Designing a Comprehensive Model for Evaluating SOA-based Services Maintainability by ijcsiseditor


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									                                                              (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                              Vol. 9, No. 10, October 2011

           Designing a Comprehensive Model for Evaluating SOA-based Services

                    Maryam Zarrin                                                             Mir Ali Seyyedi
          Computer Engineering Department,                                           Computer Engineering Department,
 Science & Research Branch of Islamic Azad University,                          Islamic Azad University, Tehran-south branch
                     Tehran, Iran                                                              Tehran, Iran

                                                        Mehran Mohsenzaeh
                                                Computer Engineering Department,
                                       Science & Research Branch of Islamic Azad University,
                                                           Tehran, Iran

Abstract- The aim of this paper is to propose a comprehensive             functionality or requirement changes [14]. Also, to measure
and practical model to evaluate the maintainability of software           whether an IT service or component configuration after
services in service-oriented architecture in the entire service           encountering failure in service maintainability area, how
lifecycle and based on the fuzzy system. This model provides              quickly and effectively could return to its normal activity is a
the possibility of making decisions concerning the                        description that has been presented by the third version of
maintainability of SOA-based services for service managers                ITIL standards [15].
and owners in various service operation and design phases.                    Presently, little research effort has been dedicated to
The proposed maintainability evaluation model consists of five            considering maintainability evaluation of SOA-based
sections: input, analysis, measurement, decision making and
                                                                          services and more significantly, practical model for
output. According to the studies conducted on the leading
article, the service structural properties in design phase as well
                                                                          evaluating maintainability of service-oriented services
as service management mechanism structures at the operation               regarding all maintainability influencing factors in entire
phase have been identified as effective factors in evaluating the         service lifecycle do not exist. In other words, the focus of
maintainability of services. So the proposed model investigates           researches of the existing models has been more on
both discussed factors and is generally categorized in two                maintainability evaluation and assessment in the software
sections: design and operation. To assess maintainability in              perspective.
both sections, the fuzzy technique is used.                                   Due to the service-oriented architecture characteristics
                                                                          and their differences with others, the factors and metrics used
   Keywords- maintainability;      service-oriented;   evaluation         in these models have not been applicable in service-oriented
model; fuzzy system                                                       approaches and they are not directly functional in the service
                                                                          orientation perspective. So in recent years, studies on
                      I.    INTRODUCTION                                  maintainability evaluation have been conducted in order to
                                                                          establish and define appropriate metrics and models in
    In recent years, the use of service-oriented architecture as          service orientation context. Nonetheless, the study conducted
one of the significant solutions for managing complexities                in this area is at research and theory level which has been
and interactions between IT-based services as well as                     investigated in limited dimensions and also a comprehensive
managing fast business shifts in a volatile business                      and practical method for evaluating the SOA-based service
environment has increased. Maintainability is one of the                  maintainability has not been presented. The only researches
major service quality attributes which has an important role              presented in this area include two evaluation models that
in user satisfaction and cost reduction of maintenance and                have been presented by Mikhail Perepletchikov [3, 5]. Linear
support. Research has shown that more than 60% of the                     regression prediction models have been used in both models
overall resources devoted to software or services                         but in the first, coupling metrics have been presented [4] and
development belongs to the maintenance phase [21]. So,                    in the second, the cohesion metrics [6] have been used as
designing services that face a difficulty at the maintenance              model predictors.
phase will greatly increase the possibility of cost or time                   Other existing researches in this context are limited to
failure of service development [21].                                      proposing new metrics for evaluating the services design
    According to the definition provided by IEEE,                         structural properties. So far by using these metrics,
maintainability is defined as a capability of the software                comprehensive and practical models for evaluating the
against possible adjustments like correcting errors,                      services maintainability in service-oriented approach have
improving efficiency or other software quality attributes or              not been introduced. In both [19, 20] researches metrics have
adaptation of the software with the environment,                          been proposed to evaluate decoupling using connections

