Terence John Parr. Enforcing strict model-view separation in template engines. In Stuart I. Feldman, Mike Uretsky, Marc Najork, Craig E. Wills, editors, Proceedings of the 13th international conference on World Wide Web, WWW 2004, New York, NY, USA, May 17-20, 2004. pages 224-233, ACM, 2004. [doi]
The mantra of every experienced web application developer is the same: thou shalt separate business logic from display. Ironically, almost all template engines allow violation of this separation principle, which is the very impetus for HTML template engine development. This situation is due mostly to a lack of formal definition of separation and fear that enforcing separation emasculates a template’s power. I show that not only is strict separation a worthy design principle, but that we can enforce separation while providing a potent template engine. I demonstrate my StringTemplate engine, used to build jGuru.com and other commercial sites, at work solving some nontrivial generational tasks.My goal is to formalize the study of template engines, thus, providing a common nomenclature, a means of classifying template generational power, and a way to leverage interesting results from formal language theory. I classify three types of restricted templates analogous to Chomsky’s type 1..3 grammar classes and formally define separation including the rules that embody separation.Because this paper provides a clear definition of model-view separation, template engine designers may no longer blindly claim enforcement of separation. Moreover, given theoretical arguments and empirical evidence, programmers no longer have an excuse to entangle model and view.