Transcript slides - DePaul University

File References, Trees, and
Computational Thinking
Craig Miller
School of Computing
DePaul University
Web Development Courses
IT 130 (The Internet and the Web)
– Formatting pages with HTML and CSS
– Coding interactive pages with Javascript
HCI 201 (Multimedia and the World Wide Web)
– Elementary HTML
– Multimedia presentations
– Inquiry methods
Both courses teach students to link to other pages
and reference image files
File References
Link to another web page
<a href="myBio.html">Click Here</a>
Include a picture in a web page
<img src="/images/myPhoto.jpg"
alt="Author's Picture"/>
Reference a style sheet of formatting rules
<link href="../newstyles.css"
rel="stylesheet" type="text/css" />
Relative and Absolute References
Relative link to file in the same folder as the current page
<a href="myBio.html">My information</a>
Relative link to a file in a sub-folder in the same folder as the
current page
<a href="stores/kozys.html">Kozy’s</a>
Absolute reference
<a href="/misc/contact.html">Contact us</a>
Absolute reference to page at another site
<a href="http://depaul.edu/about/index.asp">
DePaul University</a>
File Structure as a Tree
Using the Tree to Answer Problems
Examples:
• What is the absolute reference to the
banner.jpg file?
• What is the relative reference to the
home.html file if the current pageis bio.html?
Computational Thinking Concepts
• Distinction between relative and absolute
references
• Working with formal, abstract representations
Empirical Studies
Both studies presented students with the tree and
examples and then asked 8 file reference problems.
Pilot study with 9 students from IT 130
– Showed that students have difficulty with these problems
– Identified common errors
Full study with 95 students from IT 130 and HCI 201
– Corroborated frequencies of common errors
– Examined relative benefits of different study strategies
Common Errors
• Failure to correctly use two dots (..) to go up a
level.
• Inappropriate use of the slash to indicate an
absolute reference.
• Inappropriate naming of a folder or file when
constructing the path name.
Study Strategies
Practice Tasks: Students specify paths based on
examples.
Conceptual Questions: Students answer conceptual
questions based on examples. Conceptual
questions are based on common errors that were
identified in the preparatory analysis.
Self Study: Students are asked to study the
examples with no other direction for preparing
for the (scored) path questions.
Findings
• Benefit of conceptual questions depend on level of
the student
• Self study provides more benefit than performing
practice tasks
Our conjecture:
1. Students compare their task to an example.
2. They use simple pattern-matching to reconcile the
differences between their task and the example.
3. The process only requires a minimal understanding
of the relationship between a coded file reference
and the tree representation.
Summary
Constructing file references involves core
concepts and skills for computational thinking
– Distinction between relative and absolute
references
– Reasoning with formal, abstract representations
(e.g. tree representations of file structures)
Recommend limited use of practice tasks when
students are still learning targeted concepts