2. Conceptual Model

The conceptual model defines the foundational elements of chkpt as a deterministic execution substrate. It establishes how certified workflows are applied, how Applications are formed, and how chkpt ensures predictable behaviour, admissible behaviour enforcement, structural integrity, and complete evidence suitable for institutional review.

2.1 Certified Workflows

chkpt executes workflows that have been certified under an external governance model. The certification process is outside the scope of this specification, but chkpt assumes that each workflow version is authorised, authentic, and accompanied by defined admissible behaviour and evidence obligations. Each execution must bind to a specific certified workflow version, forming the basis for deterministic behaviour and evidence association.

2.2 Applications

An Application is a single execution of a certified workflow under chkpt. It consists of declared inputs, execution behaviour, declared results, and an evidence record. Applications are deterministic: given the same workflow version and the same declared inputs, chkpt must produce the same declared results and the same evidence. This principle is expanded further in the Execution Model.

2.3 Declared Inputs and Results

Each Application defines a set of declared inputs and declared results. Declared inputs represent the information provided to the workflow at the start of execution. Declared results represent the final outputs produced by the workflow. chkpt requires that both are explicitly defined, structurally valid, and consistent with the workflow’s specification. These elements form the core of the evidence record described in the Evidence Model.

2.4 Admissible Behaviour

Admissible behaviour defines the boundaries within which an execution is considered valid. These boundaries are defined by the certified workflow and enforced by chkpt. Any behaviour outside these boundaries constitutes a failure condition. Admissible behaviour ensures that executions remain predictable, reviewable, and aligned with the authorised workflow version. Enforcement mechanisms are detailed in the Execution Model.

2.5 Execution Versions

chkpt maintains an execution version that identifies the behaviour of the execution substrate itself. Execution versions are not certified artefacts; they exist solely for traceability and evidence association. Evidence produced by chkpt must record both the workflow version and the execution version used during the Application. Versioning rules are defined in Versioning.

2.6 Evidence

Evidence is the record produced by chkpt that enables institutional review of an Application. Evidence must be complete, tamper‑resistant, and sufficient to reconstruct the execution context. It includes declared inputs, declared results, intermediate state information where required, and metadata linking the execution to the workflow and execution versions. Evidence obligations are defined in detail in the Evidence Model.