1 SXML

SXML is a representation of XML elements using s-expressions. The following grammar describes the structure of SXML:

top		=		(*TOP* maybe-annotations        PI ...        comment ...        element)
element		=		(name maybe-annot-attributes child ...)
annot-attributes		=		(@ attribute ... maybe-annotations)
attribute		=		(name maybe-value maybe-annotations)
child		=		element
		|		character-data-string
		|		PI
		|		comment
		|		entity
PI		=		(*PI* pi-target       maybe-annotations       processing-instruction-content-string)
comment		=		(*COMMENT* comment-string)
entity		=		(*ENTITY* public-id-string system-id-string)
name		=		local-name
		|		exp-name
local-name		=		symbol conforming to XML Namespace recommendation
exp-name		=		symbol of the form namespace-id:local-name
namespace-id		=		URI-symbol
		|		user-ns-shortcut-symbol
namespaces		=		(*NAMESPACES* namespace-assoc ...)
namespace-assoc		=		(namespace-id uri-string maybe-original-prefix)
annotations		=		(@ maybe-namespaces annotation ...)
annotation		=		not yet specified

Refer to the original SXML specification for a more detailed explanation of the representation, including examples.

In short, an XML element is represented as a list consisting of its tag name as a symbol followed by its children nodes. If the XML element has attributes, they come immediately after the tag symbol, in a list tagged by an @ symbol.

For example, the XML element

<abc>def<ghi />jkl</abc>

is represented by the SXML datum

'(abc "def" (ghi) "jkl")

and the XML element

<customer specialness="gazonga">Barry White</customer>

is represented by the SXML datum

'(customer (@ (specialness "gazonga")) "Barry White")

That’s the easy part. Things get more icky when you start talking about documents and namespaces.