Create a special purpose programming language, in XML, using state transitions

Hi Folks,

Occasionally I find that I need to create a special-purpose programming language, to be used to describe how to process XML documents.

In creating the language I would mimic other programming languages such as Java, e.g.,
	
	<if>
	    <condition>...</condition>
	<then>
	    <action>...</action>

and

	<while>
	    <condition>...</condition>
	<do>
	    <action>...</action>

Then I would write an interpreter (using XSLT) to interpret "programs" written in my new programming language.

However, I recently realized that there is another approach. This illustrates the approach:

<Machine>
    <TransitionRules>
        <Transition currentState="Number" read="0" write="0"
                            nextState=Number" />
        <Transition currentState="Number" read="1" write="1"
                            nextState=Number" />
        <Transition currentState="Number" read=" " write="0"
                            nextState=Halt" />
    </TransitionRules>
</Machine>

Instructions and algorithms are expressed using state transition rules.

The neat thing about this approach is:

(1) It is very regular. I don't need to invent a bunch of new elements, such as <if> and <while>.

(2) It is very powerful - it can express any algorithm [1]. 

(3) No need to constantly extend the language to support new features.

I was inspired to this approach after reading this fantastic article [2], which represents Turing Machines in XML. 

Have you created your own special purpose programming language, formatted as XML? If so, what approach did you take to create your language?

/Roger

[1] You may recognize that this is essentially a Turing machine. Turing machines are known to be capable of expressing any algorithm.

[2] See section 2 of:
http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=F9BABBA74FAEC3276C5DEBC8CC756775?doi=10.1.1.100.3032&rep=rep1&type=pdf