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Technology Tradeoffs
John H. Krantz
Hanover College
Workshop on Web Research
Centre for Affective Sciences, May 2008
Outline
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Terms
General Perspective
Main Comparison
Server-Side Solutions
Client-Side Solutions
Some General Terms
• Server vs. Client
• Server is machine/software the study resides
• Client is the machine/software in use by the
participant
Some General Terms
• Push vs. Pull
• Client-Pull: information is drawn from server
at request of client browser
– More polite
• Server-Push: information is driven by the
server
– What is presented is now no longer under the
control of the participant
Some General Terms
• IP address
– Machine Address on the network
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IVp4: xxx.xxx.xxx.xxx
IVp6 –coming down the pike
In many cases dynamically assigned
For an server, try to get fixed IP address
• Domain Name
– We don’t like numbers
– Names to make machine location more memorable
– Tiny URL
Some General Terms
• Protocols and URL’s
– A protocol is the means of communicating
– Sort of like a language
– E.g. hypertext transfer protocol (http) vs. file transfer
protocol (ftp) vs. hypertext transfer protocol secured
(https)
• Uniform Resource Located
– Common format for getting formation:
– Protocol://server.domain/(path/filename)
– http://psych.hanover.edu/
Some General Terms
• Internet Connectivity
– People connect in different ways
– Modem
– Cable modem
– Wireless
– LAN
• These difference impact time to download
and, thus, willingness to continue
Some General Terms
• Technical Variance
– Data variation resulting from the use of
technology
• Denial of Participation:
– Prevention or reduced likelihood of participation
based upon the technical requirements of study
– e.g., visually impaired
General Perspective
• Web is a constantly changing environment
• Commercial issues are not the same as ours
• Lowest Common Denominator (Possible)
– The more complex the technology the more
participants you lose
– Loss is not random
– Complexity also often, but not always adds delay,
and people are impatient on the web
• Know the reach of your technology
General Issues Continued
• Population is changing
– Early studies: mostly male (Krantz & Dalal, 2000)
– More Recent studies: mostly female (e.g., Draper
& Elmer, 2008)
– Feminization of Psychology
– Still topic and probably technology dependent
(e.g., Braun & Drew, 2008)
– May well interact with technology
Server-Side vs. Client-Side
Server-Side
• The experiment is run on
the server
• Complexity is on the server
• The client needs only a
browser with minimal
capabilities
– Forms, Dynamically Created
Web pages
• All actions require return to
the server
Client-Side
• The experiment is run on
the client’s machine
• Complexity is on the client?
• Often requires plugin
– JavaScript, Flash Player, Java
interpreter, etc.
– Some will not be pre-installed
• No need to worry about
network traffic once
experiment begins
Division is extreme
• Every experiment uses both server-side and
client-side operations
• At the minimum:
– on the server-side, experiment must send page(s)
and collect data
– One the client-side, participant must have
browser to display html and forms
Server-Side Solutions
• Minimal requirements on the client side
– HTML
• The basic language of web pages
– Forms
• Goes back to the early versions of Mosaic (the first
media capable browser)
CGI
• Common Gateway Interface
– Interface between server and other program or
script
– Perl and PHP
– Often used to handle the data in experiments
– Can do anything any program can do
Dynamic Webpage Generation
• Use some CGI Mechanism to generate web pages
on fly
• Often from some database as well as from
information from client
• PHP
– a common open source solution can run on many
server platforms
• ASP
– Microsoft’s version and requires their server platform
• Requires browser that can handle these pages,
most can these days
Server-Side Summary
Advantages
• Low requirements for Client
• Single known platform for
most program execution
– Excepting HTML and Form
interpretation
• Great flexibility is possible
Disadvantages
• Limited control of display
– Only what is possible in
HTML, XML, PHP …
• Timing is limited
– Can get some timing
differences (see Ulf’s
Method)
– But will have a large constant
error
• Network traffic during study
Server-Side Software
• Perl: http://www.perl.com./
• PHP: http://www.php.net/
– Generic PHP Form Processor:
http://www.goeritz.net/brmic/
– MySQL: http://www.mysql.com/
Client-Side Solutions
• Program runs on participant’s computer
• Allows direct control of participant’s computer
• Usually requires some plugin or interpreter to
be present on the participant’s computer
JavaScript
• A scripting language interpreted in client
browser
– Requires a scripting interpreter in the browser
– Is an object-orienting scripting language
– Viewers of the page can get the program
– Is not related to Java though some similarity in
commands
– Installed on most browsers but some people turn
off or limit
JavaScript Editors
• JavaScript Editor Lite:
http://www.yaldex.com/JSFactory.htm
• JSEclipse (plugin for Eclipse):
http://www.interaktonline.com/Products/Ecli
pse/JSEclipse/Overview/
Java
• Object-Oriented Program Language
– Partially compiled/Partially interpreted
– Allows for more platform independence
– Runtime engines are written for each environment
• But it does change
– Comes with most browsers now and lot of other
software
• But several versions exist
– Microsoft’s version is disappearing (YEAH!)
Some Java Limitations
• Java is limited, partly to make web safe
• Cannot sync drawing to beginning of frame
– An example
• Timing is problematic (low priority and
difficult to steal priority from other machine
operations)
– Eichstadt (2001) gives way to handle timing issues
An Example of Java Timing
5000
Same
4000
Mirror
Reaction Time
3000
Shepherd
2000
1000
0
0
50
100
150
Angle of Rotation
200
Writing in Java
• Eclipse: http://www.eclipse.org/
– An open source Integrated Development
Environment
• Java not used much due to complexity
• Need an experiment library
Adobe Plugins (formerly Macromedia)
• Flash/Authorware (http://www.adobe.com)
– These are really high level languages with specially
designed IDE’s
– They require special plugins/players to run
– Flash usually preinstalled on most browsers
– Others less likely
– Support for Shockwave/Authorware on wane
– Flash is being pushed by publishers
Adobe Software
• Flash: http://www.adobe.com/products/flash/
• Authorware:
http://www.adobe.com/products/authorware/
– Authorware used at the PsychExps site
– Largely basis of experiments at Online Psychology
Laboratory (OPL) by American Psychological
Association (http://opl.apa.org)
Client-Side Summary
Advantages
• Greater control over
participant’s computer
• Can increase interactive
aspects of experiment
• Less need to communicate
with server during
experiment
Disadvantages
• Requires plugin which
participant may not have
• Greater impact of
participant’s setup
• Participants may turnoff
ability to run plugin
• May require large download
to run
• Not all timing issues have
been solved
Learning Curve vs. Power
Learning Curve
Shallow
Power
Low
Medium
High
Medium
Steep
HTML
Forms
Perl
PHP
JavaScript
Flash
Authorware
Java
Some Additional Issues to Consider
• Who can and will use the media?
• Who cannot or will not use the media?
– Issues of external vs. internal validity
• Will this impact my results?
– Will usage depend upon condition?
– If download time or complexity varies depending
upon condition you have a confound
Conclusion
• Test! Test! Test!
• Browser bugs!
• Consider is the web the best choice: not the
easiest choice