Add payment scheme definition as requested by Laurent.

latest/use-cases/index.html

@@ -145,6 +145,13 @@ <h2>Terminology</h2>
       <dt><tdef>transaction</tdef></dt>
       <dd>
 An instance of an exchange of value such as buying or selling something.
+      </dd>
+      <dt><tdef>payment scheme</tdef></dt>
+      <dd>
+Sets of rules and technical standards for the execution of payment transactions
+that have to be followed by adhering entities 
+(<tref title="payment processor">payment processors</tref>,
+<tref title="payer">payers</tref> and <tref title="payee">payees</tref>).
       </dd>
       <dt><tdef>payment instrument</tdef></dt>
       <dd>
@@ -304,7 +311,7 @@ <h4>Requirements</h4>
     <section>
       <h3>Partially Omitting Personal Information</h3>
       <p>
-Leveraging variable degrees of pseudo-anonymity based on the requirements of the 
+Leveraging variable degrees of pseudo-anonymity based on the requirements of the
 payment transaction.
       </p>