4. SXML format

In xsltproc mode (XSLT), XML data is represented as a tree of C structures. In guile mode (Scheme), the same data is automatically represented using SXML format.

From the SXML specification:

SXML is an abstract syntax tree of an XML document. SXML is also a concrete representation of the XML Infoset in the form of S-expressions. The generic tree structure of SXML lends itself to a compact library of combinators for querying and transforming SXML.

Example 2. Simple document in XML format

<article id="hw"> 
  <para>Hello <object>World</object>!</para> 

Example 3. Simple document in SXML format

(article (@ (id "hw"))
  (title "Hello")
  (para  "Hello " (object "World") "!"))

XSieve supports all features of the SXML specification except

4.1. Entities in SXML

The SXML format doesn't support unexpanded entities. Sometimes it is a serious limitation. To break the limitation, XSieve uses a dialect of SXML that is SXML plus a special & form. The form is borrowed from HtmlPrag, a permissive HTML parsing library by Neil W. Van Dyke.

Example 4. Unexpanded entities in XML and SXML




(*TOP* (x (& product) (& nbsp) (& mdash)))

The second element of the & form can be a string, symbol, or (for character ordinal values) a nonnegative integer.

Example 5. & forms

(& "rArr")
(& rArr)
(& 151)