diff --git a/src/common.rs b/src/common.rs
index f2b5a9841d9ee1e0932f4ff1613058e1e2333993..1ff11a20ccb6325adb7d29720b5c100ea6213c23 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -44,12 +44,21 @@ pub enum Polarity {
 #[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Copy, Clone, Debug)]
 pub struct Key(u64);
 
+pub enum NewMainErr {
+    NoSuchComponent,
+    NonPortTypeParameters,
+    WrongNumberOfArguments { expected: usize },
+    WrongPortPolarity { index: usize },
+}
 pub trait ProtocolDescription: Sized {
     type S: ComponentState<D = Self>;
 
     fn parse(pdl: &[u8]) -> Result<Self, String>;
-    fn main_interface_polarities(&self) -> Vec<Polarity>;
-    fn new_main_component(&self, interface: &[Key]) -> Self::S;
+    fn new_main_component(
+        &self,
+        identifier: &[u8],
+        ports: &[(Polarity, Key)],
+    ) -> Result<Self::S, NewMainErr>;
 }
 
 pub trait ComponentState: Sized + Clone {
diff --git a/src/protocol/mod.rs b/src/protocol/mod.rs
index c3deda22f0cfdfe0559ccda1054ada090fc6ae46..97986eb6333fd7cc9a11578f68d3aa8fac07799d 100644
--- a/src/protocol/mod.rs
+++ b/src/protocol/mod.rs
@@ -47,26 +47,26 @@ impl ProtocolDescription for ProtocolDescriptionImpl {
             }
         }
     }
-    fn main_interface_polarities(&self) -> Vec<Polarity> {
-        let def = &self.heap[self.main];
-        let mut result = Vec::new();
-        for &param in def.parameters().iter() {
-            let param = &self.heap[param];
-            let type_annot = &self.heap[param.type_annotation];
-            let ptype = &type_annot.the_type.primitive;
-            if ptype == &PrimitiveType::Input {
-                result.push(Polarity::Getter)
-            } else if ptype == &PrimitiveType::Output {
-                result.push(Polarity::Putter)
-            } else {
-                unreachable!()
-            }
-        }
-        result
-    }
-    fn new_main_component(&self, interface: &[Key]) -> ComponentStateImpl {
+    // fn main_interface_polarities(&self) -> Vec<Polarity> {
+    //     let def = &self.heap[self.main];
+    //     let mut result = Vec::new();
+    //     for &param in def.parameters().iter() {
+    //         let param = &self.heap[param];
+    //         let type_annot = &self.heap[param.type_annotation];
+    //         let ptype = &type_annot.the_type.primitive;
+    //         if ptype == &PrimitiveType::Input {
+    //             result.push(Polarity::Getter)
+    //         } else if ptype == &PrimitiveType::Output {
+    //             result.push(Polarity::Putter)
+    //         } else {
+    //             unreachable!()
+    //         }
+    //     }
+    //     result
+    // }
+    fn new_main_component(&self, ports: &[Key]) -> ComponentStateImpl {
         let mut args = Vec::new();
-        for (&x, y) in interface.iter().zip(self.main_interface_polarities()) {
+        for (&x, y) in ports.iter().zip(self.main_interface_polarities()) {
             match y {
                 Polarity::Getter => args.push(Value::Input(InputValue(x))),
                 Polarity::Putter => args.push(Value::Output(OutputValue(x))),
diff --git a/src/runtime/ffi.rs b/src/runtime/ffi.rs
index ddada037c9be6a85e0a518b9d59c6ea85b68a27b..39dd2eb5dfbac74e050db218eaa4be8e52d6ab78 100644
--- a/src/runtime/ffi.rs
+++ b/src/runtime/ffi.rs
@@ -129,7 +129,7 @@ pub unsafe extern "C" fn connector_configure(connector: *mut Connector, pdl: *mu
 /// # Safety
 /// TODO
 #[no_mangle]
-pub unsafe extern "C" fn port_bind_native(
+pub unsafe extern "C" fn connector_bind_native(
     connector: *mut Connector,
     proto_port_index: usize,
 ) -> c_int {
@@ -152,7 +152,7 @@ pub unsafe extern "C" fn port_bind_native(
 /// # Safety
 /// TODO
 #[no_mangle]
-pub unsafe extern "C" fn port_bind_passive(
+pub unsafe extern "C" fn connector_bind_passive(
     connector: *mut Connector,
     proto_port_index: c_uint,
     address: *const c_char,
@@ -184,7 +184,7 @@ pub unsafe extern "C" fn port_bind_passive(
 /// # Safety
 /// TODO
 #[no_mangle]
-pub unsafe extern "C" fn port_bind_active(
+pub unsafe extern "C" fn connector_bind_active(
     connector: *mut Connector,
     proto_port_index: c_uint,
     address: *const c_char,