A single metadata (metadatum) is represented by a triple: a symbol representing the type, a symbol representing the key, and either a string or a list that represent the value.
The symbol depends on the metadata key type. The value also depends somehow on the key type: a set of values is represented as a list, all other values are represented by a string, even if it is a number.
The following table maps key types to symbols and to the type of the value representation.
Key Type Symbol Value
Credential CREDENTIAL string
EString EMPTY-STRING string
Identifier ZID string
IdentifierSet ZID-SET ListValue
Number NUMBER string
String STRING string
TagSet TAG-SET ListValue
Timestamp TIMESTAMP string
URL URL string
Word WORD string
Zettelmarkup ZETTELMARKUP string
ListValue = ( String1 String2 … Stringn ).
Examples:
The title of this zettel is represented as: (EMPTY-STRING title "Encoding of Sz Metadata")
The tags of this zettel are represented as: (TAG-SET tags ("#api" "#manual" "#reference" "#zettelstore"))