{
throw new ASTWalkException("Unexpected AST tree contains zero or more then 1 child elements for root");
}
// Get expression node sub-tree from the AST nodes placed so far
EvalFactoryNode evalNode = astPatternNodeMap.values().iterator().next();
PatternStreamSpecRaw streamSpec = new PatternStreamSpecRaw(evalNode, evalNodeExpressions, new LinkedList<ViewSpec>(), null, new StreamSpecOptions());
if (evalNodeExpressions != null) {
evalNodeExpressions = new HashMap<EvalFactoryNode, String>();
}