A FRAMEWORK FOR ASPECTUAL REQUIREMENTS VALIDATION: AN EXPERIMENTAL STUDY

International Journal of Software Engineering & Applications (IJSEA), Vol.12, No.5, September 2021
DOI: 10.5121/ijsea.2021.12502 21
A FRAMEWORK FOR ASPECTUAL REQUIREMENTS
VALIDATION: AN EXPERIMENTAL STUDY
Abdelsalam M. Maatuk1
, Sohil F. Alshareef 2
and Tawfig M. Abdelaziz3
1&2
Department of Software Engineering, University of Benghazi, Benghazi, Libya
3
Libyan International Medial University, Benghazi, Libya
ABSTRACT
Requirements engineering is a discipline of software engineering that is concerned with the
identification and handling of user and system requirements. Aspect-Oriented Requirements
Engineering (AORE) extends the existing requirements engineering approaches to cope with the
issue of tangling and scattering resulted from crosscutting concerns. Crosscutting concerns are
considered as potential aspects and can lead to the phenomena “tyranny of the dominant
decomposition”. Requirements-level aspects are responsible for producing scattered and tangled
descriptions of requirements in the requirements document. Validation of requirements artefacts
is an essential task in software development. This task ensures that requirements are correct and
valid in terms of completeness and consistency, hence, reducing the development cost,
maintenance and establish an approximately correct estimate of effort and completion time of the
project. In this paper, we present a validation framework to validate the aspectual requirements
and the crosscutting relationship of concerns that are resulted from the requirements engineering
phase. The proposed framework comprises a high-level and low-level validation to implement on
software requirements specification (SRS). The high-level validation validates the concerns with
stakeholders, whereas the low-level validation validates the aspectual requirement by
requirements engineers and analysts using a checklist. The approach has been evaluated using
an experimental study on two AORE approaches. The approaches are viewpoint-based called
AORE with ArCaDe and lexical analysis based on Theme/Doc approach. The results obtained
from the study demonstrate that the proposed framework is an effective validation model for
AORE artefacts.
KEYWORDS
AORE, validation and verification, requirements engineering, aspectual requirements,
crosscutting concerns
1. INTRODUCTION
The Aspect-Oriented Requirements Engineering (AORE) aims to extract and construct good
identification and separation of crosscutting concerns [14]. Conventional requirements
engineering (RE) approaches treat the resulting intersection of concerns, i.e., aspects, as a rule, or
restriction relationship [33] [6]. Such concerns handling might lead to what so-called tyranny of
the dominant decomposition, which results in scattered and tangled implementation of concerns
to other software artefacts [16]. In terms of aspect orientation [6][16], traditional RE approaches
have been extended to support the crosscutting nature of concerns as early as possible in software
development.

