I am a Professor in Computer Science at Lund University, Sweden. I head the JastAdd project, where we develop declarative techniques and metatools for generating extensible language tools, like compilers, visual program editors, and source code analyzers. In particular, we develop the JastAdd metacompiler, see http://jastadd.org. JastAdd is based on reference attribute grammars, which is a combination of declarative object-oriented programming and attribute grammars. The most well-known application of JastAdd is ExtendJ, an extensible Java compiler (previously known as JastAddJ). ExtendJ has been used in a variety of projects to build new languages on top of Java, to experiment with new language constructs, and to analyze Java source code. Other mature applications of JastAdd include languages for simulation and control like Modelica, Optimica, and GrafChart.