Updated README.

README.md

 # RelAST Preprocessor
 
-Run preprocessor on train benchmark (output written to standard output):
+![RelAST process](relast-process.png)
 
-	$ ./gradlew jar
-	$ cat examples/TrainBenchmark.relast
-	$ java -jar relast-compiler.jar examples/TrainBenchmark.relast
-	$ java -jar build/libs/relast.jar examples/TrainBenchmark.relast
+The RelAST preprocessor takes a `.relast` file as input comprising AST rules and relations. It produces files that afterwards are processed by JastAdd to generated Java code.
+To use it in your project, build the JAR file running
 
-Run preprocessor and write output to files:
+```
 
-	$ java -jar build/libs/relast.jar examples/TrainBenchmark.relast --file
-	$ cat examples/TrainBenchmarkGen.ast
-	$ cat examples/TrainBenchmarkGen.jadd
+./gradlew jar
+```
 
-Run test cases:
+This will produce `build/libs/relast.jar`. Copy it to your project and extend your build config (preferably Gradle) with the following:
 
-	$ cd test
-	$ make
+```
+task preprocess(type: JavaExec) {
+    group = 'Build'
+    main = "-jar"
+    args = [
+            "libs/relast.jar",
+            "./src/main/jastadd/main.relast",
+            "--listClass=RefList",
+            "--jastAddList=JastAddList",
+            "--file"
+    ]
 
-Supported relations:
+    inputs.files file("./src/main/jastadd/main.relast")
+    outputs.files file("./src/main/jastadd/mainGen.ast"), file("./src/main/jastadd/mainGen.jadd")
+}
+```
+
+Note that you may have to change
+
+- the directory of `relast.jar`
+- the `.relast` file(s) both as argument(s) and input file(s)
+- the output files
+- parameters of RelAST (in this case, the list classes were renamed)
+
+## Supported relations
 
 	// Directed relations
 	A.b    -> B;