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In this context, shortcomings, such as clean mapping of requirements artefacts to later stages,
satisfactorily trade-off analysis, equality treating of concerns and validation of AORE artefacts
remain a challenge and not fully studied [1][13].
Validation in requirements engineering is the process to eliminate the conflicts among
requirements in SRS [1][2][41]. Besides, it relates to the analysis since it is involved with
detecting problems associated with the SRS, i.e., inconsistencies, incompleteness and ambiguities
[2] [43]. Inconsistent requirements are requirements that are stated and described differently at
different places in SRS, whereas ambiguous requirements referred to as one requirement has
multiple perceptions and incomplete requirement, which refers to a requirement that does not
convey a complete and meaningful requirement [43][44].
Furthermore, requirements validation is a crucial activity as it helps to reduce the cost of
maintenance. This is due to the reason that, the cost of fixing errors in later stages, i.e.,
architecture, design and code, of software development is more expensive than rectifying them in
the requirements analysis phase [2]. In addition, errors in SRS lead to huge rework costs and
effort when issues are discovered in later stages. Fixing errors in later stages of software
development requires more time, effort and cost [33][15][42]. Moreover, making changes at this
stage requires requirements engineers and analysts to properly manage the changes as they would
affect other artefacts, which are associated with the requirements and it would to re-testing of the
system when the new changes are employed.
Through the investigation described in [3], it is noticed that almost all the approaches focus on
identifying crosscutting concerns as well as representing them either using graphical models,
XML schema, templates or text-based representation. Therefore, the resulting artefacts from the
requirements phase must be validated before moving to other development stages to reduce extra
work and effort caused by missing information and unintentionally overlooked inconsistency
rules [43]. In addition, the validation can be either dynamic or static. Dynamic validation is easier
to perform and it allows the automatic checking and interpretation of software artefacts, e.g., Test
Driven Development. In contrast, static validation implies the understandability and
completeness of requirements artefacts to be validated. However, dynamic validation is often
more costly than static validation as the problem domain needs to be formalized and fully
covered at first.
As far as we can tell, the AORE proposals lack the clarity to employ techniques and methods to
validate aspectual requirements after they are identified to ensure the correctness of resulted
AORE artefacts. Some experiments and case studies were conducted in terms of aspects and
concerns identification. Therefore, we have proposed a framework, i.e., Validation Framework
for Aspectual Requirements (ValFAR) to validates the AORE artefacts in three main phases,
each of which has several activities [12]. Phase 1 is for concern handling, Phase 2 is for concern
validation, i.e., high-level validation, whereas Phase 3 consists of Aspectual requirement
specification and validation, i.e., low-level validation. However, the focus of this paper is mainly
on the experimental work of the framework and the validation problem of aspects and concerns in
the requirements engineering phase. The results of the experimental work are presented and
discussed. The data used in the experiments were the resulted analysis artefacts from two
different approaches.
The correctness of the ValFAR method has been tested with analysis artefacts from existing
AORE approaches. These artefacts are used as input to ValFAR to ensure that the resulted
concerns and aspects are valid and correct. Two different AORE approaches have been selected
to apply the proposed solution. On one hand, the first approach is a viewpoint-based model [6],
which treats aspectual requirements as concerns and encapsulates them in a simple self-

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explanatory XML schema. The schema, however, contains requirements, e.g., concerns, which
should be decomposed to sub-concerns to reduce the tangling issue and make it simpler to apply
the decomposition rules. On the other hand, the second approach is a lexical-based aspect
identification, i.e., Theme/Doc [5][10]. It uses views and action-view to identify the relationships
between concerns and requirements to extract the influential aspect. The Theme is suitable when
the requirements are well-written and documented, although it cannot identify non-functional
concerns as they are usually not associated with action words. The results from both experiments
were encouraging, although some artefacts had to be refined and modified in terms of rewriting
descriptions of concerns and requirements to validate AORE artefacts.
The remainder of the paper is organized as follows: Section 2 presents the related work to the
validation and verification of aspects and crosscutting concerns. Section 3 introduces the ValFAR
method. Section 4 presents the experimental study. Section 5 discusses some of the obtained
results. Section 6 concludes the paper.
2. RELATED WORK
Diﬀerent AORE approaches are dedicated to aspectual requirements focusing on diﬀerent stages
during the system development. However, through our investigation of the problem, we have
found that only a few AORE proposals provide the means to validate the elicited aspects
[6][11][7]. A comprehensive survey for aspect mining tools and approaches can be found in [40].
The work presented in [36] describes the synthesis and interaction of aspects in aspect-oriented
methodology.
The theme approach [5], is based on lexical analysis of the requirements and it has proven to be
an effective method to identify and extract the relationship among aspects by action verbs. AORE
with ArCaDe [6] identifies aspects as viewpoints and it encapsulates them in an XML schema
with their requirements and sup-requirements. However, this method focuses on the composition
of aspectual requirements rather than validating the concerns and the identified aspects.
The AORE model proposed in [6] applies the viewpoint-oriented approach to identify
stakeholders’ requirements using viewpoints and XML. Araŭjo et al. [6] introduced a framework
based on a viewpoint-oriented approach, which generates templates to identify crosscutting non-
functional requirements.
Grundy [8] proposed an aspect-oriented requirement engineering solution for component-based
systems, whereas Jackson [9][13] proposed a problem frame approach, which identifies aspects
from the problem domain. This method is only applicable when the problem being investigated
has been solved in the past, and the solution can be used again, by breaking down problems into
sub-problems in parallel with defining composition rules, which can be used to resolve the
conflict between aspects.
Other models, e.g., Cosmos [13] and CORE [7] are proposed for concern-oriented or
multidimensional separation of concern approach. Although Cosmos is known as the best for its
ability to analyze the relationship between concerns, it lacks the systematic means to identify any
type of concern. Moreira [7] proposes an approach, called CORE that introduces a projection
table to reduce the concern dimension.
The Theme approach [5][10] is an AORE approach that is not based on conventional
requirements engineering techniques, such as viewpoint, use case scenario and goal-oriented.
Theme solution extracts crosscutting concerns and identifies aspects by keyword and lexical
analysis.

