DSSSL

]> DSSSL DSSSL Document Style Semantics and Specification Language Used to Specify style sheets for SGML documents Why use DSSSL? SGML is machine readable SGML is not very human readable DSSSL serves to convert data in SGML into more readable form Some format it can convert to are RTF, HTML, Latex Major Components of DSSSL Style Language Flow Object Transformational Language Document Model Query Language Style Language Describes the formatting of SGML (XML) documents Based heavily on Scheme (both syntax and functionality) A "grove" is constructed from the SGML document which is formatted into a flow object by style rules. A processor then converts the tree to a document Style Language Examples


(element p 
    (make paragraph font-size: 12pt))

(element (ul li)
    (make paragraph ...))

(element empty
    (empty-sosofo))

(define four (+ 2 2))

Flow Objects Provide a mechanism for describing the layout of a document Pages, paragraphs, tables, image, etc Formatting specifications are contained within the construction rules


(make paragraph
    font-size: 12pt
    font-family-name: "Arial"
    ....)
(make sequence
    font-posture: 'italic
    ...)

Transformation Language Superset of the Expression language Used to transform one SGML document to another Allows for the creation and manipulation of document nodes Not widely used (and Jade doesn't even implement it) Document Model The Tree that gets generated from an SGML document The entire tree is known as a "grove" in the DSSSL world Elements, attributes, etc are nodes in the tree Query Language Used to select individual nodes from the grove Functions to access attributes, children, ancestors, etc Functions to retrieve a nodes position in the tree DSSSL vs XSL

DSSSL	XSL
Style Language	XSLT
Flow Object	XSL-FO
Transformation Language	XSLT
Document Model	XML Information Set
Query Language	XPath

Construction Rules DSSSL Documents consist mostly of construction rules Map elements in the source document to DSSSL flow objects Example: the para tag creates a new paragraph with a 12pt font


(element para
    (make paragraph
        font-size: 12pt))

Process Children (process-children) returns the tree that results from processing the children of a node The results are all linked to the root node Similar to "apply-templates" in XSLT Controlling Recursion Make a new paragraph containing the processed children (element para (make paragraph)) Make a paragraph containing "foo" and ignores para's children (element para (make paragraph (literal "foo"))) Make a paragraph containing the contents of the first title tag under the para


(element para 
    (make paragraph 
        (process-first-descendent "title")))

Modes Often you want different rules to apply to the same element depending on the context Table of contents for example Modes allow the specification of construction rules that only sometimes apply


(mode toc
    (element chapter ...)
    (element section ...)
    (element para (empty-sosofo)))
(element book
    (make sequence
        (with-mode toc (process-children))
        (process-children)))

Example: HTML Subset


(element html (make simple-page-sequence))

(element h1
    (make-paragraph
        font-weight: 'bold
        font-size: 20pt
        space-after: 10pt
        quadding: 'center))

(element p
    (make-paragraph
        font-size: 12pt
        quadding: 'start))

(element i
    (make sequence
        font-posture: 'italic))

Example: This presentation This presentation is generated from an XML document by DSSSL This slide looks something like


<slide type="normal">
  <title>Example: This presentation</title>
  <body>
    <item>This presentation is generated from 
          an XML document by DSSSL</item>
    <item>This slide looks something like</item>
    <code>
&lt;slide type="normal"&gt; ...
    </code>
  </body>
</slide>

Questions?