Web service

Context

Apakah ini web service?

Perbedaan

Web yg ditambah service

Komponen vs. service• reusable• To be used a component must:

– be packaged to be deployed as– part of some larger application– system– fit with the existing framework– used to develop the system

• Components can be sold.– Component developers charge on a

per-deployment basis:• whenever a new client downloads the

component.• There are many component

frameworks available for building distributed systems (e.g., J2EE, DCOM, .NET, CORBA).

• The problem is: they are not compatible.

• Web services are reusable too.• To be used a service must:

– be published on the Web– advertise its description and location to

potential clients across the Web so that they can access it using standard protocols

• Web Services can be sold too.– Service providers can charge on a per-

call basis: each time an existing client interacts with a service by exchanging a new message.

• Web services can be composed into larger systems and (of course) can be found on the Web.

• Unlike components, Web services do not have to be downloaded and deployed in order to be used by clients.

Komponen interoperability

Web service interoperability

Standard interoperability

Standard web service

• Standard diperlukan karena banyaknya pilihan• Web service juga memiliki banyak standard (standard

baru, sudah hilang, yg masih terus)• Tanpa standard, interoperability tidak kan terjadi.• Perlu waktu agar standard diterima secara luas oleh

industri. Karena spesifikasi yg diawali dg “WS” bukan jaminan interoperability ada.

• Badan standard WS:– W3C (World Wide Web Consortium)– OASIS (Organization for the Advancement of Structured

Information Standards)– WS-I (Web Services Interoperability Organization)– GGF (Global Grid Forum)

WS standard

Keterbatasan middleware

• Web service ditujukan untuk mengatasi beberaoa keterbatasan middleware

• Non standard interface– Sangat mahal untuk membangun sistem tersebar

pada berbagai macam platform middleware• Lack of trust

– Trust domain yang berbeda sangat susah• Centralized

– Tidak cocok untu B2B• RPC vs. Messaging

– Interkasi lambat dan asinkron

WS dan Middleware

• Web service bisa dianggap evolusi dari middleware secara alamiah

• WS standard memungkinkan interoperability antar middleware

• Proses integrasi lebih mudah• B2B integrasi dimungkinkan (SOAP bisa lewat firewall)

Arsitektur

• Interpretasi yg umum adalah dari IBM.

• Ada 3 elemen:– Service requester– Service provider– Service regitry

WS standard• The Web service architecture

proposed by IBM is based on two key concepts:

– architecture of existing synchronous middleware platforms

– current specifications of SOAP, UDDI and WSDL

• The architecture has a remarkable client/server flavor

• It reflects only what can be done with

– SOAP (Simple Object Access Protocol)

– UDDI (Universal Description and Discovery Protocol)

– WSDL (Web Services Description Language)

Service bus

• Service broker