                                                                                                      ISSN 1947-5500
                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 9, No. 10, October 2011

between components based on service orientation as well as              model structural design. The next thing is to define the
in [10] dynamic metrics of coupling measurement with                    concept of maintainability in the entire service lifecycle.
regards to run time relations between services. [11, 12]                According to identification of the two phases of service
includes a set of metrics to measure the complexity of the              design and operation as the major phases having influence on
service-oriented design systems. Also in [9] considering                services maintainability and its minimal effect of other
principles such as loose coupling and appropriate granularity           phases on it, it would be sufficient to define maintainability
in designing services, metrics for them have been proposed.             in the two introduced phases.
In [8] reusability, composability, granularity, cohesion and                In other words, in the service design phase, it is necessary
coupling evaluation metrics by available information in                 to divide the maintainability concept into the quality sub-
service-oriented design have been proposed.                             attribute based on the available standards. Then the
    Obviously,      the     comprehensive      evaluation    of         appropriate and associated factors must be determined from
maintainability in service-oriented architecture will have a            them. In next level, identification and selection of
perception in the service lifecycle. In other words, designing          appropriate and associated metrics to every one of these
and defining a comprehensive model for evaluating SOA-                  factors is considered another challenge in designing this
based services maintainability will be possible by                      model. Also in the operation phase, initially the concept of
considering maintainability influencing factors in the full             maintainability should be divided into appropriate sub-
service lifecycle. By having such model, senior managers                attribute. Then, based on international standards each one of
and service owners will be able to make decisions on                    them must be mapped out based on appropriate process
maintainability of SOA-based services not only at every                 factors and the final step, the maturity level of every one of
stage of the service design and operation but also when                 these process factors should be evaluated through certain
services are operational.                                               metrics. In other words, the maintainability evaluation model
    This paper makes a contribution in proposing a                      should be defined in both service design and operation
comprehensive and practical model for evaluating the                    phases.
maintainability of SOA-based services covering all                          After determining the independent variables of the two
maintainability influencing factors in full service lifecycle.          phases, identifying their affects and significance on the
The proposed evaluation model includes five sections: input,            maintainability dependent variable is an important challenge
analysis, measurement, decision making and output.                      which an appropriate solution should be adopted for it. In the
    In designing the evaluation model, the concept of                   design phase, maintainability as a dependent variable and
maintainability is based on the included definitions and                cohesion, coupling and granularity factors as independent
concepts in ITIL and four sub-attributes of ISO/IEC 9126                variables are considered. So, in the first step of this phase, it
standards namely analyzability, changeability, stability and            is necessary to determine and identify the communications,
testability. It has also been considered as a combination of            affects and significance of each independent variable versus
maintainability due to service structural properties in the             the dependent variable. In the next step through appropriate
design phase and operational phase of the service. As a                 evaluation metrics selection service maintainability must be
result, evaluating the maintainability of services is conducted         evaluated. Also in the operation phase, similar to the
in two sections: one belonging to service design and the                previous one determine the impact and the significance of
other to service operation phase factors.                               each one of the independent variables on dependent variables
    In design sections, structural characteristics such as              and linked metrics is a major challenge that an appropriate
coupling, cohesion, and granularity directly affect the                 solution for it should be adopted. In this section, service
maintainability sub-attributes and indirectly service                   maintainability as dependent variable and the supportive
maintainability in which their effects can be estimated and             process based on service management standards as
predicted. Furthermore in the operation section, ITIL service           independent variables are considered. Here, metric selection
management processes include incident management,                       and efficient methods to evaluate process maturity level is
problem management, change management, configuration                    another important challenge in this study that different
management, release management and availability                         aspects of it must be answered.
management which can directly map the maintainability sub-                  Another issue in designing this model is the selection of a
attributes, have a direct impact on maintainability.                    metric evaluation technique or method from among methods
    Further, initially the model design requirements will be            used in other similar research or studies. In selecting an
defined then methods and techniques used to answer each                 evaluation method measures such as compatibility with new
one of them will be provided. And at the end, maintainability           data, viewing the reasoning process, suitability to complex
evaluation proposed model will be described by using the                models and also emphasis on compatibility with service-
fuzzy system and its various components.                                oriented architecture characteristics namely reusability,
                                                                        business agility, interoperability, loosely coupling and
                                                                        compos ability is important. Rest sections contribute to offer
          II.   PROBLEM DEFINITION AND APPROACH                         solutions to each of discussed areas.
    To design the maintainability evaluation model in
service-oriented architecture, it is first necessary to identify
the SOA fundamental characteristics in relation to the
previous architectural styles and identify their affects on

