.

• Examples: Transaction handling, calendar service, …

Web Services Introduction(http://e-serv.ebizq.net/wbs/thomas_1.html)

• Web services have become influential since about 2002• Strong impetus for development of both major enterprise

platforms:– .NET (Microsoft)– J2EE (Sun Microsystems)

• Users, e.g.:– U.K. government: Employs web services in creating an Internet-based

infractructure for all government services by 2005.– Software vendors such as Sun, Oracle Corp., are including web

services protocols in their platform and development tools.– Microsoft is planning to offer public web services, notably .NET

Passport that lets you use your email address and a single password for secure sign-on to any participating web site.

Web Services - Trends

• Three waves of web service deployment:– Partner: support complex supply chains– Private: Web service protocols used to extend internal

EAI (Enterprise Application Integration) efforts.Dominant mode of deployment will be mixed J2EE and .NET, hence interoperability is essential

– Public: full-blown adoption of services; will be delayed until standards are finalized.

• Web services offer a fine-grained approach to EAI and thus provide attractive means for companies who want to outsource just few particular functions.

Web Services

• Definition (one of several!)– XML Web Services expose useful functionality to Web

users through a standard Web protocol. In most cases, the protocol used is SOAP.

– XML Web services provide a way to describe their interfaces in enough detail to allow a user to build a client application to talk to them. This description is usually provided in an XML document called a Web Services Description Language (WSDL) document.

– XML Web services are registered so that potential users can find them easily. This is done with Universal Discovery Description and Integration (UDDI).

What can one do with web services?

• Exposing existing applications as XML Web services will allow users to build new, more powerful applications that use XML Web services as building blocks.

• For example, a user might develop a purchasing application to automatically obtain price information from a variety of vendors, allow the user to select a vendor, submit the order and then track the shipment until it is received.

• The vendor application, in addition to exposing its services on the Web, might in turn use XML Web services to check the customer's credit, charge the customer's account and set up the shipment with a shipping company.

Web Services

• Easier than CORBA and DCE• Significant advantage over previous

efforts: web services work with standard Web protocols—XML, HTTP and TCP/IP

• Most of the information provided by web services is available now on the Web, but XML Web services will make programmatic access to it easier and more reliable.

SOAP

• SOAP is the communications protocol for XML Web services.

• SOAP is a specification that defines the XML format for messages.

• SOAP message: a well-formed XML fragment enclosed in a couple of SOAP elements.

• The Current SOAP standard assumes security is a transport issue and is silent on security issues.

SOAP

• Optional parts of the SOAP specification describe how to represent program data as XML and how to use SOAP to do Remote Procedure Calls. They are used to implement RPC-style applications where a SOAP message containing a callable function, and the parameters to pass to the function, is sent from the client. The server returns a message with the results of the executed function.

• Most current implementations of SOAP support RPC applications.

SOAP (continued)

• SOAP also supports document style applications where the SOAP message is just a wrapper around an XML document. Document-style SOAP applications provide flexibility for many new XML Web services.

• The last optional part of the SOAP specification defines the format of an HTTP message that contains a SOAP message.

• The HTTP binding is optional, but almost all SOAP implementations support it because it's the only standardized protocol for SOAP.

Web Services Description Language WSDL

• WSDL file: XML document describing a set of SOAP messages and how they are exchanged.

• WSDL is to SOAP what IDL is to CORBA or COM. • Since WSDL is XML, it is readable and editable but in

most cases, it is generated and consumed by software. • WSDL specifies what a request message must contain

and what the response message will look like in an unambiguous notation.

• A WSDL file defines everything required to write a program to work with an XML Web service.

WSDL

• The WSDL notation is based on the XML Schema standard:– It is programming-language neutral and standards-based. – It is suitable for describing XML Web services interfaces that are

accessible from a wide variety of programming languages. • In addition to describing message contents, WSDL

defines where the service is available and what communications protocol is used to talk to the service.

• There are several tools available to read a WSDL file and generate the code required to communicate with an XML Web service.

• Many current SOAP toolkits include tools to generate WSDL files from existing program interfaces, but currently there are few tools for writing WSDL directly.

WSDL Document Structure

• A WSDL document is made up of 5 sections.• The WSDL document can be divided into two

groups of sections. – The top group is comprised of Abstract Definitions,

• The abstract sections define SOAP messages in a platform- and language-independent manner; they do not contain any machine- nor language-specific elements. This helps define a set of services that several, diverse Web sites can implement.

– The bottom group consists of Concrete Descriptions. • Site-specific matters such as serialization are then relegated

to the bottom sections, which contain concrete descriptions.

WSDL Document Structurehttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwebsrv/html/wsdlexplained.asp

• Abstract Definitions – Types

Machine- and language-independent type definitions. – Messages

Contains function parameters (inputs separate from outputs) or document descriptions.

– PortTypesRefers to message definitions in Messages section to describe function signatures

• Concrete Descriptions – Bindings

Specifies binding(s) of each operation in the PortTypes section.

– Services Specifies port address(es) of each binding.

Universal Discovery Description and Integration - UDDI

• UDDI allows one to search for a company that offers the services one needs, read about the service offered and contact someone for more information.

• A UDDI directory entry is an XML file that describes a business and the services it offers. There are three parts to an entry in the UDDI directory.

– The "white pages" describe the company offering the service: name, address, contacts, etc.

– The "yellow pages" include industrial categories based on standard taxonomies such as the Standard Industrial Classification.

– The "green pages" describe the interface to the service in enough detail for someone to write an application to use the Web service.

• Services are defined through a UDDI document called a Type Model or tModel. In many cases, the tModel contains a WSDL file that describes a SOAP interface to an XML Web service.

