diff --git a/src/cholla/README.md b/src/cholla/README.md
new file mode 100644
index 0000000..a558630
--- /dev/null
+++ b/src/cholla/README.md
@@ -0,0 +1,11 @@
+# Cholla
+
+Goals of this submodule:
+
+Independent time keeping of when vehicles pass a location based on GPS position data
+
+Independent forecasting of future arrival times
+
+Effectively throwing out invalid trip update stop times and making better ones
+
+(Copying this paper: https://link.springer.com/article/10.1007/s11067-021-09541-w )
\ No newline at end of file
diff --git a/src/cholla/mod.rs b/src/cholla/mod.rs
new file mode 100644
index 0000000..77874c8
--- /dev/null
+++ b/src/cholla/mod.rs
@@ -0,0 +1,4 @@
+pub struct HistoricalKey {
+    pub date: chrono::NaiveDate,
+    pub trip_id: compact_str::CompactString,
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 71c85c7..91aeef0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -49,6 +49,7 @@ pub mod ip_to_location;
 pub mod maple_syrup;
 pub mod models;
 pub mod postgis_to_diesel;
+pub mod cholla;
 pub mod postgres_tools;
 pub mod schema;
 pub mod validate_gtfs_rt;