Layer stack — OpenIM in the standards landscape

OpenIM is a layer, and it is honest about which layer. It does not replace FIBO, it does not compete with ISDA CDM, and it is not a wire format. The diagram below shows where the model sits in relation to adjacent standards. Implementations sit above OpenIM and remain independent of the project.

The textual rendering of the same picture is in ../../PRIOR-ART.md, with the full explanation of each layer’s relationship to OpenIM.

flowchart TB
    classDef openim   fill:#1f3a5f,stroke:#0e1e33,color:#fff,font-weight:bold
    classDef reuse    fill:#e8eef7,stroke:#5b7aa6,color:#1f3a5f
    classDef govern   fill:#f0eee6,stroke:#a09578,color:#5a513a

    subgraph MODEL[OpenIM — the reference model]
        direction TB
        M1["Service-domain model<br/>17 Business Domains / 171 Service Domains<br/><i>what the firm does</i>"]:::openim
        M2["Canonical entity model<br/>86 entities — core + 5 specialisation packs<br/><i>what the firm knows</i>"]:::openim
    end

    subgraph BELOW[Layers OpenIM reuses or aligns to]
        direction TB
        B1["ISDA CDM — transaction layer<br/>trades and trade lifecycle"]:::reuse
        B2["FIBO — concept ontology<br/>instrument and legal-entity semantics"]:::reuse
        B3["Identifiers — LEI · FIGI · ISIN · Private CUSIP"]:::reuse
        B4["Wire / messaging — ISO 20022 · FIX · FpML"]:::reuse
        B5["Reporting / performance — ILPA templates · GIPS"]:::reuse
    end

    G1["FINOS AI Governance Framework<br/><i>governance · align to</i>"]:::govern

    M1 -.consumes.-> B1
    M1 -.consumes.-> B4
    M1 -.consumes.-> B5
    M2 -.builds on.-> B2
    M2 -.references.-> B3
    M2 -.aligns to.-> G1

Reading the diagram

• The model layer (OpenIM) is the new thing — service-domain decomposition (BD / SD / SO) plus the canonical entity model. This is the part with no existing open equivalent.
• Implementations may sit above the model and expose it through applications, APIs, agents or other interfaces. OpenIM does not prescribe or endorse one.
• The layers below are reused or aligned to. ISDA CDM models trades; OpenIM models the portfolio, fund and mandate above the trade. FIBO models the what of instruments and legal entities; OpenIM uses FIBO semantics where they cover the concept. ILPA / GIPS are reporting and presentation standards OpenIM consumes or conforms to. The wire formats are interop at the edges.
• The FINOS AI Governance Framework is the governance companion OpenIM aligns to, rather than inventing its own risk taxonomy.

The full prose statement of each adjacency is in ../../PRIOR-ART.md — that document is the project’s credibility artefact.