The Law of Least Power

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

Hi Folks,

I would like to expand upon (generalize) something Michael Kay said [1] the other day.

An attribute is less powerful than an element. Attributes can't repeat, they have no order, and their values are simple strings whereas elements can repeat, they may or may not have a required order, and their values may be simple or complex.

A boolean type is less powerful than a string type. The value space of boolean is true, false, 0, 1 whereas the value space of string is virtually infinite.

Corollary: an attribute or element of type boolean is less powerful than an attribute or element of type string. 

A string type that is constrained to a maxLength of 10 is less powerful than a string type that is constrained to a maxLength of 20.

We could continue to state XML constructs that are less powerful than other XML constructs.

Now we state the law:

	The Law of Least Power

Use an XML construct that has all the power 
         you need and no more.

Comments?

/Roger

[1] http://lists.xml.org/archives/xml-dev/202202/msg00120.html