Hi Folks,
I hold this to be the fundamental axiom of XML:
Make the structure of data explicit.
We accomplish that by adding a label (markup) to the data.
There are various terms for this notion of making the structure of data explicit: upconversion and uptranslation.
Elements with simple content and attributes are antithetical to the fundamental axiom of XML.
Here is an element with simple content and an attribute:
<Cost currency="USD">8.95</Cost>
The data USD is explicitly labeled. The label indicates that USD is a currency.
What about the data 8.95, is it labeled? No! It is anonymous/unlabeled. Note: Cost is
not the label for 8.95; Cost is the label for the whole package.
In my most recent post, I asked, “What is that number (8.95)?” I received excellent responses: 8.95 is a price, 8.95 is an amount, etc. External knowledge was needed to label the data. The need for
external knowledge completely contradicts the fundamental axiom of XML.
Therefore, don’t create XML like this:
<Cost currency="USD">8.95</Cost>
instead, create XML like this:
<Cost>
<Currency>USD</Currency>
<Amount>8.95</Amount>
</Cost>
Do you agree?
/Roger
