- Component-Based Software Engineering (CBSE) provides for developers the ability to easily reuse and assemble software entities to build complex software. It is based on the composition of prefabricated software entities called components. In this context, the selection step is very important. It consists of searching and selecting appropriate software components from a set of candidate components in order to satisfy the developer-specific requirements. In the selection process, both functional and nonfunctional requirements are generally considered. In this paper we present a method enabling the evaluation of software components quality. This method allows us choosing the best component in term of non-functional needs.
The components approach has become an important alternative for building software applications, and specially distributed systems. This approach tries to improve the flexibility, reusability and maintainability of applications, and helps develop complex and distributed applications deployed on a wide range of platforms, by plugging commercial off-the-shelf (COTS) components, rather than building them from scratch.
Software component. One of the definitions
most often quoted is given by Szyperski and
Pfister [
Currently, we can find several similar components .i.e. they provide the same functional requirements. The problem is "how to choose a component of good quality?". In this article we try to estimate the quality of each component in order to select the best among several equivalent propositions. Summarize the main function of our evaluation methods is to produce a single numerical value representing the quality offered by each component.
This paper is organized in three sections. After this introduction, section 2 presents an outline on software quality and in section 3 we present our assessment process.
characteristic which contributes to its quality [
evaluated via these elements [
Attributes: The quality criteria are connected to attributes which are a posteriori measurements.
A Quality Model is defined as: “The set of
characteristics and the relationships between
them which provide the basis for specifying and
evaluating quality requirements.”[
There are more than 300 developed standards
and maintained by more than 50 different
organizations[
Characteristics
Maintainability Portability Functionality Reliability Usability Efficiency
Sub-characteristics Accuracy, Security, Suitability, Interoperability ,Compliance Faults Tolerance, Recoverability, Maturity , Compliance Configurability, Understability, Learnability , Attractiveness, Operability, Compliance Time Behavior,Resource Behavior, Compliance Stability , Changeability , Testability , Analysability , Compliance Deployability, Replaceability ,
Adaptability, Reusability
The objective of this work is to calculate the software component quality value.
In such quality evaluation process, the presence
of a quality characteristics’ description of each
component is crucial; that means to be able to
satisfy the quality it is important to add the
necessary quality attributes to the product
description [
Reliability ={ Maturity = {Volatility =0,25;
Failureremoval=0.49} FaultTolerance= { Mechanismavailability=0.6; Mechanism_Efficiency =0.31}; Recoverability={ Error –Handling=0.20} }; Usability = {
Operability={ Provided_interface =0.55; Required_interface=0.36};
Configurability ={ Configuration Effort =0,3 } }.
Let assume that: F: a set of component factors: F= {fi / i=1.. n} C: a set of criteria for F: C= {cj /j=1.. m} A: a set of attributes relating to C: A= {al/ l=1.. k} The quality model is decomposed into 03 levels: the first is the attributes, the second criteria and the third represents the factors. For this we define two relations: 1. “presented by”: this relation is defined as follow: Ei is presented by ej j=1..n : means that the element Ei is presented by the set (e1,e2,e3…en) For this work two cases can be distinguished: fj ∈ F each factor fj is presented by a set of criteria
ci ∈ C, each criterion cj is presented by a set of attributes 2. “ Evaluated by ”: if an element Ei is presented by ej j=1..n the quality value of Ei : V(Ei) can be calculated based on the quality values of the elements ej: V (ej). Whereas: If Ei is presented ej j=1..n evaluated by V(ej ) / j=1..n V(Ei) is
Our evaluation process contains 03 main steps:
Step 1: In this step the user must classify the
quality characteristics (factors) according to his
non functional needs.
Step 2: Factors weights are calculated
depending on the user classification using ROC
(Rank Order Centroid) concept [
1 = For Criteria and attributes weights we assign equal weights, that is to say if an element E has n sub-element E’, the weight of each element E’ is:
W(E)=
Step 3: Evaluation : Figure.2 summarizes the calculating process, with the following rules:
_ = Such as: example, there are two quality factors: reliability
2. Usability is presented by (Learnability,
Factor International Conference on Advanced Aspects of Software Engineering
Criteria Maturity Fault Tolerance Recoverability Now, we use R2 to calculate Usability value: V(Usability)=V(operability)*W(operability)+V(Lea rnability)*W(Learnability)+
V(Configurablity)*W(Configurablity) = 0.33*0.45+0.33*0.69+0.33*0.3=0.47 V(Usability)=0.47
calculation process, V(Reliability)=0.34 will apply the same we find: Overall quality: for this level we use R1; V_qual =V(Reliability)*W(Reliability)+V(Usability) *W(Us-ability)=0.34*0.25+0.47*.75 V_qual =0.43
This paper presents a method allowing comparison of software components in term of quality. We have proposed a method for assessing the component quality. This method is Applicable to any quality model, it facilitates the comparison of components by producing a digital value represents the quality that a component can offer, and it minimizes the time to compare a few equivalent components. In order to enhance this methodology, we proposed a generalization of the proposed process of assembling software system based on the assembly of several components, i.e. to know the value of the quality offered by an application from its components.