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Software maintainability is one of the most important aspects when evaluating the quality of a software product. It is defined as the ease with which the existing software can be modified. In the literature, several researchers have proposed a large number of models to measure and predict maintainability throughout different phases of the Software Development Life Cycle. However, only a few attempts have been made for conducting a comparative study of the existent proposed prediction models. In this paper, we present a detailed classification and conduct a comparative analysis of Object-Oriented software maintainability prediction models. Furthermore, we considered the aforementioned proposed models from three perspectives, which are architecture, design and code levels. To the best of our knowledge, such an analysis that comprises the three levels has not been conducted in previous research. Moreover, this study hints at certain fundamental basics concerning the way of how measure the maintainability knowing that at each level the maintainability will be measured differently. In addition, we will focus on the strengths and weaknesses of these models. Consequently, the comparative study yields that several statistical and machine learning techniques have been employed for software maintainability prediction at code level during the last decade, and each technique possesses its specific characteristic to develop an accurate prediction model. At the design level, the majority of the prediction models measured maintainability according to the characteristics of the quality models. Whereas at the architectural level, the techniques adopted are still limited and only a few of studies have been conducted in this regard.
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Comparative Analysis of Object-Oriented Software
Maintainability Prediction Models
Narimane Zighed*, Nora Bounour *, Abdelhak-Djamel Seriai +
Abstract. Software maintainability is one of the most important aspects when evaluating
the quality of a software product. It is defined as the ease with which the existing software
can be modified. In the literature, several researchers have proposed a large number of models
to measure and predict maintainability throughout different phases of the Software
Development Life Cycle. However, only a few attempts have been made for conducting a
comparative study of the existent proposed prediction models. In this paper, we present a
detailed classification and conduct a comparative analysis of Object-Oriented software
maintainability prediction models. Furthermore, we considered the aforementioned proposed
models from three perspectives, which are architecture, design and code levels. To the best of
our knowledge, such an analysis that comprises the three levels has not been conducted in
previous research. Moreover, this study hints at certain fundamental basics concerning the
way of how measure the maintainability knowing that at each level the maintainability will
be measured differently. In addition, we will focus on the strengths and weaknesses of these
models. Consequently, the comparative study yields that several statistical and machine
learning techniques have been employed for software maintainability prediction at code level
during the last decade, and each technique possesses its specific characteristic to develop an
accurate prediction model. At the design level, the majority of the prediction models
measured maintainability according to the characteristics of the quality models. Whereas at
the architectural level, the techniques adopted are still limited and only a few of studies have
been conducted in this regard.
Keywords: Metrics; Maintainability Prediction; Object-Oriented Software; Quality
Model, Prediction Model.
1. Introduction
Software maintenance is one of the essential phases of Software Development Life Cycle
process “SDLC”. Defects introduced at this stage are the most dangerous compared to those
Badji Mokhtar University, Annaba, Algeria,
Badji Mokhtar University, Annaba, Algeria,
+ Montpellier University, Montpellier, France,
Vol. 43 (2018) No. 4
ISSN 0867-6356
e-ISSN 2300-3405DOI: 10.1515/fcds-2018-0018
which could be introduced at the other phases of software development cycle [26].
Maintenance activities start from the moment when a system comes into operation and
continues for the remainder of the product's life. Thus, according to the past studies, they
have found that for some products this can last twenty years on average, unlike the
development phase which can last from one to two years [19]. In addition, the time spent and
effort required to correct defects in this phase consumes about 40 to 70% of the cost of the
entire life cycle [21].
Therefore, McCall model which is one of the important and oldest software quality
models has cited maintainability as one of a total of eleven factors, these factors are broken
down by the 3 perspectives: product revision (maintainability, testability and flexibility),
product transition (portability, reusability, and interoperability), product operations
(correctness, reliability, efficiency, integrity, usability) [1]. Where the quality factor
maintainability would have criteria of simplicity, conciseness, and modularity as sub-
characteristics [33].
Several definitions for "software maintainability" have been considered. According to
Standard Glossary of Software Engineering IEEE it is defined as “the ease with which a
software system or component can be modified” [15]. In some studies, it has been defined as
“number of lines of code changed” [22], [24], [30], [31], [35], [36], [12], [37]. In other works,
maintainability has been defined as the time required to make changes, and time to
understand, develop and implement a modification [29].
A maintainability prediction model is used to estimate maintenance effort of systems
using some information about it and a preselected technique for developing this model. When
we talk about making prediction at code level often, we measure the maintainability by
number of lines of code changed. Although at design level maintainability prediction is based
on quality models’ factors like understandability, modifiability, extendibility and
flexibility...Etc. But for the architecture level, the maintainability is measured by estimating
the effort of change.
A good predictive model of software maintainability allows organizations to efficiently
manage their maintenance resources and also guide decision-making related to software
maintenance. Which can help further to reduce maintenance effort and hence they can
minimize the overall effort and cost of the software project [23].
In the literature, many researchers have experimented different models to predict software
maintainability, whether at the code level or at the more abstract level as design and
architecture levels. Most of these models were proposed in the code level while a few models
were proposed at design and architecture levels (see Figure.1).
In this paper, we have considered the most important techniques proposed to predict
Object-Oriented software maintainability. We focus on a classification of these models and
we highlight the main difference between them. Then a comparative analysis is conducted to
detail all the result obtained. Unlike [11], [25] which discuss the use of prediction techniques
and compared the proposed models. In this paper we focus on the way of how the
maintainability was predicted at different levels. However, no comparative analysis has been
published previously which including code, design and architecture levels.
The remainder of this paper is organized as follows: section 2 gives a categorization of
models used for predicting Object-Oriented software maintainability. The comparative
analysis of the different models and discussion are detailed in Section 3. Finally, Section 4
concludes the work and states the possible future work.
N. Zighed, N. Bounour, A-D. Seriai
2. Maintainability prediction models
Various studies have been conducted and proposed in the literature for predicting software
maintainability. We categorize these works according to the abstraction level exploited by
the model. We distinguish three levels: architecture, design and code level. In Figure.1, we
represent the number of papers submitted in each stage of SDLC within a period of time. The
papers that are classified in figure 1, they are published in journals, conferences and others
which include book chapters, technical reports, white papers, symposium. The important
journals were selected depending to the impact factor while conferences were identified
according to the international repute that address issues in the field of software maintenance.
