diff --git a/src/arg/data.rs b/src/arg/data.rs
new file mode 100644
index 0000000..15501bb
--- /dev/null
+++ b/src/arg/data.rs
@@ -0,0 +1,139 @@
+use super::*;
+
+/// A trait used to validate atoms in the `uv` module to valid ones in this module.
+trait Validate: Sized
+{
+    type Valid: Into<Inner>;
+    type Error: Into<eyre::Report> = eyre::Report;
+
+    /// Consume into the strongly validated type.
+    fn valiate(self) -> Result<Self::Valid, Self::Error>;
+
+    /// Weakly validate that this instance itself is correct.
+    fn self_validate(&self) -> Result<(), Self::Error>;
+}
+
+/// Non-validated inputs which get mapped to the validated ones in the parent module.
+mod uv {
+    use crate::*;
+    use super::Validate;
+
+    #[derive(Debug, Clone)]
+    pub struct ExecTaskAtom
+    {
+	prog: Option<String>,
+	args: Option<Vec<String>>,
+	//TODO: ...
+
+	takes_tail: Option<super::TailKind>,
+    }
+
+    impl Validate for ExecTaskAtom
+    {
+	type Valid = super::ExecTaskAtom;
+
+	fn valiate(self) -> Result<Self::Valid, Self::Error>
+	{
+	    todo!()
+	}
+
+	fn self_validate(&self) -> Result<(), Self::Error>
+	{
+	    todo!()
+	}
+    }
+    
+    pub enum Either
+    {
+	Exec(ExecTaskAtom),
+	Shell(!), //TODO
+    }
+
+    //TODO: impl Validate for Either, or something
+
+    /// Validate an atom from this module into `Inner`.
+    pub(super) fn validate<T>(inv: T) -> eyre::Result<super::Inner>
+    where T: Validate
+    {
+	Ok(inv.valiate().map_err(Into::into)
+	   .wrap_err(eyre!("Failed to validate atom"))
+	   .with_section(|| std::any::type_name::<T>().header("Type name was"))
+	   .with_section(|| std::any::type_name::<T::Valid>().header("Validating for"))?.into())
+    }
+}
+
+/// Options for a normal execution atom
+struct ExecTaskAtom
+{
+    prog: String,
+    args: Vec<String>,
+    //TODO: ...
+
+    takes_tail: TailKind,
+}
+
+enum Inner
+{
+    Exec(ExecTaskAtom),
+    Shell(!), //TODO
+}
+
+impl From<ExecTaskAtom> for Inner
+{
+    #[inline] fn from(from: ExecTaskAtom) -> Self
+    {
+	Self::Exec(from)
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum TailKind
+{
+    /// No tail parsing
+    Contained,
+    /// Parse rest of arguments
+    Rest(TailField),
+    /// Parse concurrently from stdin
+    Stdin(TailField),
+}
+
+impl Default for TailKind
+{
+    #[inline]
+    fn default() -> Self
+    {
+	Self::Contained
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum TailField
+{
+    //TODO: All possible tail fields for all exec atom types. Validating they are used for the correct atom type will be done in `uv`'s validate step.
+}
+
+/// The defaults specified for execution types
+pub struct TaskDefault(Box<(uv::ExecTaskAtom, ! /* TODO: ShellTaskAtom */)>);
+
+/// A task atom is task-specific execution directives.
+///
+/// An atom can inherit from a `TaskDefault`.
+pub struct TaskAtom(Box<Inner>); //TODO: how tf are we going to signal tail feeding? Do we just tag which field it is and let the program figure out how to handle it? I think that might be best, esp. for stdin for which reading happens concurrently.
+
+impl TaskAtom
+{
+    fn inherit(default: &TaskDefault, from: uv::Either) -> eyre::Result<Self>
+    {
+	//TODO: Clone default.0.<n>, replacing the *set* (not `None`) fields set in `from` then validate it into `Self`
+	todo!()
+    }
+    
+    /// Does this atom take tail parsing? And if so, which field?
+    pub fn tail(&self) -> &TailKind
+    {
+	match self.0.as_ref() {
+	    Inner::Exec(e) => &e.takes_tail,
+	    _ => todo!()
+	}
+    }
+}
diff --git a/src/arg/mod.rs b/src/arg/mod.rs
index ff4fb20..70203da 100644
--- a/src/arg/mod.rs
+++ b/src/arg/mod.rs
@@ -3,6 +3,7 @@ use super::*;
 use std::fmt;
 
 mod usage;
+mod data;
 
 /// The name of the process that was invoked
 #[inline] pub fn prog_name() -> &'static str
diff --git a/src/main.rs b/src/main.rs
index dccee53..adefbac 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(nightly, feature(never_type))] 
+#![cfg_attr(nightly, feature(associated_type_defaults))] 
+
 #![allow(dead_code)]
 
 #[macro_use] extern crate log;
@@ -15,6 +18,7 @@ use color_eyre::{
 	WrapErr as _,
     },
     SectionExt as _,
+    Help as _,
 };
 
 mod ext;