diff --git a/nucleus/src/arch/aarch64/caps.rs b/nucleus/src/arch/aarch64/caps.rs
index 30a1889..c61fef8 100644
--- a/nucleus/src/arch/aarch64/caps.rs
+++ b/nucleus/src/arch/aarch64/caps.rs
@@ -425,6 +425,16 @@ impl UntypedCapability {
     }
 }
 
+// Endpoints support all 10 IPC variants (see COMP9242 slides by Gernot)
+impl EndpointCapability {}
+// Notifications support NBSend (Signal), Wait and NBWait (Poll) (see COMP9242 slides by Gernot)
+// Other objects support only Call() (see COMP9242 slides by Gernot)
+// Appear as (kernel-implemented) servers
+//     • Each has a kernel-defined protocol
+//         • operations encoded in message tag
+//         • parameters passed in message words
+//     • Mostly hidden behind “syscall” wrappers
+
 // * Capability slots: 16 bytes of memory per slot (exactly one capability). --?
 // CapNode describes `a given number of capability slots` with `a given guard`
 // of `a given guard size` bits.
@@ -505,6 +515,16 @@ pub enum DerivationTreeError {
     InvalidPrev,
 }
 
+// In seL4, the MDB is stored as a doubly-linked list, representing the **preorder-DFS** through
+// the hierarchy of capabilities. This data structure allows easy insertion of a capability
+// given its immediate ancestor or a copy, and easy checking for existence of copies and descendants.
+// But when no relations are known beforehand, finding the position to place a new capability
+// requires a O(n) linear scan through the list, as does finding ancestors and descendants
+// of a capability given just the capability’s value. This operation is performed in
+// the non-preemptable kernel, creating a scheduling hole that is problematic for real-time applications.
+// To reduce the complexity of operations described above, we replace the MDB’s linked list with
+// a more suitable search data structure.
+// -- nevill-master-thesis Using Capabilities for OS Resource Management
 impl DerivationTreeNode {
     fn empty() -> Self {
         Self(LocalRegisterCopy::new(0))
@@ -594,11 +614,13 @@ impl CapTableEntry {
     }
 }
 
-// @note src and dest are swapped here, compared to seL4 api
 /*
 struct CapNodePath {
-    index: u32,
-    depth: u32,
+    /// Index contains `depth` lowermost bits of the path.
+    index: u64,
+    /// Depth specifies the remaining amount of bits left to traverse in the path.
+    /// Once depth reaches zero, the selected CapNode slot is the final target.
+    depth: usize,
 }
 
 struct CapNodeRootedPath {
@@ -608,19 +630,22 @@ struct CapNodeRootedPath {
 
 // @todo just use CapNodeCap
 //struct CapNodeConfig { <-- for each CapTable we would need these..
-//    guard: u32,
-//    guard_size: u32,
+//    guard: u64,
+//    guard_bits: usize,
 //}
 
+// @note src and dest are swapped here, compared to seL4 api
 impl CapNode {
+    // Derives a capability into a new, less powerful one, with potentially added Badge.
     fn mint(
-        src: CapNodeRootedPath,
+        src: CapNodeRootedPath, // can be just CapNodePath since it's relative (is it?) to this CapNode.
         dest: CapNodePath,
         rights: CapRights,
         badge: Badge,
     ) -> Result<(), CapError> {
         unimplemented!();
     }
+    // [wip] is copy a derivation too?
     fn copy(src: CapNodeRootedPath, dest: CapNodePath, rights: CapRights) -> Result<(), CapError> {
         unimplemented!();
     }
@@ -645,7 +670,7 @@ impl CapNode {
     fn revoke(path: CapNodePath) -> Result<(), CapError> {
         unimplemented!();
     }
-    fn save_caller(r#where: CapNodePath) -> Result<(), CapError> {
+    fn save_caller(r#where: CapNodePath) -> Result<(), CapError> { // save_reply_cap() in sel4
         unimplemented!();
     }
     fn cancel_badged_sends(path: CapNodePath) -> Result<(), CapError> {
diff --git a/nucleus/src/arch/aarch64/objects.rs b/nucleus/src/arch/aarch64/objects.rs
index a7d96d9..ef8134f 100644
--- a/nucleus/src/arch/aarch64/objects.rs
+++ b/nucleus/src/arch/aarch64/objects.rs
@@ -61,6 +61,8 @@ enum MemoryKind {
 // Boot code reserves kernel memory and initial mapping allocations (4 pages probably - on rpi3? should be platform-dependent).
 // The rest is converted to untypeds with appropriate kind and given away to start thread.
 
