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EXISTS: scoping restriction #272

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194 changes: 124 additions & 70 deletions spec/index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -8730,10 +8730,10 @@ <h4>Variable Scope</h4>
query. The definition below provides a way of determining this from the
abstract syntax tree of a query.</p>
<p>Note that a subquery with a projection can hide variables; use of a variable in
<code>FILTER</code> or in <code>MINUS</code> does not cause the variable to be in-scope
`FILTER` or in `MINUS` does not cause the variable to be in-scope
outside of those forms.</p>
<p>Let <b>P</b>, <b>P1</b>, and <b>P2</b> be graph patterns, and <b>E</b>,
<b>E1</b>,..., through <b>En</b> be expressions. A variable <code>v</code> is in-scope if:</p>
<b>E1</b>,..., through <b>En</b> be expressions. A variable `v` is in-scope if:</p>
<table style="border-collapse: collapse; border-color: #000000; border-spacing:5px; border-width: 1px">
<tbody>
<tr>
Expand All @@ -8742,70 +8742,81 @@ <h4>Variable Scope</h4>
</tr>
<tr>
<td>Basic Graph Pattern (BGP)</td>
<td><code>v</code> occurs in the BGP</td>
<td>`v` occurs in the BGP</td>
</tr>
<tr>
<td>Path</td>
<td><code>v</code> occurs in the path</td>
<td>`v` occurs in the path</td>
</tr>
<tr>
<td>Group <code>{ P1 P2 ... }</code></td>
<td><code>v</code> is in-scope if it is in-scope in one or more of P1, P2, ...</td>
<td>Group `{ P1 P2 ... }`</td>
<td>`v` is in-scope if it is in-scope in one or more of P1, P2, ...</td>
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Suggested change
<td>`v` is in-scope if it is in-scope in one or more of P1, P2, ...</td>
<td>`v` is in-scope if it is in-scope in one or more of `P1`, `P2`, ...</td>

</tr>
<tr>
<td><code>GRAPH term { P }</code></td>
<td><code>v</code> is <code>term</code> or <code>v</code> is in-scope in P</td>
<td>`GRAPH term { P }`</td>
<td>`v` is `term` or `v` is in-scope in P</td>
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<td>`v` is `term` or `v` is in-scope in P</td>
<td>`v` is `term` or `v` is in-scope in `P`</td>

</tr>
<tr>
<td><code>{ P1 } UNION { P2 }</code></td>
<td><code>v</code> is in-scope in P1 or in-scope in P2</td>
<td>`{ P1 } UNION { P2 }`</td>
<td>`v` is in-scope in P1 or in-scope in P2</td>
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<td>`v` is in-scope in P1 or in-scope in P2</td>
<td>`v` is in-scope in `P1` or in-scope in `P2`</td>

</tr>
<tr>
<td><code>OPTIONAL {P}</code></td>
<td><code>v</code> is in-scope in P</td>
<td>`OPTIONAL {P}`</td>
<td>`v` is in-scope in P</td>
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<td>`v` is in-scope in P</td>
<td>`v` is in-scope in `P`</td>

</tr>
<tr>
<td><code>SERVICE term {P}</code></td>
<td><code>v</code> is <code>term</code> or <code>v</code> is in-scope in P</td>
<td>`SERVICE term {P}`</td>
<td>`v` is `term` or `v` is in-scope in P</td>
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<td>`v` is `term` or `v` is in-scope in P</td>
<td>`v` is `term` or `v` is in-scope in `P`</td>

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Not part of this PR, but "v is term" here seems really strange? Am I not meant to read "term" as indicating the use of the SERVICE IRI form (which is the only one that has evaluation semantics)?

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I think the word "term" is misleading here. This part of the table should better be:

| SERVICE x { P } | v is x or v is in-scope in P |

Same issue for the case of GRAPH a bit earlier in the table.

</tr>
<tr>
<td><code>BIND (expr AS v)</code></td>
<td><code>v</code> is in-scope</td>
<td>`BIND (expr AS v)`</td>
<td>`v` is in-scope</td>
</tr>
<tr>
<td><code>SELECT .. v .. { P }</code></td>
<td><code>v</code> is in-scope</td>
<td>`SELECT .. v .. { P }`</td>
<td>`v` is in-scope</td>
</tr>
<tr>
<td><code>SELECT ... (expr AS v)</code></td>
<td><code>v</code> is in-scope</td>
<td>`SELECT ... (expr AS v)`</td>
<td>`v` is in-scope</td>
</tr>
<tr>
<td><code>GROUP BY (expr AS v)</code></td>
<td><code>v</code> is in-scope</td>
<td>`GROUP BY (expr AS v)`</td>
<td>`v` is in-scope</td>
</tr>
<tr>
<td><code>SELECT * { P }</code></td>
<td><code>v</code> is in-scope in <code>P</code></td>
<td>`SELECT * { P }`</td>
<td>`v` is in-scope in `P`</td>
</tr>
<tr>
<td><code>VALUES v { values }</code></td>
<td><code>v</code> is in-scope</td>
<td>`VALUES v { values }`</td>
<td>`v` is in-scope</td>
</tr>
<tr>
<td><code>VALUES varlist { values }</code></td>
<td><code>v</code> is in-scope if <code>v</code> is in <code>varlist</code></td>
<td>`VALUES varlist { values }`</td>
<td>`v` is in-scope if `v` is in `varlist`</td>
</tr>
<tr>
<td>`EXISTS` and `NOT EXISTS`</td>
<td>
`v` is in-scope if it is in-scope for the
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This formulation is a bit weird to me because it's not defining the set of in-scope variable in the pattern like the other cases but the variable in scopes inside of any sub-pattern of the pattern.

