One key insight is that bundles are really sets of packages and that what we're doing when we bundle things is really just set join operations. Imagine the possibilities if we implement arbitrary set operations. So a bunch is defined as a set of bundles (which can themselves be down to a single package of course) and the declarations in the Aptbundlefile translates under the hood to references and set operations. This is not only declarative, it's also purely functional. Still working on if arbitrary set operations should be accessible by DSL in Aptbundlefile or if that should be left to tools building on top of intermediary API. So yeah, parallels to Nix for sure but it's still apt packages, not building the world from source.