Modifying

Chunks once encoded cannot be modified, only copied (IDeclarativeModule.copyChunk()). However, if it hasn't been encoded, there are two considerations. If you have just created the chunk and no other buffers or modules might have access to it, you can merely manipulate it directly:

 IChunk chunk = ...
 ISymbolicChunk sc = chunk.getSymbolicChunk();
 
 for(ISlot slot : sc.getSlots())
  ((IMutableSlot) slot).setValue(...);

//the same applies for parameters

However, once the chunk is accessible in the system (added to a buffer, referenced by another chunk, etc), you need to be concerned about other threads accessing it. If the chunk is in a buffer, the easiest way to do this is with ChunkUtilities and its associated IChunkModifier interface. The utility class handles the locking and execution time for you.

  IModel model = ...;
  IActivationBuffer goalBuffer = model.getActivationBuffer(IActivationBuffer.GOAL);
  ChunkUtilities.manipulateChunkLater(goalBuffer, new IChunkModifier(){
    public void modify(IChunk chunk, IActivationBuffer buffer)
    {
       ISymbolicChunk sc = chunk.getSymbolicChunk();
       for(ISlot slot : sc.getSlots())
        ((IMutableSlot) slot).setValue(...);
    }
});

Otherwise, you should use the chunk's write lock to ensure no contention.

 IChunk chunk = ...
 Lock lock = chunk.getWriteLock();
 try
 {
   lock.lock();
    ISymbolicChunk sc = chunk.getSymbolicChunk();
       for(ISlot slot : sc.getSlots())
        ((IMutableSlot) slot).setValue(...);
 }
 finally
 {
  lock.unlock();
 }