Proposal: `Formula` term

[jeswr]

I would like to propose the introduction of a new RDF/JS term called a Formula to represent Notation3 Formulas / Graph Terms.

Currently, when Notation3 syntax is parsed, Graph Terms in Notation3 are represented using blank nodes. That is,

:a :b { :c :d :e } . 

will be parsed as the two quads

:a :b _:b0
:c :d :e _:b0

The fact that _:b0 represents a graph term and not a blank node in :a :b _:b0 cannot be deduced from the triple alone. Instead it has to be implicit from the presence of the quad :c :d :e _:b0 in a dataset; where _:b0 is used as a graph term.

Furthermore, empty graphs are legal in N3. That is, the statement :a :b {} . is legal in N3. This gets parsed to the RDF/JS quad :a :b _:b0 which is the same as parsing :a :b [] despite :a :b {} and :a :b [] having an entirely different semantic meaning. This means that without having a notion of Notation3 Formulas / Graph Terms, or at least the empty graph, we are enable to represent all N3 concepts within RDF/JS.