title: SHTML Encoding
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
back: 00001004051200 00001012920500
backward: 00001004051200 00001012920500
box-number: 1
copyright: (c) 2020-present by Detlef Stern <ds@zettelstore.de>
created: 20230316181044
forward: 00001012920510 00001012920516 00001012930000
lang: en
license: EUPL-1.2-or-later
modified: 20230403150657
published: 20230403150657
visibility: public

A zettel representation that is a [[s-expression|00001012930000]], syntactically similar to the [[Sz encoding|00001012920516]], but denotes [[HTML|00001012920510]] semantics.
It is derived from a XML encoding in s-expressions, called [[SXML|https://en.wikipedia.org/wiki/SXML]].

It is (relatively) easy to parse and contains everything to transform it into real HTML.
In contrast to HTML, SHTML is easier to parse and to manipulate.
For example, take a look at the SHTML encoding of this page, which is available via the ""Info"" sub-page of this zettel:
* [[/z/00001012920525?enc=shtml&part=zettel|//z/00001012920525?enc=shtml&part=zettel]],
* [[/z/00001012920525?enc=shtml&part=meta|//z/00001012920525?enc=shtml&part=meta]],
* [[/z/00001012920525?enc=shtml&part=content|//z/00001012920525?enc=shtml&part=content]].
If transferred via HTTP, the content type will be ''text/plain''.

Internally, if a zettel should be transformed into HTML, the zettel is translated into the [[Sz encoding|00001012920516]], which is transformed into this SHTML encoding to produce the [[HTML encoding|00001012920510]].
=== Syntax of SHTML
There are only two types of elements: atoms and lists, similar to the Sz encoding.

A list always starts with the left parenthesis (""''(''"", U+0028) and ends with a right parenthesis (""'')''"", U+0029).
A list may contain a possibly empty sequence of elements, i.e. lists and / or atoms.
Before the last element of a list of at least to elements, a full stop character (""''.''"", U+002E) signal a pair as the last two elements.
This allows a more space economic storage of data.

An HTML tag like ``< a href="link">Text</a>`` is encoded in SHTML with a list, where the first element is a symbol named a the tag.
The second element is an optional encoding of the tag's attributes.
Further elements are either other tag encodings or a string.
The above tag is encoded as ``(a (@ (href . "link")) "Text")``.
Also possible is to encode the attribute without pairs: ``(a (@ (href "link")) "Text")`` (note the missing full stop character).