[devin-ai-integration]

What and why

The second of the three expression-parts parity follow-ups (after #1817, whose branch this one is built on — its diff reads as its own three commits once #1817 lands): a body expression.

For

attribute y = { in q : ScalarValues::Real; attribute k = 2; q * k };

the RDF/API-JSON writer (bodyExpression in internal/translate/export/rdf_expr.go) states the { … } as a FeatureReferenceExpression whose referent is the body Expression it owns through a FeatureMembership; the body owns its parameters and members through FeatureMemberships and its result through a ResultExpressionMembership, in source order; the reference owns its own out. The native read had the body's parameters and members as symbols in a body-local scope with no owner at all, no body Expression, no result membership, and no ids for any of them.

Now:

• the semantics synthesize the body Expression (role ExpressionBody, metaclass Expression) as the reference's referent, owned through a FeatureMembership ahead of the ReturnParameterMembership; the body owns the symbols its scope declares (parameters and members, in the writer's order) and its result (role ExpressionBodyResult, ResultExpressionMembership); ownerOf a body parameter or member is the body, found through the declaration whose value holds it when nothing reflected the body yet (bodyDeclaredBy);
• ownedElement/ownedFeature of the reference list the body ahead of its result, and of the body its parameters, members and result; parameter/directedFeature list parameters only (a body's result expression is a ResultExpressionMember, not a parameter);
• ast.BodyDeclarations is the one source-order numbering the writer (bodyDeclarations), the id reader and the semantics share, so in%d/m%d slots agree by construction;
• the id reader (internal/translate/export/element_ids.go) registers body, every parameter (by its own span — a body's parameters all share the body node) and member (with their value expressions, recursively), result and out as the writer mints them; queryexec.ElementIDOf reads a body parameter and its membership through that span;
• one writer fix: bodyMembership states ownedFeatureMembership/ownedFeature/ownedMemberFeature for every FeatureMembership subclass it owns, so a body's ResultExpressionMembership (a FeatureMembership, KerML 8.3.4.1) is listed as the pilot lists it.

A referee call made on the way, kept as the writer has it: KerMLExpressions' BodyParameterMember returns ParameterMembership, but both notations override ExpressionBody with a type body (KerML.xtext FunctionBodyPart, SysML.xtext CalculationBody) whose in feature is a FeatureMember, i.e. a FeatureMembership — and the pilot writes that (switching to ParameterMembership flipped 32 matched body-parameter memberships to unmatched in every corpus root). The native read states FeatureMembership for a body parameter explicitly, with the citation. docs/reference/rdf-mapping.md records it.

Not in this PR: the chain Feature a dotted name owns (last follow-up). A body member written as a bare expression ahead of the result has no symbol and is not listed natively (the writer writes it at m%d).

Specification basis

KerML 1.0 §8.2.5.8.4 / KerMLExpressions BodyExpression, ExpressionBodyMember (a FeatureReferenceExpression owning the body Expression through a FeatureMembership), ResultExpressionMember (ResultExpressionMembership); KerML.xtext ExpressionBody : '{' FunctionBodyPart '}' and SysML.xtext ExpressionBody : CalculationBody for the parameters' FeatureMembership; KerML 8.3.4.1 ResultExpressionMembership specializes FeatureMembership. No spec-compliance.md row moves: the reflective read agreeing with the conversion, not a new rule.

How it was verified

• internal/semantic/semantics — TestBodyExpressionOwnsItsBodyParametersAndResult: the reference's two memberships, referent, the body's three memberships and their metaclasses/members in order, owners of parameter, member and result, the result's operator and parameters, repeated-read identity; and on a fresh model, a reduce body's parameter finds its owner before anything reflected the body.
• internal/translate/export — TestElementIDReaderSpellsABodyExpressionAsTheConversionWritesIt: body/result/out parts, the parameter by span (…_pin0, FeatureMembership), the member (…_pm1), its value, the result (…_presult) and the result's operand — all as the conversion writes them.
• Five RDF goldens re-recorded (tests/export): the only movement is the ResultExpressionMembership now listed under ownedFeatureMembership/ownedFeature with ownedMemberFeature; the .golden.sysml round trips are unchanged.
• go build ./..., go vet ./..., gofmt -l . (empty), go test -count=1 ./... (full suite, run after the last change), the corpus round trip with the corpora required.
• api-json: pilot-apijson-diff -update then -check; elements unchanged, properties 1144182 / 27977 → 1144254 present-equal / 27934 present-different; exactly three rows moved, all to equal (Expression.ownedFeatureMembership, Expression.ownedFeature, ResultExpressionMembership.ownedMemberFeature), accounted for in docs/project/api-json-differential.md; go -C tools test ./referee/apijson/... ./oracle/baseline/... and make docs-counts green.

Checklist

• make test and make lint pass locally
• Tests added or updated for the change
• Documentation extended where it already covers the surface (see CONTRIBUTING.md)
• Changelog entry added as changes/unreleased/<slug>.<section>.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (compliance rows need nothing: the census is counted at docs build)
• No internal work-item labels (waves, slices, F4, K5) in the body, docs, or changelog

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/18ad47adf36f44e9b6824a4472f9678d
Open in Devin Desktop: https://nasa-jpl-demo.devinenterprise.com/desktop/session/18ad47adf36f44e9b6824a4472f9678d?variant=devin
Requested by: @NicolasRouquette

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring