feat(runtime): evaluate the unbounded value * and elem.metadata

api/proto/sysml.proto

@@ -700,6 +700,10 @@ message Value {
     Vector vector = 13;         // numeric components, never a sequence
     VectorQuantity vector_quantity = 14; // components each with their unit
     MeasurementRef measurement_ref = 15; // a unit by itself, no magnitude
+    // The unbounded value `*`, which is no number and no string: ordered above
+    // every finite magnitude and refused by arithmetic. Always true when set,
+    // as DocumentValue.infinity is.
+    bool infinity = 16;
   }
 }
 

changes/unreleased/infinity-and-metadata-values.added.md

@@ -0,0 +1,9 @@
+- **`*` is a value.** In an expression position `*` evaluates to the unbounded value: it exceeds
+  every finite Integer, Real and Natural, equals itself, prints as `*` in the REPL and in traces,
+  and crosses gRPC on its own `Value.infinity` arm under the `infinity_value` capability — never
+  as the ordinary string `"*"`. Arithmetic over it is refused with a typed error naming the
+  operation rather than an infinity or a NaN.
+- **`elem.metadata` reads an element's metadata.** `ref.metadata` yields the metadata annotating
+  the element as a sequence of metadata instances, in declaration order, with the feature values
+  the annotation body binds and the metadata type's own defaults where it binds none. An element
+  with no metadata yields the empty sequence, and reading metadata off a value is a typed error.

clients/java/opensysml-client/src/main/java/org/openmbee/opensysml/Capabilities.java

@@ -47,6 +47,9 @@ public final class Capabilities {
   /** A bare measurement unit ({@code SI::m}, {@code m / s}) travels as itself rather than as an unsupported null. */
   public static final String MEASUREMENT_REFS = "measurement_refs";
 
+  /** The unbounded value {@code *} travels as itself rather than as an unsupported null. */
+  public static final String INFINITY_VALUE = "infinity_value";
+
   /** The {@code ApplyEdits} RPC edits a parsed model's own source. */
   public static final String APPLY_EDITS = "apply_edits";
 

clients/java/opensysml-client/src/main/java/org/openmbee/opensysml/Value.java

@@ -67,6 +67,14 @@ record NullValue() implements Value {}
    */
   record UnsetValue() implements Value {}
 
+  /**
+   * The unbounded value {@code *}: no number, ordered above every finite magnitude.
+   *
+   * <p>Only a service advertising the {@code infinity_value} capability reports it as itself rather
+   * than as an unsupported {@link NullValue}.
+   */
+  record InfinityValue() implements Value {}
+
   /**
    * A reference to a runtime instance, by the id the service assigned it.
    *

clients/java/opensysml-client/src/main/java/org/openmbee/opensysml/internal/Protos.java

@@ -54,6 +54,7 @@ public static Optional<Value> value(org.openmbee.opensysml.proto.Value value) {
       case QUANTITY -> Optional.of(new Value.QuantityValue(quantity(value.getQuantity())));
       case ENUM_LITERAL -> Optional.of(new Value.EnumerationValue(literal(value.getEnumLiteral())));
       case UNSET -> Optional.of(new Value.UnsetValue());
+      case INFINITY -> Optional.of(infinity(value));
       case ARRAY -> Optional.of(array(value.getArray()));
       case VECTOR -> Optional.of(vector(value.getVector()));
       case VECTOR_QUANTITY -> Optional.of(vectorQuantity(value.getVectorQuantity()));
@@ -62,6 +63,17 @@ public static Optional<Value> value(org.openmbee.opensysml.proto.Value value) {
     };
   }
 
+  /** Only an asserted arm carries the unbounded value. */
+  private static Value infinity(org.openmbee.opensysml.proto.Value value) {
+    if (!value.getInfinity()) {
+      throw new TransportException(
+          "the service answered a malformed value: the infinity arm states no value unless it is"
+              + " true",
+          null);
+    }
+    return new Value.InfinityValue();
+  }
+
   private static Value array(org.openmbee.opensysml.proto.Array array) {
     List<Value> elements = new ArrayList<>(array.getElementsCount());
     for (org.openmbee.opensysml.proto.Value element : array.getElementsList()) {