4 files changed, 53 insertions, 9 deletions
diff --git a/compatibility/Context.java b/compatibility/Context.java
index 1ec0f54..afd0b15 100644
--- a/compatibility/Context.java
+++ b/compatibility/Context.java
@@ -1,22 +1,43 @@
 package cbt;
 import java.io.*;
-import java.util.concurrent.ConcurrentHashMap;
+import java.util.*;
+import java.util.concurrent.*;
 
 // TODO: try to reduce the number of members
-public abstract class Context{
+public interface Context{
+  // recently added methods that needs default values for old versions to work
+  public default long cbtLastModified(){
+    throw new IncompatibleCbtVersionException("You need to define method cbtLastModified.");
+  };
+  public default Map<Object,Object> persistentCache(){
+    throw new IncompatibleCbtVersionException("You need to define method persistentCache.");
+  };
+  public default Map<Object,Object> transientCache(){
+    throw new IncompatibleCbtVersionException("You need to define method transientCache.");
+  };
+  public default long start(){
+    throw new IncompatibleCbtVersionException("You need to define method start.");
+  };
+
+  // methods that exist for longer which every CBT version in use should have by now, no default values needed
   public abstract File projectDirectory();
   public abstract File cwd(); // REPLACE by something that allows to run cbt on some other directly
   public abstract String[] argsArray(); // replace this by https://github.com/cvogt/cbt/issues/172 ?
   public abstract String[] enabledLoggersArray();
-  public abstract Long startCompat();
-  public abstract Boolean cbtHasChangedCompat();
   public abstract String scalaVersionOrNull(); // needed to propagate scalaVersion to dependendee builds
-  public abstract ConcurrentHashMap<String,Object> permanentKeys();
-  public abstract ConcurrentHashMap<Object,ClassLoader> permanentClassLoaders();
-  public abstract ConcurrentHashMap<Object,Object> taskCache();
   public abstract File cache();
   public abstract File cbtHome();
   public abstract File cbtRootHome(); // REMOVE
   public abstract File compatibilityTarget(); // maybe replace this with search in the classloader for it?
   public abstract BuildInterface parentBuildOrNull();
+
+  // deprecated methods
+  @java.lang.Deprecated
+  public abstract Long startCompat();
+  @java.lang.Deprecated
+  public abstract Boolean cbtHasChangedCompat();
+  @java.lang.Deprecated
+  public abstract ConcurrentHashMap<String,Object> permanentKeys();
+  @java.lang.Deprecated
+  public abstract ConcurrentHashMap<Object,ClassLoader> permanentClassLoaders();
 }
diff --git a/compatibility/Dependency.java b/compatibility/Dependency.java
index d491174..1f719c2 100644
--- a/compatibility/Dependency.java
+++ b/compatibility/Dependency.java
@@ -2,9 +2,22 @@ package cbt;
 import java.io.*;
 
 public interface Dependency{
+  // recently added methods that needs default values for old versions to work
+  public default String moduleKey(){
+    throw new IncompatibleCbtVersionException("You need to define method moduleKey.");
+  };
+  public default long lastModified(){
+    throw new IncompatibleCbtVersionException("You need to define method lastModified.");
+  };
+
+  // methods that exist for longer which every CBT version in use should have by now, no default values needed
   public abstract String show();
-  public abstract Boolean needsUpdateCompat();
   public abstract Dependency[] dependenciesArray();
   public abstract File[] dependencyClasspathArray();
   public abstract File[] exportedClasspathArray();
+
+  // deprecated methods
+  @java.lang.Deprecated
+  public abstract boolean needsUpdateCompat();
 }
+
diff --git a/compatibility/IncompatibleCbtVersionException.java b/compatibility/IncompatibleCbtVersionException.java
new file mode 100644
index 0000000..dee50fb
--- /dev/null
+++ b/compatibility/IncompatibleCbtVersionException.java
@@ -0,0 +1,10 @@
+package cbt;
+
+public class IncompatibleCbtVersionException extends RuntimeException{
+	public IncompatibleCbtVersionException( String msg, Throwable parent ){
+		super( msg, parent );
+	}
+	public IncompatibleCbtVersionException( String msg ){
+		super( msg );
+	}
+}
diff --git a/compatibility/Result.java b/compatibility/Result.java
index 220aa3a..dadc3af 100644
--- a/compatibility/Result.java
+++ b/compatibility/Result.java
@@ -2,7 +2,7 @@
 package cbt;
 import java.io.*;
 public interface Result<T>{
-  public abstract Integer exitCode();
+  public abstract int exitCode();
   public abstract OutputStream out();
   public abstract OutputStream err();
   public abstract InputStream in();