LAPIS A user interface, a programmable web browser and text editor that demonstrates how lightweight structure can be used Lightweight Structure is the ability to recognize text structure automatically, using an extensible library of patterns and parsers. Structure can be detected in lots of ways: grammars (e.g. Java or HTML), regular expressions, even manual selections by the user. With lightweight structure, it doesn't matter how the structure was detected--whether by a regular expression, or by a grammar, or by a hand-coded parser. All that matters is the result: a region set, which is a set of intervals in the text. * Text constraints, a new pattern language that lets you write simple but powerful patterns using lightweight structure. * Simultaneous editing, a technique for doing repetitive text edits by controlling multiple cursors. * Selection guessing, a technique that infers multiple selections and text constraint patterns