diff --git a/server/src/bin.rs b/server/src/bin.rs
index a40bc6c5..1e9a62be 100644
--- a/server/src/bin.rs
+++ b/server/src/bin.rs
@@ -8,6 +8,8 @@ extern crate serde;
 extern crate serde_json;
 extern crate regex;
 
+pub mod rbx_session;
+pub mod id;
 pub mod web;
 pub mod core;
 pub mod project;
diff --git a/server/src/id.rs b/server/src/id.rs
new file mode 100644
index 00000000..a27a9d8c
--- /dev/null
+++ b/server/src/id.rs
@@ -0,0 +1,21 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+/// A unique identifier, not guaranteed to be generated in any order.
+pub type Id = usize;
+
+lazy_static! {
+    static ref LAST_ID: AtomicUsize = AtomicUsize::new(0);
+}
+
+/// Generate a new ID, which has no defined ordering.
+pub fn get_id() -> Id {
+    LAST_ID.fetch_add(1, Ordering::SeqCst)
+}
+
+#[test]
+fn it_gives_unique_numbers() {
+    let a = get_id();
+    let b = get_id();
+
+    assert!(a != b);
+}
diff --git a/server/src/rbx_session.rs b/server/src/rbx_session.rs
new file mode 100644
index 00000000..67cbc0ae
--- /dev/null
+++ b/server/src/rbx_session.rs
@@ -0,0 +1,126 @@
+use std::path::{Path, PathBuf};
+use std::collections::HashMap;
+use std::io::Read;
+use std::fs::{self, File};
+
+use id::{Id};
+
+#[derive(Debug, Clone)]
+struct FileRoute {
+    partition: String,
+    route: Vec<String>,
+}
+
+impl FileRoute {
+    pub fn to_path_buf(&self, partition_path: &Path) -> PathBuf {
+        let mut result = partition_path.to_path_buf();
+
+        for route_piece in &self.route {
+            result.push(route_piece);
+        }
+
+        result
+    }
+
+    pub fn extended_with(&self, pieces: &[&str]) -> FileRoute {
+        let mut result = self.clone();
+
+        for piece in pieces {
+            result.route.push(piece.to_string());
+        }
+
+        result
+    }
+}
+
+enum FileItem {
+    File {
+        contents: String,
+    },
+    Directory {
+        children: HashMap<String, FileItem>,
+    },
+}
+
+struct RbxInstance {
+    parent: Option<Id>,
+}
+
+struct RbxSession {
+    partitions_path: HashMap<String, PathBuf>,
+    partition_instances: HashMap<String, Id>,
+}
+
+impl RbxSession {
+    fn load(&self) {
+        for (partition_name, partition_path) in &self.partitions_path {
+        }
+    }
+
+    fn read(&self, route: &FileRoute) -> Result<FileItem, ()> {
+        let partition_path = self.partitions_path.get(&route.partition)
+            .ok_or(())?;
+        let path = route.to_path_buf(partition_path);
+
+        let metadata = fs::metadata(path)
+            .map_err(|_| ())?;
+
+        if metadata.is_dir() {
+            self.read_directory(route)
+        } else if metadata.is_file() {
+            self.read_file(route)
+        } else {
+            Err(())
+        }
+    }
+
+    fn read_file(&self, route: &FileRoute) -> Result<FileItem, ()> {
+        let partition_path = self.partitions_path.get(&route.partition)
+            .ok_or(())?;
+        let path = route.to_path_buf(partition_path);
+
+        let mut file = File::open(path)
+            .map_err(|_| ())?;
+
+        let mut contents = String::new();
+
+        file.read_to_string(&mut contents)
+            .map_err(|_| ())?;
+
+        Ok(FileItem::File {
+            contents,
+        })
+    }
+
+    fn read_directory(&self, route: &FileRoute) -> Result<FileItem, ()> {
+        let partition_path = self.partitions_path.get(&route.partition)
+            .ok_or(())?;
+        let path = route.to_path_buf(partition_path);
+
+        let reader = fs::read_dir(path)
+            .map_err(|_| ())?;
+
+        let mut children = HashMap::new();
+
+        for entry in reader {
+            let entry = entry
+                .map_err(|_| ())?;
+
+            let path = entry.path();
+            let name = path.file_name().unwrap().to_string_lossy().into_owned();
+
+            let child_route = route.extended_with(&[&name]);
+
+            match self.read(&child_route) {
+                Ok(child_item) => {
+                    children.insert(name, child_item);
+                },
+                Err(_) => {},
+            }
+        }
+
+        Ok(FileItem::Directory {
+            children,
+        })
+    }
+}