I would rephase the sentence to something like v is in-scope of all graph pattern contained in P if v is in-cope for a solution mapping where the expression containing EXISTS P or NOT EXISTS P is applied.

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I find that weird as well. I would not include such a row in this table because the intended way to read this particular row would be very different from the way all the other rows are meant to be read.

<a href="#defn_sparqlSolutionMapping">solution mapping</a>
where the expression containing `EXISTS` or `NOT EXISTS` is applied.
</td>
</tr>
</tbody>
</table>
<p>The variable <code>v</code> must not be in-scope at the point of the <code>(expr AS
v)</code> form. The scoping for <code>(expr AS v)</code> applies immediately in
<code>SELECT</code> expressions.</p>
<p>In <code>BIND (expr AS v)</code> requires that the variable <code>v</code> is not
in-scope from the preceeding elements in the group graph pattern in which it is used.</p>
<p>In <code>SELECT</code>, the variable <code>v</code> must not be in-scope in the graph
pattern of the <code>SELECT</code> clause, nor used in another select expression earlier in
the clause.</p>
<p>The variable `v` must not be in-scope at the point of the
`(expr AS v)` form. The scoping for `(expr AS v)`
applies immediately in `SELECT` expressions.
</p>
<p>In `BIND (expr AS v)` requires that the variable `v` is not
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Suggested change
<p>In `BIND (expr AS v)` requires that the variable `v` is not
<p>`BIND (expr AS v)` requires that the variable `v` is not

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or

Suggested change
<p>In `BIND (expr AS v)` requires that the variable `v` is not
<p>In `BIND (expr AS v)`, the variable `v` is required to not be

in-scope from the preceeding elements in the group graph pattern in which it is used.
</p>
<p>In `SELECT`, the variable `v` must not be in-scope in the graph
pattern of the `SELECT` clause, nor used in another select expression earlier in
the clause.
</p>
</section>
<section id="convertGraphPattern">
<h4>Converting Graph Patterns</h4>
Expand Down Expand Up @@ -10971,52 +10982,95 @@ <h3>Grammar</h3>
section 6 <a data-cite="xml11#sec-notation">Notation</a>.</p>
<p>Notes:</p>
<ol>
<li>Keywords are matched in a case-insensitive manner with the exception of
the keyword '<code>a</code>' which, in line with Turtle and N3, is used
in place of the IRI <code>rdf:type</code>
(in full, <code><a href="http://www.w3.org/1999/02/22-rdf-syntax-ns#type">http://www.w3.org/1999/02/22-rdf-syntax-ns#type</a></code>).</li>
<li>Escape sequences are case sensitive.</li>
<li>When tokenizing the input and choosing grammar rules, the longest match is chosen.</li>
<li>The SPARQL grammar is LL(1) when the rules with uppercased names are used as terminals.</li>
<li>There are two entry points into the grammar: <code>QueryUnit</code> for the SPARQL query language
and <code>UpdateUnit</code> for the SPARQL update language.</li>
<li>In signed numbers, no white space is allowed between the sign and the number.
<li>
Keywords are matched in a case-insensitive manner with the exception of
the keyword '`a`' which, in line with Turtle and N3, is used
in place of the IRI `rdf:type` (in full,
<code><a href="http://www.w3.org/1999/02/22-rdf-syntax-ns#type">http://www.w3.org/1999/02/22-rdf-syntax-ns#type</a></code>).
Comment on lines +10986 to +10989
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The boolean sugars -- true and false -- are also case sensitive.

(I hate that these exist. We're well and truly stuck with a, which I hate almost as much, but I truly wish that true and false were treated just like any other untyped literal -- and just like any other capitalization of those words would be. Talk about a foot-gun...)

</li>
<li>
Escape sequences are case sensitive.
</li>
<li>
When tokenizing the input and choosing grammar rules, the longest match is chosen.
</li>
<li>
The SPARQL grammar is LL(1) when the rules with uppercased names are used as terminals.
</li>
<li>
There are two entry points into the grammar: `QueryUnit` for the SPARQL query language
and `UpdateUnit` for the SPARQL update language.
Comment on lines +11001 to +11002
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Suggested change
There are two entry points into the grammar: `QueryUnit` for the SPARQL query language
and `UpdateUnit` for the SPARQL update language.
There are two entry points into the grammar: `QueryUnit` for the SPARQL Query language
and `UpdateUnit` for the SPARQL Update language.

