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Re: SPARQL and Turtle Prefix Placement

From: Eric Prud'hommeaux <eric@w3.org>
Date: Fri, 15 Jun 2012 10:00:56 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Cc: public-rdf-wg@w3.org
Message-ID: <20120615140054.GE4447@w3.org>
* Eric Prud'hommeaux <eric@w3.org> [2012-06-15 05:32-0400]
> * Andy Seaborne <andy.seaborne@epimorphics.com> [2012-06-15 09:25+0100]
> > 
> > >btw, i've been updating the grammar to deal with some LL(1).LALR(1) and other conflicts. should be synched soon.
> > 
> > As this is very close to LC, could you point out the changes being made?
> 
> Indeed. There are three kinds of changes:
>   1 get rid of extra ()s, à la "(statement)*"
>   2 make explicit that turtle parses '"ab"@base' as a literal with a language tag.
>   3 fix lalr(1)/ll(1) conflict in
>     [6] triples ::= subject predicateObjectList | blankNodePropertyList predicateObjectList?
>     by moving blankNodePropertyList from [14] blank to 12 [object].

r442 (just committed) removed some spurious \s (there's no escaping in <http://www.w3.org/TR/REC-xml/#sec-notation>) and entity-encoded the <>s in the excluded lists in IRIREF.

Andy, rq25's IRIREF
  [138] IRIREF ::= '<' ([^<>"{}|^`\]-[#x00-#x20])* '>'
uses the A - B notation. When we added "| UCHAR", we ran into an ambiguity in the notation because there's no relative precedence between - and | in A - B | C. This could have been solved with ()s, but we decided to collapse the excluded range minus a range into a larger excluded range. Is SPARQL going to add UCHARs (\uXXXX notation)? If so, we can share that production.

=Turtle re-using SPARQL productions=
The intro currently says "The two grammars share production and terminal names where possible." To make this absolutely true, we used to use SPARQL's:

NumericLiteral         ::= NumericLiteralUnsigned
		         | NumericLiteralPositive
			 | NumericLiteralNegative
NumericLiteralUnsigned ::= <INTEGER>
		         | <DECIMAL>
			 | <DOUBLE>
NumericLiteralPositive ::= <INTEGER_POSITIVE>
		         | <DECIMAL_POSITIVE>
		         | <DOUBLE_POSITIVE>
NumericLiteralNegative ::= <INTEGER_NEGATIVE>
		         | <DECIMAL_NEGATIVE>
			 | <DOUBLE_NEGATIVE>

<INTEGER>              ::= ([0-9])+
<DECIMAL>              ::= ([0-9])* "." ([0-9])+
<DOUBLE>               ::= ([0-9])+ "." ([0-9])* EXPONENT
		         | "." ([0-9])+ EXPONENT
		     	 | ([0-9])+ EXPONENT
<INTEGER_POSITIVE>     ::= "+" INTEGER
<DECIMAL_POSITIVE>     ::= "+" DECIMAL
<DOUBLE_POSITIVE>      ::= "+" DOUBLE
<INTEGER_NEGATIVE>     ::= "-" INTEGER
<DECIMAL_NEGATIVE>     ::= "-" DECIMAL
<DOUBLE_NEGATIVE>      ::= "-" DOUBLE

A just slightly terser but non-parallel representation is:

NumericLiteral ::= <INTEGER> | <DECIMAL> | <DOUBLE>
<INTEGER>      ::= [+-]? [0-9]+
<DECIMAL>      ::= [+-]? ([0-9]* '.' [0-9]+)
<DOUBLE>       ::= [+-]? (([0-9]+ '.' [0-9]* <EXPONENT>)
                 | ('.' [0-9]+ <EXPONENT>)
                 | ([0-9]+ <EXPONENT>))

I presume the intention is the latter but I'd like to confirm before I irradicate this complex markup:
  [61s] NumericLiteral         ::= NumericLiteralUnsigned | NumericLiteralPositive | NumericLiteralNegative
  [62s] NumericLiteralUnsigned ::= INTEGER | DECIMAL | DOUBLE
  [63s] NumericLiteralPositive ::= INTEGER_POSITIVE | DECIMAL_POSITIVE | DOUBLE_POSITIVE
  [64s] NumericLiteralNegative ::= INTEGER_NEGATIVE | DECIMAL_NEGATIVE | DOUBLE_NEGATIVE

Another issue is that by stating that we use the same productions as SPARQL, we have to synchronize with SPARQL. In principle, this is easily resolve by a bit of friendly competition on the part of the editors: which ever makes it to PR second has to tweak their foreign production numbers (e.g. "[132s]" or "[17t]") to reference the winner. (Some specs simply don't include referenced productions, e.g. Namespaces in XML's reference to XML in "[4] NCName ::= Name - (Char* ':' Char*)", but for something as intimate as SPARQL and Turtle, I think that would be hard on readers.) I'm comfortable with changing the production numbers up to PR as it is clearly not a change to the language. Maybe a little at-risk-like text could readers of this volatility.