We restricted our search to the period from 1993 to 2017 and the search strategy were
developed according to the following steps:
1) Derive major search strings from the research questions
2) Use Boolean OR to construct search strings from the search terms with similar meanings.
Use Boolean AND to concatenate the search terms and restrict the research.
3) The resulting were the keywords given bellow: (maintainability prediction OR effort
maintainability prediction OR software maintainability estimation) AND (machine learning
techniques OR regression techniques OR methods) AND (Object Oriented metrics) AND
(code and design and architecture)
Figure 1. Distribution of papers submitted for maintainability prediction
from different perspective
The most obvious from the graph is that few works have been proposed in early stages:
architecture and design, also we noticed that most studies have treated the prediction of
maintainability at code level. In the next sections, we will represent the most important
models in each level.
Comparative Analysis of Object-Oriented Software Maintainability ...
2.1. Prediction models at architectural level
Software architecture is one such a key artifact which can be used in early maintenance
prediction. According to Bass [7] “the software architecture of a program or computing
system is the structure of the system, which comprise software elements, the externally
visible properties of those elements, and the relationships among them”. Among the
important recent works that dealt with maintainability prediction using software architecture
the studies that were led by Anwar and al in [5], [6] and Bengeston and al in [9], the proposed
approach has several inputs: architecture specification, engineer expertise, maintenance data
history. The authors developed a probability-based approach. They estimated " maintenance
effort " at the software architecture level using the scenario profiles.
The first step was to identify the different change scenarios that can be encountered during
the maintenance phase. Once the growth scenario profile is developed, the next step was to
classify scenarios based upon their complexity levels (Simple, Average, Complex), then each
scenario is assigned a certain probabilistic weight. The weight measure of the scenario is
defined as relative probability during a specific time interval; the weights are assigned based
upon historical maintenance data. If no historical maintenance data is available then domain
expert or software architect estimates the scenario weight. Once the change impact analysis
has been performed, it is possible to predict the maintenance effort according to a proposed
mathematic formula. We clearly perceive that the approach proposed in [5, 6] is inspired by
the one that was presented in [9].
2.2. Prediction models at design level
The software design of an application has a considerable effect on quality factors such as
maintainability. Using software design to quantify some quality factors will help
organizations to plan resources accordingly. In terms of prediction, some techniques are
available for the software engineer’s community to predict system maintainability at the
design level.
In a series of studies [14-15], Marcela Genero investigates the possibility of the use
structural complexity and size metrics as good predictors of maintainability by constructing
maintainability prediction models based on metrics of UML class diagrams. In 2003 she
developed four models which relate the size and structural complexity metrics of UML class
diagrams with maintainability measures like understandability time, modifiability time,
modifiability completeness, modifiability correctness. In these models, she defined
modifiability and understandability as maintainability’s sub-characteristics. The metrics from
this model can be used for software maintainability prediction resolutions. In order to test her
hypothesis, she used Multivariate Linear technique which is commonly used, it allows to
figure out the relationship between dependent and independent variables. The results
achieved have an accurate prediction.
In another study Kiewkanya and al [20] proposed a methodology for constructing
maintainability model of Object-Oriented System by using two concepts understandability
and modifiability. They carried out a controlled experiment with undergraduate students, with
the purpose of building models for the maintenance level (easy, medium and difficult). These
models are developed by using three different techniques and were based on measurement
values calculated from UML class diagrams and sequence diagrams. The first maintainability
model used the metrics-based discriminant technique which analyzed the pattern of
N. Zighed, N. Bounour, A-D. Seriai
correlation between maintainability levels and structural complexity design metrics. The
second model was built using the weighted-score-level technique by taking a weighted sum
of understandability and modifiability scores. The third model was proposed using the
weighted-predicted-level technique that uses a weighted sum of predicted understandability
and modifiability levels, obtained by applying understandability and modifiability models.
However, a comprehensive set of examination questions were required to capture
understandability and modifiability score for each software design model. Further, those
scores might suffer from subjectivity due to different levels of understanding and of subjects
in the experiments.
In 2010, in a research conducted by Rizvi and Khan [29], the authors carried out an
empirical study which investigated the relation between the software maintainability of the
class diagram and his Understandability and Modifiability. They found that
Understandability and modifiability are strongly correlated with maintainability and can
therefore be used as good predictors of maintainability of software. Then a prediction model
was developed to predict the maintainability of a class diagram in terms of the
Understandability and the modifiability of these classes by using a multiple (multivariate)
regression method. The study involved values of understandability, modifiability,
maintainability and eleven measures of size and structural complexity previously collected
by controlled experiments on 28 class diagrams. They applied a multivariate linear regression
to construct models to estimate the comprehensibility and modifiability of class diagrams
using the eleven measurements and to estimate the maintainability of the class diagram using
Understandability and modifiability as attributes.
Further, in the year 2013 Alshayeb [2] performed an empirical study to evaluate the
relationship between four stability metrics and indices of maintenance effort, they found that
classes with higher values of Class Stability Metrics (CSM) are associated with lower values
of perfective maintenance effort measured by hours while none of the stability metrics is
correlated with maintainability measured by the number of changed lines.
From the point of view of Kumar and Dhanda [21], they saw that maintainability of an
Object-Oriented software design is affected by several factors, in which extendibility and
Flexibility that are taken as a major and key factor. The data used during the study is the same
as [29]. They developed three models to compute flexibility, extendibility and maintainability
of the class diagrams, the prediction model measures the maintainability of Object-Oriented
design in terms of their flexibility and extendibility. All the models have been developed
using the process of multiple linear regressions.
Whereas Soni and al [34], had developed three models to compute maintainability
prediction for class diagram using Extendibility and Reusability of the class diagrams. The
maintainability is measured in terms of their extendibility and reusability. All the three
models have been developed using the method of multiple linear regressions.
