10 Operational intent§
AGREED Intent is decomposed rather than composite, and Sequence sits outside it. Both differ from the earlier technical specification; see Decision Record D-1 and D-2.
10.1 Why intent is modeled separately§
A building has three tenses. What it is meant to do. What it is doing. What it did. Systems routinely store the first inside the third — an intent becomes a setpoint value in a database, indistinguishable from any other stored number — and when the system is replaced, the intent is what does not survive.
Modeling intent separately is what lets a receiving system answer the question an operator asks in the first week: not what is this value, but what was this supposed to achieve.
10.2 The intent classes§
| Class | What it carries |
|---|---|
bus:Objective | What is to be achieved, its rationale, a category, and a priority. Prose, deliberately. |
bus:Target | A quantified expectation attached to a point or quantity kind: a value or range, a tolerance, a condition, and a schedule reference. |
bus:Constraint | A limit that holds regardless of objectives, with a constraintKind of safety, limit, deadband, interlock, regulatory, warranty, or operational. |
bus:Schedule | When intent applies. Segments carry an [RFC5545] recurrence rule, local clock bounds, and a value. Exceptions carry explicit dates. |
Each is separately addressable, which is what makes it possible to say twenty years later that this specific target was relaxed on a date, by a person, for a reason. A composite intent object is easier to author and blurs exactly that audit trail; authoring convenience is a tooling problem and addressability is not.
bus:Objective is prose because objectives are not reducible without loss. The rationale field carries what a later engineer most needs and most rarely gets: why the number is what it is.
10.3 Sequences§
bus:Sequence is the logic that implements an intent, connected by bus:implements. It is not part of intent. A sequence names the language it is written in — prose, ashrae-231-cdl, ashrae-guideline-36, iec-61131-3, or vendor — and carries either inline source or a resource reference.
NOTE ANSI/ASHRAE Standard 231-2026, Control Description Language, published February 2026, is the first citable machine-readable form for control sequences. It is design-time: it describes what logic should be, not what a deployed controller is running. BUS-1 references sequences rather than extracting them for that reason, and extraction remains open (Annex E).
10.4 Constraints and safety§
A constraint MAY carry a machine-readable expression, which MUST name its language. This standard does not define an expression language and does not require a receiver to evaluate one. Naming the language is what lets a receiver decide honestly whether it can.
Constraints are also referenced from write bindings (13.7), so that a limit enforced at the graphic is the same limit recorded in the model rather than a second copy that will diverge.