diff --git a/src/database/constants.rs b/src/database/constants.rs
index ff51580..c535a8c 100644
--- a/src/database/constants.rs
+++ b/src/database/constants.rs
@@ -1,11 +1,13 @@
 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 (hierarchical) relation, in the "upwards" direction. For example, a file `IN` a group, an image `IN` photos, etc.
+pub const ATTR_IN: &str = "IN";
 /// 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";
+pub const ATTR_BY: &str = "BY";
+/// Attribute denoting that an attribute belongs to a given "tagging" entity. If an entity belongs to (`IN`) a "tagging" entity, it is expected to have attributes that are `OF` that entity.
+pub const ATTR_OF: &str = "OF";
 
 /// Attribute denoting a human readable label.
 pub const LABEL_ATTR: &str = "LBL";
diff --git a/src/database/hierarchies.rs b/src/database/hierarchies.rs
index aa31f19..1c70795 100644
--- a/src/database/hierarchies.rs
+++ b/src/database/hierarchies.rs
@@ -11,7 +11,7 @@ use crate::database::constants::LABEL_ATTR;
 use crate::database::entry::Entry;
 use crate::database::lang::{PatternQuery, Query, QueryComponent, QueryPart};
 
-use super::constants::{HIER_ROOT_ADDR, HIER_ROOT_INVARIANT, IS_OF_ATTR};
+use super::constants::{ATTR_IN, HIER_ROOT_ADDR, HIER_ROOT_INVARIANT};
 use super::UpEndConnection;
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
@@ -80,7 +80,7 @@ pub fn list_roots(connection: &UpEndConnection) -> Result<Vec<Address>> {
     Ok(connection
         .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
             entity: QueryComponent::Variable(None),
-            attribute: QueryComponent::Exact(IS_OF_ATTR.into()),
+            attribute: QueryComponent::Exact(ATTR_IN.into()),
             value: QueryComponent::Exact((*HIER_ROOT_ADDR).clone().into()),
         })))?
         .into_iter()
@@ -121,7 +121,7 @@ pub fn fetch_or_create_dir(
         Some(parent) => connection
             .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
                 entity: QueryComponent::Variable(None),
-                attribute: QueryComponent::Exact(IS_OF_ATTR.into()),
+                attribute: QueryComponent::Exact(ATTR_IN.into()),
                 value: QueryComponent::Exact(parent.into()),
             })))?
             .into_iter()
@@ -151,7 +151,7 @@ pub fn fetch_or_create_dir(
                 connection.insert_entry(if let Some(parent) = parent {
                     Entry {
                         entity: new_directory_address.clone(),
-                        attribute: String::from(IS_OF_ATTR),
+                        attribute: String::from(ATTR_IN),
                         value: parent.into(),
                         provenance: "SYSTEM FS".to_string(),
                         timestamp: chrono::Utc::now().naive_utc(),
@@ -159,7 +159,7 @@ pub fn fetch_or_create_dir(
                 } else {
                     Entry {
                         entity: new_directory_address.clone(),
-                        attribute: String::from(IS_OF_ATTR),
+                        attribute: String::from(ATTR_IN),
                         value: HIER_ROOT_ADDR.clone().into(),
                         provenance: "SYSTEM FS".to_string(),
                         timestamp: chrono::Utc::now().naive_utc(),
diff --git a/src/database/stores/fs/mod.rs b/src/database/stores/fs/mod.rs
index a42893f..66bd705 100644
--- a/src/database/stores/fs/mod.rs
+++ b/src/database/stores/fs/mod.rs
@@ -3,7 +3,7 @@ use self::db::files;
 use super::{Blob, StoreError, UpStore, UpdatePathOutcome};
 use crate::addressing::Address;
 use crate::database::constants::{
-    ADDED_ATTR, ATTR_BY_ATTR, IS_OF_ATTR, LABEL_ATTR, TYPE_HASH_ADDRESS,
+    ADDED_ATTR, ATTR_BY, ATTR_IN, ATTR_OF, LABEL_ATTR, TYPE_HASH_ADDRESS,
 };
 use crate::database::entry::Entry;
 use crate::database::hierarchies::{
@@ -110,13 +110,13 @@ impl FsStore {
         upend_insert_addr!(
             upconnection,
             Address::Attribute(FILE_SIZE_KEY.to_string()),
-            IS_OF_ATTR,
+            ATTR_OF,
             TYPE_HASH_ADDRESS
         )?;
         upend_insert_addr!(
             upconnection,
             Address::Attribute(FILE_MIME_KEY.to_string()),
-            IS_OF_ATTR,
+            ATTR_OF,
             TYPE_HASH_ADDRESS
         )?;
 
@@ -465,7 +465,7 @@ impl FsStore {
 
         let dir_has_entry = Entry {
             entity: blob_address.clone(),
-            attribute: IS_OF_ATTR.to_string(),
+            attribute: ATTR_IN.to_string(),
             value: parent_dir.clone().into(),
             provenance: "SYSTEM INIT".to_string(),
             timestamp: chrono::Utc::now().naive_utc(),
@@ -485,7 +485,7 @@ impl FsStore {
 
         let alias_entry = Entry {
             entity: dir_has_entry_addr,
-            attribute: ATTR_BY_ATTR.to_string(),
+            attribute: ATTR_BY.to_string(),
             value: label_entry_addr.into(),
             provenance: "SYSTEM INIT".to_string(),
             timestamp: chrono::Utc::now().naive_utc(),