Looks like Glimmer's wits regarding the distinction of static and dynamic parts of the template should be applicable to JST, HAML and the rest as well. The dynamic parts are clearly marked with template tags, and local (changed) variables would be easy to scan for within the dynamic parts of the code. This would probably mean that the template engine should decompose the template into smaller bits, and provide metadata by which the view can map DOM fragments to template fragments (DocumentFragment, DOMNode, DOMAttribute, TextNode) and related Model attributes. Attrubte-level change events could then either directly expire the relevant fragments, or the View onChange/render function would skip repainting the unchanged parts and use appropriate (previously decomposed) fragments of the template function to render changes.