Update extracted files (#485)

Co-authored-by: Luther Tychonievich <tychonievich@users.noreply.github.com>

extracted-files/tags/DATE

@@ -14,6 +14,19 @@ specification:
     The principal date of the subject of the superstructure. The payload is a
     `DateValue`.
 
+    When the superstructure is an event, the principal date indicates when the
+    event took place.
+
+    When the superstructure is an attribute, the principal date indicates when the
+    attribute was observed, asserted, or applied. A date period might put bounds on
+    the attributes applicability, but other date forms assume that the attribute
+    may have also applied on other dates too.
+
+    When the superstructure is a `https://gedcom.io/terms/v7/SOUR-DATA`, the
+    principal date indicates when the data was entered into the source; or, for a
+    source like a website that changes over time, a date on which the source
+    contained the data.
+
     See `DATE_VALUE` for more details.
   - |
     A date, optionally with a time and/or a phrase. If there is a `TIME`, it

extracted-files/tags/PLAC

@@ -35,8 +35,12 @@ specification:
     - The payload contains a comma-separated list of region names, ordered from
       smallest to largest. The specific meaning of each element is given by the
       `FORM` substructure, or in the `HEAD`.`PLAC`.`FORM` if there is no `FORM`
-      substructure. Elements should be left blank if they are unknown, do not apply
-      to the location, or are too specific for the region in question.
+      substructure. If neither `FORM` exists, the meaning of the elements are not
+      defined in this specification beyond being names of jurisdictions of some
+      kind, ordered from smallest to largest.
+
+      Elements should be left blank if they are unknown, do not apply to the
+      location, or are too specific for the region in question.
 
       <div class="example">
         A record describing births throughout Oneida county could be recorded as

extracted-files/tags/WWW

@@ -11,8 +11,18 @@ standard tag: WWW
 specification:
   - Web address
   - |
-    A URL or other locator for a World Wide Web page, as defined by any relevant
-    standard such as [whatwg/url], [RFC 3986], [RFC 3987], and so forth.
+    A URL or other locator for a World Wide Web page of the subject of the
+    superstructure, as defined by any relevant standard such as [whatwg/url],
+    [RFC 3986], [RFC 3987], and so forth.
+
+    Like other substructures, the `WWW` structure provides details about the
+    subject of its superstructure. For example, a `MARR`.`WWW` is a world wide web
+    page of the marriage event, not the personal website of the couple or an entry
+    in an online database serving as a source documenting the marriage. However,
+    the meaning of `WWW` was only implicit when it was introduced in version 5.5.1
+    and many files were created that use `WWW` to store a more tangentially-related
+    web address, so applications are recommended to interpret the `WWW` structure's
+    meaning cautiously.
 
     If an invalid or no longer existing web address is present upon import, it
     should be preserved as-is on export.