diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
index 48a44b2..c91f95d 100644
--- a/ARCHITECTURE.md
+++ b/ARCHITECTURE.md
@@ -1,8 +1,11 @@
 # vaultik architecture
 
-This document describes how the `vaultik` code is organised. It covers the
-packages, how they are wired together, and what happens during a backup, a
-restore, a verify and a prune.
+This document describes how the `vaultik` code is organised. It covers three
+things:
+
+- the packages
+- how they are wired together
+- what happens during a backup, a restore, a verify and a prune
 
 Two other documents cover the stored data:
 
@@ -170,11 +173,18 @@ The walk handles each kind of entry differently:
 Data is stored once at two levels.
 
 - **Files.** A file is not read again when its record in the index still matches
-  it. The record matches when the size, modification time, mode, owner, group
-  and link target are all the same.
+  it.
 - **Chunks.** A chunk is named by the SHA-256 hash of its content. A chunk whose
   hash is already in the index is not stored again.
 
+A file's record matches when all of these are unchanged:
+
+- the size
+- the modification time
+- the mode
+- the owner and group
+- the link target
+
 One case overrides the file check. A file is read again when it lists a chunk
 that no uploaded blob holds. This happens after the only snapshot that used
 such a blob is removed. `loadFilesToRechunk` finds these files.