> 3 is the biggest change, necessitated by the addtion of " | blankNodePropertyList predicateObjectList?" to [6] triples. I believe I properly chased down the grammar combos and tested them with <http://w3.org/brief/MjY0>, but I'd like a second.
> 
> [[
> -[1]     turtleDoc              ::= (statement)*
> +[1]     turtleDoc              ::= statement*
> -[2]     statement              ::= (directive '.') | (triples '.')
> +[2]     statement              ::= directive '.' | triples '.'
>  [3]     directive              ::= prefixID | base
> -[4]     prefixID               ::= '@prefix' PNAME_NS IRIREF
> +[4]     prefixID               ::= PREFIX PNAME_NS IRIREF
> -[5]     base                   ::= '@base' IRIREF
> +[5]     base                   ::= BASE IRIREF
> -[6]     triples                ::= (subject predicateObjectList) | (blankNodePropertyList (predicateObjectList)?)
> +[6]     triples                ::= subject predicateObjectList | blankNodePropertyList predicateObjectList?
>  [7]     predicateObjectList    ::= verb objectList (';' verb objectList)* (';')?
>  [8]     objectList             ::= object (',' object)*
>  [9]     verb                   ::= predicate | 'a'
>  [10]    subject                ::= iri | blank
>  [11]    predicate              ::= iri
> -[12]    object                 ::= iri | blank | literal
> +[12]    object                 ::= iri | blank | blankNodePropertyList | literal
>  [13]    literal                ::= RDFLiteral | NumericLiteral | BooleanLiteral
> -[14]    blank                  ::= BlankNode | blankNodePropertyList | collection
> +[14]    blank                  ::= BlankNode | collection
>  [15]    blankNodePropertyList  ::= '[' predicateObjectList ']'
> -[16]    collection             ::= '(' (object)* ')'
> +[16]    collection             ::= '(' object* ')'
> -[60s]   RDFLiteral             ::= String (LANGTAG | ('^^' iri))?
> +[60s]   RDFLiteral             ::= String (LANGTAG | '^^' iri)?
>  [61s]   NumericLiteral         ::= NumericLiteralUnsigned | NumericLiteralPositive | NumericLiteralNegative
>  [62s]   NumericLiteralUnsigned ::= INTEGER | DECIMAL | DOUBLE
>  [63s]   NumericLiteralPositive ::= INTEGER_POSITIVE | DECIMAL_POSITIVE | DOUBLE_POSITIVE
> @@ -24,24 +24,26 @@
>  [67s]   iri                    ::= IRIREF | PrefixedName
>  [68s]   PrefixedName           ::= PNAME_LN | PNAME_NS
>  [69s]   BlankNode              ::= BLANK_NODE_LABEL | ANON
> +[17]    BASE                   ::= '@base'
> +[18]    PREFIX                 ::= '@prefix'
>  [132s]  IRIREF                 ::= '<' ([^#x00-#x20<>\"{}|^`\\] | UCHAR)* '>'
> -[133s]  PNAME_NS               ::= (PN_PREFIX)? ':'
> +[133s]  PNAME_NS               ::= PN_PREFIX? ':'
>  [134s]  PNAME_LN               ::= PNAME_NS PN_LOCAL
>  [135s]  BLANK_NODE_LABEL       ::= '_:' (PN_CHARS_U | [0-9]) ((PN_CHARS | '.')* PN_CHARS)?
> -[19]    LANGTAG                ::= '@' ([a-zA-Z])+ ('-' ([a-zA-Z0-9])+)*
> +[19]    LANGTAG                ::= BASE | PREFIX | '@' [a-zA-Z]+ ('-' [a-zA-Z0-9]+)*
