---
name: fhir-ig-analysis
description: Measures one or more FHIR Implementation Guides read-only and reports the numbers as
  JSON and Markdown — scope, complexity, content hygiene, duplication, linguistics, maturity and
  risk — and compares several IGs side by side using normalised metrics. It builds, changes and
  publishes nothing. Use this skill when reviewing or QA-ing an MII KDS module IG before a release,
  when comparing a module against kerndatensatz-basis or another Implementierungsleitfaden, when
  tracking how a module grows between releases, or when someone asks how large, how clean or how
  mature a guide actually is. Do not use for migrating a guide onto the module template or for
  translating one; see mii-ig-migration and fhir-ig-translation.
license: CC-BY-4.0
allowed-tools: Read Grep Glob Bash(python3:*) Bash(git clone:*)
metadata:
  fgdh.tier: "domain"
  fgdh.domain: "fhir-ig"
  fgdh.owner: "@msusky"
  fgdh.language: "en"
  fgdh.status: "stable"
---

# Measuring a FHIR Implementation Guide

Measures a FHIR IG objectively and reports what it counted. **Strictly read-only:** it never
builds, changes, or publishes anything, and it does not forecast.

## Preconditions

Discover the context; do not assume it, and never create it.

1. **The tool.** `python3` must be runnable. The analyser is standard-library only — nothing to
   install. If `python3` is absent, say so and stop; do not fetch an interpreter.

2. **The subject.** One or more IGs, each given as a **local path**, a **git URL**, or a **package
   `.tgz`**. `run` resolves each itself (shallow clone for a URL, download for a package). Nothing
   needs to be discovered inside the repository beyond what the tool reads.
   - A local path with neither `sushi-config.yaml` nor `input/` is not an IG project. Report that
     and stop.
   - A git URL requires network access; if cloning fails, report the failure rather than reporting
     an empty measurement.

3. **Static by default, and know what that costs.** Without a build, the analysis is **static**:
   sushi-config/package metadata, FSH counts, narrative, directives, dependencies, linguistics,
   duplication, hygiene. Build-derived metrics (`qa.json`: errors, warnings, broken links,
   validation) stay `null` and are marked *Build* in the catalog. A package `.tgz` yields a further
   **reduced** analysis — generated resources only.

   State which mode produced the numbers whenever you report them. A `null` is not a zero.

## Procedure

**The generated reports are in German**; this skill's instructions are in English. That is
deliberate and does not follow from either fact on its own — the report prose was inherited and has
not been translated. Do not "fix" it silently, and do not translate the numbers.


> **Resolve the script path first.** The commands below name the tool relative to **this skill's
> own directory**, not to your working directory — which is the project you are operating on. Set
> `SKILL_DIR` to the directory containing this `SKILL.md` (you just read it, so you know where it
> is) and use it in every invocation:
>
> ```bash
> SKILL_DIR=<the directory containing this SKILL.md>   # e.g. .claude/skills/fhir-ig-analysis
> ```
>
> Running a bare `scripts/...` from the project root does not merely fail — if the project happens
> to have its own `scripts/` directory with a same-named file, it silently runs **that** instead.

1. **Measure.** One IG or several, from the IG's root or anywhere:

   ```bash
   python3 "$SKILL_DIR/scripts/ig-stats.py" run <input…> [-o OUTDIR] [--label a,b]
   ```

   With two or more inputs this writes one report per IG **plus** `compare-report.md`
   automatically. `--label` sets the **display label** (report heading, compare columns), one
   per input; output **filenames** always derive from the IG id.

   Two consequences of how inputs resolve, so the numbers are read correctly: a **git URL is
   shallow-cloned**, so the git-history metrics (bus factor, maintenance cadence) are reported
   as *not derivable* (`git.history_complete: false`, values `null`) — measure a full local
   clone when you need them. And the tool reports **counted maturity components without an
   aggregated score**: a 0–100 "readiness" number would be a forecast, which this skill
   deliberately does not produce.

2. **Power-user entry points**, when you want the stages separately:

   ```bash
   python3 "$SKILL_DIR/scripts/ig-stats.py" analyze <ig-dir> [-o stats.json]
   python3 "$SKILL_DIR/scripts/ig-stats.py" report  <stats.json>  [-o report.md]
   python3 "$SKILL_DIR/scripts/ig-stats.py" compare <stats.json…> [-o compare.md]
   ```

3. **Read the mandatory-page finding carefully.** The page set the tool checks against lives in
   [`references/report-content.json`](references/report-content.json) under `mandatory_pages` and is
   **hand-editable on purpose**. It is seeded with the MII KDS module template's actual page names.

   If a measured IG legitimately uses a different page set, correct the list rather than reporting
   its pages as missing — and say in your report which list you used. A page-completeness metric is
   only as good as the set it compares against.