Lu and al in [32] proposed a methodology for assessing software maintainability at design
level and more precisely the maintainability of class diagram. Considering a set of metrics
for class diagram measurement, the authors have made a comprehensive study on
maintainability assessment from the defect-correction perspectives. Using a defect repository
and corrective maintenance history of Apache Tomcat (maintained from 2006 to 2014), they
have concluded that software maintainability can be accurately estimated in terms of time
span, number of modified lines of code and impact span for a defect correction using size,
coupling and inheritance metrics.
Comparative Analysis of Object-Oriented Software Maintainability ...
2.3. Prediction models at code level
Several techniques and approaches have been proposed in the literature to predict the
maintainability at code level, these methods vary from simple statistical models such as
regression analysis to complex automatic learning algorithms, such as “neural networks,
genetic algorithms, etc.”. Various methods proposed in the literature for the prediction of
maintainability are summarized in Table 1.
Table 1. List of shortlisted studies
Authors and year
Techniques used
[Li and al, 93]
Multiple Linear Regression
[Fioravanti and al, 01]
Multilinear regression analysis
[Dagpinar and al, 03]
Multiple Linear Regression
[Misra, 05]
Multivariate Regression Analysis
[Van koten and al, 06]
Bayesian Network
[Zhou and al, 07]
Multivariate Adaptive Regression Splines
[Aggarwal and al, 08]
Artificial Neural Network (Multilayer
Feed Forward)
[Elish and al, 09]
TreeNet « or also known as Multiple Addi-
tive Regression Trees »
[Li-jin and al, 09]
Projection Pursuit Regression
[Jin, and Liu, 10]
Support Vector Machine (SVM)
[Malhotra and al, 12]
Genetic Algorithms
Probabilistic Neural Network
Group Method of Data Handling
[Baqais and al, 13]
Neural Network
Genetic Algorithms
[Malhotra and al, 14]
Group Method of Data Handling
[Jindal and al, 15]
Neural Network
(Radial Basis Function NN)
[Jain and al, 16]
Evolutionary Algorithm
2.3.1 Statistical models
In order to monitor maintenance and reengineering, quantitative metrics to assess and predict
system characteristics should be used. There are many predictive models of maintainability
of software published in the literature that suggest a way to establish the relationship between
metrics and software maintenance.
Several studies have used linear regression techniques to construct models for predicting
the maintainability of software. For example, Li and Henry [22] they used these techniques
to predict maintenance effort, with a combination of metrics collected from the software
source code can be used as input to predict maintenance effort using multivariate regression
N. Zighed, N. Bounour, A-D. Seriai
analysis model (MLR).
In [13] a study was carried out by Fioravanti and Nesi with the aim of building and
evaluating a prediction model and the measurements for estimating the adaptive maintenance
effort of Object-Oriented systems.
According to Misra [27], the MI "maintainability index" have been used as an indicator
of the maintainability of Object-Oriented systems. It has studied the effect of the twenty
different metrics at the design / code level on maintainability using statistical techniques of
linear regression to predict the effort of maintainability.
Zhou and Leung in [35] also used a multivariate adaptive regression splines technique,
which allows to model the relationship between a desired value (also called a target variable)
and several predictive variables to construct a prediction model of the maintenance effort
using the metric data collected from two different Object-Oriented systems presented in [22].
These metrics represent cohesion, coupling, inheritance and size.
In a study conducted by Li-jin and al [31], a predictive model of maintainability was
developed using the static technique "Projection Pursuit Regression" and this by means of a
set of Object-Oriented metrics which is constituted as maintainability predictors. The values
of these metrics were collected from two software products UIMS (User Interface
Management System) and QUES (Quality Evaluation System).
Jun and Liu [18] validated their prediction model using the datasets collected from the
software systems developed by graduate students. Their results show that when Support
Vector Machine (SVM) is combined with clustering for the purpose of maintenance effort
predictions, correlation between Chidamber and Kemerer “C&K” metric suite and
maintainability was found to be as high as 0.769 which is statistically quite significant.
Figure 2. The general process of using ML in maintainability prediction
Comparative Analysis of Object-Oriented Software Maintainability ...
2.3.2. Machine learning techniques-based models
Machine learning (ML) is used for the study of information which helps in the mechanization
of the development of a prediction model. A great variety of experimental work has been
carried out which recommends the use of automatic learning techniques [28].
However, the link between Object-Oriented metrics and maintainability is often complex and
non-linear, limiting the accuracy of classical approaches. Different prediction models- based
ML techniques and Object-Oriented metrics have been proposed for the prediction of
software maintenance effort.
Using a single technique
Van and Gray in [30] have constructed a model for predicting the software maintainability of
OO systems using Bayesian networks. The authors used the Object-Oriented metric data set
presented by Li and Henry [22]. In this study, maintainability is measured as the number of
code’s changes during a maintenance period. To build the Bayesian network the Bayda tool
was used. Bayda allows users to build a special type of Bayesian networks called Bayesian
naive classifier. In which a single node representing a classification variable (change) is
connected to all the other nodes that represent the predictor variables (ten of OO metrics).
Then the precision of the model predictions is evaluated and compared with models-based
regression. The results suggest that the Bayesian network model can predict maintainability
more accurately than regression-based models for one system (UIMS) and almost as
accurately as the best regression-based model for the other system (QUES).
Elish [12] used TreeNet to construct a software maintainability prediction model using
the same data collected by Li and Henry [22]. They explored their experience on two popular
data sets in the field of maintainability known as UIMS and QUES. The authors have proved
that it also provides competitive results compared to other models.
Aggarwal and al [3] used ANN as a technique to construct a prediction model to estimate
the maintenance effort of OO software at the class level by estimating the number of rows
modified per class, On the other hand, the authors of [3] aim to explore empirically the
relationship between OO metrics and maintainability estimation. The values of the metrics
studied were collected from a total of 110 classes from two software systems: UIMS and
QUES [22]. A common problem that assumes when using metrics is called correlation. This
problem arises when the dependent variables are strongly correlated with each other and this
is the case with the OO metrics to remedy this problem Principal Component Analysis is a
statistical technique that has been used in this study to transform the data in uncorrelated
variables and reduce the correlation between the independent variables. The constructed
ANN model belongs to the whole of the multilayer perceptron [4] and the results of the latter's
evaluation showed that the relative absolute mean error (MARE) was 0.265 of the model.
