It seems BNF grammars  can't get us our semantic approach because there are distinct operators/operations.

We can think of it like this:

• ::=  means "is comprised of" and is for constructing new structures out of semantically identified elements. e.g  Latlong ::= tree ( lat, long )
• -->  means "is a named reference to" and is used to creating a semantic use of a particular structure/construct.  e.g.  Lat --> Float [ranged -90 - 90]
• And maybe we need some symbole for instance.  43.2351, -103.2405 is an instance of a latlong