DMX Sub Query Issue

Question

I am trying to query the Mining Model I have created in SSAS. And my query is like this:

SELECT FLATTENED MODEL_NAME, NODE_UNIQUE_NAME, 
     [PARENT_UNIQUE_NAME], NODE_TYPE, NODE_DESCRIPTION, NODE_SUPPORT, 
     (SELECT ATTRIBUTE_VALUE, [SUPPORT] 
      FROM NODE_DISTRIBUTION 
      WHERE ATTRIBUTE_VALUE = 'True') AS ND 
FROM DecisionTreeMM.CONTENT 
WHERE NODE_DESCRIPTION <> '';    

But it gives error as

Error (Data mining): A Boolean expression is not allowed in the context at line 2, column 65.