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Solway Firth Tunnel — Milestones and interface checks

A fictional tunnel programme: move a shared gate, see the workstream dates change, then inspect the declared checks between teams.

– of declared checks pass
– interfaces need attention
– items affected by slips

A director’s question: what does a consent delay change?

The Solway tunnel teams share consent, design and safety gates. If consents move, the programme must decide whether later gates also move. This demo applies that decision to the dates of named deliverables while retaining each team’s supplied offset and exemption.

Trace one effect: M2 consents +60 days → with forward delay on, M3 design freeze +60 days → the ground model’s due date stays 10 days before M3. Its version can still disagree with Civil’s alignment: a later date does not resolve an interface mismatch.

Fictional teaching data. These are coordination rules, not a design, construction plan or verified engineering result.

1) Programme gates and dates

Try a scenario
Try +60 days at consents, carry the delay forward, then exempt one deliverable. Inspect the dates and the session audit.
Tip Due date = base date + effective slip + supplied offset. Exempt items ignore slip, but still follow edits to the base date. Forward delay carries the largest positive upstream slip; without one, a gate keeps its own advance or delay. Advances do not propagate. This supplied chain rule is not critical-path scheduling.

2) Workstream deliverables

3) Declared interface checks

Rule Computed: references, gate/date bounds, matching nonempty version labels and both statuses “done”. The engineering acceptance evidence described below is not executed or verified.

4) Session audit (what changed and why)

Idea This is a temporary session log. Reset or reloading clears it. A logged label or “done” status is not engineering acceptance or an approval.

What this example establishes

Computed: date offsets, a declared chain of gate delays, and five interface predicates.

Supplied: gates, deliverables, versions, offsets and interface rules are toy inputs. Marking work “done” is a user assertion.

Unchecked: actual geometry, evidence quality, resources, costs, engineering feasibility and unlisted dependencies. Passing these checks does not establish a global plan or a categorical fibration.

Compared with a schedule: an ordinary dependency/rules model can produce these same results. Scheduling tools already support cross-project relationships, concurrent tasks, baselines and time-based float. This example adds an explicit view of gate anchors and declared interfaces; its categorical interpretation remains a hypothesis.

Method and companion scenario: Milestones under changing constraints.

Sources: Stacks Project, fibred categories; Oracle P6 relationships; baselines; scheduling and float.