diff --git a/wfassoc_cdylib/src/lib.rs b/wfassoc_cdylib/src/lib.rs
index a1a8cec..5046c90 100644
--- a/wfassoc_cdylib/src/lib.rs
+++ b/wfassoc_cdylib/src/lib.rs
@@ -4,6 +4,7 @@ use thiserror::Error as TeError;
 
 mod last_error;
 mod string_cache;
+mod wrapper;
 
 // region: Error
 
diff --git a/wfassoc_cdylib/src/wrapper.rs b/wfassoc_cdylib/src/wrapper.rs
new file mode 100644
index 0000000..d7dca53
--- /dev/null
+++ b/wfassoc_cdylib/src/wrapper.rs
@@ -0,0 +1,83 @@
+use std::collections::HashMap;
+
+use thiserror::Error as TeError;
+
+/// Error occurs in this module.
+#[derive(Debug, TeError)]
+pub enum Error {}
+
+/// Result type used in this module.
+type Result<T> = std::result::Result<T, Error>;
+
+/// Schema is the sketchpad of complete Program.
+///
+/// We will create a Schema first, fill some properties, add file extensions,
+/// then convert it into immutable Program for following using.
+#[derive(Debug)]
+pub struct Schema {
+    identifier: String,
+    path: String,
+    clsid: String,
+    icons: HashMap<String, String>,
+    behaviors: HashMap<String, String>,
+    exts: HashMap<String, SchemaExt>,
+}
+
+/// Internal used struct as the Schema file extensions hashmap value type.
+#[derive(Debug)]
+struct SchemaExt {
+    name: String,
+    icon: String,
+    behavior: String,
+}
+
+impl Schema {
+    pub fn new() -> Self {
+        Self {
+            identifier: String::new(),
+            path: String::new(),
+            clsid: String::new(),
+            icons: HashMap::new(),
+            behaviors: HashMap::new(),
+            exts: HashMap::new(),
+        }
+    }
+
+    pub fn set_identifier(&mut self, identifier: &str) -> Result<()> {}
+
+    pub fn set_path(&mut self, exe_path: &str) -> Result<()> {}
+
+    pub fn set_clsid(&mut self, clsid: &str) -> Result<()> {}
+
+    pub fn add_icon(&mut self, name: &str, value: &str) -> Result<()> {}
+
+    pub fn add_behavior(&mut self, name: &str, value: &str) -> Result<()> {}
+
+    pub fn add_ext(
+        &mut self,
+        ext: &str,
+        ext_name: &str,
+        ext_icon: &str,
+        ext_behavior: &str,
+    ) -> Result<()> {
+    }
+
+    pub fn into_program(self) -> Result<Program> {
+        Program::new(self)
+    }
+}
+
+/// Program is a complete and immutable program representer
+pub struct Program {}
+
+impl TryFrom<Schema> for Program {
+    type Error = Error;
+
+    fn try_from(value: Schema) -> std::result::Result<Self, Self::Error> {
+        Self::new(value)
+    }
+}
+
+impl Program {
+    pub fn new(schema: Schema) -> Result<Self> {}
+}
diff --git a/wfassoc_exec/src/cli.rs b/wfassoc_exec/src/cli.rs
index 53afacf..8765df7 100644
--- a/wfassoc_exec/src/cli.rs
+++ b/wfassoc_exec/src/cli.rs
@@ -112,5 +112,5 @@ pub struct RequestExtCommand {
 /// This is the mechanism of clap crate.
 pub fn parse() -> Request {
     let cli = Cli::parse();
-
+    todo!()
 }
diff --git a/wfassoc_exec/src/manifest.rs b/wfassoc_exec/src/manifest.rs
index 1d2eb44..e896a3d 100644
--- a/wfassoc_exec/src/manifest.rs
+++ b/wfassoc_exec/src/manifest.rs
@@ -6,11 +6,12 @@ use toml;
 
 /// Error occurs in this module.
 #[derive(Debug, TeError)]
-#[error("{0}")]
 pub enum Error {
     /// Io error
+    #[error("IO error when reading manifest file")]
     Io(#[from] std::io::Error),
     /// Toml deserialization error
+    #[error("given TOML manifest file has bad format")]
     Toml(#[from] toml::de::Error),
 }
 
diff --git a/wfassoc_exec/src/runner.rs b/wfassoc_exec/src/runner.rs
index e69de29..1c2f70c 100644
--- a/wfassoc_exec/src/runner.rs
+++ b/wfassoc_exec/src/runner.rs
@@ -0,0 +1,45 @@
+use crate::cli::Request;
+use thiserror::Error as TeError;
+
+/// Error occurs in this module.
+#[derive(Debug, TeError)]
+#[error("{0}")]
+pub enum Error {
+    
+}
+
+/// Result type used in this module.
+type Result<T> = std::result::Result<T, Error>;
+
+// region: Respective Runners
+
+fn run_register() -> Result<()> {
+    todo!()
+}
+
+fn run_unregister()  -> Result<()> {
+    todo!()
+}
+
+fn run_status() -> Result<()> {
+    todo!()
+}
+
+fn run_ext_link() -> Result<()> {
+    todo!()
+}
+
+fn run_ext_unlink() -> Result<()> {
+    todo!()
+}
+
+fn run_ext_list() -> Result<()> {
+    todo!()
+}
+
+
+// endregion
+
+pub fn run(request: Request) -> Result<()> {
+    todo!()
+}