Separate the data model from presentation and make the data modelelement

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

Assertion: Accessing/manipulating element nodes is simpler, easier, and faster than accessing/manipulating text. An element-based data model is better suited to XML's strengths than is a text-based data model.

Proof by example:

Case 1: Retrieve "west"

Text-based data model:

	<edge>garden west door home</edge>

XPath to retrieve "west": 

	substring-before(substring-after(., ' '), ' ')

Element-based data model:

	<edge>
		<garden/>
		<west/>
		<door/>
		<home/>
	</edge>

XPath to retrieve "west": 

	*[2]/name()

Clearly, retrieving "west" in the element-based data model is simpler, easier, and faster.

Case 2: Retrieve a range of data items (2nd to 3rd data items)

Text-based data model:

	<edge>garden west door home</edge>

XPath to retrieve the desired range of data items: 

	tokenize(., ' ')[position() = (2,3)]

Element-based data model:

	<edge>
		<garden/>
		<west/>
		<door/>
		<home/>
	</edge>

XPath to retrieve the desired range of data items: 

	*[position() = (2,3)]/name()

Clearly, retrieving a range of data items in the element-based data model is simpler, easier, and faster.

Of course, at the point of presentation we will want to convert the element-based data model to a text-based data model. 

Recommendation: Separate the data model from presentation details and make data models element-based.

Let's take a dramatic example. Rather than this: 

        <living-room>
            you are in the living room.
            a wizard is snoring loudly on the couch.
        </living-room>

use this as your data model: 

        <living-room>
            <you/><are/><in/><the/><living-room./>
            <a/><wizard/><is/><snoring/><loudly/><on/><the/><couch./>
        </living-room>

and use the former only for presentation.

Do you agree?

/Roger