invariant re: accumulated_amount added; typo fixed

1 files changed, 9 insertions, 5 deletions

diff --git a/design-documents/028-deposit-policies.rst b/design-documents/028-deposit-policies.rst
index 6d1a9589..bf6c5ec5 100644
--- a/design-documents/028-deposit-policies.rst
+++ b/design-documents/028-deposit-policies.rst
@@ -87,7 +87,7 @@ TODO: Description
                 label=<<B>policy_details</B>>
                 margin=20
                 policy_details [
-                  label="<id>id\l|<hash>hash_code (unique)\l|deadline\l|commitment (amount)\l|accumulated_total (amount)\l|fee (amount)\l|transferable (amount)\l|fulfillment_state\l|<fid>fulfillment_id (null)\l"
+                  label="<id>id\l|<hash>policy_hash_code (unique)\l|deadline\l|commitment (amount)\l|accumulated_total (amount)\l|fee (amount)\l|transferable (amount)\l|fulfillment_state\l|<fid>fulfillment_id (null)\l"
                 ]
         }
 
@@ -107,7 +107,7 @@ TODO: Description
 
 The field ``policy_hash_codes`` in table ``policy_fulfillments`` is a binary
 blob that consists of the concatenation of the sorted
-``policy_details.hash_code`` entries from all policies that are fulfilled by
+``policy_details.policy_hash_code`` entries from all policies that are fulfilled by
 this proof.
 
 
@@ -152,16 +152,20 @@ The following invariants need to be fulfilled and be checked by the auditor:
   ``policy_details.accumulated_total``.
 
 - The sum of amounts in ``policy_details.fee`` and
-  ``policy_details.transferable`` must be less or equal to the amount in
+  ``policy_details.transferable`` MUST be less or equal to the amount in
   ``policy_details.accumulated_total``.
 
+- The amount in ``policy_details.accumulated_total`` MUST be equal to the total
+  sum of contributions of the individual coins of the deposits that reference
+  this policy.
+
 - Each hash code encoded in ``policy_fulfillments.policy_hash_codes`` MUST
   refer to an existing ``policy_details.hash_code`` AND its ``.fulfillment_id``
   MUST point to the same ``policy_fulfillments.id``.
 
 - Conversely: If a ``policy_details.fulfillment_id`` points to an entry in
-  ``policy_fulfillment``, the ``policy_details.hash_code`` MUST be present in
-  that entry's ``.policy_hash_codes``.
+  ``policy_fulfillment``, the ``policy_details.policy_hash_code`` MUST be
+  present in that entry's ``.policy_hash_codes``.