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CORE
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Property Tree
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- Add 'loadXML' templatize function that given a XML stream returns a PropertyTree. Or, that given a file name and a 
object type (as a template), it calls 'loadXML' which returns a pointer to the object type.
- This pointer does not need to belong to a newly created object: if an identical object already existed, return the 
pointer to that one (Flyweight).
- To support the previous functionality, we need to be able to tell whether an object needs to be created or not. If we 
construct a PropertyTree with the parameters to build an object, we could get a hash-key from that PropertyTree (in a 
generic way, and then decide.
- Work on templatizing the get/put/add functions to do something like 'pt.get<Sphere>()". Well explained with examples in http://akrzemi1.wordpress.com/2011/07/13/parsing-xml-with-boost/.

Factory
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- Standarize the process of creating objects: for example, using the 'template'/'factory' patterns.