The landscape of spec, intent, and AI-native development.
Three currents are running in parallel: SDD, IDD, and a growing list of products that put either word in their name. This page maps the terrain.
SDD levels are stacked — each one fixes the previous level's failure mode.
IDD schools are parallel choices — each makes a different bet. Don't confuse the two.
SDD — three levels of investment
Birgitta Böckeler observed three levels of how SDD tools treat the spec. The levels stack: each fixes the failure mode of the one below.
"Spec-as-source, and even spec-anchoring, may carry both the rigidity of MDD and the non-determinism of LLMs — Inflexibility AND non-determinism."— Birgitta Böckeler · martinfowler.com
IDD — three schools
Where SDD levels are stacked, IDD schools are parallel choices. We have observed three so far. The naming is ours; the schools are real.
Build-First IDD
Implementation-Last IDD
Tree-Structured Operational IDD
How IDD relates to SDD
GitHub Spec-Kit treats IDD as the upstream of SDD. The lingua franca of development moves to a higher level; code is the last-mile approach.
At-a-glance comparison
| Axis | SDD | IDD (general) | Intent-System |
|---|---|---|---|
| Source of truth | spec | one intent doc / file | structured intent tree |
| Primary language | technical, implementation-near | natural, customer-facing | structured (Purpose / User / Means) |
| Code-spec relationship | spec → code (level-dependent) | intent → spec → code | intent tree → issue → code |
| Freshness | depends on level | depends on author | enforced via closeout |
| Review compares against | spec | intent | intent diff + code quality |
| Frontend & tech intent | not addressed | not addressed | same tree |
| Multi-domain reuse | typically one codebase | typically one codebase | multiple submodules / domains |
| Operational loop | limited | limited | built-in (review / closeout) |
Intent-as-source
Intent-System is an implementation of Tree-Structured Operational IDD. Where Tessl makes the spec the SSoT, we make intent the SSoT.
Intent isn't just product goals. The tree also carries the technical decisions that constrain implementation — chosen architecture and frameworks, interface contracts, UI patterns down to text-input best practices. Each issue inherits the relevant slice of that tree, so the agent (and the human reviewer) sees the same map of what "correct" looks like before a single line is written. Cross-linking intents into a tree is how we hand AI both a map and a compass for the right implementation, and how implementation mistakes become easy to spot.
Intent-System is orthogonal to SDD tools — you can run it for the IDD layer and Spec-Kit, Tessl, or Augment Intent for the SDD layer in the same project.