4. **Report both artefacts.** The JSON is the durable one: it has a fixed schema, so a series of
   runs diffs cleanly and shows how a module grows between releases. The Markdown is for people.

5. **Compare only on normalised metrics.** Absolute counts across IGs of different size say almost
   nothing; the comparison report aggregates a Σ total for scope but the fair columns are the
   normalised ones.

6. **Same-module verification is automatic.** When every compared input carries the same
   `packageId`, the inputs are states of ONE module (typically: the platform source vs its
   migrated copy) and the report switches to **Same-Module-Verifikation**: identity-field
   equality, published-artifact-set equality (internal FSH constructs reported separately —
   template adoption adds scaffold rulesets legitimately), canonical-URL equality (read from
   `fsh-generated` when both inputs have it), and narrative per language level
   (default / translations / retained platform pages) with word-coverage indicators. The Σ
   column is dropped (meaningless for one module). Every verdict is counted, none forecast.
   Order matters: the FIRST input is the reference.

## Pre-flight aspects (migration Gate 0)

From v0.17.0 every measurement carries a `preflight` section with
migration-decisive aspects, measured OFFLINE from the tree alone:

- **Licence evidence, tiered** — every place a licence is declared
  (sushi-config/package.json, LICENSE file, narrative copyright statements),
  with absence and contradiction as first-class findings.
- **Canonical-space census** — resources whose `url` lies outside the IG
  canonical, plus id↔url mismatches inside it: together the
  `special_url_prediction`, the publisher's `special-url` list a migration
  will need; `example.org` canonicals are called out separately. A
  sushi-config-vs-package.json canonical disagreement is reported as
  `config_contradiction` (measured live: PROs' package.json carries a
  modul-dok canonical).
- **Dependency-pin health** — old-style/virtual packages, whether
  THO/Extensions-Pack are pinned DIRECTLY (absent → the IG Publisher injects
  the latest release at build time), and external parent canonicals. The
  parser reads BOTH SUSHI dependency forms (flat and nested id/version
  sub-keys); `dependency_block_unparsed: true` flags a block that exists but
  yielded no entries — a parser finding, never a dependency-free source.
- **Package layout** — for distributed packages: `.index.json` presence
  (absent → index-based oracles run dry) and nested resource directories
  (flat globs lose them; the census here is recursive).
- **Narrative sources** — which trees carry prose (`pagecontent`,
  `intro-notes`, `implementation-guides/`); `dual_source: true` plus each
  tree's last commit date makes the authoritative-copy decision a measured
  one instead of a rank default.
- **QA baseline** — a rendered `qa.json` in the tree, if any. `None` means:
  obtain it (build the unmigrated source, or fetch its rendered qa) — never
  assume it.

Three census honesty rules sit behind these aspects: instances of canonical
base types (ConceptMap, Measure, ObservationDefinition, …) are counted in an
open `artifacts.other` bucket instead of being absorbed as "examples"; where
FSH declarations AND generated resources both exist, their counts are
cross-checked and every mismatch is reported (`generated_crosscheck` — the
generated resourceType census is the authoritative one for page decisions);
and a repository whose SUSHI project nests below the root (strukturdaten's
`Resources/`) is re-rooted with a page-one warning instead of yielding an
empty identity without a finding.

`None` values name what this instrument cannot measure from the tree — the
consumer obtains it elsewhere, never assumes it (the "a null is not a zero"
rule). The `mii-ig-migration` skill runs this measurement on the unmigrated
source as its REQUIRED Gate-0 pre-flight.

## Verification

```bash
python3 "$SKILL_DIR/scripts/ig-stats.py" run <ig-dir> -o /tmp/igstats
python3 -c "import json;d=json.load(open('/tmp/igstats/<name>-stats.json'));print(d['mode'],d['schemaVersion'])"
```

- The run exits 0 and writes one `*-stats.json` and one `*-report.md` per input.
- With ≥2 inputs, `compare-report.md` exists.
- `mode` in the JSON matches what you claim (`static` / `reduced`), and `schemaVersion` is present.
- **Every metric you quote is either a counted number or `null`** — never an estimate. If a field is
  `null`, report it as not derivable statically rather than as zero.
- The mandatory-page result is plausible against the IG you measured. All-missing usually means the
  wrong page set, not a broken IG.
- On a same-module comparison, the Befund block states IDENTISCH/DIVERGIERT per aspect — a
  migration is only faithful when identity, published artifact set and canonical URLs are all
  IDENTISCH; the migration skill's Definition of Done requires exactly that.

## Scope and delimitation

Covers **measurement and comparison**: what is in an IG, how clean it is, how it compares, how it
changes over time.

