Web applications incorporate important business assets and offer a convenient way for
businesses to promote their services through the internet. Many of these web applica-
tions have evolved from simple HTML pages to complex applications that have a high
maintenance cost. This is due to the inherent characteristics of web applications, to
the fast internet evolution and to the pressing market which imposes short development
cycles and frequent modifications. In order to control the maintenance cost, quantita-
tive metrics and models for predicting web applications’ maintainability must be used.
Maintainability metrics and models can be useful for predicting maintenance cost, risky
components and can help in assessing and choosing between different software artifacts.
Since, web applications are different from traditional software systems, models and met-
rics for traditional systems can not be applied with confidence to web applications. Web
applications have special features such as hypertext structure, dynamic code generation
and heterogenousity that can not be captured by traditional and object-oriented metrics.
This research explores empirically the relationships between new UML design met-
rics based on Conallen’s extension for web applications and maintainability. UML web
design metrics are used to gauge whether the maintainability of a system can be im-
proved by comparing and correlating the results with different measures of maintain-
ability. We studied the relationship between our UML metrics and the following main-
tainability measures: Understandability Time (the time spent on understanding the soft-
ware artifact in order to complete the questionnaire), Modifiability Time(the time spent
on identifying places for modification and making those modifications on the software
artifact), LOC (absolute net value of the total number of lines added and deleted for com-
ponents in a class diagram), and nRev (total number of revisions for components in a class diagram). Our results gave an indication that there is a possibility for a relationship
to exist between our metrics and modifiability time. However, the results did not show
statistical significance on the effect of the metrics on understandability time. Our results
showed that there is a relationship between our metrics and LOC(Lines of Code). We
found that the following metrics NAssoc, NClientScriptsComp, NServerScriptsComp,
and CoupEntropy explained the effort measured by LOC(Lines of Code). We found that
NC, and CoupEntropy metrics explained the effort measured by nRev(Number of Revi-
sions). Our results give a first indication of the usefulness of the UML design metrics,
they show that there is a reasonable chance that useful prediction models can be built
from early UML design metrics
