File References, Trees, and Computational Thinking

1. File References, Trees, and Computational Thinking Craig Miller School of Computing DePaul University

2. 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

3. File References Link to another web page <a href="myBio.html">Click Here</a> Include a picture in a web page <imgsrc="/images/myPhoto.jpg" alt="Author's Picture"/> Reference a style sheet of formatting rules <link href="../newstyles.css" rel="stylesheet" type="text/css" />

4. 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>

5. File Structure as a Tree

6. 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 pageisbio.html?

7. Computational Thinking Concepts • Distinction between relative and absolute references • Working with formal, abstract representations

8. 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

9. 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.

10. 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.

11. Findings • Benefit of conceptual questions depend on level of the student • Self study provides more benefit than performing practice tasks Our conjecture: • Students compare their task to an example. • They use simple pattern-matching to reconcile the differences between their task and the example. • The process only requires a minimal understanding of the relationship between a coded file reference and the tree representation.

12. 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