Add prototype for nested-computations

CHANGELOG.md

@@ -16,6 +16,23 @@ not always match the Git tags; section versions follow the tags.
 
 ## [Unreleased]
 
+### Added
+
+- `integrity-lineage-models`: a `ComputationRegistration` can record when it ran
+  and which OpenTelemetry span it was, through `ComputationStatement::create_with_span`
+  and `ComputationSpan`. `startTime` and `endTime` are when the work began and ended,
+  separate from the registration `timestamp`. `span` and `parentSpan` identify the
+  computation's span and the span it ran inside, as `urn:uuid` version 5 UUIDs of
+  `"{traceId}/{spanId}"` in `OTEL_SPAN_NAMESPACE` (`otel_span_urn`,
+  `ComputationSpan::from_otel`). A computation names its parent rather than its
+  children, so each one can be registered as soon as its own span ends, on any node;
+  the nesting is read back by matching each `parentSpan` to a `span`.
+- `integrity-jsonld`: the computation context
+  (`urn:cid:bafkr4iduavib2lgjcmx5n4ydefbbc62ngyannzi566zv5fsozgbwwfw27u`,
+  `ig_computation_context_link`), which extends the common context with those
+  four terms. Only statements that use them reference it; every other
+  `ComputationRegistration` keeps the common context and its CID.
+
 ## [0.0.19] - 2026-10-16
 
 ### Added

integrity-jsonld/src/lib.rs

@@ -25,6 +25,20 @@ pub fn ig_common_context_link() -> String {
     format!("urn:cid:{cid}").trim_end().to_owned()
 }
 
+/// Returns the computation context link as a CID URN.
+///
+/// This context extends the IG common context with the `startTime`, `endTime`,
+/// `span` and `parentSpan` terms of a `ComputationRegistration`. Statements that
+/// use none of those terms keep the common context, so their CIDs are unchanged.
+///
+/// # Returns
+/// URN string in format `urn:cid:{cid}` for the computation context.
+pub fn ig_computation_context_link() -> String {
+    let cid: &'static str = "bafkr4iduavib2lgjcmx5n4ydefbbc62ngyannzi566zv5fsozgbwwfw27u";
+
+    format!("urn:cid:{cid}")
+}
+
 /// Computes RDFC CID for JSON-LD data.
 ///
 /// Converts JSON-LD to N-Quads, canonicalizes using URDNA2015, and computes a CID.

integrity-jsonld/src/loader.rs

@@ -136,8 +136,8 @@ mod tests {
                 .keys()
                 .filter(|k| k.starts_with("urn:cid:"))
                 .count(),
-            25,
-            "expected all 25 urn:cid: contexts to be embedded"
+            26,
+            "expected all 26 urn:cid: contexts to be embedded"
         );
 
         // A representative CID context (also returned by `ig_common_context_link`).

integrity-jsonld/static_contexts/cid/bafkr4iduavib2lgjcmx5n4ydefbbc62ngyannzi566zv5fsozgbwwfw27u

@@ -0,0 +1,28 @@
+{
+    "@context": [
+        "urn:cid:bafkr4icploa577ziqnb57jlpoj7l2hi5kgt3knxpdtunlttjd3q33zeqpy",
+        {
+            "@protected": true,
+
+            "startTime": {
+                "@id": "https://eqtylab.io/terms/startTime",
+                "@type": "http://www.w3.org/2001/XMLSchema#dateTime"
+            },
+
+            "endTime": {
+                "@id": "https://eqtylab.io/terms/endTime",
+                "@type": "http://www.w3.org/2001/XMLSchema#dateTime"
+            },
+
+            "span": {
+                "@id": "https://eqtylab.io/terms/span",
+                "@type": "@id"
+            },
+
+            "parentSpan": {
+                "@id": "https://eqtylab.io/terms/parentSpan",
+                "@type": "@id"
+            }
+        }
+    ]
+}

integrity-lineage-models/Cargo.toml

@@ -23,6 +23,7 @@ serde_jcs = "0.2.0"
 serde_json = "1.0"
 ssi = { version = "0.16", default-features = false, features = ["w3c", "ed25519", "secp256k1", "secp256r1"] }
 utoipa = { version = "3", features = ["axum_extras", "openapi_extensions"] }
+uuid = { version = "1.4", features = ["v5"] }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 blake3 = "1.5"