We are going to today identify the brand new syntax using the familiar EBNF notation
Up to now, so you’re able to identify the fresh syntax from RIF-FLD i made use of “statistical English,” a unique version of English to possess interacting mathematical definitions, advice, an such like. The next issues regarding EBNF notation can be kept in mind:
- The brand new syntax out of RIF-FLD relies on the brand new signature apparatus which can be not perspective-totally free, very EBNF does not need that it sentence structure precisely. Thus, bbpeoplemeet the EBNF grammar defines a strict superset of RIF-FLD (never assume all algorithms which might be derivable utilizing the EBNF sentence structure are well-formed).
- The EBNF syntax is not a concrete syntax: it does not address the details of how constants (defined in [RIF-DTB]) and variables are represented, and it is not sufficiently precise about the delimiters and escape symbols. White space is informally used as a delimiter, and is implied in productions that use Kleene star. For instance, TERM* is to be understood as Name Label . Term, where each ‘ ‘ abstracts from one or more blanks, tabs, newlines, etc. This is done intentionally since RIF’s presentation syntax is used as a tool for specifying the semantics and for illustration of the main RIF concepts through examples.
- RIF defines a concrete syntax only for exchanging guidelines, and that syntax is XML-oriented, acquired once the a sophistication and serialization of one’s EBNF sentence structure thru the latest speech-syntax-to-XML mapping having RIF-FLD.
Keeping the above mentioned in your mind, brand new EBNF grammar is visible just like the just a mediator ranging from this new analytical English plus the XML. Although not, in addition, it gives a succinct view of the new syntax from RIF-FLD and as such can be useful having dialect music artists and you may pages exactly the same.
For every single RIF-FLD algorithm and name are going to be prefixed with you to definitely optional annotation
The RIF-FLD presentation syntax does not commit to any particular vocabulary and permits arbitrary sequences of Unicode characters in constant symbols, argument names, and variables. Such sequences are denoted with UNICODESTRING in the above syntax. Constant symbols have this form: "UNICODESTRING"^^SYMSPACE, where SYMSPACE is a ANGLEBRACKIRI or CURIE that represents the identifier of the symbol space of the constant. UNICODESTRING, ANGLEBRACKIRI, and CURIE are defined in Section Shortcuts for Constants in RIF’s Presentation Syntax of [RIF-DTB]. Constant symbols can also have several shortcut forms, which are represented by the non-terminal CONSTSHORT. These shortcuts are also defined in the same section of [RIF-DTB]. One of them is the CURIE shortcut, which is used in the examples in this document. Names are Unicode character sequences that form valid XML NCNames [XML-Names]. Variables are composed of Names prefixed with a ?-sign.
, which is used in several places in the grammar, is a non-terminal whose definition is left to the dialects. It is intended to specify the protocol by which external sources, remote modules, and imported RIF documents are located. This must include the basic form , where IRI is a Unicode string in the form of an absolute IRI.
The symbols NEWCONNECTIVE, NEWQUANTIFIER, NEWAGGRFUNC, and NEWTERM are RIF-FLD extension points. They are not actual symbols in the alphabet. Instead, dialects are supposed to replace NEWCONNECTIVE, NEWQUANTIFIER, and NEWAGGRFUNC, by zero or more actual new symbols, while NEWTERM is to be replaced by zero or more new kinds of terms. Note that the extension point NEWSYMBOL is not shown in the EBNF grammar completely avoids mentioning the alphabet of the language (which is infinite).
IRIMETA, for identification and metadata. IRIMETA is represented using (*. *)-brackets that contain an optional rif:iri constant as identifier followed by an optional Frame or cones as metadata. One such specialization is '"' IRI '"^^' 'rif:iri' from the Const production, where IRI is a sequence of Unicode characters that forms an internationalized resource identifier as defined by [RFC-3987].