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Araŭjo et al. [16] proposed a use-case-based requirement approach, which identifies concerns
from different scenarios of the system. It is a template-based approach for identifying aspectual
use-cases, which are modelled, providing traceability similar to the multidimensional separation
of concerns techniques. In addition, there are many approaches to identify aspects by use-case
[14][15][16].
Domain analysis of existing component and aspect approaches for crosscutting concerns is
described in [39]. They identify a set of requirements to be fulfilled for modeling of dynamic and
crosscutting features using aspect-oriented. After that, the identified requirements are grouped
into an evaluation model to be checked against capability of existing combinations to validate the
model.
A process that identifies the relations that can be observed between architectural aspects, quality
attributes, and requirements is presented in [38]. The relations are created with the aid of
mappings from non-functional requirements to quality attributes and architectural aspects. The
process uses the MultiCoS approach in managing requirements and concerns by matching
function and crosscutting coefficients to identify the crosscutting concerns.
In terms of identification, an aspect frame structure is proposed, which is a pattern for aspects
that share a common concern, behavior, and how are integrated into a rational of the functional
requirements, which they crosscut [37]. These frames are used to describe the concrete aspects by
requirements engineers and analysts.
In the context of aspectual requirements validation, we have found only one framework presented
in [4], which argues that the validation of aspectual requirements can be accomplished with two
levels of validation. It amalgamates three AORE approaches: viewpoint-oriented approach, goal-
oriented approach and a use case-oriented approach. It converts the identified concerns from each
AORE approach into their respective graphs. An aspectual graph is produced and provided as an
input to the aspectual graph parser, which generates an XML file for the aspectual graph to
compare it with each XML file from each approach to remove any duplicated concerns and
ambiguities. However, there is no way to validate the framework in general. It was presented
without actual results or case studies to prove that the method is working properly with these
three approaches. The conversion process itself is not clearly defined with specific steps to follow
neither the integration of the three models into one XML file.
Validation of requirements artefacts in traditional requirements engineering is supported by using
one of the common validation techniques, e.g., formal review, inspection, or paper prototyping.
In addition, there is a separate activity involving validating the requirements in traditional
requirements engineering. In contrast to that, AORE approaches are focused more on the
identification and specification of aspects and concerns without equally giving attention to the
test and validate those artefacts. However, the analysis techniques presented by each model
provide a great granularity of information to conduct the validation. The challenge was the ability
to use one validation method on different approaches without the need to change the validation to
cope with each AORE model. This paper introduces a novel method to validate and evaluate
aspectual requirements in the early stages using experimental study.
3. THE PROPOSED APPROACH
This section describes the proposed solution, i.e., the Validation Framework for Aspectual
Requirements (ValFAR) [12]. It validates the AORE artefacts in three main phases, each of
which has its activities as shown in Figure 1. Phase 1 is for concern handling, Phase 2 is for
concern validation, i.e., high-level validation, whereas Phase 3: consists of Aspectual requirement

