1. Introduction to Web Services
Asst. Prof. Chaiporn Jaikaeo, Ph.D.
Computer Engineering Department
Kasetsart University, Bangkok, Thailand

2. Traditional World-Wide-Web
Designed for human-to-app interactions
Information sharing
(Non-automated) E-commerce
Built on top of
HTTP – for data transfer
HTML – for representing document

3. What's Next? Try taking humans out of the loop
Systematic application-to-application interaction over the web
Automated e-commerce
Resource sharing
Distributed computing
Web services
(another) effort to build distributed computing platform for the web

4. Web Services vs. Web Apps
Web application
Provides service directly to user
Web service or (Web API)
Provides service to other programs
browser
web server
HTTP
web server (service provider)
app (service user)
HTTP

5. Web Service Protocols Simple Object Access Protocol (SOAP)
Service requests and responses are always done via XML messages, called SOAP envelope
Formally supported by World Wide Web Consortium (W3C)
Representational State Transfer (REST)
Service requests are done via generic HTTP commands: GET, POST, PUT, DELETE
Simpler set of operations

6. Other Web Service Protocols
Web feeds
RSS
Atom
Remote procedure call
JSON-RPC
XML-RPC
JavaScript

7. Sample SOAP Message E.g., message requesting IBM stock price
POST /InStock HTTP/1.1
Host:
Content-Type: application/soap+xml; charset=utf-8
Content-Length: 299
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="
<soap:Header>
</soap:Header>
<soap:Body>
<m:GetStockPrice xmlns:m="
<m:StockName>IBM</m:StockName>
</m:GetStockPrice>
</soap:Body>
</soap:Envelope>
HTTP Header
SOAP Envelope
Desired operation (Verb)
Object of interest (Noun)

8. Sample REST Request E.g., message requesting IBM stock price
The above corresponds to the URL
GET /stock/ibm HTTP/1.1
Host:
HTTP Header
Desired operation (Verb)
Object of interest (Noun)

9. Data Interchange Formats
XML – eXtensible Markup Language
E.g., RSS, Atom
Large collection of libraries for processing XML
<?xml version="1.0" encoding="ISO "?>
<rdf:RDF xmlns:rdf="
xmlns="
<title>Slashdot</title>
<link>
<description>News for nerds, stuff that matters</description>
<dc:subject>Technology</dc:subject>
<items>
<rdf:Seq>
<rdf:li rdf:resource=" />
</ref:Seq>
</items>
</rdf:RDF>

10. Data Interchange Formats
JSON – JavaScript Object Notation
Can be directly evaluated in JavaScript
Typically smaller than XML
Libraries for other languages are also available {
"Person":
"firstName": "John",
"lastName": "Smith",
"age": 25,
"Address":
"streetAddress":"21 2nd Street",
"city":"New York",
"state":"NY",
"postalCode":"10021" },
"PhoneNumbers":
"home":" ",
"fax":" " }
<Person>
<firstName>John</firstName>
<lastName>Smith</lastName>
<age>25</age>
<Address>
<streetAddress>21 2nd Street</streetAddress>
<city>New York</city>
<state>NY</state>
<postalCode>10021</postalCode>
</Address>
<PhoneNumbers>
<home> </home>
<fax> </fax>
</PhoneNumbers>
</Person>
XML
JSON

11. Example –Wikipedia RESTful API reference Example
Example

12. Example – HostIP.info RESTful
Determines geographical location of the specified IP address
API documentation
Example

13. Coding Example E.g., accessing HostIP.info from Python import sys
import json
from urllib import urlencode
from urllib2 import urlopen
response = urlopen(' +
urlencode({
'ip' : sys.argv[1],
}))
data = json.loads(response.read())
print 'IP Address: %s' % data['ip']
print 'City: %s' % data['city']
print 'Country: %s' % data['country_name']

14. Mashups
A mashup is a webpage or application that offers new services by combining data or functionality from two or more sources
Main characteristics of mashups
Combination
Visualization
Aggregation
They aim to make existing data more useful
Example: Wikipediavision
Google Maps + Wikipedia

15. More Resources Search engine for web APIs and mashups