What's Left?

• SOAP, WSDL, and UDDI constitute a set of baseline specifications that provide the foundation for application integration and aggregation. From these, companies are building real solutions and getting real value from them.

• Today, people are having success with XML Web services, but there are still things that are left, e.g. security, operational management, transactions, reliable messaging.

• The Global XML Web Services Architecture will help take XML Web services to the next level by providing a coherent, general purpose model for adding new advanced capabilities to XML Web services which is modular and extensible.

Web Services and Distributed Objects: Competing or Complementary?

(http://e-serv.ebizq.net/wbs/conway_1.html)

• The premise is that, when used correctly, Web services and distributed objects have different paradigms--"document-oriented" and "object-oriented"--and that a combination of both paradigms is required to achieve end-to-end business integration.

• The object-oriented platforms CORBA and J2EE have been successful for building and integrating applications within the enterprise.

• The document-oriented XML technologies associated with Web services are rapidly gaining popularity for business-to-business integration between enterprises.

• Total business integration needs to address both these areas.

Object-Oriented vs. Document-Oriented

• Web services look like yet another distributed object system. It is tempting to expose existing CORBA or Java objects as Web services by mapping them to WSDL.

• However, XML is document-oriented, not object-oriented. Web services should implement document exchange systems and not distributed object systems.

Object-Oriented vs. Document-Oriented

• Document exchange systems have:– Larger, richer data structures--so much richer that we

call them "documents" – Looser coupling between agents – More asynchronous communication

• Communicating objects have:– Simple data structures– Tight coupling– Synchronous communication: Because of the tight

coupling one must be able to associate replies with requests.

Web Services and Distributed Objects Design Issues

• Distributed object platforms are the ideal underpinning for a Web service.

• Some of the distributed objects have to be designed with the knowledge that they are going to be Web services. These "service objects" will typically delegate their work to many smaller-grained distributed objects in a distributed system that underlies the Web service.

• Larger chunks of data will be passed in a single call than the objects in the underlying distributed system.

• Web services are built on distributed objects; distributed objects are built on nondistributed programming objects. At each step, the granularity becomes finer.

Web Services and Distributed Objects – Application Areas

• Web services are unlikely to perform adequately as high-performance system components because of the size and parsing overhead of XML documents. – For example, it's hard to imagine a telephone exchange being

successfully implemented as a set of intercommunicating Web services.

– However, it's easy to imagine some types of access such as allowing other carriers to request special phone numbers on their network to such a system as Web services.

• Web services are ideal in the case that one cannot assume agreement on CORBA or EJB interfaces.

• Use distributed objects to build high-performance systems with a well-defined architecture, and Web services to connect independent systems in a loosely coupled fashion based on shared business processes and documents.

. NET

• Microsoft® .NET is a set of Microsoft software technologies for connecting information, people, systems, and devices. It enables a high level of software integration through the use of XML Web services—small, discrete, building-block applications that connect to each other as well as to other, larger applications over the Internet.

• .NET is infused into the products that make up the Microsoft platform, providing the ability to quickly and reliably build, host, deploy, and utilize connected solutions using XML Web services, all with the protection of industry-standard security technologies.

Basic Elements of .NET

Smart Devices and.NET• Each smart device optimizes the way information is presented and

gathered—from converting text to speech to recognizing handwriting.

• Using XML, SOAP, and UDDI, smart devices are able to consume XML Web services.

• Smart devices are PCs, laptops, workstations, phones, handheld computers, Tablet PCs, Microsoft® Xbox™ game consoles,… What makes them "smart" is their ability to access XML Web services, enabling you to interact with your data regardless of the location, type, and number of devices you use.

• Smart devices allow access to your information in an appropriate form anytime and anywhere.

• Smart devices "consume" (use) XML Web services and provide Microsoft .NET experiences.

Microsoft Servers and .NET

• With Microsoft® .NET, businesses will be able to turn key processes into XML Web services. From the schedule for a doctor's office to the catalog for a book seller to an exchange rate calculator for world currencies.

• Windows Servers facilitate the aggregation and accelerate the integration of systems, applications, and partners using XML Web services through the servers' deep level support of XML.

• Simple access to mainframes with Microsoft Host Integration Server• Automatic conversions of existing data formats into XML with

Microsoft BizTalk Server.• Scalable servers that deeply integrate XML and are protected by

industry-standard technologies will provide the backbone for hosting and deploying .NET software and services. – Microsoft Windows® 2000 Server, Microsoft Windows Server 2003, and

the Microsoft .NET Enterprise Servers fill this role.

Developer Tools and .NET

• With Microsoft® Visual Studio® .NET and the Microsoft .NET Framework, developers can develop XML Web services quickly and integrate them easily with other applications.

• Existing skills, can be deployed, because the .NET Framework allows you to develop Web services using any modern program language.

• Microsoft Visual Studio .NET and the Microsoft .NET Framework supply a complete solution for developers to build, deploy, and run XML Web services.

• These tools help enhance the performance, reliability, and security of XML Web services.

• Microsoft Visual Studio .NET represents the best development environment for .NET-connected software and services.

• Visual Studio .NET advances the programming languages: – Microsoft Visual Basic®, with new object-oriented programming features;– Microsoft Visual C++®, which enables you to build .NET-connected applications;– C#, which brings RAD to the C and C++ developer.

MapPoint® .NET

• Microsoft® MapPoint® .NET is a hosted, programmable XML Web Service for integrating maps, driving directions, distance calculations, proximity searches and other location intelligence into your applications, business processes, and Web sites.