Text boundary analysis provides the ability to locate significant boundaries within a region of text, such as boundaries between words or sentences, or candidate positions for line breaks when laying out text on a screen or page. The Unicode Consortium technical reports TR 14 and TR 29 provide basic definitions for identifying boundaries or break positions.

The ICU Unicode support library from IBM provides a very high performance and customizable implementation of boundary analysis. The rules for identifying break positions within the text are expressed in a form of regular expression, allowing for special purpose text breaking by means of rules specified by the application. ICU also includes a dictionary based word break for use with Thai. New boundary analysis features for ICU 2.2 include support for Unicode 3.2, user-customizable boundary rules in C/C++, and tagging identified break positions with additional information for use by the application.

This paper will review the basics of boundary analysis, and describe the features and implementation approach in ICU 2.2. Future directions, including possible new features for later versions of ICU, will also be discussed.