                                                                                                     ISSN 1947-5500
                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 9, No. 10, October 2011

A.              Maintainability evaluation factors                               TABLE I.              OPERATIONAL INDEPENDENT VARIABLES
    In services design phase, documentation-related factors                  ISO/IEC 9126 sub-attribute               Appropriate processes of ITIL
and structural properties of design are significant influencing                                                      incident management, problem
factors     in    term     of    maintainability    evaluation.                                                               management
Documentation-related factors impact on maintainability are                                                        change management, configuration
minimal because the proper of documentation increase the                                                                      management
                                                                                         stability                      availability management
ability to analyze the failure in system or analyzability sub-
attribute but it doesn’t affect on service changeability and                         testability                          release management
stability sub-attribute [2]. But according to the research
conducted in the past, the structural properties which reflect
the internal properties of services have a direct affect on all             It should be noted in evaluation model designing, the
aspects of maintainability [22, 23 and 24]. As a result, if the         addition of maintainability sub-attribute of ISO/IEC 9126
structural properties of the product are appropriate,                   standard has been omitted because the addition of the
maintenance activities will simply be carried out. Thus,                mentioned level would increase the complexity and error of
Documentation-related factors will be completely eliminated             this model. So the considered category is solely for a better
from the selection ones.                                                and more precise selection of suitable and related processes.
    General structural properties of services include
coupling, cohesion, size and complexity And SOA-specific                B.              The selection of metrics for maintainability
structural properties services including service granularity,               evaluation factors
parameter granularity and consumability [1]. Selective
                                                                            Another challenge for this research is the selection of
structural properties include coupling, cohesion and
                                                                        suitable metrics for evaluating maintainability factors which
granularity of the service. Complexity has been eliminated
                                                                        belong to the two phases of service design and operation. In
arguing the complexity of the design phase can be viewed as
                                                                        services design phase, studies and research in the software
the combination of coupling and cohesion and in fact
                                                                        and service-oriented metrics were studied. Overall, two
complexity is in a way duplicating two discussed properties
                                                                        metric categories were identified: 1) service-oriented specific
[25]. The reason for eliminating the size by using a similar
                                                                        metrics 2) software specific metrics. In the service-oriented
argument is the coverage of this feature with service
                                                                        architecture, the metrics related to structural properties are
granularity. Also the parameter granularity and
                                                                        completely different from the software metrics [26].
consumability have been eliminated by documenting the
                                                                        Therefore, these types of metrics were completely
shortage of their suggested sources as maintainability
influence factors and as a result their minimal effect is
                                                                            Further, by using GQM technique and by accentuating on
overlooked. Therefore in design phase, maintainability is
                                                                        service-oriented architecture characteristics in terms of GQM
considered as a dependent variable and granularity, coupling
                                                                        components include Purpose, Aspects, Subject and
and cohesion factors as independents.
                                                                        Viewpoint, the appropriate questions were defined and based
    In the operational phase, based on ISO/IEC 9126
                                                                        on them, the appropriate metrics of evaluating coupling [10],
standard maintainability was divided into four sub-attribute
                                                                        cohesion [1] and granularity [1] factors were chosen. Table 2
of analyzability, changeability, stability and testability [27].
                                                                        exhibits the selection metrics for the design phase.
Furthermore, for selecting the appropriate factors related to
the sub-attributes, various service management standards                      TABLE II.              EVALUATION METRICS FOR MAINTAINABILITY
such as ITIL and COBIT were evaluated. According to the                                                        FACTORS
purpose of this model, international ITIL framework that
consists of two main areas of support and delivery were                      property
                                                                                               Complete name                     metric
selected. ITIL framework focuses more on operational and                                     Degree           of
tactical levels of service support and also includes effective                               Coupling within a
procedures and processes to support services.                                                given    set     of
    Efficient services managements depend on four areas:                                     services     metric   Max = K*V*(V-1)
                                                                                             (DCSS)                Max only appears when all of
processes, products, people and provider. In other words, for
                                                                                                                   nodes in graph do not connect
optimal service management in the ITIL standard these four                   coupling                              together
areas need to be properly assessed and evaluated. Further, by
mapping the ITIL standard processes in the support area with                                                       Min = V*(V-1)
maintainability sub-attribute, related and appropriate process                                                     Min only appears when all of
according to table 1 were identified. So in this phase                                                             nodes in graph connect to others.
dependent variable is service maintainability and
                                                                                             Inverse      of
independent variables are support process levels include                                     Average
incident management, problem management, change                                              Number of Used
management,         configuration     management,        release             cohesion        Message (IAUM )       SSNS: System Size in Number of
management and availability management.                                                                            Services
                                                                                                                   TMU: Total Number of Message

