Web Transactions

Web-based Transactions

Fulvio Corno

08/10/09 Web Transactions 1

Evolution
The world wide web, if we analyze the involved
technologies, evolved through 3 main phases:
1.Static and informative Web
2.Dynamic and interactive Web
3.Integrated and application-oriented Web
E-commerce and e-business are a particular
application domain of Phase 3.


Summary
 StaticTransactions
 Dynamic Transactions
 Database-driven Transactions
 Rich-Client Asynchronous Transactions


Static web transaction
Internet Web HTML
server files

Client

http request path
URL
HTML
display http response
page send

browser TCP/IP server file system


Adopted standards
 URL (uniform resource locator) for finding
web pages
 HTML (hyper text markup language) for
writing web pages
 GIF (graphics interchange format) for
images
 HTTP (hyper text transfer protocol) for
client-server interaction
 TCP/IP (transmission control protocol over
internet protocol) for data transfer

RFC 2396
URL http://www.w3.org/Addressin
g/

http://elite.polito.it/~corno/index.html

DNS URI Rewriting

130.192.5.26 /home/corno/public_html/index.html

TCP File system

Contact server HTML file contents


RFC 2616, RFC 2617
HTTP protocol http://www.w3.org/Protoc
ols

GET /~corno/index.html HTTP/1.0
Accept: text/html
Accept: image/gif
User-Agent: CornoSoft SuperBrowser 9.45
HTTP/1.0 200 OK
Date: Monday, 01-Jan-2001 00:00:00 GMT
Server: Apache 1.3.0
MIME-Version: 1.0
Last-Modified: 31-Dec-2000
Content-type: text/html
Content-lemgth: 3021

<HTML> . . .

Static web transaction

t1 t8 t’1
Browser
t0 t9 t’0
Web t3 t6
server t2 t7
Disk
access t4 t5

server response time user think time
network transfer time
total response time

Response time
t1
Browser
t0
Server
t2
Disk

 Browser elaboration time (t0-t1): power uf
the users’ computer
 Transmission time for http request (t1-t2):
latency of Internet connection

Response time
t1
Browser
t0 t3 t6
Server
t2 t7
Disk
t4 t5
 Server elaboration time (t2-t3, t6-t7): power
of the server and number of simultaneous
accesses
 Disk access time (t3-t6): I/O architecture
del server and number of simultaneous
accesses

Response time
t1 t8
Browser
t0 t3 t6 t9
Server
t2 t7
Disk
t4 t5
 Transmission time for the HTML page (t7-
t8): size of the page and of the images,
latency, available bandwidth
 Visualization time of the page (t8-t9): power
of the users’ computer and complexity of
the page

Examples

www.w3c.org


Summary


Dynamic web transaction
Internet Web Application
server

Client

http request com- para-
URL meters
& POST data mand
display logic
http response
page send
HTML
browser TCP/IP server application

Adopted standards
 HTTP-POST for sending user-specified data
 CGI (common gateway interface), ISAPI
(internet information server application
programming interface), server-side script,
java servlet for integrating application logic
into web servers
 ASP (active server pages), PHP, PERL as
new languages for application development


URL (HTTP GET)

http://www.cad.polito.it/pap/pap.pl?author=Corno

Application Parameters

CPU
Disk
Libraries
HTML


Dynamic web transaction

t1 t8 t’1
Browser
t0 t9 t’0
Web t3 t6
server t2 t7
Application
server t4 t5

application time
total server time
total response time

Response time
t1 t8
Browser
t0 t3 t6 t9
Web
t2 t7
Application
t4 t5
 Communication time between web server
and application server (t3-t4, t5-t6): speed of
the local network
 Execution time of the application (t3-t6):
server power, number of accessese,
complexity of the application

Examples

 www.sun.com
 www.lastampa.it
 www.altavista.com


Summary


Database-driven transactions

Internet Web Application Database
server

Client

http com- para- query
URL meters
& POST mand
display http
page send data
HTML
browser TCP/IP server application database

Adopted standards
 Cookies for storing the state of a session
 Java, JavaScript, ActiveX, Flash to program
the user interface on the browser
 SQL (structured query language), ODBC
(open database connectivity) to access data
bases


URL (HTTP GET)

http://www.cad.polito.it/pap/pap.pl?author=Corno

Application Parameters

CPU
Disk
Libraries
HTML
Database


Database-driven transaction
t1 t8 t’1
Browser
t0 t9 t’0
Web t3 t6
server t2 t7
Application
server t4 t5
Database
server
application time database time
total server time
total response time

Response time
t1 t8
t’1
Browser t3 t6
t0 t9 t’0
Web
t2 t7
Application
t4 t5
Database
 Application: server power, number of
accesses, complexity of application
 Database: number of queries, complexity
of queries, size of the database
 Communications: local network


Examples

 www.amazon.com


Summary


Web 2.0
 Web applications support social interaction
models
 Peer exchange and user-contributed content
instead of rigid publisher/reader pattern
 Online communities
 Rich,dynamic, interactive user interfaces
 Integration of contents across web sites
(mashups)

08/10/09 eBWA-www2eB 28

Rich-Client Asynchronous
Transactions
Web Application
Internet Database
server

Client-side Client
Application http

http com- para- query
URL meters
& POST mand
DOM
display http
page send data
events HTML
runtime browser TCP/IP server application
database
08/10/09 XML/JSON Web Transactions 29

Adopted standards
 Dynamic HTML: DOM, Javascript, CSS
 JavaScript, Flash to handle a runtime
environment on the browser
 DOM (XHTML Document Object Model) to allow
on-the fly modification of the web page
 CSS 2.1 to modify attribute and handle objects

 AJAX: Asynchronous Javascript and XML
 XMLHttpRequest for asynchronous
communication to the server
 Data transfer formats: JSON, XML, RDF, RSS,
Atom, FOAF, ...
 Mash-up technology

Rich-client transaction
t1 t8 t’1
Browser
t0 t9 t’0

Runtime

Web t3 t6
server t2 t7
Application
server t4 t5
Database
server

Web Transactions

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