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specification and validation, i.e., low-level validation. These phases will be described in the
subsequent subsections. Before Phase 1, the correlation between concerns that form the
crosscutting relationship should be structurally addressed with a matrix. In addition, it is useful to
link the source of information of each concern with the corresponding stakeholder.
More importantly, ValFAR does not identify concerns or crosscutting concerns. It operates on the
assumption that AORE artefacts are identified in the form of the used approach, e.g., goal-
oriented (soft-goal and sub-goals), viewpoint-oriented, themes. However, before using the
ValFAR, these conditions have to be met:
 The SRS, i.e., the requirements document is produced
 Crosscutting concerns are identified using an AORE approach
 Aspectual requirements and concerns are specified in the SRS
3.1. Phase 1: Concern Handling
AORE approaches treat concerns based on the approach being used to identify concerns and
aspects. In a viewpoint-oriented approach, concerns are treated as viewpoints. Goal-oriented
approaches are based on soft-goal and sub-goal concepts and aspects are discovered and
identified as operationalities that affect the sub-goal, i.e., non-functional concern. In the
Theme/Doc approach, the theme and base theme is functional and non-functional concerns
respectively. Thus, we propose this phase to treat each artefact, i.e., viewpoint, goal, sub-goal,
base theme and crosscutting theme, which is used to identify aspects, like a concern to perform
the activities to achieve high granularity. This phase comprises three activities described as
follows:
Figure 1. illustrates the process of the ValFAR
3.1.1. Activity 1: Determine Concern Type
The Concern type should be determined before processing. A concern might be functional or
non-functional. Reviewing the analysis documents and the requirements specification helps to
understand the nature of concerns, hence determining its type. Functional concerns are treated
differently from non-functional in terms of specification, modelling. Thus, determining concern
type is crucial for granularity.

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3.1.2. Activity 2: Determine Concern Type
Concerns often have tangled nature in their descriptions, which poses as a difficulty to analysts to
handle them uniformly [20]. In addition, these entanglements contain additional information that
should be separated or new ones that are derived but encapsulated when needed [19][21][22]. To
tackle this difficulty, and if one or more of the rules are met, concerns should be decomposed
based on the following rules:
 If some parts of the concern present a limitation as to how a specific goal is achieved
 If there are parts implied design constraints on the original concern.
 If there are parts of the concern that are not used by other concerns, but they are used to
describe the issue
 If the description of the issue is too long
 If the concern contains a reference of description to other different concerns
 if a concern requires information from different concerns
 If there is a need to derive new concerns from the original concern
 If there are some parts of the original concern that are going to be associated with other
concerns
3.1.3. Activity 3: Describe Concern
Concerns often have a tangled nature in their descriptions, which poses a difficulty to analysts to
handle them uniformly [20]. In addition, these entanglements contain additional information that
should be separated or new ones that are derived but encapsulated when needed [19][21][22]. To
tackle this difficulty, and if one or more of the rules are met, concerns should be decomposed
based on the following rules:
 Concern ID: the unique identifier of the concern for traceability purposes.
 Concern name: a name that should not be repeated elsewhere to prevent inconsistencies and
confusion.
 Objective: a brief description of concerns objective written in a clear language.
 Type: type of concern, whether it is a functional or non-functional concern.
 Successful scenarios: a concise and complete description of the process executed by the
concern.
 Alternative scenarios: an alternative to the main scenario when limitations constraint it.
 Revision date: the date that the concern was modified last.
 Review count: indicates the number of iterations performed to process the concern.
 Reference: a reference to the concern analysis process and concern representation.
3.2. Phase 2: Concern Validation (high-level validation)
In Phase 1, concerns are decomposed and described structurally based on the type of concern.
Moreover, in Phase 2, functional concerns are validated using a semi-formal technique [2] [35].
In addition, non-functional concerns that constraint the functional concerns are linked to the
influenced concerns described and separated in a dedicated template. The stakeholder is part of
this phase as the developer validates the functional concerns and gets immediate feedback from
the stakeholder. The following three activities describe this phase.