> -[20]    INTEGER                ::= ([+-])? ([0-9])+
> +[20]    INTEGER                ::= [+-]? [0-9]+
> -[21]    DECIMAL                ::= ([+-])? (([0-9])* '.' ([0-9])+)
> +[21]    DECIMAL                ::= [+-]? ([0-9]* '.' [0-9]+)
> -[22]    DOUBLE                 ::= ([+-])? ((([0-9])+ '.' ([0-9])* EXPONENT) | ('.' ([0-9])+ EXPONENT) | (([0-9])+ EXPONENT))
> +[22]    DOUBLE                 ::= [+-]? (([0-9]+ '.' [0-9]* EXPONENT) | ('.' [0-9]+ EXPONENT) | ([0-9]+ EXPONENT))
> -[148s]  EXPONENT               ::= [eE] ([+-])? ([0-9])+
> +[148s]  EXPONENT               ::= [eE] [+-]? [0-9]+
>  [149s]  STRING_LITERAL1        ::= '"' ([^#x27#x5C#xA#xD] | ECHAR | UCHAR)* '"'
>  [150s]  STRING_LITERAL2        ::= "'" ([^#x22#x5C#xA#xD] | ECHAR | UCHAR)* "'"
>  [151s]  STRING_LITERAL_LONG1   ::= "'''" (("'" | "''")? ([^'\] | ECHAR | UCHAR))* "'''"
>  [152s]  STRING_LITERAL_LONG2   ::= '"""' (('"' | '""')? ([^"\] | ECHAR | UCHAR))* '"""'
> -[19]    UCHAR                  ::= ('\u' HEX HEX HEX HEX) | ('\U' HEX HEX HEX HEX HEX HEX HEX HEX)
> +[23]    UCHAR                  ::= ('\u' HEX HEX HEX HEX) | ('\U' HEX HEX HEX HEX HEX HEX HEX HEX)
>  [153s]  ECHAR                  ::= '\' [tbnrf\"']
> -[154s]  NIL                    ::= '(' (WS)* ')'
> +[154s]  NIL                    ::= '(' WS* ')'
>  [155s]  WS                     ::= #x20 | #x9 | #xD | #xA
> -[156s]  ANON                   ::= '[' (WS)* ']'
> +[156s]  ANON                   ::= '[' WS* ']'
>  [157s]  PN_CHARS_BASE          ::= [A-Z] | [a-z] | [#00C0-#00D6] | [#00D8-#00F6] | [#00F8-#02FF] | [#0370-#037D] | [#037F-#1FFF] | [#200C-#200D] | [#2070-#218F] | [#2C00-#2FEF] | [#3001-#D7FF] | [#F900-#FDCF] | [#FDF0-#FFFD] | [#10000-#EFFFF]
>  [158s]  PN_CHARS_U             ::= PN_CHARS_BASE | '_' | ':'
>  [160s]  PN_CHARS               ::= PN_CHARS_U | '-' | [0-9] | #00B7 | [#0300-#036F] | [#203F-#2040]
> ]]
> 
> I haven't changed
> -[22]    DOUBLE                 ::= [+-]? (([0-9]+ '.' [0-9]* EXPONENT) | ('.' [0-9]+ EXPONENT) | ([0-9]+ EXPONENT)) to
> +[22]    DOUBLE                 ::= [+-]? ( [0-9]+ '.' [0-9]* EXPONENT  |  '.' [0-9]+ EXPONENT  |  [0-9]+ EXPONENT )
> 'cause I wasn't sure if others found the former more readable (though I personally prefer fewer ()s (they get a bit oppressive (when used in excess))).
> 
> 
> > This does not make it very easy to see any material changes:
> > http://dvcs.w3.org/hg/rdf/rev/8b47a7006c8c
> > 
> > The hg log is to changes of the HTML and it's very hard to see the
> > real changes when it has:
> > 
> >  1.7 -    <td>[1]<td>
> >  1.8 -    <td><code>turtleDoc</code><td>
> >  1.9 +    <td>[1]</td>
> > 1.10 +    <td><code>turtleDoc</code></td>
> > 
> > - - - - - - - - - - - - -
> > 
> > I noticed there are 2 * 17's:
> > 
> > [17] 	BASE 	::= 	'@base'
> > [17] 	PREFIX 	::= 	'@prefix'
> > 
> > 	Thanks
> > 	Andy
> > 
> > 
> 
> -- 
> -ericP

-- 
-ericP
Received on Friday, 15 June 2012 14:01:35 GMT

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