Programmatic WWW authoring

Kurt Nørmark ©
Department of Computer Science, Aalborg University,
Denmark

Abstract

Index References Contents		This is the presentation of the paper Programmatic WWW authoring using Scheme and LAML at the WWW2002 conference, Honolulu, USA, May 2002.

Where is Denmark?
Slide Note Contents Index
References 

Figure. The location of Denmark in Europe

Where is Aalborg?
Slide Note Contents Index
References 

Figure. The location of Aalborg in Denmark

Programmatic Authoring
Premises
Slide Note Contents Index
References 

  • Programmatic authoring of static documents

    • Derivation of a set of HTML documents from a single document source

  • Authoring of complex material

    • Material in several versions

    • Comprehensive linking

    • Multiple overlapping views

LAML is also oriented towards server dynamic pages calculated at document access time

Programmatic authoring
Slide Note Contents Index
References 

  • Document source language

    • A programming language

  • Program execution

    • Generates the underlying HTML pages

  • Abstraction

    • Document details can be encapsulated in functions

  • Automation

    • Routine tasks can be programmed in procedures

Authoring of complex web materials involves the same problems and solutions as development of non-trivial software

An example of programmatic authoring
Slide Note Contents Index
References 

Program: A very simple HTML document. 
<html>
   <head> 
     <title>This is the document title</title>
   </head>
   <body>
      <h1>Document title</h1>
      <p>Here is the first paragraph of the document</p>
      <p>The second paragraph has an <em>emphasized item</em>
         and a <b>bold face item</b>.
      </p>
   </body>
</html>

Program: The LAML counterpart. 
(load (string-append laml-dir "laml.scm"))
(style "simple-html4.01-transitional-validating")

(write-html '(raw prolog epilog)
 (html
  (head 
   (title "This is the document title")
   )

  (body 
   (h1 "Document title")

   (p "Here is the first paragraph of the document")

   (p "The second paragraph has an" (em "emphasized item")
      "and a" (b "bold face item")_".")
   ))
)

Program: An extended LAML counterpart. 
(load (string-append laml-dir "laml.scm"))
(style "simple-html4.01-transitional-validating")

(define (normark-url suffix)
 (string-append "http://www.cs.auc.dk/~normark/" suffix))

(define complex (even? (current-time)))

(write-html '(raw prolog epilog)
 (html
  (head 
   (title "This is the document title")
   )

  (body 
   (h1 "Document title")

   (if complex
       (p "A first paragraph with a link to" 
          (a 'href (normark-url "laml/") "LAML"))
       (p "Here is the first paragraph of the document"))

   (if complex
       (p "The second paragraph has a link to" 
          (a 'href (normark-url "scheme/") "the LAML software"))
       (p "The second paragraph has an" (em "emphasized item")
         "and a" (b "bold face item")_"."))

   (kn)
  )
 )
)

References

The HTML Mirrors
Mirroring of HTML (1)
Slide Note Contents Index
References 

Attributes are handled by simulated keyword parameters

Textual content is passed as quoted strings

There is white space between content strings unless explicitly suppressed

Program: An illustration of the most basic mirror rules of LAML. 
(a 'href "http:www11.org" 'target "main" "A link to" "WWW2002")

Program: The HTML counterpart. 
<a href = "http:www11.org" target = "main">A link to WWW2002</a>

Mirroring of HTML (2)
Slide Note Contents Index
References 

Instead of specifying where to add white space we tell where to suppress it

Program: Illustration of white space suppression. 
(p "Use" (kbd "HTML") _ ","  (kbd "XHTML") _ ","
    (kbd "XML")  _ ","  "or" (kbd "LAML") _ ".")

Program: The HTML counterpart. 
<p>
  Use <kbd>HTML</kbd>, <kbd>XHTML</kbd>, 
  <kbd>XML</kbd>, or <kbd>LAML</kbd>.
</p>

Mirroring of HTML (3)
Slide Note Contents Index
References 

Lists of contents and lists of attributes are processed recursively and spliced together with their context

Program: Passing of attribute lists and lists of textual contents. 
(body

    (ul 
      (map li (list "one" "two" "three")))
    
    (let ((attributes (list 'start "3"))
          (contents   (map li (list "one" "two" "three"))))
       (ol 'id "demo" contents attributes)))
  )
)

Program: The HTML counterpart. 
<body>
   <ul><li>one</li> <li>two</li> <li>three</li></ul>
    
   <ol id="demo" start="3"><li>one</li> <li>two</li> <li>three</li></ol>
</body>

Reference

Mirroring of HTML (4)
Slide Note Contents Index
References 

CSS attributes and HTML attributes are uniformly specified

CSS attributes are prefixed with css:

Program: Using CSS attributes together with HTML attributes. 
(em 'class "c1" 'css:background-color "yellow" "WWW2002")

Program: The HTML counterpart. 
<em class = "c1" style = "background-color: yellow;">WWW2002</em>

