The data encoding represents the zettel as a special symbolic expression. In contrast to the similar-looking sz encoding, a much simpler structure is used.
If transferred via HTTP, the content type will be text/plain; charset=utf-8.
A full zettel, both metadata and content, is encoded by the list
(zettel Metadata Access rights Content encoding Content ).
If you only want to encode the metadata of a zettel, the following format will be used:
(list Metadata Access rights ).
Metadata
Metadata is basically a sequence of key / value pairs:
Metadata = (meta ( Key Value ) … ).
Key = Symbol.
Value = String.
Each Key is a symbol, derivied from the metadata key. The Value is a string containing the value of the corresponding metadata entry.
Access rights
This element encodes access rights of a zettel:
Access rights = (rights Number ).
Content encoding
The content encoding specifies, how the zettel content is encoded. Currently, two values are supported: the empty string and the string "base64".
Content encoding = (encoding "") | (encoding "base64").
The empty string indicates that the content is not encoded and can be used as is. "base64" indicates that the content string is Base64-encoded (typically used for binary content).
Content
The content of a zettel is always encoded as a readable string. For binary content, it is first encoded using Base64.
Content = (content String ).