Add [expires] to ripple.txt

ripple.txt

@@ -1,10 +1,8 @@
 #
 # Sample ripple.txt
 #
-# Publishing this file allows a site to declare in a trustworthy manor that
-# their node_public_key is the authorized signature for the domain. This does
-# not imply that a node serving the Newcoin protocol is avilable at the web
-# host providing the file.
+# Publishing this file allows a site to declare in a trustworthy manor ripple
+# associated information.
 #
 # This file is stored on the web server for a domain.  This file is searched
 # for in the following order:
@@ -17,6 +15,16 @@
 # Undefined sections are reserved.
 # No escapes are currently defined.
 #
+# [expires]
+#   Number of days after which this file should be considered expire.  Clients
+#   are expected to check this file when they have cause to believe it has
+#   changed or expired. For example, if a client discovers an account declares
+#   that it is associated with the domain, it should check to see if this file
+#   has been updated. If an expiration date is not declared, the default
+#   expiration for this file is 30 days.
+#
+#   Example: 30
+#
 # [accounts]
 #   Only valid in "ripple.txt". A list of accounts that are declared to be
 #   controlled by this domain. A client wishing to indicate that an account is
@@ -30,7 +38,10 @@
 #
 # [validation_public_key]:
 #   Only valid in "ripple.txt". A validation public key that is declared
-#   to be used by this domain for validating ledgers. 
+#   to be used by this domain for validating ledgers and that it is the
+#   authorized signature for the domain. This does not imply that a node
+#   serving the Ripple protocol is avilable at the web host providing the
+#   file.
 #
 #   Example: n9MZTnHe5D5Q2cgE8oV2usFwRqhUvEA8MwP5Mu1XVD6TxmssPRev
 #