+// Untyped.retype() derives cap to a typed cap (derivation tree must be maintained)
+
 trait Untyped {
     // Uses T::SIZE_BITS to properly size the resulting object
     // in some cases size_bits must be passed as argument though...
@@ -135,13 +137,13 @@ struct Page {}
 impl Page {
     // VirtSpace-like interface.
     /// Get the physical address of the underlying frame.
-    fn get_address() -> Result<PhysAddr>;
-    fn map(virt_space: VirtSpace/*Cap*/, vaddr: VirtAddr, rights: CapRights, attr: VMAttributes) -> Result<()>;
+    fn get_address() -> Result<PhysAddr> { todo!() }
+    fn map(virt_space: VirtSpace/*Cap*/, vaddr: VirtAddr, rights: CapRights, attr: VMAttributes) -> Result<()> { todo!() }
     /// Changes the permissions of an existing mapping.
-    fn remap(virt_space: VirtSpace/*Cap*/, rights: CapRights, attr: VMAttributes) -> Result<()>;
-    fn unmap() -> Result<()>;
+    fn remap(virt_space: VirtSpace/*Cap*/, rights: CapRights, attr: VMAttributes) -> Result<()> { todo!() }
+    fn unmap() -> Result<()> { todo!() }
     // MMIO space.
-    fn map_io(iospace: IoSpace/*Cap*/, rights: CapRights, ioaddr: VirtAddr) -> Result<()>;
+    fn map_io(iospace: IoSpace/*Cap*/, rights: CapRights, ioaddr: VirtAddr) -> Result<()> { todo!() }
 }
 
 impl PageCacheManagement for Page {
@@ -167,8 +169,8 @@ impl PageCacheManagement for Page {
 struct PageTable {}
 
 impl PageTable {
-    fn map(virt_space: VirtSpace/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()>;
-    fn unmap() -> Result<()>;
+    fn map(virt_space: VirtSpace/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()> { todo!() }
+    fn unmap() -> Result<()> { todo!() }
 }
 
 // AArch64 - probably just impl some Mapping trait for these "structs"?
@@ -176,16 +178,16 @@ impl PageTable {
 struct PageDirectory {}
 
 impl PageDirectory {
-    fn map(pud: PageUpperDirectory/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()>;
-    fn unmap() -> Result<()>;
+    fn map(pud: PageUpperDirectory/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()> { todo!() }
+    fn unmap() -> Result<()> { todo!() }
 }
 
 // L1 table
 struct PageUpperDirectory {}
 
 impl PageUpperDirectory {
-    fn map(pgd: PageGlobalDirectory/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()>;
-    fn unmap() -> Result<()>;
+    fn map(pgd: PageGlobalDirectory/*Cap*/, vaddr: VirtAddr, attr: VMAttributes) -> Result<()> { todo!() }
+    fn unmap() -> Result<()> { todo!() }
 }
 
 // L0 table
@@ -195,17 +197,17 @@ struct PageGlobalDirectory {
 }
 
 impl PageCacheManagement for PageGlobalDirectory {
-    fn clean_data(start_offset: usize, end_offset: usize) -> _ {
+    fn clean_data(start_offset: usize, end_offset: usize) -> ! {
         todo!()
     }
 
-    fn clean_invalidate_data(start_offset: usize, end_offset: usize) -> _ {
+    fn clean_invalidate_data(start_offset: usize, end_offset: usize) -> ! {
         todo!()
     }
 
-    fn invalidate_data(start_offset: usize, end_offset: usize) -> _ { todo!() }
+    fn invalidate_data(start_offset: usize, end_offset: usize) -> ! { todo!() }
 
-    fn unify_instruction_cache(start_offset: usize, end_offset: usize) -> _ {
+    fn unify_instruction_cache(start_offset: usize, end_offset: usize) -> ! {
         todo!()
     }
 }
@@ -274,7 +276,87 @@ struct TCB {
     // Thread.read_registers(cap, ... call for example.
 }
 
