All supported metadata keys conform to a type.
User-defined metadata keys conform also to a type, based on the suffix of the key.
Suffix Type
-date Timestamp
-number Number
-role Word
-time Timestamp
-title Zettelmarkup
-url URL
-zettel Identifier
-zid Identifier
-zids IdentifierSet
any other suffix EString
The name of the metadata key is bound to the key type
Every key type has an associated validation rule to check values of the given type. There is also a rule how values are matched, e.g. against a search value when selecting some zettel. And there is a rule how values compare for sorting.
Credential
EString
Identifier
IdentifierSet
Number
String
TagSet
Timestamp
URL
Word
Zettelmarkup