The results show that the ANN is capable of providing an adequate model for predicting
maintenance effort and that OO metrics can be useful in guiding prediction.
Jindal and al [19] also used neural networks to develop a prediction model, but by using
another type of neural network "radial basis function network. Malhotra and Chug [23]
constructed a model using automatic learning algorithms to predict the maintainability of
Object-Oriented software such as Genetic Algorithms (GA) and Group Method of Data
Handling (GMDH). They evaluated the execution of this model using UIMS and QUES
systems, and found that the GMDH network model is one of the better methods of
demonstration to anticipate the maintainability of the product.
N. Zighed, N. Bounour, A-D. Seriai
In 2016 a recent study was conducted by Jain, Tarwani and Chug [17] to propose the use
of genetic algorithms for predicting the software maintainability, and to compare its
performance with various automatic learning techniques. They extracted the OO metrics from
four open source projects jTDS , jWebUnit, jXLS and SoundHelix, using the tool (Chidamber
and Kemerer Java Metrics). The Weka tool was also used to construct the prediction model.
In their study, maintainability was measured by counting the number of changes at the code
level, which was calculated by comparing each class of the two versions using the Beyond
Compare tool. To evaluate the accuracy of predictions found they used Mean Absolute Error
(MAE) and Root Mean Square Error (RMSE) as precision measures of prediction which were
proposed by Kitchenham. According to the results, the genetic algorithm gives more accurate
predictions compared to other models of automatic learning- based prediction.
Using hybrid techniques
From 2012 onwards, hybrid methods proved that their results are even better in predicting
Baqais and al [8] also used neural networks to propose a model of maintenance effort
prediction. This model is classified as a hybrid model because they used the ANN to construct
it while the genetic algorithm was used to speed up the ANN process by adjusting the
parameters of its design in order to achieve an optimized topology. In this study, four groups
of metrics were evaluated to conclude their direct influence on maintainability, which was
measured by the use of the maintainability index, the LOC (Line of Codes), NOA (Number
of Attributes), NLM (Number of Local Methods) and WMC (Weighted Methods per Class)
that represent: size, cohesion, coupling and inheritance, they were collected from the Android
project and they were analyzed empirically to understand their relationship to maintainability.
The Metamata tool was used to calculate the metrics while another tool called JHawk was
also used to calculate the maintainability index. After this, the data was provided to another
tool called DTREG to build the predictive model based on AI techniques. The results show
that the size of the code and the coupling metrics are a good indicator to provide an accurate
prediction of the maintainability measure.
Malhotra and Chug [24] deployed static measurements and found that the performance
of the Group Data Management Method (GMDH) was concise in terms of prediction
accuracy and can be viewed as a prediction of maintainability.
3. Discussion and comparison
In this part, we compare the different works presented previously. The comparative study is
elaborated by answering the following research questions:
Q1: How the software maintainability was measured using different artifacts of the
aforementioned abstraction levels?
Q2: Have the OO metrics been used at all the considered levels? What is the set of OO metrics
used for the software maintainability prediction? And which of these were the most influen-
tial on maintainability prediction?
Q3: What kinds of datasets used for empirical validations?
Comparative Analysis of Object-Oriented Software Maintainability ...
Q4: How can we judge the performance of prediction models?
Q5: What are the most accurate techniques to use for predicting maintainability?
3.1. Measurement and definition of software maintainability during the
considered SDLC phases.
Table 2. Different measurements of maintainability
Measurement of software Maintainability
[5], [6], [9]
The maintainability is measured by estimating change effort
(hours effort) required for dealing with changes in
maintenance phase by using mathematical model.
Understandability: The ease with which a class diagram
can be understood.
Analyzability: The capability of a class diagram to be
diagnosed for deficiencies or to identify parts to be
Modifiability: The capability of a class diagram to enable a
specified modification to be implemented.
[20], [29]
Two sub-characteristics of maintainability are considered:
Understandability: is the degree to which the software
design model can provide its clear meaning to evaluator.
Modifiability: is the degree to which the software design
model can be changed.
The authors correlates class stability with maintainability
effort measured by the number of hours spent on
maintenance activities and by the line
of code changes
The authors estimate the maintainability of class diagrams
in respect of their Extendibility.
[27], [8]
Maintainability was measured using the widely accepted
Maintainability Index (MI).
[30], [35], [31],
[12], [3], [19],
[17], [24]
The number of changes made to the code during a
maintenance period.
The maintainability of a software system can be measured in different ways. At code level
most of studies have measured maintainability by estimating the number of changes made to
the code during a maintenance period, and in few of studies, the maintainability has been
quantified by the Maintainability Index (MI) [27-8]. On other hand at design level the
maintainability can be estimated by measuring some of the sub-characteristics of
maintainability such as understandability, analyzability, modifiability and testability. In some
N. Zighed, N. Bounour, A-D. Seriai
studies, they have measured it by measuring two or even three sub-characteristics but the
understandability still an important sub-characteristic of maintainability, since professionals
spend at least half of their time analyzing software to understand it [15-20,29]. But at
architectural level they estimated the effort of change for measuring the maintainability.
Table 2 shows different measurements of software maintainability.
3.2. Metrics suite used in software maintainability prediction.
The link between OO design/code metrics and software maintainability has been proposed
by many researchers. These studies [3], [10], [22], [15], [27], [30] have found that a strong
link between these metrics and software maintainability exist. Due to the help of many
empirical studies, it has been established that the quality of software design, as well as code,
is very important to improve the maintainability of software. Numerous measures have been
proposed in the literature to capture the structural quality of code and design of Object-
Oriented programs, when at architecture level the OO metrics were not used for
maintainability prediction. Such measures are aimed at providing means of evaluating the
quality of the software, among which the most well-known metrics are those of Chidamber
and Kemerer “CK”, Lee and Henry [22].
Table 3. List of OO metrics
Software metrics used
Code level
[22], [27], [30],
[3], [12], [23], [24]
CK metrics, Li and Henry metrics, and Size
CK metrics, and Li and Henry
Design level
[15], [29]
Set Metrics for UML Class Diagrams
As can be concluded, the performance of the maintainability prediction models depends on
choosing the right set of Object-Oriented design/code metrics.
In [8] the results suggested that coupling metrics are a good indicator to provide an
accurate prediction of the maintainability measure. In [10] the results indicate that size and
import direct coupling metrics serve as the important predictors measuring maintainability of
classes while inheritance, cohesion, and indirect/export coupling measures are not. Zhou
[33] found that the average control flow complexity per method (OSAVG) appears to be the
most important maintainability factor.
Comparative Analysis of Object-Oriented Software Maintainability ...
While studies [15], [30], [12], [3] and others did not provide any explicit decision for
successful predictors of maintainability.
Overall it was observed that metrics related to size, complexity and coupling were to date
the most successful maintainability predictors employed.
3.3. Kinds of dataset used to elaborate software maintainability models
Many researchers and studies have conducted empirical studies in part to prove and show
that the values of OO design metrics had a considerable effect on maintainability. All of these
studies are based on small projects, proprietary software databases, open source software,
Building and evaluating software maintainability prediction techniques rely mainly on
datasets, some research studies have taken real-life data whereas some studies have used the
dataset proposed by Li and Henry [22] from two commercial software packages namely user
interface management system (UIMS) and quality evaluation system (QUES). Maintenance
efforts are generally calculated by counting the number of lines added, deleted or modified
during operations. The source code of old and new versions were collected and analyzed
against modifications made in every class. Values of OO software design metrics suite were
calculated and combined with corresponding changes made into that class so as to generate
datasets which were further divided into 3:1:1 for training, testing and validation,
respectively, during model implementations [24].
Table 4. List of datasets used and its characteristics
Referred in studies
Code characteristic
[30], [35], [3], [12],
[31], [22], [23], [24].
- UIMS (User Interface Management
System, 39 classes)
- QUES (Quality Evaluation System, 71
Both systems were implemented in ADA
Open Source Datasets:
, jTDS,
jWe- BUnit, JXLS,
Sound Helix,
Tomcat server.
[8], [17], [32].
- jTDS (64 classes) [17]
- jWebUnit (22 classes) [17]
- jXLS (78 classes) [17]
- SoundHelix (67 classes) [17]
Android project (78 classes) [8]
Apache Tomcat [32]
All systems are written in Java
Propriety software
[10], [27].
- 50 projects written in C++ total of
15637 classes [27]
-Two systems written in Java
Fujaba-UML (FUML) and Dynamic Ob-
Browser (dobs) [10]
Design diagrams
[21], [29], [15]
Twenty-eight UML class diagrams
N. Zighed, N. Bounour, A-D. Seriai
3.4. Measures to judge the performance of prediction models.
When we develop a maintainability prediction model, the results obtained must be tested and
compared with the actual values of maintainability. There is a number of statistical measures
that have been proposed by several authors to measure the accuracy and precision of the
prediction and to ensure that a precise prediction is not due to a simple coincidence rather, it
exists in fact by proposing formulas with their corresponding interpretations, among the
measures most used by the authors of papers presented in above sections: magnitude of
relative error (MRE)[30-12-18-35-3-24-23], mean magnitude of relative error (MMRE)[30-
12-35-23], residual error (RE), absolute residual error (ARE)[35], mean of ARE (MARE)[18-
3],, Standard deviation of ARE (StdevARE), Pred (q)[35-23], Mean Absolut Error [19], R-
square[23], root mean square error (RMSE)[19] and Normalized mean square error [8].
3.5. The most accurate techniques to use for predicting maintainability
The aim of prediction models is to estimate Object-Oriented software maintainability but
getting an accurate result remains the primary goal of each study that was carried out in
literature. At code level the use of OO metric is inevitable in order to quantify the
characteristics of the code and also it provides ways to evaluate the maintainability of
software. The link between these metrics and maintainability is often complex and non-linear
which limit the accuracy of statistical approaches. The use of ML techniques to develop
prediction model gives more accurate results.
4. Threats to validity
In this section, we discuss the main threats to validity which need to be considered when
interpreting the results from our study and the way we attempted to alleviate them. The
identified threats are given as under:
The first threat to validity in our study is biased in our selection of the works to be included
and the research databases. Therefore, in order to ensure that we have chosen the most
important studies, we have adopted a selection process and it was unbiased, in which different
databases were identified like: Google Scholar, Science Direct, Springer, ACM Digital
Library, IEEE Xplore.
The second threat to validity is related to the search strings used for selecting relevant
studies. The search strings were derived from the research questions which we have
formulated for conducting and guiding our analysis.
5. Conclusion
In this paper, we have presented the most important techniques applied in the literature that
were used for the purpose of software maintainability estimation and constructing prediction
models. In contrast to other studies that took mostly one level and they analyzed the proposed
models, in our study we considered the code, design, and architecture level of SDLC. We
Comparative Analysis of Object-Oriented Software Maintainability ...
performed a comparative analysis by answering the research questions which are presented
in section 3. We conclude that only few works have been done at the design and architectural
level. For future work, we could explore the use of machine learning techniques at the design
and architectural level.
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Received. 5.07.2018, Accepted 16.11.2018
N. Zighed, N. Bounour, A-D. Seriai
... Consequently, one of the essential objectives of software engineering is to develop techniques and tools for high-quality software solutions that are stable and maintainable [5]. Software maintainability is one of the most important aspects when evaluating the quality of a software product [6] and is one of key stages in the software development lifecycle [7]. ...
... The relationship between software design metrics and their maintainability has been proposed and validated by many researchers [6,9]. Based on the empirical study by Malhotra and Chug, it has been established that the quality of the software design, as well as code, is very important to enhance software maintainability [9]. ...
... The indirect maintainability measures combined with a variety of software metrics that capture the quality of software's internal quality, represent efficient input for either statistical or machine learning algorithms to make useful prediction models. To establish a relationship between software design metrics as the independent variable and maintainability as the dependent variable, various techniques have been practised in the last two and half decades [9], including statistical algorithms, machine learning algorithms, nature-inspired techniques, expert judgment, and hybrid techniques [6,19]. ...
