A recurring research question is: what does HDC add beyond a strong symbolic baseline? One possible answer is to build a separate “pure term engine” backend (unification + backtracking) that runs Sys2DSL without vectors.
In practice, AGISystem2 already contains substantial symbolic machinery (direct matches, rules, transitive reasoning, CSP, proof validation), and a fully separate backend would create a large maintenance burden (semantic drift, proof formatting parity, graph/macro parity). Because of this, the “pure term engine backend” remains a research reference, not an implementation plan.
DS24 – Pure Symbolic Term Engine (Exploratory) captures the design motivation and what a full backend would look like.
When we need a “pure symbolic” comparison for performance, the preferred approach is to add a symbolic-only profile to the existing engine (disable holographic candidate generation) rather than introducing a new backend.