Looking for a simple example of Transition Semantics
What do you mean by "transitional semantics"? If you mean structural operational semantics using transition systems, then maybe a good place to start is a good text on the semantics of programming languages, Examples: 


Winskel's Formal Semantics of Programming Languages. 
Hennessy's Semantics of Programming Languages.
Nielson &amp; Nielson's Semantics with Applications. 


I recommend ignoring denotational semantics for your task. 

Since the semantics of programming languages is really well-understood, most of the work in formalising DSLs usually comes from the domain-specific part of the language.