design -> architecture, add motivation

following ideas found in Architecture of Gazelle[1]

[1]: https://github.com/bazelbuild/bazel-gazelle/blob/56d35f8db086bb65ef876f96f7baa7b71516daf8/Design.rst

14 files changed, 5 insertions, 4 deletions

diff --git a/doc/manual/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in
index ec457126a..c029e30bf 100644
--- a/doc/manual/src/SUMMARY.md.in
+++ b/doc/manual/src/SUMMARY.md.in
@@ -15,7 +15,7 @@
     - [Multi-User Mode](installation/multi-user.md)
   - [Environment Variables](installation/env-variables.md)
   - [Upgrading Nix](installation/upgrading.md)
-- [Design and Data Model](design/design.md)
+- [Architecture](architecture/architecture.md)
   - [Store](design/store/store.md)
     - [Store Objects](design/store/objects.md)
     - [Store Paths](design/store/paths.md)
diff --git a/doc/manual/src/design/design.md b/doc/manual/src/architecture/architecture.md
index 16c51533b..b17eacd2e 100644
--- a/doc/manual/src/design/design.md
+++ b/doc/manual/src/architecture/architecture.md
@@ -1,8 +1,9 @@
-# Design and Data Model
+# Architecture
 
-This chapter is about the technical principles behind Nix.
+This chapter describes how Nix works.
+It should help users understand why Nix behaves as it does, and it should help developers understand how to modify Nix and how to write similar tools.
 
-## Architecture
+## Overview
 
 Nix consists of hierarchical [layers](https://en.m.wikipedia.org/wiki/Multitier_architecture#Layers).
 
diff --git a/doc/manual/src/design/store/building.md b/doc/manual/src/architecture/store/building.md
index f4f2649a3..f4f2649a3 100644
--- a/doc/manual/src/design/store/building.md
+++ b/doc/manual/src/architecture/store/building.md
diff --git a/doc/manual/src/design/store/drvs/ca.md b/doc/manual/src/architecture/store/drvs/ca.md
index e69de29bb..e69de29bb 100644
--- a/doc/manual/src/design/store/drvs/ca.md
+++ b/doc/manual/src/architecture/store/drvs/ca.md
diff --git a/doc/manual/src/design/store/drvs/drvs.md b/doc/manual/src/architecture/store/drvs/drvs.md
index 766a7b47f..766a7b47f 100644
--- a/doc/manual/src/design/store/drvs/drvs.md
+++ b/doc/manual/src/architecture/store/drvs/drvs.md
diff --git a/doc/manual/src/design/store/drvs/ia.md b/doc/manual/src/architecture/store/drvs/ia.md
index e69de29bb..e69de29bb 100644
--- a/doc/manual/src/design/store/drvs/ia.md
+++ b/doc/manual/src/architecture/store/drvs/ia.md
diff --git a/doc/manual/src/design/store/input-addressing.md b/doc/manual/src/architecture/store/input-addressing.md
index 1333ed77b..1333ed77b 100644
--- a/doc/manual/src/design/store/input-addressing.md
+++ b/doc/manual/src/architecture/store/input-addressing.md
diff --git a/doc/manual/src/design/store/nar.md b/doc/manual/src/architecture/store/nar.md
index 1333ed77b..1333ed77b 100644
--- a/doc/manual/src/design/store/nar.md
+++ b/doc/manual/src/architecture/store/nar.md
diff --git a/doc/manual/src/design/store/object-ca.md b/doc/manual/src/architecture/store/object-ca.md
index 1333ed77b..1333ed77b 100644
--- a/doc/manual/src/design/store/object-ca.md
+++ b/doc/manual/src/architecture/store/object-ca.md
diff --git a/doc/manual/src/design/store/objects.md b/doc/manual/src/architecture/store/objects.md
index e4f49a170..e4f49a170 100644
--- a/doc/manual/src/design/store/objects.md
+++ b/doc/manual/src/architecture/store/objects.md
diff --git a/doc/manual/src/design/store/paths.md b/doc/manual/src/architecture/store/paths.md
index cf51eb866..cf51eb866 100644
--- a/doc/manual/src/design/store/paths.md
+++ b/doc/manual/src/architecture/store/paths.md
diff --git a/doc/manual/src/design/store/related-work.md b/doc/manual/src/architecture/store/related-work.md
index b64b41988..b64b41988 100644
--- a/doc/manual/src/design/store/related-work.md
+++ b/doc/manual/src/architecture/store/related-work.md
diff --git a/doc/manual/src/design/store/relocatability.md b/doc/manual/src/architecture/store/relocatability.md
index c7f869135..c7f869135 100644
--- a/doc/manual/src/design/store/relocatability.md
+++ b/doc/manual/src/architecture/store/relocatability.md
diff --git a/doc/manual/src/design/store/store.md b/doc/manual/src/architecture/store/store.md
index d4add52f5..d4add52f5 100644
--- a/doc/manual/src/design/store/store.md
+++ b/doc/manual/src/architecture/store/store.md