Serialization types

[amedranogil]

As discussed in #7 SerializationTypes needs to be sorted out.
for starters, This only affects object properties.
I propose changing a serialization type, and define them as:

• ref_only serialize only uses the object's URI, the rest of properties are not serialized (including type).
• optional does not serialize if the subject (or any atecesor) is minimal
• minimal serialize all properties except those marked as optional (at any level of the subtree).
• full serialize all properties, even if marked as ref_only, optional or reduced by other subjects.

undefined, is used when importing external ontologies, which don't add this information. I propose external ontologies to use minimal or full as default.

Additionally consider:

• never don't serialize even if marked as full by other subject (used in case of sensitive information such as passwords, private certificiates, etc...)
• complete serialize all properties, and all subtree recursively (should not be used often)

[amedranogil]

another way to model this is to have a simple ontology which can be used to anotate other ontologies, this might be useful in the case of direct importing of ontologies, this information can be added through ontological mapping.

[amedranogil]

This is a graphical representation of the proposal, defines which properties are serialized (and how).

[amedranogil]

Actually the case minimal -> full, the second should be considered as minimal, unless there is another subject with full (according to description above).
Another discussion might be that optional only applies to direct subject being true minimal (ie not referenced full by another subject), essentially minimal only applies to the next level and not the whole subtree.