web-services

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Nov 3, 2013 (4 years and 6 months ago)

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(c) University of Toronto MIE456 2004

1

Web Services

Information Systems Infrastructure II

Chris Lau

christopher.lau@utoronto.ca

(c) University of Toronto MIE456 2004

2

Overview


What are they?


Examples of web services


Technologies associated with web
services


Misconceptions of web services


(c) University of Toronto MIE456 2004

3

* Glass, G.

The Web
Services (r)evolution.



What are Web Services?


A collection of functions packaged together as a
single entity that is published onto network for
use by other programs
*


What it is
NOT
:


win
32
technologies, J
2
EE, CORBA, CGI scripting


all the above are based on different standards


Web services based on XML (eXtensible
Markup Language)


standard way of representing data


(c) University of Toronto MIE456 2004

4

Examples of Web Services


Microsoft Passport authentication service


Dentist appointment booking service that returns
dentist availability when given a date and time


Procurement service where supplies can be
purchased when provided with an item code and
quantity


Translation service converting English to French


Numerous other examples

(c) University of Toronto MIE456 2004

5

Major Web Services Technologies


3
main technologies:


Simple Object Access Protocol (SOAP)


standard packaging structure for XML documents over
variety of Internet protocols (e.g. SMTP, HTTP, FTP)


Web Service Description Language (WSDL)


XML technology describing interface of web service in a
standard way


Universal Description, Discover, and Integration
(UDDI)


worldwide registry of web services

(c) University of Toronto MIE456 2004

6

Major Web Services Technologies
(cont’d)


Functionality as a whole greater than the sum
of its parts


Relationship between the three technologies:


Source: “Java Web Services.” Chappell, D., and Jewel, T

(c) University of Toronto MIE456 2004

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Web Services Architecture


Web services can contain other web
services


e.g.
www.toronto.com

portal may have a
restaurant finder as a web service


May access Mapquest as a web service to
retrieve directions and map

(c) University of Toronto MIE456 2004

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Web Services Architecture

Source: “Java Web Services.” Chappell, D., and Jewel, T

(c) University of Toronto MIE456 2004

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Web Services in a Broad
Perspective

Source: “Performance Considerations for Mobile Web Services.” M. Tian, T. Voight, T. Naumowicz, H. Ritter, J. Schiller

(c) University of Toronto MIE456 2004

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Web Service Cost
-
Benefit Example


Dollar Rent A Car integration with
Southwest Airlines Co.


both companies operate different servers


Southwest customers can book flights AND rent
cars from Dollar Rent
-
A
-
Car without leaving their
site


only cost ~$1 / transaction, compared with $5
/ transaction through travel agent network


savings in the millions ($$)!!!

(c) University of Toronto MIE456 2004

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Benefits


Interoperability


all three technologies supported by major vendors


Ubiquity


communicate through various protocols


Low barrier to entry


concept easy to understand, free toolkits to
implement web services


Industry support


e.g. allow Microsoft .NET web service communicate
with IBM VisualAge service


(c) University of Toronto MIE456 2004

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Basic Web Service Model



3 main components


processing of data into well
-
defined XML documents


XML document


the cornerstone of Web Services


contains all information sent to service for processing


documents a web service can process defined via an XML
schema


two entities in communication must have access to same
description


usually described using WSDL


address (aka port reference)


where is the service?


additional component is the
envelope


a protocol used for message encapsulation


ensures XML document separated from other communication
processes

(c) University of Toronto MIE456 2004

13

Basic Web Service Model



Almost all web
services use SOAP
protocol


Two elements:


header


contains all
system info


body


contains XML
document to be
processed

Source: “Web Services and the Sun ONE

Developer Platform.” Ort, E.

(c) University of Toronto MIE456 2004

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Misconceptions of Web Services


Web services often hyped as the latest
distributed object technology


misconception lead to limited acceptance


Disagreements among standards bodies,
vendors greatest threat to large
-
scale
success of web services


(c) University of Toronto MIE456 2004

15

Misconception: Web services are
just like distributed objects


FACT:
not reliable and transaction processing
not up
-
to
-
par with distributed systems


no distributed object characteristics (e.g.
CORBA):


e.g. objects, object references, life cycle (instantiate
to release), serialization, method interfaces, garbage
collection, etc.


do not define relationships or body