Full-text available
Software maintenance is one of the key stages in the software lifecycle and it includes a variety of activities that consume the significant portion of the costs of a software project. Previous research suggest that future software maintainability can be predicted, based on various source code aspects, but most of the research focuses on the prediction based on the present state of the code and ignores its history. While taking the history into account in software maintainability prediction seems intuitive, the research empirically testing this has not been done, and is the main goal of this paper. This paper empirically evaluates the contribution of historical measurements of the Chidamber & Kemerer (C&K) software metrics to software maintainability prediction models. The main contribution of the paper is the building of the prediction models with classification and regression trees and random forest learners in iterations by adding historical measurement data extracted from previous releases gradually. The maintainability prediction models were built based on software metric measurements obtained from real-world open-source software projects. The analysis of the results show that an additional amount of historical metric measurements contributes to the maintainability prediction. Additionally, the study evaluates the contribution of individual C&K software metrics on the performance of maintainability prediction models.
... However, such surveys involve high costs and are also very time consuming and may produce biased opinions due to the subjectiveness involved in the external quality attributes. Contrarily, measurement of internal quality attributes using Object-Oriented (OO) metric suites has been validated by many researchers for predicting maintainability keeping in view the relationship that exists between the OO metrics & maintainability [4]- [9]. Hence, the current study also uses these OO metrics for Software Maintainability Prediction (SMP). ...
... However, there exist different software metrics based on whether the paradigm is procedural or OO. As per the existing literature, software systems have been analyzed from three perspectives, i.e., the architecture of the system, its design, and the code for SMP [4]. However, out of these, code-level analysis for SMP is the most widely used perspective. ...
Software Maintainability is an indispensable factor to acclaim for the quality of particular software. It describes the ease to perform several maintenance activities to make a software adaptable to the modified environment. The availability & growing popularity of a wide range of Machine Learning (ML) algorithms for data analysis further provides the motivation for predicting this maintainability. However, an extensive analysis & comparison of various ML based Boosting Algorithms (BAs) for Software Maintainability Prediction (SMP) has not been made yet. Therefore, the current study analyzes and compares five different BAs, i.e., AdaBoost, GBM, XGB, LightGBM, and CatBoost, for SMP using open-source datasets. Performance of the propounded prediction models has been evaluated using Root Mean Square Error (RMSE), Mean Magnitude of Relative Error (MMRE), Pred(0.25), Pred(0.30), & Pred(0.75) as prediction accuracy measures followed by a non-parametric statistical test and a post hoc analysis to account for the differences in the performances of various BAs. Based on the residual errors obtained, it was observed that GBM is the best performer, followed by LightGBM for RMSE, whereas, in the case of MMRE, XGB performed the best for six out of the seven datasets, i.e., for 85.71% of the total datasets by providing minimum values for MMRE, ranging from 0.90 to 3.82. Further, on applying the statistical test and on performing the post hoc analysis, it was found that significant differences exist in the performance of different BAs and, XGB and CatBoost outperformed all other BAs for MMRE. Lastly, a comparison of BAs with four other ML algorithms has also been made to bring out BAs superiority over other algorithms. This study would open new doors for the software developers for carrying out comparatively more precise predictions well in time and hence reduce the overall maintenance costs.
... The researchers behind the Software Maintainability Prediction (SMP) Framework use several different types of mathematical, machine learning, and evolving models on historical data in order to train various types of complex models with the purpose of keeping track of all kinds of software updates. [22,[24][25][26][27]. ...
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The software industry's competitive nature makes it natural that software managers and developers face several crucial decisions in managing the software project. These decisions are taken to enhance processes maturity and product quality with improved planning accuracy and monitoring control. In this study, the factors determining the growth of software project management were analyzed. This study used an online survey to collect the necessary data relating to the development, classification, consideration, priority setting, and preparation in software projects. It was observed that team incapability, time constraint, limited testing criteria, customer's inability to understand quality specifications, Budget limitation, limited ability to handle quality requirements, and lack of customer involvement are the major constraints in software project development. The analysis indicates that quality criteria, performance, security, usability, team capability, and customer involvement gained more consideration in the context of software development. Finally, it was recommended that project managers and developers should learn how essential it is to delegate specific roles to avoid difficulties resulting from a lack of clear accountability for the required specifications in the production of software.
... Most of these models were suggested in the level of code while a few models were suggested at levels of design and architecture [8]. In this paper, we will be considering the most recent proposed techniques to predict Object-Oriented software maintainability utilizing artificial intelligent techniques. ...
... Object-Oriented metrics are an estimation procedure of product metrics in which computation is done on real-world entities to depict them as indicated by plainly characterized rules. These metrics encourage programming specialists to discover the profitability of the product application (6) . ...
... The results showed that bagging ensemble model significantly improved the accuracy of prediction. Recently, Zighed et al. [14] conducted a comparative analysis of different OO SMP models from three perspectives i.e. the architectural level, design level and the code level. It was revealed that a number of statistical and ML techniques have been employed at the code level. ...
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Software Maintainability refers to the ease with which software maintenance activities like correction of faults, deletion of obsolete code, addition of new code etc. can be carried out to adapt to the modified environment. Predicting maintainability in early stages of development helps in reducing the cost of maintenance and ensures optimum utilization of resources. Sometimes, it becomes difficult to train prediction models using historical data of the same dataset for which the model is being developed because of the unavailability of sufficient amount of training data, in turn making a way for Cross-Project technique for Software Maintainability Prediction (CPSMP). In order to evaluate the proposed CPSMP technique, QUES dataset is used as training set and UIMS dataset is used as test set in this study with 19 different regression modelling methods. Performance of CPSMP model is evaluated using Root Mean Square Error (RMSE) as an accuracy measure. Results show that cross-project technique can successfully be applied for maintainability prediction. The average RMSE value calculated for all the modelling methods is found to be 82.310 without CPSMP whereas an average RMSE value of 71.532 is obtained with CPSMP resulting in an overall improvement in prediction performance by 13.09%. Also, 84.21% of the total techniques used in this study performed better with CPSMP.
