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   Why is there little usage of XML on the "visible Web"?

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  • To: <xml-dev@lists.xml.org>
  • Subject: Why is there little usage of XML on the "visible Web"?
  • From: "Costello, Roger L." <costello@mitre.org>
  • Date: Sun, 16 Jul 2006 09:06:53 -0400
  • Thread-index: Acao2LT1EgIcVtsRRgmNYjmMj0XqBw==
  • Thread-topic: Why is there little usage of XML on the "visible Web"?

Hi Folks,

 

DEFINITION - VISIBLE WEB

 

By “visible Web” I mean the portion of the Web that produces information intended for human consumption.  In particular, in this message I will focus on the portion of the Web that produces information to be consumed by humans via a browser. 

 

DEFINITION – HIDDEN WEB

 

The “hidden Web”, on the other hand, is the portion of the Web that produces the information intended to be consumed by machines (i.e., machine-to-machine interaction).

 

USING XML ON THE VISIBLE WEB VERSUS NOT USING XML ON THE VISIBLE WEB

 

Below are two examples to demonstrate what I mean by using XML on the visible Web versus not using XML on the visible Web. 

 

Note: I realize that XHTML is XML, but for this discussion when I refer to “XML” I am not referring to XHTML. 

 

EXAMPLE: USING XML ON THE VISIBLE WEB

 

Suppose that you have a Web site where you make available your grocery list to anyone with a browser.  “Using XML on the visible Web” means that you create an XML document that contains the raw grocery list, and a separate document (e.g., XSLT) which transforms the raw grocery list into a visually appealing form.  Here is grocery.xml:

 

<?xml version=“1.0”?> “

<?xml-stylesheet type=“text/xsl” href="“grocery.xsl”?>

<grocery-list>

    <fruit>Orange</fruit>

    <meat>Chicken</meat>

    <vegetable>Corn</vegetable>

</grocery-list>

 

Here is the URL to your grocery list resource:

 

    http://www.example.org/food/grocery-list

 

A browser client that issues this URL will receive grocery.xml, and then it will dynamically transform the XML into HTML using grocery.xsl 

 

Let’s imagine that grocery.xsl displays the grocery items as an unordered bulleted list, and so the XML is rendered by the browser like this:

 

  • Orange
  • Chicken
  • Corn

 

Your Web site is employing XML on the visible Web!

 

EXAMPLE: NOT USING XML ON THE VISIBLE WEB

 

Now let’s contrast the above example with not using XML on the visible Web, instead, using HTML.  A browser client that issues the above URL will receive from your Web site this HTML:

 

<HTML>

    <body>

        <ul>

            <li>Orange</li>

            <li>Chicken</li>

            <li>Corn</li>

        </ul>

    </body>

</HTML>

 

The browser immediately renders the HTML.  The same bulleted list shown above is displayed.

 

Your Web site is not employing XML on the visible Web!

 

ADVANTAGES OF USING XML ON THE VISIBLE WEB

 

1. The tags <grocery-list>, <fruit>, <meat>, <vegetable> are more “semantically rich” than the tags <ul> and <li>.  Thus, it seems plausible that a search tool could recognize that the above XML document is not relevant to a query for, say, orange cars.  But the search tool would not be able to recognize that the above HTML document is not relevant.  So, using XML on the visible Web has the potential to facilitate more accurate searches.

 

2. The job of styling the information is offloaded to the clients.  The Web server is relieved of the transformation burden and thus can potentially process more requests.

 

ASSERTION #1

 

There is little usage of XML on the visible Web.

 

Below are several assertions which attempt to explain why there is little usage of XML on the visible Web.

 

ASSERTION #2

 

There is not the necessary “critical mass” of browsers which support the styling of XML using either CSS or XSLT.

 

ASSERTION #3

 

Advantage 1 listed above is a myth, i.e., <grocery-list>, <fruit>, <meat>, <vegetable> is not more “semantically rich” than <ul> and <li>.  In fact, the opposite is the case.  The tags <ul> and <li> have clear semantics (i.e., an unordered list of items) that are understood by every browser on the planet.  Conversely,   <grocery-list>, <fruit>, <meat>, <vegetable> have vague semantics, are understood only by English-speaking people, and probably zero applications on the visible Web would be able to do anything useful with the tags or the data within the tags.

 

ASSERTION #4

 

Advantage 2 listed above is also an advantage of HTML, i.e., the data is contained in an HTML document and the presentation instructions are contained in a separate CSS document.

 

ASSERTION #5

 

XML is not appropriate for the visible Web.  XML will continue to have limited usage on the visible Web.  As Len Bullard says, “XML is plumbing”. 

 

ASSERTION #6

 

On the visible Web, HTML will continue to be the primary markup language for the foreseeable future.

 

QUESTION #1

 

Which assertions do you accept, and which do you reject?  For those assertions you reject, why?

 

QUESTION #2

 

Suppose that you are in charge of a Web (you control the funding of all the Web sites).  Would you issue this mandate to all the Web site developers: “All information on the visible Web must be in XML”?  If you would issue this mandate, why?

 

QUESTION #3

 

Do you think that XML should have a more prominent role on the visible Web?  If so, how would you stimulate greater usage of XML on the visible Web?

 

/Roger

 





 

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