                                                                                                               ISSN 1947-5500
                                                                 (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                                 Vol. 9, No. 10, October 2011

                  Complete name                  metric                    together with known facts from experts as well as by
                                                                           emphasizing compatibility with service-oriented architecture
                 Squared      Avg.
                 Number         of                                         characteristics was evaluated and consequently in the end,
                 Operations     to                                         fuzzy system was selected as an appropriate method [16].
                 Squared      Avg.                                             As proposed evaluation structure includes two kinds of
                 Number         of                                         predictor or independent variables namely design phase
                 Messages            NAO: Number of Asynchronous
  Granulari                          Operations                            metrics and operation phase metrics, so each of them needs a
     ty                              NSO: Number of Synchronous            separate fuzzy system. A Discrete collection of real values
                                     Operations                            from structural properties metrics namely coupling, cohesion
                                     SSNS: System Size in Number of        and granularity form the fuzzy systems inputs which belong
                                                                           to service design phase. Also, real values or scores from
                                     TMU: Total Number of Message
                                     Used                                  selected processes maturity level evaluation include incident
                                                                           management, problem management, change management,
                                                                           configuration management; release management and
    In the operational phase, due to the inefficiency of the               availability management are fuzzy system inputs that belong
GQM method in selecting the appropriate metrics, such as a                 to the operation phase metrics.
lack of comprehensive questions in the method, self                            According to the type of problem and real value of the
assessment techniques of OGC (the Office of Government                     evaluation model inputs, the most suitable type of fuzzy
Commerce) has been used as evaluation metrics for the                      system to use in this model is fuzzy system with fuzzier and
operation phase [28]. This method includes a questionnaire                 defuzzier. In this type of fuzzy system, a fuzzier transforms
that consists of all four dimensions of services management                real value of inputs into a fuzzy set as well as a defuzzier
and evaluates them in nine levels through a variety of                     transforms fuzzy value output into a real value. This type of
questions. Maturity level of selection process factors include             fuzzy system, in addition to the mentioned parts namely
prerequisites, management intent, process capability, internal             fuzzier and defuzzier, it has two other parts of logic rules and
integration, products, quality control, information                        logic engine. TMF membership function, Centroid Average
management, integration and external interface with the                    (CA) defuzzier, Mamdani logic engine is selected for the
customer.                                                                  construction of the metric evaluation method.
                                                                               The only issue remaining with reference to the
                                                                           introduced evaluation fuzzy system is the creation of logic
C.              Evaluation method                                          rules and their related approvals by the experts in that field.
    In a vast view, the proposed model with the modulation                 Measuring maintainability, relations and the effects of
of design phase as well as service operations creates a                    dependent and independent variables in the service design
maintainability evaluation structure. In this model, as for the            and operation phase which have been identified in the
offered evaluation structure, to provide a clear and unified               previous section, defined in the form of fuzzy rules and
response to, an evaluation technique is needed. Similar                    through a questionnaire was validated and approved by
research and studies on prediction methods and quality                     service-oriented experts.
characteristics were investigated [16, 17, 18, 7 and 13].
Generally two methods for predicting maintainability were
identified: 1) Algorithmic technique model and 2)                                 III. PROPOSED MODEL FOR SERVICE-ORIENTED
Hierarchical dimensional assessment model. To achieve the                        ARCHITECTURAL MAINTAINABILITY EVALUATION
relationship function between independent and dependent                        To design the model, in the previous sections the
variables, in the first batch from existing data set and in the            proposed solutions to solve each one of the maintainability
second batch from expert opinions, probabilistic models and                evaluation requirements were introduce in two service design
soft computing techniques are used [18]. So given the                      and operation phase. In this section the proposed model is
limited data set for maintainability metrics in the leading                offered according to the previous concepts.
research, the first batch were completely removed.
    Fuzzy systems, neural networks, Case-Based Reasoning                   A.            Overall conceptual model of maintainability
(CBR) and Bayesian networks are some models based on                          evaluation
Hierarchical Dimensional Assessment Model. further, the                       The proposed model consists of five sections: input,
introduced methods, by ingratiating the desired modeling                   analysis, measurement, decision making and output. In “Fig.
attributes namely Output Explanation ability, being suitable               1” Components of model and their relations are presented.
for small data sets, adjustment to new data, visibility of
Reasoning process, being suitable for complex models,