Today, when a company designs, develops and manufactures goods or services, it must not only target a high level of quality for the products to satisfy customers, but also comply with many standards and regulations. This is particularly true with transportation systems where we can name few famous standards and guidelines: the ISO 26262 [1] addresses the software functional safety in automotive, the ARP4754 [2] provides guidelines for the development of civil aircrafts, and the DO-178C addresses software safety [3] in aeronautics. Furthermore, these safety guidelines impose to the company to be at the state of the art for processes and methods, when designing and developing a new vehicle.In the context of automotive systems’ development, our research aims to strengthen and unify quality definition, assessment, control, or prediction activities for automotive embedded software. Thus, to resolve this problematic, first we have to explore quality concept, qualimetry -the science of quality quantification [4]-, and the state of the art about quality modeling for embedded software. The result is not only to popularize and synthetize the knowledge behind these complex concepts but also, to confirm the choice of qualimetry as the right approach to solve our problematic, for which no proper solution exists yet.We then continue our study considering biology as key factor in our research. Therefore, we create a classified collection of clades of more than 450 quality models for software. We select the most appropriate quality model from this pool of quality models, and after introducing the concept of polymorphism in quality modeling, we demonstrate how to adapt and operationalize this model to automotive embedded software. This last achievement consequently replies to our original problematic.As a further conclusion of our research, we finally investigate whether a unique quality model for software product, as Zouheyr Tamrabet et al. [5] aim to propose, is more appropriate than a meta-model as quality model aggregator for software product, giving a first glimpse of the model result whose qualifier is the genome of software quality model.[1] “ISO 26262-6:2011 - Road vehicles - Functional safety - Part 6: Product development at the software level,” International Organization for Standardization, 2011.[2] “ARP4754A - Guidelines for Development of Civil Aircraft and Systems,” SAE International, Dec. 2010, [Online]. Available:[3] “DO-178C - Software Considerations in Airborne Systems and Equipment Certification,” Radio Technical Commission for Aeronautics, Dec. 2011, [Online]. Available:[4] G. G. Azgaldov et al., “Qualimetry: the Science of Product Quality Assessment,” Standart y i kachest vo, no. 1, 1968.[5] Zouheyr Tamrabet, Toufik Marir, and Farid MOKHATI, “A Survey on Quality Attributes and Quality Models for Embedded Software,” International Journal of Embedded and Real-Time Communication Systems (IJERTCS), vol. 9, no. 2, pp. 1–17, 2018, doi: 10.4018/IJERTCS.2018070101.
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Software engineering is a discipline of Computer Science in which the new sub-areas are constantly added, especially in the area of quality, data management, and architectural design. Nowadays software development languages and processes are rapidly changing to deliver high-quality software products, i.e., usable systems, hybrid, and fulfill users’ needs. This paper aims to identify and classify different process models proposed by the researchers based on characteristics of software quality, data management, and software integration and redesign. From a study of several models through a systematic mapping study, we identify different parameters and presented them in a traceability matrix. The parameters are classified into six areas. This paper provides an in- depth theoretical insight into the models and characteristics. A systematic mapping study was conducted through a literature review. The methodology used in this paper is both qualitative and quantitative. Initially, through a systematic mapping study, we study different models working on different parameters. And then proposed a model that can cover all the aspects of software implementation and management. We select ERP systems for it. Later we perform the GAP analysis and statistical evaluation of the model. It has been observed that all of the models are area specific either focused on quality parameters or management issues or architectural-based. The proposed model covers all aspects. The primary research shows that industrialists also need a better model for quality implementation. Our statistical analysis can serve as a decision-making tool for them to add to their decision-making processes. The other could use it to further enhance the framework for quality management. This model will enhance further in the future for better implementation.
The software systems worldwide increase in a density on a daily basis. The success in nowadays competitive market requires sustainable and quality software product. Controversially to the quantity of software products, the quality and cost of the software are tend to depend on several aspects. However, they are not fully inculcated yet as a fundamentally essential. The full control over the software quality requires software metrics to be introduced. By effective usage of software quality metrics one can monitor the software development process, minimize the cost, track the resource usage and maintain the expected results. This paper reviews the late phases and the existing software quality models to track software process quality metrics in these late phases. And based on the summarized studies we describe our system architecture in the way to evaluate the software quality with embedded external systems. This paper find outs additional metrics we can measure with the help of our framework.
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Most of the currently used software development metrics are concentrated on the latter stages like development and testing. However, early revealing of errors during the SDLC(Software Development Life Cycle) tremendously affects the efficiency of the team work by spending more time on prevention and less on correction in later stages. Furthermore, reworking in later stages increase the cost of quality, lead to extra waste of time of the development team. The objective of this review is to examine the classification of the existing SDLC(Software Development Life Cycle) early phases and define the set of software process quality metrics. Based on the SRL research protocol, we selected the most relevant studies from overall 200 publications by the use of search keywords and inclusion/exclusion criteria for quality assessment of primary studies. This systematic literature review yields the correlation of cost, time and software product quality with the SDLC stages.
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Software maintenance is an expensive activity that consumes a major portion of the cost of the total project. Various activities carried out during maintenance include the addition of new features, deletion of obsolete code, correction of errors, etc. Software maintainability means the ease with which these operations can be carried out. If the maintainability can be measured in early phases of the software development, it helps in better planning and optimum resource utilization. Measurement of design properties such as coupling, cohesion, etc. in early phases of development often leads us to derive the corresponding maintainability with the help of prediction models. In this paper, we performed a systematic review of the existing studies related to software maintainability from January 1991 to October 2015. In total, 96 primary studies were identified out of which 47 studies were from journals, 36 from conference proceedings and 13 from others. All studies were compiled in structured form and analyzed through numerous perspectives such as the use of design metrics, prediction model, tools, data sources, prediction accuracy, etc. According to the review results, we found that the use of machine learning algorithms in predicting maintainability has increased since 2005. The use of evolutionary algorithms has also begun in related sub-fields since 2010. We have observed that design metrics is still the most favored option to capture the characteristics of any given software before deploying it further in prediction model for determining the corresponding software maintainability. A significant increase in the use of public dataset for making the prediction models has also been observed and in this regard two public datasets User Interface Management System (UIMS) and Quality Evaluation System (QUES) proposed by Li and Henry is quite popular among researchers. Although machine learning algorithms are still the most popular methods, however, we suggest that researchers working on software maintainability area should experiment on the use of open source datasets with hybrid algorithms. In this regard, more empirical studies are also required to be conducted on a large number of datasets so that a generalized theory could be made. The current paper will be beneficial for practitioners, researchers and developers as they can use these models and metrics for creating benchmark and standards. Findings of this extensive review would also be useful for novices in the field of software maintainability as it not only provides explicit definitions, but also lays a foundation for further research by providing a quick link to all important studies in the said field. Finally, this study also compiles current trends, emerging sub-fields and identifies various opportunities of future research in the field of software maintainability.
