-JVM := $(JAVA_HOME)/bin/java
-JAVADOC := $(JAVA_HOME)/bin/javadoc
-ECJ_JAR := $(A2_BASE)/org.argeo.tp.sdk/org.eclipse.jdt.core.compiler.batch.3.29.jar
-BNDLIB_JAR := $(A2_BASE)/org.argeo.tp.sdk/biz.aQute.bndlib.5.3.jar
-SLF4J_API_JAR := $(A2_BASE)/org.argeo.tp/org.slf4j.api.1.7.jar
-
-#ARGEO_MAKE = $(JVM) -cp $(ECJ_JAR):$(BNDLIB_JAR):$(SLF4J_API_JAR):$(BUILD_BASE)/bin org/argeo/build/Make
+# The following variables are found in the sdk.mk file which is generated by the configure script:
+# SDK_SRC_BASE the base of the source code, typically the root of the cloned git repository
+# SDK_BUILD_BASE the base of the output
+# JAVA_HOME the base of the JDK used to build
+A2_OUTPUT := $(SDK_BUILD_BASE)/a2
+JVM ?= $(JAVA_HOME)/bin/java
+JAVADOC ?= $(JAVA_HOME)/bin/javadoc
+
+# The following variables should be declared in the Makefile:
+# BUNDLES the space-separated list of bundles to be built
+# A2_CATEGORY the a2 category the bundles will belong to
+#
+# The following variables have default values which can be overriden in the Makefile
+# DEP_CATEGORIES the a2 categories the compilation depends on
+# JAVADOC_PACKAGES the space-separated list of packages for which javadoc will be generated
+# A2_BASE the space-separated directories where already built a2 categories can be found
+DEP_CATEGORIES ?=
+JAVADOC_PACKAGES ?=
+A2_BASE ?= $(A2_OUTPUT)
+
+ECJ_JAR ?= $(A2_BASE)/org.argeo.tp.sdk/org.eclipse.jdt.core.compiler.batch.3.29.jar
+BNDLIB_JAR ?= $(A2_BASE)/org.argeo.tp.sdk/biz.aQute.bndlib.5.3.jar
+SLF4J_API_JAR ?= $(A2_BASE)/org.argeo.tp/org.slf4j.api.1.7.jar