Andrew J. Ko

As an HCI researcher and teacher, I'm fascinated by software. I'm intrigued with how it's built, the people who build it, and its far reaching effects on society. I study beginners, end-user programmers, and professionals with lab studies, classroom and corporate field work, and artifact analysis. I use the results to invent tools that better support the design, creation and repair of software.

I'm working on...

Why questions for developers (for Java and Alice). Imagine a debugging tool that lets you point to program output and ask a 'why' question, then get an explanation than pinpoints the answer...

Why questions in user interfaces. Ever wonder why your software is doing something strange? These tools let you click on the confusing output and ask 'why' questions.

Supporting design decisions. Design decisions are what primarily determine software quality, but we know so little about how they're made. I want to design tools that better support these decisions. (With Parmit Chilana and Jacob Wobbrock)

Making programming fun. What gets people excited about computing? Too many programming languages, even those designed for beginners, make code something sterile and cryptic. I want to make code something people play with.

I've worked on many other projects, most of which appear below.

Tools

These are technologies that I'm no longer actively working on. If something here seems interesting, however, drop me a line. I'm always open to new perspectives on past work.

Barista is a toolkit for creating flexible structured code editors. The key different between Barista editors and prior structured editors is that they use standard text editing interaction techniques, but a structured visual representation.

Jasper is a workspace for gathering task-relevant code during software maintenance tasks. Its motivated by findings from one of my studies that showed that most of what developers do during such tasks is navigate between relevant code. \

Slate is a spreadsheet language with a novel labeling system. Users give labels to data and the data is propagated through formulas, causing unexpected combinations of labels in the presence of errors.

Citrus is a novel programming language that supports one way constraints, events, value restrictions, and object ownership. I used Citrus to implement the Barista toolkit above and lots of other prototype user interfaces.

The Whyline for Alice is a debugging tool that allows developers to ask why and why not questions about their program's output. The prototype that I wrote for Alice helped developers solve problems 8 times faster than normal tools.

Studies

Information Needs in Co-located Software Development Teams. What kinds of information do software developers look for on a minute-by-minute basis? Rob DeLine (MSR) and I spent a summer hanging out in software developers' offices and took extensive notes on the information they were looking for. They spend a lot of time staying aware of their teammates' activities as well as seeking design rationale (but never finding).

The Linguistics of Problem Reports. Are there linguistic trends in people's descriptions of software problems? To find out, we analyzed nearly 200,000 open source bug reports, specifically studying their one-line summaries.

Bottlenecks in Software Maintenance Tasks. We studied several expert Java programmers using Eclipse to fix bugs and add features to a painting application. The study identified several trends in these activities, including that developer's spent an average of 35% of their time scrolling within files and switching between files, to code they had already seen but needed to reference again. If you're curious, you can view the source code for the Paint application used in the study.

Text Editing Strategies in Code Editors. How do programmers edit textual code (as opposed to visual or otherwise)? We did a fine grained analysis of several programmers character-by-character edits, finding that programmers generally preserve the syntactic integrity of their code. Almost all edits, however, require them to pass through some syntactically invalid state momentarily.

Learning Barriers in Visual Basic.NET We studied a classroom full of non-programmers attempting to learn Visual Basic.NET and found that, while many barriers were difficulty with syntax errors, many others had to do with searching for, using, coordinating, and debugging uses of abstractions in APIs. We identified many ways that programming environments might lower or remove these barriers.

What causes people to insert errors in code? Traditional perspectives blame the programmers or the languages. We observed and documented groups developing interactive 3D simulations, the errors introduced into their code, and their efforts to find and repair these errors. About half of the errors introduced occurred as a result of efforts to repair other errors that were based on these false assumptions.