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3.2.1. Activity 1: Model Functional Concerns
In this activity, the functional concerns are validated in a semi-formal manner [24]. The UML
sequence diagram model is used to verify the interactions with corresponding artefacts of the
system [27]. Besides, the specification of the concern must be validated to ensure the correctness
and it satisfies its objective. Additionally, the stakeholder, i.e., end-user or customer, is involved
for better results [25][26]. The number of iterations of this activity depends on the granularity of
the feedback between the customer and the analyst.
3.2.2. Activity 2: Describe Non-functional Concerns
In contrast to functional concerns, non-functional concerns usually are not associated with verbs
that express action and cannot be modelled by UML models [29][34]. In addition, non-functional
concerns employ how the system should respond and react to the user’s interaction, i.e., response
time or performance [30] [28]. Therefore, we propose a structured template to describe non-
functional constraints or design limitations that limit the structure of the functional concern. The
elements to be included in the non-functional template are:
 Name: name of the non-functional concern as described by developers.
 ID: a unique identifier to avoid redundancy and increase the ability to trace and concern.
 Related concerns: functional concerns that are constrained by this non-functional concern.
 Specification: clear and concise description of the limitation of this concern on other
concerns.
 Revision date: a date on which the concern was last reviewed or altered.
 Review count: number of iterations performed by developers to process the concern.
A functional concern might be constrained by more than one non-functional concern [29][30].
Using this technique to document and specify non-functional concerns benefits in several ways:
 Developers can derive architectural choices from the template and behavior of the functional
concern.
 Separate functional and non-functional concern specifications to improve the
understandability and readability of the artefacts.
 Separate overlapping quality attributes that might be included without detailed analysis
within the functional concern.
 Improve traceability of non-functional concerns, since the template can be altered at any
given time during the development in terms of evolution or refinement.
3.2.3. Activity 3: Evaluate Concerns Correctness and Completeness
Concerns that are part of the crosscutting relationship must be investigated to validate the
relationship and the integrity of the aspect through inspecting the concerns using a checklist that
contains quality questions aimed at evaluating the completeness and consistency, i.e., logical and
grammatical consistency [43]. This activity helps to ensure that concerns and requirements have
been extracted well and are ready to be moved to the next stage. In addition, all of the questions
of the checklist must be answered as satisfactory to each element; otherwise, the process is
repeated until all questions are answered with “Yes” except for missing details or anything
forgotten, the answer is “No” [11]. The questions to be included in the template are:
 Is the concern defined clearly?
 Are there any missing details or anything forgotten?
 Is there any association with other concerns or requirements?
 Does it include all the necessary information to make an architectural decision and design it?
 Is there enough information to develop a test case for the concern?

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 Is the successful scenario of each concern written in clear language?
 Is the description written so that it won’t lead to misinterpretation?
 Are there any parts of the concern repeated in other concerns?
 Are there any conflicts with other concerns or requirements?
 Is the concern traceable to its origins and stakeholder?
3.3. Phase 3: Aspectual Requirement Specification and Validation
The crosscutting relationship among concerns is validated according to the defined criteria in
Phase 2. The area of intersection, i.e., common interest with other concerns or requirements is
considered as a candidate aspect. Thus, aspectual requirements should be specified correctly.
Although aspects are systematically extracted with the aid of AORE approaches, the lack of
capturing all the necessary information in a single unit structurally, e.g., aspectual requirement
document remains overlooked. To overcome this issue, we propose a structured template to
document the critical details and the required information to validate the aspect statically as
Phase 3 of the solution, which contains two main activities.
3.3.1. Activity 1: Describe as an Aspectual Requirement
Aspectual requirements should not be too technical and have to be as abstract as possible [33].
The aspectual requirement describes the solution concept of the crosscutting concern, which has
to be carefully treated when designing and implementing the aspect in later stages. Besides, the
description of the aspectual requirements has to be clear and concise [31]. The details to be
included in the aspect document are:
 Aspect ID: a unique identifier for the aspect.
 Aspect name: a name to describe the aspect and it should not be repeated with other aspects.
 Concerns: list of concerns or concerns that are influenced by this aspect.
 Aspect description: a brief and concise description of the aspect of behavior.
 Aspect priority: the degree of importance for the aspect demanded by stakeholders.
 Aspect post-condition: a service that the aspect will provide.
 Reference: Reference to the analysis material, documentation and representation of the aspect
for understandability.
After documenting the aspectual requirement, a matrix is developed if there is a dependency
between aspects in terms of execution and responsibility [32]. In order to achieve a good result
from this matrix, the analysis of the requirements and concerns must have addressed the aspect
life cycle. It could be shown as a graphical representation of the aspect or through tables provided
by some of the AORE approaches that handle this issue.
3.3.2. Activity 2: Validate the Aspectual Requirement
To ensure the quality of the information acquired by the requirements engineers, we propose to
develop a list of questions that are targeting the core concepts of the aspects at the requirements
level. In other words, the other development stages, i.e., architecture, design and coding should
not be included in the description of the aspectual requirements. Therefore, the requirements
section of the validation form must be answered to “Yes”. This means that all the necessary
information for the aspectual requirements is available in the correct format. The description of
the aspectual solution should not limit the ability of developers to design the aspect. However, if
there are constraints or design limitations that should be mentioned in the description, developers
need to consider that to perform trade-off analysis and negotiation with stakeholders. The
questions to be included in the template are:

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 Does the aspect describe the solution concept for the problem?
 Does the aspect define the process with an accurate description and understandable
language?
 Does the aspect contain all the related parts of the crosscutting concerns?
 Have the areas of intersection with other requirements or concerns have been identified and
specified within the scope of the aspect?
 Are the requirements and concerns affected by the aspect identified and represented clearly?
4. EXPERIMENTAL STUDY
This section demonstrates the experimental work of ValFAR that is conducted on the analysis
artefacts resulted from two existing AORE approaches. These approaches have been chosen for
this study due to their nature in handling the AORE artefacts. The Theme is uniquely designed
for the analysis and design of aspectual requirements. It uses action words and action clipped
view to capture and model the crosscutting relationship respectively, which is unlikely in other
approaches that use UML as modelling tool. The AORE with ArCaDe, on the other hand,
encapsulates the functional and non-functional concerns in XML schema and treats it as an
aspect. This encapsulation presents a challenge in determining the degree of interaction among
the inter-related concerns. For these reasons, these two approaches have been selected to
demonstrate the ValFAR method. For the lack of space, we have chosen to show the final results
of the refinement process for requirements and concerns in Table 4 and Table 10. There are
several iterations to reach the desired output. Although, changes have been made to the artefacts
without harming the relevancy of the crosscutting relationship. Besides, Tables 2, 6 and 12 have
reviewed to the corresponding number in the count section of each table. The refinement of the
artefacts was necessary to improve the results obtained from the approaches. Some of the
requirements and concerns have been re-written and re-analyzed for better understanding and
granularity.
4.1. Viewpoint and XML Approach
The case study demonstrated by AORE with ArCaDe is a simplified version of the toll collection
system [6]. The approach has identified a number of viewpoints TollGate, Vehicle, ATM, Police,
Gizmo and DebitingSystem. In this paper, the TollGate viewpoint will be demonstrated and
ResponseTime, i.e., an aspect which crosscuts multiple viewpoints, is demonstrated as well.
Besides, concerns and requirements are treated as a viewpoint in this approach. The study shows
that aspects can be composed and identified using viewpoint methodology. The TollGate
viewpoint contains tangled information, e.g., exiting and entering the toll, type of toll and capture
plate number for unauthorized vehicles. For better granularity, this viewpoint should be
decomposed to separate the tangled description of the included requirements. Table 1 illustrates
the final results of the decomposition process.

