Web Services

Web Services: Introduction

• Building blocks for constructin distributed Web-based applicaitons
• Independence:
  • platform
  • object model
  • language
• Based on open Internet standards: http, XML
• Web Services Architecture (W3C)

SOAP: Simple Object Access Protocol

"SOAP Version 1.2 provides the definition of the XML-based information which can be used for exchanging structured and typed information between peers in a decentralized, distributed environment." [W3C]

• SOAP is a communication protocol
• SOAP is for communication between applications
• SOAP is a format for sending messages
• SOAP is designed to communicate via Internet
• SOAP is platform independent
• SOAP is language independent
• SOAP is based on XML
• SOAP is simple and extensible
• SOAP allows you to get around firewalls
• SOAP will be developed as a W3C standard

• What is SOAP (flash)
• Tutorials
• Google Web API
• SOAP Version 1.2 Part 0: Primer (W3C)
• SOAP Version 1.2 Part 1: Messaging Framework (W3C)
• SOAP Version 1.2 Part 2: Adjuncts (W3C)

Python (2.0) examples (with SOAP.py):
import SOAP

from SOAPpy import SOAPProxy
====
server = SOAP.SOAPProxy("http://services.xmethods.net/soap")
print server._ns("urn:xmethods-delayed-quotes").getQuote(symbol = "AMZN")
====
server = SOAP.SOAPProxy("http://services.xmethods.net/soap")
print server._ns("urn:xmethods-CurrencyExchange").getRate(country1="usa", country2="canada")
print server._ns("urn:xmethods-CurrencyExchange").getRate(country1="usa", country2="japan")
====
server = SOAP.SOAPProxy("http://services.xmethods.net:80/perl/soaplite.cgi")
print server._ns("urn:xmethodsBabelFish").BabelFish(translationmode="en_fr", sourcedata="soap is good for translation") ====

WSDL: Web Services Description Language

• Describe XML-based services
• A collection of metadata about an XML-based service
• Desribes functionality and how that functionality is made available.
• Most prominent current use of WSDL is to describe services by SOAP
• WSDL Version 2.0 (W3C)

UDDI: Universal Description, Discovery and Integration

• A specification for distributed Web-based information registries of Web services.
• A publicly accessible registries of services
• Allow businesses to register information about the Web services they offer so that other busines can find them
• uddi.org