diff --git a/DESIGN.md b/DESIGN.md
index 92bc49b..0862dfb 100644
--- a/DESIGN.md
+++ b/DESIGN.md
@@ -68,4 +68,5 @@ What about situations where data is configured by a web app, etc? Taints are a g
 ## Assumptions
 
 - Job -> partition relationships are canonical, job runs are idempotent
+- The data deps / partitions read by a fully parameterized job run is consistent over time: same parameters = same read partitions