Proposal (incomplete) to change Requirement Def. from Ordered List to a Map

Currently, the listing of requirement definitions in Node Types are in the form of an Ordered List to assure determinism by type/template authors to provide deterministic order to orchestrators when fulfilling them.

Thomas proposes we make this a simple "map" (or hashmap), but this has acknowledged problems and cannot be done without a comprehensive proposal that addresses them including:

• Hashmaps cannot have duplicate keynames however, TOSCA allows duplication of symbolic requirement names.
• Maps are "sets" and have no order.

In any event, we have a (potential) ordering problem when Node Types are sublcassed and the child type adds new Requirement defintions. There is currently no way to indicate how these new requirements introduced by the child Type should be ordered relative to the parents' requirements.