                                                                                                       ISSN 1947-5500
                                                           (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                           Vol. 9, No. 10, October 2011

                                         Figure 1. Components of model and their relations

Input                                                                  metrics) in the design phase which have been previously
    The inputs of design section of maintainability evaluation         approved and validated by the SOA experts is placed in the
model include all types of service-oriented architecture               analysis section. It must be noted that similarly, information
relationship. In this part, software services were derived from        related to sub-attributes, factors, metrics and their
business services in a form of atomic or compound services             relationship in the operation phase are also placed in the
being analyzed. The relevant information of service                    analysis section.
component including Implementation elements, service
interface and the relationship between them are obtained               Measurement
through an interview with the service owner or by surveying                This section of the model includes performing a set of
the technical documentation design and handed over to the              rules that have been collected in the analysis section about
analysis section. Additionally, the information is received            service. By using fuzzy logic, the measurement section
from the operation section inputs from organizational experts          analyzes the collected information from the analysis section.
or service owners through a questionnaire.                             In another word, measurement section is a collection of math
                                                                       functions and formulas which are based on collected
Analysis                                                               information from the previous section. This part evaluates
    This section of the proposed model includes the                    the maintainability based on the fuzzy system in each of
relationships between dependent and independent variables              service design and operation phase. The operation
in the design and operation phase. In other words, this part           mechanism in design section is to facilitate the assessment
consist of the relationship between maintainability variables          tool receives coupling, cohesion and granularity metrics
with coupling, cohesion, service granularity variables and             relevant information from analysis section, next by means of
also association of the former three variables with related            defined rules begins to evaluate the maintainability. Also in
metrics in the design phase. Also, the rules defined between           operation section, scores resulting from maturity level
the model’s different levels (sub-attributes, factors and              questionnaire (OGC) is received from analysis section, and

                                                                                                  ISSN 1947-5500
                                                          (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                          Vol. 9, No. 10, October 2011

then maintainability of operation phase is evaluated by using             Further, based on analysis of the collected information,
associated fuzzy rules.                                               fuzzy rules were define and used to evaluate the
                                                                      maintainability in the service lifecycle. This model provides
Decision making                                                       the possibility to judge and make decisions about the
    As mentioned, this model provides decision making                 software service maintainability status in every step of the
possibility about the maintainability status after the                service lifecycle. So based on these decisions, the owner and
completion of the service design phase and before their               manager will be able to take control effort or make the
operation phase and even after the completion of the                  necessary corrections in the fastest possible time.
operation phase. In another words, measurement section
results in design section allow a service owner or manager to
adopt the necessary decisions and give a recommendation
about the maintainability status of software services in the                                        REFERENCES
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                                                                                                        ISSN 1947-5500
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                                                                                                                      Vol. 9, No. 10, October 2011

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