Conference Paper
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Software maintenance is one of the tedious as well as costly phases in the software development life cycle. It starts immediately after the software product is delivered to the customer and ends when the product is no longer in use. There are various activities carried out during software maintenance phase such as the addition of new features, deletion of obsolete features, correction of errors, adaption to new environment etc. Software maintainability is the quality attribute of the software product which determines the ease with which these modifications can be performed. If we can predict the maintainability accurately, cost and time associated with the maintenance activity can be highly reduced. The main aim of this study is to propose the use of evolutionary technique particularly genetic algorithm for the software maintainability prediction and compare its performance with various machine leaning techniques such as Decision Table, Radial Basis Function Neural Network, Bayes Net and Sequential Minimal Optimization (SMO). In order to carry out this empirical investigation, datasets from four open source software systems are collected. The maintenance effort is calculated by counting the number of changes in terms of line of code from one version of the software to another. Based on the experiments conducted, we conclude that the evolutionary algorithm outperformed all the other classifiers, thus, very useful for the concise prediction of software maintainability. Results of this would be helpful to practitioners as they can use the maintainability prediction in order to achieve precise planning of resource allocation.
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Maintenance is an important activity in the software life cycle. No software product can do without undergoing the process of maintenance. Estimating a software's maintainability effort and cost is not an easy task considering the various factors that influence the proposed measurement. Hence, Artificial Intelligence (AI) techniques have been used extensively to find optimized and more accurate maintenance estimations. In this paper, we propose an Evolutionary Neural Network (NN) model to predict software maintainability. The proposed model is based on a hybrid intelligent technique wherein a neural network is trained for prediction and a genetic algorithm (GA) implementation is used for evolving the neural network topology until an optimal topology is reached. The model was applied on a popular open source program, namely, Android. The results are very promising, where the correlation between actual and predicted points reaches 0.91.
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Abstract—Can software maintainability be assessed at the early design stage? For a preliminary answer, we conducted a case study. The study adopts a set of metrics for class diagram measurement, and defines three indices for maintainability assessment from the defect-correction perspectives. The dataset under investigation includes the defect repository and corrective maintenance history of Apache Tomcat (maintained from 2006 to 2014). Statistical findings show that some class diagram metrics (such as the number of class association across packages, the number of classes, the inheritance depth for a class et al.) are significantly correlated with the maintainability assessment in this software. The result can guide maintenance-oriented software design, and also motivates us to do a stronger empirical evaluation.
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Object-oriented methodology has emerged as most prominent in software industry for application development. Maintenance phase begins once the product is delivered and by software maintainability we mean the ease with which existing software could be modified during maintenance phase. We can improve and control software maintainability if we can predict it in the early phases of software life cycle using design metrics. Predicting the maintainability of any software has become critical with the increasing importance of software maintenance. Many authors have practiced and proved theoretical validation followed by empirical evaluation using statistical and experimental techniques for evaluating the relevance of any given metrics suite using many models. In this paper, we have presented an empirical study to evaluate the effectiveness of novel technique called Group Method of Data Handling (GMDH) for the prediction of maintainability over other models. Although many metrics have been proposed in the literature, software design metrics suite proposed by Chidamber et al. and revised by Li et al. have been selected for this study. Two web-based customized softwares developed using C# Language have been used for empirical study. Source code of old and new versions for both applications were collected and analysed against modifications made in every class. The changes were counted in terms of number of lines added, deleted or modified in the classes belonging to new version with respect to the classes of old version. Finally values of metrics were combined with “change” in order to generate data points. Hence, in this study an attempt has been made to evaluate and examine the effectiveness of prediction models for the purpose of software maintainability using real life web based projects. Three models using Feed Forward 3-Layer Back Propagation Network (FF3LBPN), General Regression Neural Network (GRNN) and GMDH are developed and performance of GMDH is compared against two others i.e. FF3LBPN and GRNN. With the aid of this empirical analysis, we can safely suggest that software professionals can use OO metric suite to predict the maintainability of software using GMDH technique with least error and best precision in an object oriented paradigm.
During the last few years, software evolution research has explored new domains such as the study of socio-technical aspects and collaboration between different individuals contributing to a software system, theuse of search-based techniques and meta-heuristics, the mining of unstructured software repositories, the evolution of software requirements, and the dynamic adaptation of software systems at runtime. Also more and more attention is being paid to the evolution of collections of inter-related and inter-dependent software projects, be it in the form of web systems, software product families, software ecosystems or systems of systems. Withthis book, the editors present insightful contributions on these and other domains currently being intensively explored, written by renowned researchers in the respective fields of software evolution. Each chapter presents the state of the art in a particular topic, as well as the current research, available tool support and remaining challenges. The book is complemented by a glossary of important terms used in the community, a reference list of nearly 1,000 papers and books and tips on additional resources that may be useful to the reader(reference books, journals, standards and major scientific events in the domain of software evolution and datasets). This book is intended for all those interested in software engineering, and more particularly, software maintenance and evolution. Researchers and software practitioners alike will find in the contributed chapters an overview of the most recent findings, covering a broad spectrum of software evolution topics. In addition, it can also serve as the basis of graduate or postgraduate courses on e.g., software evolution, requirements engineering, model-driven software development or social informatics.
Importance of software quality is increasing leading to development of new sophisticated techniques, which can be used in constructing models for predicting quality attributes. One such technique is Artificial Neural Network (ANN). This paper examined the application of ANN for software quality prediction using Object- Oriented (OO) metrics. Quality estimation includes estimating maintainability of software. The dependent variable in our study was maintenance effort. The independent variables were principal components of eight OO metrics. The results showed that the Mean Absolute Relative Error (MARE) was 0.265 of ANN model. Thus we found that ANN method was useful in constructing software quality model.