Analysis and Testing of Ajax-based Single-page Web Applications

client/server and network-based environments, can be of help in understanding
the essential components and architectural properties of Ajax-based web
applications. In such a context, a software architecture is defined (Perry and
Wolf, 1992; Fielding, 2000) by a configuration of architectural elements – processing,
connecting, and data – constrained in their relationships in order to
achieve a desired set of architectural properties.
Through such an understanding, we could gain a more abstract perspective
on the actual differences between the classical web model and the modern
Ajax-based settings. An abstract model would also enable us to anticipate the
tradeoffs between, e.g., interactivity and scalability, of adopting Ajax techniques.
Thus, our first main research question can be formulated as follows:
Research Question 1
What are the fundamental architectural differences and tradeoffs between
designing a classical and an Ajax-based web application? Can current
architectural styles describe Ajax? If not, can we propose an architectural
style taylored for Ajax?
An architectural style is defined by a coordinated set of architectural constraints
that restricts the roles of architectural elements and the allowed relationships
among those elements within any architecture that conforms to that
style (Fielding, 2000). Our hypothesis is that Ajax changes the web interaction
model so significantly that it cannot be fit into the existing architectural
styles, and hence requires its own architectural style.
1.3.2 Reengineering
Once an abstract perspective on the target model is gained, we focus on ways
classical web applications could be reengineered to Ajax settings.
Many organizations are beginning to consider migration, also known as
Ajaxification, possibilities of their web-based systems to this new paradigm.
Usually, significant investments have been made for classical web-based systems
and most organizations are not likely to throw these valuable assets away
to adopt a new emerging technology.
As a result, the well-known problems of software legacy renovation
(van Deursen et al., 1999) and migration (Brodie and Stonebraker, 1995) are
becoming increasingly important for web applications. If until a few years
ago, the problem revolved solely around migrating legacy desktop systems to
web-based settings, today we have a new challenge of reengineering classic
web applications to Ajax applications as well.
Our assumption is that a multi-page web application already exists, and
our intention is to explore techniques to support its comprehension, analysis,
and restructuring by recovering abstract models from the current implementation.
Chapter 1. Introduction 15