A new breed of web application, dubbed AJAX, is emerging in response to a
limited degree of interactivity in large-grain stateless Web interactions. At
the heart of this new approach lies a single page interaction model that
facilitates rich interactivity. We have studied and experimented with several
AJAX frameworks trying to understand their architectural properties. In this
paper, we summarize three of these frameworks and examine their properties and
introduce the SPIAR architectural style. We describe the guiding software
engineering principles and the constraints chosen to induce the desired
properties. The style emphasizes user interface component development, and
intermediary delta-communication between client/server components, to improve
user interactivity and ease of development. In addition, we use the concepts
and principles to discuss various open issues in AJAX frameworks and
application development.Comment: 2nd revision: references ordered, images resized, typo