</li>
<li>
In signed numbers, no white space is allowed between the sign and the number.
The <code><a href="#rAdditiveExpression">AdditiveExpression</a></code> grammar rule allows for this by
covering the two cases of an expression followed by a signed number. These
produce an addition or subtraction of the unsigned number as appropriate.</li>
<li>The tokens <code><a href="#rInsertData">INSERT DATA</a></code>,
produce an addition or subtraction of the unsigned number as appropriate.
</li>
<li>
The tokens <code><a href="#rInsertData">INSERT DATA</a></code>,
<code><a href="#rDeleteData">DELETE DATA</a></code> and
<code><a href="#rDeleteWhere">DELETE WHERE</a></code> allow any amount of white space between the words.
The single space version is used in the grammar for clarity.</li>
<li>The <code><a href="#rQuadData">QuadData</a></code> and
The single space version is used in the grammar for clarity.
</li>
<li>
The <code><a href="#rQuadData">QuadData</a></code> and
<code><a href="#rQuadPattern">QuadPattern</a></code>
rules both use rule <code><a href="#rQuads">Quads</a></code>. The rule
<code><a href="#rQuadData">QuadData</a></code>, used in
<a href="#rInsertData"><code>INSERTDATA</code></a> and
<a href="#rDeleteData"><code>DELETE DATA</code></a>,
must not allow variables in the quad patterns.</li>
<li>Blank node syntax is not allowed in <code><a href="#rDeleteWhere">DELETE WHERE</a></code>,
the <code><a href="#rDeleteClause">DeleteClause</a></code> for
<code>DELETE</code>,
nor in <code><a href="#rDeleteData">DELETE DATA</a></code>.</li>
<li>Rules for limiting the use of blank node identifiers are given in <a href="#grammarBNodes">section 19.6</a>.</li>
<li>The number of variables in the variable list of <code>VALUES</code> block
must be the same as the number of each list of associated values in the <code>DataBlock</code>.</li>
<li>Variables introduced by <code>AS</code> in a <code>SELECT</code> clause
must not already be <a href="#variableScope">in-scope</a>.</li>
<li>The variable assigned in a <code>BIND</code> clause must not be already
must not allow variables in the quad patterns.
</li>
<li>
Blank node syntax is not allowed in
<code><a href="#rDeleteWhere">DELETE WHERE</a></code>,
in a <code><a href="#rDeleteClause">DeleteClause</a></code>,
nor in <code><a href="#rDeleteData">DELETE DATA</a></code>.
</li>
<li>
Rules for limiting the use of blank node identifiers are given in
<a href="#grammarBNodes">section 19.6</a>.
</li>
<li>
The number of variables in the variable list of <code>VALUES</code> block
must be the same as the number of each list of associated values in the
<code>DataBlock</code>.
</li>
<li>
Variables introduced by <code>AS</code> in a <code>SELECT</code> clause
must not already be <a href="#variableScope">in-scope</a>.
</li>
<li>
The variable assigned in a <code>BIND</code> clause must not be already
in-use within the immediately preceding <code><a href="#rTriplesBlock">TriplesBlock</a></code> within a
<code><a href="#rGroupGraphPattern">GroupGraphPattern</a></code>.</li>
<li>Aggregate functions can be one of the
<code><a href="#rGroupGraphPattern">GroupGraphPattern</a></code>.
</li>
<li>
Aggregate functions can be one of the
<a href="#rAggregate">built-in keywords for aggregates</a>
or a custom aggregate, which is syntactically a <a href="#rFunctionCall">function
call</a>. Aggregate functions may only be used in
or a custom aggregate, which is syntactically a
<a href="#rFunctionCall">function call</a>.
Aggregate functions may only be used in
<a href="#rSelectClause">SELECT</a>, <a href="#rHavingClause">HAVING</a>
and <a href="#rOrderClause">ORDER BY</a> clauses.</li>
<li>The expression argument of an aggregate function can not contain an aggregate function.</li>
<li>Only custom aggregate functions use the <code>DISTINCT</code> keyword
in a <a href="#rFunctionCall">function call</a>.</li>
<li>A <a href="#rReifier">reifier</a> or
and <a href="#rOrderClause">ORDER BY</a> clauses.
</li>
<li>
Any variable that is assigned to in the graph pattern of `EXISTS` or `NOT EXISTS`
must not be <a href="#variableScope">in-scope</a>. This applies to `BIND`,
variables introduced by `AS` in a `SELECT` clause,
variables introduced by `AS` in `GROUP BY`,
and variables in a `VALUES` clause.
</li>
<li>
The expression argument of an aggregate function can not contain an aggregate function.
</li>
<li>
Only custom aggregate functions use the <code>DISTINCT</code> keyword
in a <a href="#rFunctionCall">function call</a>.
</li>
<li>
A <a href="#rReifier">reifier</a> or
<a href="#rAnnotationBlockPath">annotation syntax</a>
is only permitted after a triple when the property position is
a simple path (an IRI, the keyword <code>a</code>, or a variable),
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