refactor(language): module and node declarations

* New default file extension: .refinery (.problem is also supported).
* Add module keyword for self-contained modules.
* Rename indiv declarations to atom declaration.
* Add node and multi declarations for explicitly declared nodes and
  multi-objects, respectively.

1 files changed, 8 insertions, 5 deletions

diff --git a/subprojects/frontend/src/language/problem.grammar b/subprojects/frontend/src/language/problem.grammar
index ce3baa02..b08a9c36 100644
--- a/subprojects/frontend/src/language/problem.grammar
+++ b/subprojects/frontend/src/language/problem.grammar
@@ -28,7 +28,7 @@ statement {
     (":" Expr)? "."
   } |
   ProblemDeclaration {
-    kw<"problem"> QualifiedName "."
+    (ckw<"module"> | kw<"problem">) QualifiedName "."
   } |
   ClassDefinition {
     kw<"abstract">? kw<"class"> RelationName
@@ -37,7 +37,7 @@ statement {
   } |
   EnumDefinition {
     kw<"enum"> RelationName
-    (EnumBody { "{" sep<",", IndividualNodeName> "}" } | ".")
+    (EnumBody { "{" sep<",", AtomNodeName> "}" } | ".")
   } |
   PredicateDefinition {
     (
@@ -56,8 +56,11 @@ statement {
   //  RuleName ParameterList<Parameter>?
   //  RuleBody { ":" sep<OrOp, Conjunction> "==>" sep<OrOp, Consequent> "." }
   //} |
-  IndividualDeclaration {
-    kw<"indiv"> sep<",", IndividualNodeName> "."
+  AtomDeclaration {
+    ckw<"atom"> sep<",", AtomNodeName> "."
+  } |
+  NodeDeclaration {
+    (ckw<"node"> | ckw<"multi">) sep<",", NodeName> "."
   } |
   ScopeDeclaration {
     kw<"scope"> sep<",", ScopeElement> "."
@@ -161,7 +164,7 @@ RelationName { QualifiedName ~name }
 
 //RuleName { QualifiedName }
 
-IndividualNodeName { QualifiedName }
+AtomNodeName { QualifiedName }
 
 VariableName[@dynamicPrecedence=10] { QualifiedName ~name }