DEFER - CSD05 - Instance model (design considerations)

We have reached a point where we need to define an instance model. We should consider describing the following:
1) How a template causes node and relationship instances to be created
2) The schemas of node and relationship instances based on their respective types
3) The ability of a TOSCA runtime to add its own properties to an instance
4) The ability of a node or relationship operations to set attributes
5) Navigation of the instance model
6) Navigation from the instance to their respective templates and types.
7) Serialization of the instance model in YAML