data: clarify FreshnessPeriod=0 semantics
refs #5268
Change-Id: I58ae182637a5377f3e54db69119a94a9620db51d
diff --git a/changelog.rst b/changelog.rst
index 7c8f197..be79186 100644
--- a/changelog.rst
+++ b/changelog.rst
@@ -38,7 +38,7 @@
- **Data**
+ Make ``MetaInfo`` and ``Content`` elements optional
- + Change semantics of omitted (or set to zero) ``FreshnessPeriod`` element: it cannot be used to satisfy Interests with ``MustBeFresh``
+ + Change semantics of omitted (or set to zero) ``FreshnessPeriod`` element: it cannot be used to satisfy Interests with ``MustBeFresh`` during content store lookup
- **Signature**
diff --git a/data.rst b/data.rst
index 50b224c..9850bc4 100644
--- a/data.rst
+++ b/data.rst
@@ -73,10 +73,10 @@
Note that the "non-fresh" data is still valid data; the expiration of ``FreshnessPeriod`` only means that the producer may have produced newer data.
If the Data packet carries a ``FreshnessPeriod`` greater than zero, a node should initially consider it "fresh". After the Data has resided in the node for ``FreshnessPeriod`` milliseconds, it will be marked as "non-fresh".
-If the Data does not have a ``FreshnessPeriod`` or if it has a ``FreshnessPeriod`` equal to zero, it MUST be immediately marked "non-fresh".
+If the Data does not have a ``FreshnessPeriod`` or if it has a ``FreshnessPeriod`` equal to zero, it MUST be marked "non-fresh" immediately after processing any pending Interests.
-If an Interest contains ``MustBeFresh`` element, a node MUST NOT return "non-fresh" Data in response to this Interest.
-The effect is the same as if that "non-fresh" Data did not exist (i.e., the Interest might be matched by some other Data in the store, or, failing that, get forwarded to other nodes).
+If an Interest contains ``MustBeFresh`` element, a content store MUST NOT return "non-fresh" Data in response to this Interest.
+The effect is the same as if that "non-fresh" Data did not exist (i.e., the Interest might be matched by some other Data in the content store, or, failing that, get forwarded to other nodes).
When an exact duplicate of the "non-fresh" Data packet with a positive ``FreshnessPeriod`` value arrives at the node, the node SHOULD re-mark it as "fresh" for the specified duration.
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