So far, so you can indicate the syntax out of RIF-FLD we made use of «mathematical English,» yet another style of English having communicating mathematical definitions, instances, etcetera. The second factors in regards to the EBNF notation will likely be stored in mind:
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- The brand new syntax from RIF-FLD utilizes new signature apparatus that’s perhaps not context-totally free, very EBNF will not grab that it syntax accurately. This is why, the latest EBNF sentence structure describes a rigid superset off RIF-FLD (never assume all algorithms which can be derivable with the EBNF sentence structure try 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 Name . Identity, 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 describes a concrete syntax simply for investing laws, which syntax is XML-mainly based, gotten while the an elegance and you will serialization of your own EBNF sentence structure through new demonstration-syntax-to-XML mapping to own RIF-FLD.
Keeping the aforementioned in mind, the latest EBNF grammar is seen since the just an intermediary ranging from the new mathematical English and also the XML. However, additionally offers a brief look at the brand new sentence structure off RIF-FLD and as such can be handy to possess dialect performers and you will profiles alike.
Each RIF-FLD formula and you will title shall be prefixed with that elective 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
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 taimi premium, 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 Body type 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].