diff --git a/src/database/constants.rs b/src/database/constants.rs
index 8baae01..08cd6d7 100644
--- a/src/database/constants.rs
+++ b/src/database/constants.rs
@@ -1,15 +1,24 @@
 use crate::addressing::Address;
 use crate::database::entry::InvariantEntry;
 
+/// Attribute denoting (hierarchical) relation, in the upwards direction. For example, a file `OF` a group, an image `OF` photos, etc.
 pub const IS_OF_ATTR: &str = "OF";
+/// Attribute denoting that an entry belongs to the set relating to a given (hierarchical) relation.
+/// For example, a data blob may have a label entry, and to qualify that label within the context of belonging to a given hierarchical group, that label entry and the hierarchical entry will be linked with `BY`.
 pub const ATTR_BY_ATTR: &str = "BY";
 
+/// Attribute denoting a human readable label.
 pub const LABEL_ATTR: &str = "LBL";
+/// Attribute denoting the date & time an entity was noted in the database.
+/// (TODO: This info can be trivially derived from existing entry timestamps, while at the same time the "Introduction problem" is still open.)
 pub const ADDED_ATTR: &str = "ADDED";
 
+/// Attribute for cross-vault unambiguous referencing of non-hashable (e.g. UUID) entities.
+pub const KEY_ATTR: &str = "KEY";
+
 lazy_static! {
     pub static ref HIER_ROOT_INVARIANT: InvariantEntry = InvariantEntry {
-        attribute: String::from(IS_OF_ATTR),
+        attribute: String::from(KEY_ATTR),
         value: "HIER_ROOT".into(),
     };
     pub static ref HIER_ROOT_ADDR: Address = HIER_ROOT_INVARIANT.entity().unwrap();