diff --git a/.gitignore b/.gitignore
index 1f7ab21..fab500c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
/venv/
*~
*.bak
+.*.sw?
diff --git a/api.bs b/api.bs
index 8fa8923..052aa3f 100644
--- a/api.bs
+++ b/api.bs
@@ -302,6 +302,19 @@ Typical outcomes that advertisers might seek to measure include:
* Signing up for an account.
* Visiting a webpage.
+The remainder of this section describes
+how the Private Attribution API operates
+in conjunction with an [=aggregation service=]
+to produce an aggregate attribution measurement.
+That operation is illustrated in the following figure.
+
+
+
+path:images/overview.svg
+
+Overview of Private Attribution Operation
+
+
When an [=impression=] occurs,
the saveImpression() method can be used
to request that the browser save information.
diff --git a/images/overview.svg b/images/overview.svg
new file mode 100644
index 0000000..f35ce3a
--- /dev/null
+++ b/images/overview.svg
@@ -0,0 +1,120 @@
+