The LINQ translator often needs to know what serializer should be used at a particular node of the expression tree. In LINQ3 we will use a more general purpose strategy of gathering up all known serializers for a node in the tree. The known serializers for each node are the set of serializers known by the child nodes. This will provide a single strategy for finding a serializer when we need one, and will also allow us to throw an exception if there are multiple conflicting serializers.