A concrete supply problem, a risk assessment, a choice

Trace a project decision through risk and value

A fictional construction team finds variation in concrete quality. Should it strengthen checks, change supplier, or investigate a revised mix? Follow how a material problem becomes a risk judgement, a value judgement and a decision.

Fictional teaching case adapted from the former HS2 decision graph. The quality failure, supplier replacement, two-week delay and 3% component cost increase are invented assumptions. No real HS2 incident or supplier performance is evidenced.

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Drag nodes or pan; use buttons to zoom. Tab to a node and press Enter for details. Node size shows its visible connection count.

Dashed arrows: assumed relationships in the fictional story. Arrowheads show direction. Labels appear on selected links.

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    Card index — the same visible nodes

    Every card opens the same detail panel as its graph node. Search and filters apply to both.

    Read every visible relationship and its rationale

      The fictional decision story

      1. Context: the construction manager wants timely delivery; the quality team assesses concrete against the required specification.
      2. Threat and vulnerability: assumed production-control weaknesses may lead to inconsistent material and possible quality failure. The viaduct is the object at risk.
      3. Potential loss: rejected or remediated material could delay construction and affect dependent work. A likelihood node is included, but no numeric probability is supplied.
      4. Options: retain the current supplier with additional quality control; switch to an alternative; or investigate a revised mix through engineering review. A changed mix would still need to meet the approved design and safety requirements.
      5. Value judgement: the fictional team gives long-term reliability greater weight than immediate schedule. It chooses the alternative supplier, subject to qualification and material assurance.
      6. Assumed outcome: the story accepts two weeks of delay and a 3% increase in this component’s cost. These figures are illustrative, with no calculation or evidence that quality is guaranteed.
      Sources, corrections and modelling choices

      The 22 original entities remain, along with all 25 original relationships in corrected or qualified form and three explicit story links that make the decision reading continuous. Original labels and changed arrows remain inspectable in the relationship list and exported data.

      The graph is inspired by COVER, the Common Ontology of Value and Risk. Its foundational paper distinguishes agents, objects, events and evaluative relationships. Here an intention points to its agent, and risk/value qualities point to their assessments or ascriptions. “Threat capability” for a production weakness and some abbreviated roles remain informal teaching analogies. This is not an ontology-conformance result.

      The original “Chiltern Viaduct” label was not supported as an incident source. HS2’s official Colne Valley viaduct account describes a real structure but does not substantiate this toy story. The maintained case therefore uses a fictional viaduct and unnamed fictional suppliers.

      Adapted from hs2-decision-graph.html at source revision cd0528939fd0. Review date: 3 October 2026. The source hash and retention details are in the app documentation. The graph runs locally in your browser.

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      View files and links preserve filters, reading, layout settings and selection. Manual node positions, pins, map zoom and online-tile choice remain session-only. Data export includes the full graph, sources and correction notes.