diff --git a/meilidb-data/Cargo.toml b/meilidb-data/Cargo.toml
index f0046bc1a..18881367b 100644
--- a/meilidb-data/Cargo.toml
+++ b/meilidb-data/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2018"
 bincode = "1.1.2"
 linked-hash-map = { version = "0.5.2", features = ["serde_impl"] }
 meilidb-core = { path = "../meilidb-core", version = "0.1.0" }
+ordered-float = { version = "1.0.2", features = ["serde"] }
 serde = { version = "1.0.88", features = ["derive"] }
 serde_json = { version = "1.0.39", features = ["preserve_order"] }
 sled = "0.20.0"
diff --git a/meilidb-data/src/lib.rs b/meilidb-data/src/lib.rs
index a2f028ecd..96d6bdf6e 100644
--- a/meilidb-data/src/lib.rs
+++ b/meilidb-data/src/lib.rs
@@ -1,5 +1,9 @@
 mod database;
-mod schema;
+pub mod schema;
+mod ranked_map;
+mod number;
 
 pub use self::database::{Database, Index};
-pub use self::schema::{Schema, SchemaAttr, SchemaBuilder};
+pub use self::schema::{Schema, SchemaAttr};
+pub use self::ranked_map::RankedMap;
+pub use self::number::Number;
diff --git a/meilidb-data/src/number.rs b/meilidb-data/src/number.rs
new file mode 100644
index 000000000..9a2d0ea24
--- /dev/null
+++ b/meilidb-data/src/number.rs
@@ -0,0 +1,55 @@
+use std::num::{ParseIntError, ParseFloatError};
+use std::str::FromStr;
+use std::fmt;
+
+use ordered_float::OrderedFloat;
+use serde::{Serialize, Deserialize};
+
+#[derive(Serialize, Deserialize)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Number {
+    Unsigned(u64),
+    Signed(i64),
+    Float(OrderedFloat<f64>),
+}
+
+impl FromStr for Number {
+    type Err = ParseNumberError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let uint_error = match u64::from_str(s) {
+            Ok(unsigned) => return Ok(Number::Unsigned(unsigned)),
+            Err(error) => error,
+        };
+
+        let int_error = match i64::from_str(s) {
+            Ok(signed) => return Ok(Number::Signed(signed)),
+            Err(error) => error,
+        };
+
+        let float_error = match f64::from_str(s) {
+            Ok(float) => return Ok(Number::Float(OrderedFloat(float))),
+            Err(error) => error,
+        };
+
+        Err(ParseNumberError { uint_error, int_error, float_error })
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct ParseNumberError {
+    uint_error: ParseIntError,
+    int_error: ParseIntError,
+    float_error: ParseFloatError,
+}
+
+impl fmt::Display for ParseNumberError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.uint_error == self.int_error {
+            write!(f, "can not parse number: {}, {}", self.uint_error, self.float_error)
+        } else {
+            write!(f, "can not parse number: {}, {}, {}",
+                self.uint_error, self.int_error, self.float_error)
+        }
+    }
+}
diff --git a/meilidb-data/src/schema.rs b/meilidb-data/src/schema.rs
index c73b8b067..bff7806dc 100644
--- a/meilidb-data/src/schema.rs
+++ b/meilidb-data/src/schema.rs
@@ -8,8 +8,6 @@ use std::sync::Arc;
 use serde::{Serialize, Deserialize};
 use linked_hash_map::LinkedHashMap;
 
-use meilidb_core::DocumentId;
-
 pub const STORED: SchemaProps  = SchemaProps { stored: true,  indexed: false, ranked: false };
 pub const INDEXED: SchemaProps = SchemaProps { stored: false, indexed: true,  ranked: false };
 pub const RANKED: SchemaProps  = SchemaProps { stored: false, indexed: false, ranked: true  };