Andrew J. Ko

Associate Professor

The Information School

Computer Science & Engr. (adjunct)

University of Washington

Box 352840

Seattle, WA 98195

ajko | @ | uw | edu

Mary Gates Hall 015E

Chief Scientist + Co-Founder


Winter 2016
On sabbatical, learning things
Office hours by appt

Play Gidget, our new debugging game!

AnswerDash is a spinout of Parmit Chilana's work on LemonAid, serving instant contextual answers in web applications.

New NSF project! Variations to Support Exploratory Programming


  • Ko, A. J. and Myers, B. A. (2006). Barista: An Implementation Framework for Enabling New Tools, Interaction Techniques and Views in Code Editors CHI 2006, to appear.

Barista is a new implementation framework, implemented in Citrus, which enables the creation of a new class of highly visual, highly interactive code editors. Editors built with Barista can offer standard features such as conventional text-editing interaction techniques, immediate feedback about errors and code-completion menus. However, Barista editors can also support drag and drop interaction techniques, new types of embedded tools, and alternative views of code.

The key difference between Barista and other editing frameworks, its that it maintains both the abstract syntax tree representing a program, as well as a corresponding, fully-structured visual representation on-screen. This fully-structured tree of interactive views allows editors to have all kinds of new views, interaction techniques, and embedded tools.

creating code

With Barista, you can type code like in a regular text editor...

...drag and drop it like in Alice and other modern structured editors...

...and use auto-complete menus.

embedding tools

Barista also allows for a whole new class of embedded tools. For example, here's a tool for storing alternative expressions:

Here's a graphical html header for a method that includes live links, diagrams and live example code:

alternative views

Because of the flexibility of defining views of code, Barista editors can swap between alternative views depending on the type of task the programmer is engaged in. For example, here is a programmer alternating between pretty-printed and textual versions of arithmetic code.

Here is a programmer switching between a conventional textual view of a logical expression and a "match form" view, which has been shown to improve people's comprehension over textual versions.

reading code

Because Barista editor's have complete control over a view's scale, focus + context interaction techniques are simple to implement. In this editor, programmers can double-click Java blocks to shrink them by 50%, rather than having to fully collapse or expand them.