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dangtv · Nov 27, 2019 · 946a46c · 946a46c
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diff --git a/docs/syntax.html b/docs/syntax.html
@@ -67,7 +67,7 @@ <h2 id="abbreviated-syntax">Abbreviated syntax</h2>
 
 <h3 id="primary-key">Primary key</h3>
 
-<p>BIRDS provides a shorthand syntax to declare primary key on relations.
+<p>BIRDS provides a shorthand syntax to declare primary keys on relations.
 Given a relation t(<strong>A</strong>, B, C), we can declare <strong>A</strong> as a primary key of t by:</p>
 
 <div class="language-prolog highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">PK</span><span class="p">(</span><span class="ss">t</span><span class="p">,[</span><span class="nv">A</span><span class="p">]).</span>
@@ -87,9 +87,9 @@ <h3 id="primary-key">Primary key</h3>
 </code></pre></div></div>
 <p>That is an abbreviation for the following rules:</p>
 
-<div class="language-prolog highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="err">%</span> <span class="ss">for</span> <span class="ss">the</span> <span class="ss">functional</span> <span class="ss">dependency</span> <span class="nv">A</span><span class="p">,</span><span class="nv">B</span> <span class="o">-&gt;</span> <span class="nv">C</span><span class="o">:</span>
+<div class="language-prolog highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="err">%</span> <span class="ss">for</span> <span class="ss">the</span> <span class="ss">functional</span> <span class="ss">dependency</span> <span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nv">C</span><span class="o">:</span>
 <span class="nv">_</span><span class="p">|</span><span class="nv">_</span> <span class="p">:-</span> <span class="ss">s</span><span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">,</span><span class="nv">C1</span><span class="p">,</span><span class="nv">_</span><span class="p">),</span> <span class="ss">s</span><span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">,</span><span class="nv">C2</span><span class="p">,</span><span class="nv">_</span><span class="p">),</span> <span class="ss">not</span> <span class="nv">C1</span> <span class="o">=</span> <span class="nv">C2</span><span class="p">.</span>
-<span class="err">%</span> <span class="ss">for</span> <span class="ss">the</span> <span class="ss">functional</span> <span class="ss">dependency</span> <span class="nv">A</span><span class="p">,</span><span class="nv">B</span> <span class="o">-&gt;</span> <span class="nv">D</span><span class="o">:</span>
+<span class="err">%</span> <span class="ss">for</span> <span class="ss">the</span> <span class="ss">functional</span> <span class="ss">dependency</span> <span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nv">D</span><span class="o">:</span>
 <span class="nv">_</span><span class="p">|</span><span class="nv">_</span> <span class="p">:-</span> <span class="ss">s</span><span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">,</span><span class="nv">_</span><span class="p">,</span><span class="nv">D1</span><span class="p">),</span> <span class="ss">s</span><span class="p">(</span><span class="nv">A</span><span class="p">,</span><span class="nv">B</span><span class="p">,</span><span class="nv">_</span><span class="p">,</span><span class="nv">D2</span><span class="p">),</span> <span class="ss">not</span> <span class="nv">D1</span> <span class="o">=</span> <span class="nv">D2</span><span class="p">.</span>
 </code></pre></div></div>
 

diff --git a/webpage/syntax.md b/webpage/syntax.md
@@ -30,7 +30,7 @@ In general, the verification in BIRDS is sound. BIRDS guarantees the completenes
 
 ### Primary key
 
-BIRDS provides a shorthand syntax to declare primary key on relations.
+BIRDS provides a shorthand syntax to declare primary keys on relations.
 Given a relation t(**A**, B, C), we can declare **A** as a primary key of t by:
 
 ```prolog
@@ -54,8 +54,8 @@ PK(t,[A,B]).
 That is an abbreviation for the following rules:
 
 ```prolog
-% for the functional dependency A,B -> C:
+% for the functional dependency (A,B) -> C:
 _|_ :- s(A,B,C1,_), s(A,B,C2,_), not C1 = C2.
-% for the functional dependency A,B -> D:
+% for the functional dependency (A,B) -> D:
 _|_ :- s(A,B,_,D1), s(A,B,_,D2), not D1 = D2.
 ```