feat: partial references

References marked as partial are not concretized during model generation. The
should be managed by the user manually using propagation rules instead.

3 files changed, 12 insertions, 9 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext b/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
index ebb5bf71..10e994a0 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
+++ b/subprojects/language/src/main/java/tools/refinery/language/Problem.xtext
@@ -45,7 +45,7 @@ AggregatorDeclaration:
         "extern" "aggregator" name=Identifier ".";
 
 enum ReferenceKind:
-        REFERENCE="refers" | CONTAINMENT="contains" | CONTAINER="container";
+        REFERENCE="refers" | CONTAINMENT="contains" | CONTAINER="container" | PARTIAL="partial";
 
 ReferenceDeclaration:
         (referenceType=[Relation|NonContainmentQualifiedName] |
diff --git a/subprojects/language/src/main/java/tools/refinery/language/utils/ProblemUtil.java b/subprojects/language/src/main/java/tools/refinery/language/utils/ProblemUtil.java
index 9daa8f61..e1820261 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/utils/ProblemUtil.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/utils/ProblemUtil.java
@@ -42,13 +42,11 @@ public final class ProblemUtil {
         }
 
         public static boolean isImplicit(EObject eObject) {
-                if (eObject instanceof Node node) {
-                        return isImplicitNode(node);
-                } else if (eObject instanceof Variable variable) {
-                        return isImplicitVariable(variable);
-                } else {
-                        return false;
-                }
+                return switch (eObject) {
+                        case Node node -> isImplicitNode(node);
+                        case Variable variable -> isImplicitVariable(variable);
+                        default -> false;
+                };
         }
 
         public static boolean isError(EObject eObject) {
@@ -119,7 +117,7 @@ public final class ProblemUtil {
                         return false;
                 }
                 return switch (kind) {
-                        case CONTAINMENT -> false;
+                        case CONTAINMENT, PARTIAL -> false;
                         case CONTAINER -> true;
                         case DEFAULT, REFERENCE -> {
                                 var opposite = referenceDeclaration.getOpposite();
diff --git a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index 9f5fdeae..754572d1 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -318,6 +318,11 @@ public class ProblemValidator extends AbstractProblemValidator {
                                                 referenceDeclaration, ProblemPackage.Literals.REFERENCE_DECLARATION__OPPOSITE, 0,
                                                 INVALID_OPPOSITE_ISSUE);
                         }
+                } else if (kind == ReferenceKind.PARTIAL && opposite != null && opposite.getKind() != ReferenceKind.PARTIAL) {
+                        acceptError("Opposite '%s' of partial reference '%s' is not a partial reference."
+                                                        .formatted(opposite.getName(), referenceDeclaration.getName()),
+                                        referenceDeclaration, ProblemPackage.Literals.REFERENCE_DECLARATION__OPPOSITE, 0,
+                                        INVALID_OPPOSITE_ISSUE);
                 }
         }