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Table 1. Decomposition of TollGate concern
Decomposed Concern
Core and sub-concerns Description
TollGate <<core cocnern>> A gate with installed cameras and sensors that vehicle passes through.
EntryToll Detects the installed gizmo on the vehicle.
SingleToll Turn the light into the green for authorized vehicles and display the amount
of money to be paid.
PayToll Display the amount of money to be paid by authorized vehicles.
PlateCapture It captures the plate numbers of unauthorized vehicles.
ExitToll Checks the entrance of the vehicle through the gate whether it is a valid
entrance or not.
Note The PayToll and PlateCapture concerns are added as new sub-concerns
after analyzing the initial scenario of the system. Thus, this refinement
should provide a clear and concise understanding of these two concerns.
However, when validating the concern, these sub-concerns have to be
taken into consideration as a whole.
Once the type of concerns is determined and are decomposed, concerns, as demonstrated in Table
2, are described in the template as shown in Activity 3 of Phase 1 of ValFAR. This task is only
applied to functional concerns to be validated in Phase 2. The functional concerns are modeled
and validated using a sequence diagram with the involvement of the concerned stakeholders, i.e.,
analysts and users. The validation of Vehicle and Gizmo concerns are shown in Figures 1 and 2
respectively
.
Table 2. Description of TollGate concern
Concern Description Template
ID Con04
Name TollGate
Objective Passing fees payment
Type Functional
Successful
scenario
See decomposition template for the TollGate concern.
Alternative
scenario
Revision date 1st
May, 2020
Review count Two times. Reviewed for tangled requirements and missing information. Therefore, the
concern had to be decomposed for containing tangled descriptions of requirements.
Reference Figure 2 and 3
Note This concern has several sub-concerns, which are described in a separate template. To
avoid inconsistencies in describing the concern, the decomposition template provides
all the necessary information related to the main and sub-concerns.

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Figure 2. Demonstrates the semiformal validation of Gizmo concern
Figure 3. Demonstrates the semi-formal validation of Vehicle concern
In contrast to functional concerns, non-functional concerns cannot be validated or measured using
the same techniques. Thus, we propose to document the non-functional concern in a separate
template with a reference to the related functional concerns. The elements of Table 3 are
explained in Activity 2 of Phase 2. The list of figures in the Reference row represents the analysis
process and the influenced artefacts by ResponseTime. The concerns are then to be evaluated for
consistency and correctness. To cope with this, we propose to use the structure in Table 4, which
is a list of questions to test the consistency and correctness. This activity is explained in Activity
3 of Phase 2. This concern has been subject to several iterations of modifications. Thus, for
simplicity, only the final result is presented.

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Table 3. Description of ResponseTime non-functional concern
Non-functional concern description
Name Response time
ID Asp-01
Related concerns ATM, Gizmo, Vehicle and TollGate
Specification The aspect shall respond in time to the specified concerns that are restricted by
this aspect.
Revision date May 4, 2020
Reference Figure 2 and 3
Table 4. Response time evaluation concern template
Concern completeness
Is the concern defined clearly? Yes
Are there missing details or anything forgotten? No
Is there any association with other concerns or requirements? Yes
Does it include all the necessary information to make an architectural decision and design it? Yes
Is there enough information to develop a test case for the concern? Yes
Concern consistency
Is the successful scenario of each concern written in clear language? Yes
Is the description written so that it won’t lead to misinterpretation? Yes
Are there any parts of the concern repeated in other concerns? Yes
Are there any conflicts with other concerns or requirements? Yes
Is the concern traceable to its origins and stakeholder? Yes
Table 5. Description of ResponseTime aspectual requirement
Aspectual Requirement Document
ID Asp01
Name ResponseTime
Concerns ATM, Gizmo, Vehicle and TollGate
Description Response time has been described and analyzed as a non-functional concern. The ATM
transaction must be processed and validated immediately as the customer request the
ticket from the machine in the station. Similarly, when the vehicle passes the toll gate,
the system must respond quickly to the gizmo installed in the vehicle, which identifies
the vehicle in terms of valid entrance, billing or authorized vehicle.
Priority High
Pre-condition The ATM, Gizmo, Vehicle and TollGate concern conditions must be satisfied and
operate without any errors; hence the aspect will operate correctly and efficiently.
Reference All functional concerns analyzed and validated in a semi-formal fashion are influenced
by this aspect.
At this stage, the aspects of the system should be identified and specified using the techniques
provided by AORE approach. Moreover, the aspects are identified in different representations. As
a result, we propose to document the aspectual requirements in a structured template as shown in
Table 5. In most cases, there is a dependency among aspects, e.g., aspect A depends on aspect B
to perform a certain task or goal. Thus, this relationship should be captured and documented so
requirements engineers and analysts would have all the critical parts of each relationship. In our
experiment, we did not come across any dependency between the identified aspects. The aspect
then is validated to ensure that nothing important is left out of the process. For this issue, we
propose to use the validation template presented in Table 6. The aspectual requirement status has
to be checked against the changes made to the related concerns. As those crosscutting concerns
form the aspect.

