diff --git a/src/report.mjs b/src/report.mjs
new file mode 100644
index 0000000..97ea9e0
--- /dev/null
+++ b/src/report.mjs
@@ -0,0 +1,8 @@
+export function summarize(result) {
+  const outstanding = [], anomalies = [];
+  for (const [key, state] of result.groups) {
+    if (state.open) outstanding.push({ key, since: state.firstAlarm, acknowledged: state.acknowledged });
+    for (const reason of state.anomalies) anomalies.push({ key, reason });
+  }
+  return { outstanding, anomalies, rejected: result.rejected };
+}