-impl Thread for TCB {}
+impl Thread for TCB {
+    fn configure(fault_endpoint: _, cap_space_root: _, cap_space_root_data: _, virt_space_root: _, ipc_buffer_frame: _, ipc_buffer_offset: usize) -> _ {
+        unimplemented!()
+    }
+
+    fn set_space(fault_endpoint: _, cap_space_root: _, cap_space_root_data: _, virt_space_root: _) -> _ {
+        unimplemented!()
+    }
+
+    fn configure_single_stepping(bp_num: u16, _: _) {
+        unimplemented!()
+    }
+
+    fn get_breakpoint(bp_num: u16) -> _ {
+        unimplemented!()
+    }
+
+    fn set_breakpoint(bp_num: u16, bp: _) -> _ {
+        unimplemented!()
+    }
+
+    fn unset_breakpoint(bp_num: u16) -> _ {
+        unimplemented!()
+    }
+
+    fn suspend() -> _ {
+        unimplemented!()
+    }
+
+    fn resume() -> _ {
+        unimplemented!()
+    }
+
+    fn copy_registers(source: TCB, suspend_source: bool, resume_target: bool, transfer_frame_regs: bool, transfer_integer_regs: bool, arch_flags: u8) -> _ {
+        unimplemented!()
+    }
+
+    fn read_registers(suspend_source: bool, arch_flags: u8, num_regs: u16, register_context: &mut _) -> _ {
+        unimplemented!()
+    }
+
+    fn write_registers(resume_target: bool, arch_flags: u8, num_regs: u16, register_context: &_) -> _ {
+        unimplemented!()
+    }
+
+    fn bind_notification(notification: _) -> _ {
+        unimplemented!()
+    }
+
+    fn unbind_notification() -> _ {
+        unimplemented!()
+    }
+
+    fn set_priority(authority: TCB, priority: u32) -> _ {
+        unimplemented!()
+    }
+
+    fn set_mc_priority(authority: TCB, mcp: u32) -> _ {
+        unimplemented!()
+    }
+
+    fn set_sched_params(authority: TCB, mcp: u32, priority: u32) -> _ {
+        unimplemented!()
+    }
+
+    fn set_affinity(affinity: u64) -> _ {
+        unimplemented!()
+    }
+
+    fn set_ipc_buffer(ipc_buffer_frame: _, ipc_buffer_offset: usize) -> _ {
+        unimplemented!()
+    }
+
+    fn set_tls_base(tls_base: usize) -> _ {
+        unimplemented!()
+    }
+
+    fn set_ept_root(eptpml: _) -> _ {
+        unimplemented!()
+    }
+}
 impl KernelObject for TCB {
     const SIZE_BITS: usize = 12;
 }
@@ -320,8 +402,53 @@ trait API {
     // Plus some debugging calls...
 }
 
-struct Kernel {} // Nucleus, actually...
-impl API for Kernel {}
+struct Nucleus {}
+
+impl API for Nucleus {
+    fn send(cap: _, msg_info: _) {
+        unimplemented!()
+    }
+
+    fn recv(src: _, reply: _) -> _ {
+        unimplemented!()
+    }
+
+    fn call(cap: _, msg_info: _) -> _ {
+        unimplemented!()
+    }
+
+    fn reply(msg_info: _) {
+        unimplemented!()
+    }
+
+    fn nb_send(dest: _, msg_info: _) {
+        unimplemented!()
+    }
+
+    fn reply_recv(src: _, reply: _, msg_info: _) -> _ {
+        unimplemented!()
+    }
+
+    fn nb_send_recv(dest: _, msg_info: _, src: _, reply: _) -> _ {
+        unimplemented!()
+    }
+
+    fn nb_recv(src: _) -> _ {
+        unimplemented!()
+    }
+
+    fn nb_send_wait(cap: _, msg_info: _, src: _) -> _ {
+        unimplemented!()
+    }
+
+    fn wait(src: _) -> _ {
+        unimplemented!()
+    }
+
+    fn r#yield() {
+        unimplemented!()
+    }
+}
 
 trait DomainSet {
     // ??