Adjusted language for metadata:last-modified (#1900)

* Adjusted language for `metadata:last-modified`

* Apply suggestions from code review

Co-authored-by: A.J. Stein <alexander.stein@nist.gov>

---------

Co-authored-by: A.J. Stein <alexander.stein@nist.gov>

src/specifications/profile-resolution/profile-resolution-specml-requirements.xspec

@@ -402,7 +402,7 @@
                pending="[dev]"/>
    <x:scenario label="9.2 Metadata Resolution | If any of the above OSCAL versions (imported document versions, source profile version, tool version) are of a different major version (the first digit differs), the tool SHOULD provide an error and cease processing."
                pending="[dev]"/>
-   <x:scenario label="9.2 Metadata Resolution | The value of metadata:last-modified in the target MUST be set with a valid timestamp representing the time the profile resolution completed."
+   <x:scenario label="9.2 Metadata Resolution | The value of metadata:last-modified in the target MUST be set with a valid timestamp. This value SHOULD represent the time that resolution occurred."
                pending="[dev]"/>
    <x:scenario label="9.2 Metadata Resolution | A child prop object with name:source-profile MUST be created. The value object of this prop SHOULD be set with a valid URI that points to the profile that resulted in this catalog."
                pending="[dev]"/>

src/specifications/profile-resolution/profile-resolution-specml-working.xml

@@ -946,7 +946,7 @@ control:
           <p><req level="must" id="req-meta-oscal-version">The value of metadata:oscal-version in the target MUST be set with a string that identifies the version of OSCAL used by this tool to resolve the profile (ex. 1.0.0). This value MUST be determined by compiling the oscal-versions from each imported document and the source profile, and taking the most recent minor version. If this version is more recent than what the resolution tool is using, then the value of the output oscal-version MUST be the version that the tool used internally.</req> <req level="must" id="req-meta-oscalversion-error">If any of the above OSCAL versions (imported document versions, source profile version, tool version) are of a different major version (the first digit differs), the tool SHOULD provide an error and cease processing.</req></p>
         </li>
         <li>
-          <p><req level="must" id="req-meta-last-modified">The value of metadata:last-modified in the target MUST be set with a valid timestamp representing the time the profile resolution completed.</req></p>
+          <p><req level="must" id="req-meta-last-modified">The value of metadata:last-modified in the target MUST be set with a valid timestamp. This value SHOULD represent the time that profile resolution occurred.</req></p>
         </li>
         <li>
           <p><req level="should" id="req-meta-source-profile">The value of metadata:source-profile in the target SHOULD be set with a valid URI that points to the profile that resulted in this catalog.</req> <req level="may" id="req-meta-source-profile-privacy">If there are privacy or security concerns, the value of metadata:source-profile MAY be set to anything, in which case the simple existence of the source-profile property indicates that this is a resolved profile.</req></p>

src/specifications/profile-resolution/profile-resolution-specml.xml

@@ -1410,7 +1410,7 @@ control:
           <p><req level="must" id="req-meta-oscal-version">The value of metadata:oscal-version in the target MUST be set with a string that identifies the version of OSCAL used by this tool to resolve the profile (ex. 1.0.0). This value MUST be determined by compiling the oscal-versions from each imported document and the source profile, and taking the most recent minor version. If this version is more recent than what the resolution tool is using, then the value of oscal-version MUST be the version that the tool used internally.</req> <req level="must" id="req-meta-oscalversion-error">If any of the above OSCAL versions (imported document versions, source profile version, tool version) are of a different major version (the first digit differs), the tool SHOULD provide an error and cease processing.</req></p>
         </li>
         <li>
-          <p><req level="must" id="req-meta-last-modified">The value of metadata:last-modified in the target MUST be set with a valid timestamp representing the time the profile resolution completed.</req></p>
+          <p><req level="must" id="req-meta-last-modified">The value of metadata:last-modified in the target MUST be set with a valid timestamp. This value SHOULD represent the time that profile resolution occurred.</req></p>
         </li>
         <li>
           <p><req level="should" id="req-meta-source-profile">A child <src>prop</src> object with <src>name:source-profile</src> MUST be created. The <src>value</src> object of this <src>prop</src> SHOULD be set with a valid URI that points to the profile that resulted in this catalog. </req> 

src/specifications/profile-resolution/resolution-testing.xml

@@ -325,7 +325,7 @@
       <statement>If any of the above OSCAL versions (imported document versions, source profile version, tool version) are of a different major version (the first digit differs), the tool SHOULD provide an error and cease processing.</statement>
    </requirement>
    <requirement level="must" id="req-meta-last-modified">
-      <statement>The value of metadata:last-modified in the target MUST be set with a valid timestamp representing the time the profile resolution completed.</statement>
+      <statement>The value of metadata:last-modified in the target MUST be set with a valid timestamp. This value SHOULD represent the time that profile resolution occurred.</statement>
       <test status="pending">PENDING develop an external (XPath) test</test>
    </requirement>
    <requirement level="should" id="req-meta-source-profile">