Development and Implementation of an AJAX framework for dynamic

96 Pages·2007·4.41 MB·English

Development and Implementation of an AJAX
framework for dynamic context injection
in Web 2.0 applications
Diploma Thesis
by
Simone Heil
submitted to
Prof. Dr. Anatol Badach
Hochschule Fulda
University of Applied Sciences
12th December 2006
carried out at: Supervisor:
NEC Network Laboratories Heidelberg MSc Miquel Martin

Declaration of Originality
I declare in lieu of an oath that the thesis submitted has been produced by me without
illegal help from other persons. I state that all passages which have been taken out of
publications of all means or un-published material either whole or in part, in words or
ideas, have been marked as quotations in the relevant passage. I also confirm that the
quotes included show the extent of the original quotes and are marked as such. I know
that a false declaration will have legal consequences.
12th December 2006, Heidelberg

ABSTRACT
Today’s World Wide Web is richer than ever, capable of providing not just dynamic
content but also complex applications. Hence, the information content and the offers of
webservicesaregrowingconstantly. Thisisthemomentwhentheideaofdynamiccontext
injection into Web 2.0 applications is coming up. While numerous sites present person-
alization aspects, there is no standard way of providing, using, or updating the user’s
preferences. This forces users to configure each site individually and mostly statically.
The scope of this thesis is to realize a framework which allows AJAX based applications
to dynamically use both preferences and context, with a focus on service simplicity and
privacy. With the research of different technologies and the development of sequence and
flow diagrams, it was possible to realize this framework. The resulting architecture is
divided into four main parts: a Firefox Extension injecting the context information with
the use of AJAX, a Local Demon, forwarding the information to the user and to the other
parts, a Context Server getting the context information from a database and a Policy
Enforcement Point verifying the permission to release the requested context information.
It is conceivable that context injection will become more significant in future as it facil-
itates the workflow and provides a convenience which is not met with traditional Web
applications.

ACKNOWLEDGEMENTS
”At times our own light goes out and is rekindled by
a spark from another person. Each of us has cause to think with deep
gratitude of those who have lighted the flame within us.”
Albert Schweitzer
I really enjoyed my time at NEC while I wrote my thesis. I can’t compare this experience
with something else in my life as I never had the possibility to meet so many people
from other countries and other cultures at one place. Especially, I want to thank for the
support of my supervisor Miquel Martin and my professor Dr. Anatol Badach which have
always relighted the flame within me when there were coming up doubts.
I am also very thankful about the people who became real friends and always supported
me. You will always be in my mind and I hope that I will see all of you again.
And of course I don’t want to forget my parents and all my other friends who believed in
me and made all this possible.
Thank you very much!
Simone Heil

Contents
1 Introduction and Objectives 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Thesis Organisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Problem Statement 4
2.1 Definition of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Example Usage Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Abstraction of the problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1 Delivery of context information . . . . . . . . . . . . . . . . . . . . . 6
2.3.2 Security of the User Data . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3.3 Simulation of context information and demonstration of results . . . 8
2.3.4 Responsiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.5 Portability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.6 Legal Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.7 Modularity of the components . . . . . . . . . . . . . . . . . . . . . 9
2.4 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Restrictions and Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 State of the Art 11
3.1 Background technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1.1 Web development technique AJAX . . . . . . . . . . . . . . . . . . . 11
3.1.2 Access control policy language XACML . . . . . . . . . . . . . . . . 15
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CONTENTS
3.1.3 Rules Engine Drools . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.4 Web Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.5 URI scheme HTTPS . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.6 Daemon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Existing applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.1 AJAX Example Applications . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 Firefox Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.3 Web 2.0 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4 Design of the Framework 28
4.1 Procedures to access Context Information . . . . . . . . . . . . . . . . . . . 28
4.1.1 Server-Side Context Transfer . . . . . . . . . . . . . . . . . . . . . . 29
4.1.2 Client-Side Context Transfer . . . . . . . . . . . . . . . . . . . . . . 29
4.1.3 Evaluation of Context Access . . . . . . . . . . . . . . . . . . . . . . 31
4.2 Security of the User Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.2.1 Security on the data path . . . . . . . . . . . . . . . . . . . . . . . . 34
4.2.2 User Notification of unknown Context Information . . . . . . . . . . 36
4.3 Handling Context Information. . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.4 Policy Management System . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.5 Web Development Technique . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.6 Overview of the developed architecture . . . . . . . . . . . . . . . . . . . . . 41
4.7 Communication between the components . . . . . . . . . . . . . . . . . . . 42
5 Implementation of the Framework 43
5.1 Main Architecture and Relations . . . . . . . . . . . . . . . . . . . . . . . . 43
5.2 Firefox Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.3 Local Daemon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.4 Tray Icon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.5 Context Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.5.1 Simulation of the context . . . . . . . . . . . . . . . . . . . . . . . . 52
5.6 Policy Enforcement Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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