revert back the change to BGP matching; this part may be adapted later

Author: hartig

spec/index.html

@@ -8993,8 +8993,8 @@ <h4>SPARQL Basic Graph Pattern Matching</h4>
             <p>μ is a <b>solution</b> for BGP from G when there is a pattern instance mapping P such
               that P(BGP) is a subgraph of G and μ is the restriction of P to the query variables in
               BGP.</p>
-            <p><a href="#defn_Multiplicity">multiplicity</a><sup>Ω</sup>(μ) = number of distinct RDF instance mappings, σ, such that P = μ(σ)
-              is a pattern instance mapping and P(BGP) is a subgraph of G</p>
+            <p>card[Ω](μ) = card[Ω](number of distinct RDF instance mappings, σ, such that P = μ(σ)
+              is a pattern instance mapping and P(BGP) is a subgraph of G).</p>
           </div>
           <p>If a basic graph pattern is the empty set, then the solution is Ω<sub>0</sub>.</p>
         </section>