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Fixes inconsistencies in definition of evaluation of property path with sequence #351

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hartig merged 4 commits into from
Jan 23, 2026
Merged

Fixes inconsistencies in definition of evaluation of property path with sequence #351

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Fixes inconsistencies in definition of evaluation of property path wi…
hartig Jan 18, 2026
8b78815
changes the order of things in the definition of evaluation of proper…
hartig Jan 18, 2026
9003d9c
adds missing space
hartig Jan 19, 2026
6297ece
v -> prjVar
hartig Jan 23, 2026
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8 changes: 4 additions & 4 deletions spec/index.html
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Expand Up @@ -9948,10 +9948,10 @@ <h3>Property Path Patterns</h3>
<div class="defn">
<p><b>Definition: <span id="defn_evalPP_sequence">Evaluation of Sequence Property Path</span></b></p>
<p>Let <var>ppe<sub>1</sub></var> and <var>ppe<sub>2</sub></var> be <a href="#defn_AlgebraicPropertyPathExpression">algebraic property path expressions</a>. Let |V| be a fresh variable.</p>
<pre class="nohighlight"><var>A</var> = <a href="#defn_algJoin" class="algFct">Join</a>( ppeval(<var>X</var>, <var>ppe<sub>1</sub></var>, <var>V</var>), ppeval(<var>V</var>, <var>ppe<sub>2</sub></var>, <var>Y</var>) )</pre>
<pre class="nohighlight">ppeval(<var>X</var>, <a href="#defn_ppeSeq" class="ppeOp">Seq</a>(<var>ppe<sub>1</sub></var>, <var>ppe<sub>2</sub></var>), <var>Y</var>) = <a href="#defn_algProject" class="algFct">Project</a>(<var>A</var>, <var>PV</var>)</pre>
<p>where |PV| = { |v| ∈ {|X|,|Y|} | |v| is a variable}.</p>
<div class="issue" data-number="266"><a href="#defn_algJoin" class="algFct">Join</a> produces a multiset of solution mappings but <a href="#defn_algProject" class="algFct">Project</a> expects a sequence as its first argument. Moreover, <a href="#defn_algProject" class="algFct">Project</a> produces a sequence but ppeval(..) should be a multiset.</div>
<pre class="nohighlight">ppeval(<var>X</var>, <a href="#defn_ppeSeq" class="ppeOp">Seq</a>(<var>ppe<sub>1</sub></var>, <var>ppe<sub>2</sub></var>), <var>Y</var>) = <a href="#defn_algToMultiSet" class="algFct">ToMultiSet</a>( <a href="#defn_algProject" class="algFct">Project</a>(<a href="#defn_algToList" class="algFct">ToList</a>(<var>A</var>), <var>PV</var>) )</pre>
<p>where |A| =
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@afs afs Jan 22, 2026

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Miinor/preference: I find it easier if things are defined before they are used -- i.e. A = before ToList(A).

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@hartig hartig Jan 23, 2026

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Honestly, I don't find that easier. At least not in the way it looks like at the moment (i.e., before this PR):

Image

There I am just wondering: what is this A about, why isn't this definition just defining the ppeval as all other definitions in this section do?

<a href="#defn_algJoin" class="algFct">Join</a>( `ppeval`(|X|, <var>ppe<sub>1</sub></var>, |V|), `ppeval`(|V|, <var>ppe<sub>2</sub></var>, |Y|) )
and |PV| = { |projVar| ∈ {|X|,|Y|} | |projVar| is a variable }.</p>
</div>
<p>Informally, this is the same as:</p>
<pre class="nohighlight">SELECT * { <var>X</var> <var>P<sub>1</sub></var> _:a . _:a <var>P<sub>2</sub></var> <var>Y</var> }</pre>
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