I downloaded the Drools source code (drools-5.0-src.zip) and I'm trying to build Drools according to the instructions in the README.txt. Typing this command: mvn -Declipse -Ddocumentation clean install I get this error [INFO] Scanning for projects... [INFO] ------------------------------------------------------------------------ [ERROR] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] The projects in the reactor contain a cyclic reference: Edge between 'Vertex{label='org.drools:docbook-xsl-drools'}' and 'Vertex{label='org.drools:docbook-style-drools'}' introduces to cycle in the graph org.drools:docbook-style-drools --> org.drools:docbook-xsl-drools --> org.drools:docbook-style-drools [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 3 seconds [INFO] Finished at: Tue Sep 15 10:19:49 MDT 2009 [INFO] Final Memory: 10M/81M [INFO] ------------------------------------------------------------------------ OS: Ubuntu 9.04 JDK: Sun 1.6.14 for x86_64 Maven version: 2.2.1 More generally, is there documentation anywhere about the build architecture and infrastructure? It's my first time trying Maven.