Deliberately not covered:

- **Effort forecasting.** The tool reports what it counted. It does not estimate person-days, cost
  or a readiness score, and an earlier version of this skill that framed the numbers as migration
  scoping was narrowed on purpose. Do not reintroduce it: a measurement dressed as a forecast is
  the least trustworthy thing this skill could produce.
- **Migration** onto the MII KDS module template — see `mii-ig-migration`. **Verifying a migrated
  guide against its source belongs there too**, in its `scripts/verify-migration.py`: artefact
  *reachability*, menu structure, content placement, rendered header metadata and toolchain
  provenance are pass/fail gates that read the migration's page map and run log — inputs that are
  not properties of an IG and would break this skill's "a path, a URL or a `.tgz`" contract. The
  same-module verification below is the *measurement* that gate consumes, not a substitute for it:
  it proves an artefact is PRESENT, never that anything links to it.
- **Translation** — see `fhir-ig-translation`.
- **Convention and naming checks** against the MII meta wiki or the metadata contract. Those are a
  different check, and the module template ships its own skill for them.
- **Building or publishing anything.** Read-only is a guardrail, not a default.

If a skill of this name is provided both by this catalog and locally, the local one wins.

## Guardrails

- **Read-only.** Never modify the analysed IG; never force a build.
- **Measurement, not forecasting.** See above.
- **Fair comparison only via normalised metrics.**
- **No invention.** A missing input yields `null`, never a guess. Heuristic metrics are marked as
  heuristics in the catalog and must be reported as such.

## References

- [`references/metrics-catalog.md`](references/metrics-catalog.md) — the parameter catalog
  (groups A–N), each metric with its source and its use. Hand-extensible; this is the SSOT for what
  is measured.
- [`references/ig-stats-schema.json`](references/ig-stats-schema.json) — the schema of
  `ig-stats.json`.
- [`references/report-content.json`](references/report-content.json) — plain-language texts,
  glossary, directive patterns, metric explanations, and the `mandatory_pages` list. Hand-editable.
- [`references/triggers.md`](references/triggers.md) — the Gate 3 prompt set.
- [`scripts/ig-stats.py`](scripts/ig-stats.py) — the analyser (`run` / `analyze` / `report` /
  `compare`).

## Provenance

Derived from `skills/ig-analyze` in
`medizininformatik-initiative/mii-kds-module-template` at commit
`b5beedb17a66a4397d597429668c7b6d54202c62`, which in turn adapted the `ig-analyze` skill of
`forschungsgruppe-digital-health/mii-kds-sample-ig-inoffiziell` (CC-BY-4.0). Both steps of that
lineage are recorded deliberately.

Reworked on 2026-07-31 for this catalog. Beyond the catalog contract, three substantive changes:

- The analyser now ships **with** the skill. It previously lived in the source repository's
  `scripts/` and was referenced by parent traversal, so the skill pointed at a file it could not
  reach once installed elsewhere.
- `scripts/ig-stats.py` locates `references/report-content.json` relative to **its own path**. It
  previously built that path from a computed repository root plus a hard-coded
  `skills/ig-analyze/references/…`, which broke twice here: there is no repository root to compute,
  and the skill was renamed.
- The mandatory-page list moved out of the code into `references/report-content.json` and was
  corrected. The inherited list named eleven pages of which **six do not exist** in the template
  modules are built from (`use-cases`, `data-sets`, `uml`, `context`, `references`,
  `security-privacy`), so every measurement reported six false missing pages.

Revised on 2026-08-01 after the skill's first real-task exercise (a dry run against
`kerndatensatz-dokument` + `kerndatensatz-basis`). Four output defects were fixed, all in the
direction of "measurement, not forecasting": the aggregated `Reifegrad`/"Freigabe-Indikator"
score was removed (components are now reported unaggregated — schemaVersion 1.4); the
"Empfehlungen" table's migration-scoping prose became neutral "Befunde & Einordnung"
measurement explanations and its metric-less "Arbeitsweise" row was dropped; git-history
metrics on shallow clones (including every clone the tool makes itself) now report
`history_complete: false` and `null` instead of a fictive "100 % top author"; and
`references/ig-stats-schema.json` was regenerated from the real output after drifting
(`mandatory_missing` was declared but never emitted). The dry-run findings live in the
`mii-kds-dokument-ig-inoffiziell` sandbox under `docs/reports/dry-run-2026-07-31/`.

Original licence: CC-BY-4.0, as declared by both source repositories. `scripts/` is Apache-2.0,
matching this repository's code licence.

Promoted to `stable` on 2026-08-05: repeated real-task use: module measurement/comparison across four KDS modules, and the same-module verification gate of two completed migrations. The trigger set in
[references/triggers.md](references/triggers.md) was exercised by those runs.