This class represents 1 or more instances of a single SimDM/OutputDataObjectType-s produced by an SimDM/Experiment. 
No assumption is made how a SimDM/OutputDataset is represented in the real world. It may consist of one or multiple files, or possibly one or more tables in a database, or subsets thereof. The exact storage is not currently modelled.
The class represents an actual collection of objects without (necessarily) listing these all. Instead it is to be used to allow statistical summaries/characterisation of these products.
A special feature is that a SimDM/OutputDataset may define a dependency on another, 'parent' data set. This reflects to possibility in the SimDM/Protocol to model relationships between different SimDM/OutputDataObjectType-s. 
This is implemented using two references, one to the parent SimDM/OutputDataset, the other to the SimDM/Relationship.