UD, yet another unification device

This article describes some of the features of a sophisticated language and environment designed for experimentation with unification-oriented linguistic descriptions. The system, called UD, has to date been used successfully as a development and prototyping tool in a research project on the application of situation schemata to the representation of real text, and in extensive experimentation in machine translation. While the UD language bears close resemblances to all the well-known unification grammar formalisms, it offers a wider range of features than any single alternative, plus powerful facilities for notational abstraction which allow users to simulate different theoretical approaches in a natural way. After a brief discussion of the motivation for implementing yet another unification device, the main body of the article is devoted to a description of the most important novel features of UD.