linkml · cmungall · Jun 30, 2021 · Apr 2, 2021 · Jun 9, 2021 · Jun 30, 2021
diff --git a/model/schema/meta.yaml b/model/schema/meta.yaml
@@ -505,6 +505,21 @@ slots:
     range: boolean
     description: indicator that this is the root class in tree structures
 
+  unique_keys:
+    domain: class_definition
+    range: unique_key
+    multivalued: true
+    inlined: true
+    description: Set of unique keys for this slot
+    mappings:
+      - owl:hasKey
+
+  unique_key_slots:
+    domain: unique_key
+    multivalued: true
+    required: true
+    range: slot_definition
+    description: list of slot names that form a key
 
   # -----------------------------------
   # Slot definition slots
@@ -628,12 +643,12 @@ slots:
     range: boolean
     inherited: true
     description: >-
-      True means that the key slot(s) uniquely identify the container. In future releases, it will be possible for there
-      to be compound keys, where several slots combine to produce a unique identifier
+      True means that the key slot(s) uniquely identify the container.
     comments:
+      - see also 'unique_key'
       - key is inherited
       - a given domain can have at most one key slot (restriction to be removed in the future)
-      - identifiers and keys are mutually exclusive.  A given domain cannot have bot
+      - identifiers and keys are mutually exclusive.  A given domain cannot have both
       - a key slot is automatically required.  Keys cannot be optional
 
   identifier:
@@ -891,37 +906,43 @@ slots:
 # Classes                         #
 #==================================
 classes:
+  common_metadata:
+    description: Generic metadata shared across definitions
+    mixin: true
+    slots:
+      - description
+      - alt_descriptions
+      - deprecated
+      - todos
+      - notes
+      - comments
+      - examples
+      - in_subset
+      - from_schema
+          - imported_from
+      - see_also
+      - deprecated element has exact replacement
+      - deprecated element has possible replacement
+
   element:
     description: a named element in the model
     abstract: true
     mixins:
       - extensible
       - annotatable
+      - common_metadata
     slots:
       - name
       - id_prefixes
       - definition_uri
       - aliases
       - local_names
       - mappings
-      - description
-      - alt_descriptions
-      - deprecated
-      - todos
-      - notes
-      - comments
-      - examples
-      - in_subset
-      - from_schema
-      - imported_from
-      - see_also
       - exact mappings
       - close mappings
       - related mappings
       - narrow mappings
       - broad mappings
-      - deprecated element has exact replacement
-      - deprecated element has possible replacement
     see_also:
       - https://en.wikipedia.org/wiki/Data_element
 
@@ -1100,6 +1121,7 @@ classes:
     mixins:
       - extensible
       - annotatable
+      - common_metadata
     slot_usage:
       is_a:
         range: permissible_value
@@ -1109,18 +1131,14 @@ classes:
       - text
       - description
       - meaning
-      - alt_descriptions
-      - deprecated
-      - todos
-      - notes
-      - comments
-      - examples
-      - in_subset
-      - from_schema
-      - imported_from
-      - see_also
-      - deprecated element has exact replacement
-      - deprecated element has possible replacement
+
+  unique_key:
+    description: a collection of slots whose values uniquely identify an instance of a class
+    mixins:
+      - extensible
+      - annotatable
+    slots:
+      - unique_key_slots
 
 
 #==================================