+
+/** @brief The tracks database
+ * - Keys are UTF-8(NFC(unicode(path name)))
+ * - Values are encoded key-value pairs
+ * - Data is reconstructable data about tracks that currently exist
+ */
+DB *trackdb_tracksdb;
+
+/** @brief The preferences database
+ *
+ * - Keys are UTF-8(NFC(unicode(path name)))
+ * - Values are encoded key-value pairs
+ * - Data is user data about tracks (that might not exist any more)
+ * and cannot be reconstructed
+ */
+DB *trackdb_prefsdb;
+
+/** @brief The search database
+ *
+ * - Keys are UTF-8(NFKC(casefold(search term)))
+ * - Values are UTF-8(NFC(unicode(path name)))
+ * - There can be more than one value per key
+ * - Presence of key,value means that path matches the search terms
+ * - Only tracks fond in @ref tracks_tracksdb are represented here
+ * - This database can be reconstructed, it contains no user data
+ */
+DB *trackdb_searchdb;
+
+/** @brief The tags database
+ *
+ * - Keys are UTF-8(NFKC(casefold(tag)))
+ * - Values are UTF-8(NFC(unicode(path name)))
+ * - There can be more than one value per key
+ * - Presence of key,value means that path matches the tag
+ * - This is always in sync with the tags preference
+ * - This database can be reconstructed, it contains no user data
+ */