Why the name of a element can not start with a digital letters?

[SutterCreek]

I know the w3c recommendation has the defination about that.
But, I am just curious, where does this restriction come from? What is
the purpose?

Thanks in advance.

 

[Peter Flynn]

I know the w3c recommendation has the defination about that.
But, I am just curious, where does this restriction come from? What is
the purpose?

It's inherited from SGML, where it was the default.
In SGML, however, it would be possible to redefine your SGML Declaration
to allow digits as name start characters. In XML, the Declaration is
fixed and invariable, so you can't.

///Peter