Properties of the HTML mirrors
Slide Note Contents Index
References 

An HTML mirror is automatically derived from a DTD

  • Well-formed and valid documents

    • Guaranties generation of well-formed and valid HTML documents

  • Structural document representation

    • The mirror functions return abstract syntax trees which can be rendered as 'HTML text'

  • HTML layout

    • Supports optional pretty printing of the resulting HTML code

  • Convenient rendering of reserved HTML characters

    • '<' and '>' are rendered as the corresponding character entities

Document styles
Document styles
Slide Note Contents Index
References 

LAML supports a number of domain specific languages called document styles

  • From a set of abstractions to a language

    • A coherent set of functions can be considered as a new language

  • Examples

    • Software manuals, questionnaires, lecture notes, course home pages, scientific papers

  • Example in the paper

    • A quiz style

It is attractive to bring the document styles as close as possible to XML

XML in LAML
Slide Note Contents Index
References 

It is attractive to mirror XML languages in Scheme along the same lines as HTML

  • Derived from a DTD

    • An XML mirror in Scheme can be produced almost automatically from a DTD

  • Validating

    • The mirror functions do full document validation 'on the fly'

  • Name spaces

    • Prepared to deal with overlapping name spaces at the Scheme level

  • Action procedures

    • Selected XML elements can be specified to initiate an action (transformation)

LENO: An XML-in-LAML example language
Slide Note Contents Index
References 		We here give an example of an XML-in-LAML language including a study of the concrete document representation

The document source of these slides is written in an XML-in-LAML language called LENO

  • Produces complex material

    • Heavily interlinked pages with multiple views of the materials

  • Multiple author interfaces

    • LENO supports both an original primitive Scheme interface, XML-in-LAML, and XML

  • Relatively mature

    • We have used LENO to produce E-learning material the last four years

For this presentation we have used the XML-in-LAML interface.

Program: The LAML document source of this page. 
(note-page 'id "xmlinlaml-leno"

  (title
   (main-text
    "LENO: An XML-in-LAML example language"
    )
   (annotation
    "We here give an example of an XML-in-LAML language including a 
     study of the concrete document representation"
    )
  )


  (point 'margin-top "4em"
   (main-text 
    "The document source of these slides is 
     written in an XML-in-LAML language called LENO"
    )
  )

  (items 'margin-bottom "4em"
   (item   
    (main-text (b "Produces complex material")
               )
    (items 
     (item   
      (main-text "Heavily interlinked pages with multiple views of the materials"
                 ))))

   (item   
    (main-text (b "Multiple author interfaces")
               )
    (items 
     (item   
      (main-text "LENO supports both an original primitive Scheme interface, 
                  XML-in-LAML, and XML")
      (annotation "For this presentation we have used the XML-in-LAML interface.")
      
   )))

   (item   
    (main-text (b "Relatively mature")
               )
    (items 
     (item   
      (main-text "We have used LENO to produce E-learning material 
                 the last four years"
                 )))))


  (source-program
   'src "www2002.laml"
   'from-mark "(note-page 'id \"xmlinlaml-leno\""
   'to-mark demo-end-mark
   'slide-mode "external"
   'book-mode "inline"
   (color-decorations
    (color-decoration 'from-mark "note-page" 'to-mark "" 'color "red" 'face "bold" )

    (color-decoration 'from-mark "title" 'to-mark "" 'color "blue" 'face "bold" )
    (color-decoration 'from-mark "point" 'to-mark "" 'color "blue" 'face "bold" 'repetition "1")
    (color-decoration 'from-mark "items" 'to-mark "" 'color "blue" 'face "bold" 'repetition "4")
    (color-decoration 'from-mark "source-program" 'to-mark "" 'color "blue" 'face "bold" )

    (color-decoration 'from-mark "item  " 'to-mark "" 'color "brown" 'face "bold" 'repetition "6")

    (color-decoration 'from-mark "main-text" 'to-mark "" 'color "brown" 'face "bold" 'repetition "10")
    (color-decoration 'from-mark "annotation" 'to-mark "" 'color "brown" 'face "bold" 'repetition "2")
   )
   (main-text
    "The LAML document source of this page" )
  )

) ; end xml-in-laml

Reflections and conclusions
Reflections
Slide Note Contents Index
References 

  • The programming paradigm

    • Good fit between functional programming and descriptive markup

    • Similar work is well-represented in the functional programming communities

    • Imperative programming is less attractive in a programmatic authoring context

  • Mixing fragments of markup and programs

    • Less powerful than a solution that involves a single linguistic framework

    • Aesthetically unpleasing

We have gone for inclusion of the less powerful language in the more powerful language

Conclusions
Slide Note Contents Index
References 

  • LAML usage

    • I have used LAML for all my generated documents and all server-side programs the last four years

    • LAML has been downloaded numerous times and used at least for educational purposes

  • The programming language Scheme

    • A Lisp language can deliver the necessary flexibility and power for support of programmatic authoring

LAML is available as free software from the LAML home page at http://www.cs.auc.dk/~normark/laml/

Collected references
Contents Index
The HTML rendering of the programmatic extension - complex
The HTML rendering of the programmatic extension - simple
The resulting HTML page

 

Programmatic WWW authoring
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