Correct explanation of contents of unsecured document.

Co-authored-by: Dave Longley <[email protected]>

index.html

@@ -1067,20 +1067,19 @@ <h3>Proof Graphs</h3>
 
         <p>
 When securing data in a document, it is important to clearly delineate the data
-being protected, called the <dfn class="export">default graph</dfn>, from the
-data associated with a securing mechanism, called a
-<dfn class="export">proof graph</dfn>. Creating this separation enables the
-processing algorithms to be able to deterministically protect and verify a
-secured document.
+being protected, which is every graph expressed in the document except the
+one containing the data associated with a securing mechanism, which is called
+a <dfn class="export">proof graph</dfn>. Creating this separation enables the
+processing algorithms to be able to deterministically protect and verify a secured
+document.
         </p>
 
         <p>
 For an unsecured document, the information contained in the document before a
-[=data integrity proof=] is added to the document is called the [=default
-graph=]. A single document can contain multiple proof graphs. To ensure that
-information from different [=data integrity proofs=] are not accidentally
-co-mingled, the concept of a [=proof graph=] is used to encapsulate each [=data
-integrity proof=]. Each value associated with the `proof` property of the
+[=data integrity proof=] is added to the document is expressed in one or more
+graphs. To ensure that information from different [=data integrity proofs=] are not
+accidentally co-mingled, the concept of a [=proof graph=] is used to encapsulate
+each [=data integrity proof=]. Each value associated with the `proof` property of the
 document is a separate graph, which is sometimes referred to as a
 <dfn class="export">named graph</dfn>, of type
 <dfn class="export">ProofGraph</dfn>, which contains a single [=data integrity