Replace hkl with opaque identifiers for reflections (#506)

* Replace hkl with opaque identifiers for reflections

hkl are inadequate to identify reflections as twinning or incommensurate
structures will cause them to be repeated.

cif_core.dic

@@ -10,7 +10,7 @@ data_CIF_CORE
     _dictionary.title             CIF_CORE
     _dictionary.class             Instance
     _dictionary.version           3.3.0
-    _dictionary.date              2024-10-21
+    _dictionary.date              2024-11-12
     _dictionary.uri
         https://raw.githubusercontent.com/COMCIFS/cif_core/master/cif_core.dic
     _dictionary.ddl_conformance   4.2.0
@@ -3532,7 +3532,7 @@ save_DIFFRN_REFLN
 ;
     _name.category_id             DIFFRN
     _name.object_id               DIFFRN_REFLN
-    _category_key.name            '_diffrn_refln.hkl'
+    _category_key.name            '_diffrn_refln.id'
 
 save_
 
@@ -3889,6 +3889,26 @@ save_diffrn_refln.hkl
 
 save_
 
+save_diffrn_refln.id
+
+    _definition.id                '_diffrn_refln.id'
+    _definition.update            2024-11-12
+    _description.text
+;
+    _diffrn_refln.id must uniquely identify the reflection.
+
+    Note that this item need not be a number; it can be any unique
+    identifier.
+;
+    _name.category_id             diffrn_refln
+    _name.object_id               id
+    _type.purpose                 Key
+    _type.source                  Assigned
+    _type.container               Single
+    _type.contents                Word
+
+save_
+
 save_diffrn_refln.index_h
 
     _definition.id                '_diffrn_refln.index_h'
@@ -5842,20 +5862,15 @@ save_REFLN
     _definition.id                REFLN
     _definition.scope             Category
     _definition.class             Loop
-    _definition.update            2021-06-29
+    _definition.update            2024-11-12
     _description.text
 ;
     The CATEGORY of data items used to describe the reflection data
     used in the refinement of a crystallographic structure model.
 ;
     _name.category_id             DIFFRACTION
     _name.object_id               REFLN
-
-    loop_
-      _category_key.name
-         '_refln.index_h'
-         '_refln.index_k'
-         '_refln.index_l'
+    _category_key.name            '_refln.id'
 
 save_
 
@@ -6547,6 +6562,26 @@ save_refln.hkl
 
 save_
 
+save_refln.id
+
+    _definition.id                '_refln.id'
+    _definition.update            2024-11-12
+    _description.text
+;
+    _refln.id must uniquely identify the reflection.
+
+    Note that this item need not be a number; it can be any unique
+    identifier.
+;
+    _name.category_id             refln
+    _name.object_id               id
+    _type.purpose                 Key
+    _type.source                  Assigned
+    _type.container               Single
+    _type.contents                Word
+
+save_
+
 save_refln.include_status
 
     _definition.id                '_refln.include_status'
@@ -27961,7 +27996,7 @@ save_
        Changed the purpose of the _diffrn_radiation_wavelength.id data item
        from 'Encode' to 'Key'.
 ;
-         3.3.0                    2024-10-21
+         3.3.0                    2024-11-12
 ;
        # Please update the date above and describe the change below until
        # ready for the next release
@@ -28049,4 +28084,6 @@ save_
 
        Added the _audit_support.funding_organization_url and
        _audit_support.special_details data items.
+
+       Added opaque identifiers for diffrn_refln and refln categories.
 ;