1 Web-Centric Projects in Computer Science Courses Kwok-Bun Yue University of Houston - Clear Lake ...
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1 Web-Centric Projects in Computer Science Courses Kwok-Bun Yue University of Houston - Clear Lake http://dcm.cl.uh.edu/yue/ [email protected] @copyright 2002 April 12, 2002
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Transcript of 1 Web-Centric Projects in Computer Science Courses Kwok-Bun Yue University of Houston - Clear Lake ...
1
Web-Centric Projects in ComputerScience Courses
Kwok-Bun Yue
University of Houston - Clear Lake
http://dcm.cl.uh.edu/yue/
@copyright 2002
April 12, 2002
April 7, 2002 http//dcm.cl.uh.edu/yue;
Introduction
Web-Centric applications development is becoming critical.
Challenges exist for offering Web-Centric Projects.
This talk presents: Our experience, and Some recommendations.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Contents
Web-Centric Software Architecture Web-Centric Projects Teaching Experience Recommendations Conclusions
April 7, 2002 http//dcm.cl.uh.edu/yue;
Web-Centric Software Architecture
Software architectures have changed through the years.
A very coarse evolution: Phase 1: Mainframe. Phase 2: Traditional 2-tiered Client-
Server. Phase 3: Web-Based N-tiered Client-
Server Phase 4: Web-Centric.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 1: Mainframe
Highly centralized. Very thin clients: dumb terminals. Largely disconnected to outside of the
organization.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 2: Traditional 2-tiered Client-Server
Fat clients: PC. Proprietary protocols. Many dedicated servers. Still largely within the organization.
clients serversservices
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 3: Web-Based N-tiered Client-Server (1)
clients
servers
services
ApplicationServer
Web Server
intranet
clients
Internet
Major flow of services
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 3: Web-Based N-tiered Client-Server (2)
Open Web protocols. Middle layer for definition of business
logic: better software development. Serving clients outside of the organization:
Internet. The browser has become the universal
client. Thinner clients.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 4: Web-Centric (1)
clients
servers
services
ApplicationServer
Web Server
intranet
clients
Internet
Major flow of services
Organization
XMLServers
XMLservers
April 7, 2002 http//dcm.cl.uh.edu/yue;
Phase 4: Web-Centric (2)
Potentially thin clients. Clients and servers can be blurred Data/services in and out of the
organization. Data/services from many servers, inside
and outside of the organization. No single organization can provide
'everything.'
April 7, 2002 http//dcm.cl.uh.edu/yue;
Contents
Web-Centric Software Architecture
Web-Centric Projects Teaching Experience Recommendations Conclusions
April 7, 2002 http//dcm.cl.uh.edu/yue;
Web-Centric Projects
In our university, web-centric projects are assigned in: CSCI 4230 Internet Application
Development CSCI 5733 XML Application Development
Some examples follow.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Weather Report (3)
Assigned in Spring 2000. Wrote ASP program to retrieve weather
information in 'XML' format. External source:
http://zowie.metnet.navy.mil/cgi‑bin/oleg/get‑obs.
Use MS XML parser.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Language Interest (3)
Assigned in Fall 2000. Wrote CGI-Perl programs to retrieve
various indexed page numbers by Google of different languages.
External source: http://www.google.com. Use CGI-Perl, LWP and regular expressions.
April 7, 2002 http//dcm.cl.uh.edu/yue;
WML Newsfeed (3)
Assigned in Spring 2002: http://dcm.cl.uh.edu/yue/courses/xml/spring2002/h3.asp
Wrote programs to fetch newsfeed and deliver it to mobile phones.
External source: http://www.moreover.com.
Use JSP, WML (Wirelss Markup Language) and SAX (an API).
April 7, 2002 http//dcm.cl.uh.edu/yue;
Contents
Web-Centric Software Architecture Web-Centric Projects
Teaching Experience Recommendations Conclusions
April 7, 2002 http//dcm.cl.uh.edu/yue;
Teaching Experience
Highly relevant project assignments. Students excited about the projects. Posted many technical questions. Found good jobs because of the course. Rated consistently as one of the best
computer courses.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Challenges
No control on the the external sites on: Availability Quality of services Format consistence.
Beginner students will make many programming mistakes.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Challenge Example
"Denial of Services" attack to Google:
“Someone at UH has been spamming Google with repetitive queries this weekend, from (ip and dsn omitted), in violation of our terms of service: http://www.google.com/terms_of_service.html
We saw over 60,000 such queries yesterday (Saturday), and over 45,000 in the first two hours today (Pacific time). These queries (over six per second) are consuming a significant amount of our bandwidth, and constitute a borderline denial-of-service attack, since it is adversely affecting response times for our users.
Most of the queries have been one of the following:
PERL , PERL Rules, PERL Sucks, HTML, HTML sucks, HTML rules
We obviously do not want to have to shut off Google access to UH, but if this attack continues, we may have no choice.
Can you please investigate this immediately and update us on the situation? Thank you.”
April 7, 2002 http//dcm.cl.uh.edu/yue;
Contents
Web-Centric Software Architecture Web-Centric Projects Teaching Experience
Recommendations Conclusions
April 7, 2002 http//dcm.cl.uh.edu/yue;
Recommendations (1)
Select the external Web site sources carefully: Study the responsiveness, availability and
format stability of the sources. Read the terms of usage and privacy policy
carefully.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Recommendations (2)
Select the external Web sites carefully: XML sources much better than HTML
sources. XML DTD (Document Type Definition)
with industry-wise support is usually more stable.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Recommendations (3)
Consider using local caching of external resources.
Examples: Local caching of Google's search
language interest pages. Local caching for the newsfeed: http://dcm
.cl.uh.edu/yue/courses/xml/notes/general/news.pl?topic=China
April 7, 2002 http//dcm.cl.uh.edu/yue;
Advantages of Local Caching
Instructors have full control on the cached pages. Reduced risks. Improved availability and quality of
services. May change cache contents for testing
and grading. Examples: Freeze contents for grading. Add "$" for WML testing.
April 7, 2002 http//dcm.cl.uh.edu/yue;
Problems of Local Caching
Local caching requires programming. Examples: approximately 2 hours of
programming for each of the Google's language interest cache the newsfeed cache the stock quote cache
April 7, 2002 http//dcm.cl.uh.edu/yue;
A Caching Tool for Web-Centric Projects A Web-based tool for caching instructor
selected pages: using JSP/MySQL. Allow definitions of
external site URL and HTTP parameters Cache refresh method Snapshot taking Password Protection Statistics
In progress!
April 7, 2002 http//dcm.cl.uh.edu/yue;
Contents
Web-Centric Software Architecture Web-Centric Projects Teaching Experience Recommendations
Conclusions
April 7, 2002 http//dcm.cl.uh.edu/yue;
Conclusions
More difficult to set up Web-Centric Project Assignments.
Efforts are worthy. Challenges are mostly solvable. Working on a cache tool for Web-centric
projects. Further research: Web services will
provide challenges to the cache tool!