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Table 6. Validation form aspectual requirements ResponseTime
Aspectual requirement validation Aspect ID: Asp01 Review
count: 2
Does the aspect describe the solution concept for the problem? Yes
Does the aspect define the process in accurate description and understandable
language?
Yes
Does the aspect contain all the related parts of the crosscutting concerns? Yes
Have the areas of intersection with other requirements or concerns have been
identified and specified within the scope of the aspect?
Yes
Are the requirements and concerns affected by the aspect identified and represented
clearly?
Yes
4.2. Theme/Doc Approach
The case study presented in the Theme/Doc approach is a course management system [6]. In this
case study, a student can register and unregister for a course, the action performed by the student
must be logged into the student record. The professor can register and unregister a student for a
course and it must be logged in. The professor as well can give marks to the student. The lexical
analysis of the requirements has addressed the following action verbs: Give, Register, Unregister
and Flagged, which are functional requirements.
The functional concerns, i.e., base-themes, are modeled using a sequence diagram with the
involvement of the concerned stakeholders. Figures 3 and 4 demonstrate the process of each
concern that the Theme approach has produced. Figure 5 shows the clipped-view action in the
Theme/Doc tool, which identifies Logged as an aspectual requirement, i.e., crosscutting the
system functionalities.
Figure 4. clipped action view of the main actions in requirements
The non-functional requirements produced by Theme/doc process in behavior, which logs each
action performed by either student or professor into their records or system’s database
respectively. Table 9 describes the non-functional behavior, which constrains the behavior of the
other functional concerns. In Table 10, the logged is evaluated against the criteria questions.
There have been few refinements to the way requirements were written to formalize the last
version of the evaluation template

34
Figure 5. Sequence diagram for Give concern
Figure 6. Sequence diagram for Register concern
The Logged requirements is a non-functional requirement. However, based on the lexical
analysis of Themes, the granularity of concerns does not require the need to decompose the
concerns. The description of Give and Register concerns is presented in Tables 7 and 8
respectively. The lexical nature of the analysis process has produced a solid description of
requirements and concerns without the need to refine.
Table 7. Description of Give concern: base-theme
ID Theme_01
Name Give
Objective Enables the professor to give marks
Type Functional
Successful scenario The professor logs into the system and enters the marks for the specified
course.
Alternative
scenario
Review count 0
Reference Listed in system requirements in Figure. 5 and Figure. 6
Note This behaviour needs to be recorded into the log file. Each time the professor
makes a change in the system and the database, this must be recorded.

35
Table 8. Description of Register concern: base-theme
ID Theme_02
Name Register
Objective Enables student to register for a course
Type
Successful scenario The student will be asked to enter their credentials, and when credentials
are correct, the system shall let students enter the course they wish to
register for and submit the request.
Alternative scenario
Review count 0
Reference Figure 6
Note A log file is needed to record this activity in the system.
Since logged is a non-functional concern and the non-functional behaviors are more candidates to
be aspects. However, the logged behavior crosscuts several requirements of the system. Thus, it
is an aspectual requirement. Table 11 describes the aspectual requirements based on the
granularity of the information obtained in the case study conducted by the Theme/doc. Table 12
validates the aspectual requirement using the proposed checklist. The original logged has been
reviewed two times in terms of concern relationship. Thus, as an aspectual requirement, it has to
be checked against the changes made to the concern refinement.
Table 9. Description of non-functional concern Logged
Non-functional concern description
Name Logged
ID Theme_a
Related concerns This concern is a potential aspect and it cuts across all the functional concerns,
i.e., give marks, register student, unregister student, register course and
unregister courses
Specification Logged keeps track of the activities performed by the authorized actor. Each
actor has a scope of interaction with the system. These interactions have to be
logged into the individual’s record.
Reference Figure 4. Figure 5. Figure 6
Table 10. Logged concern evaluation template
Concern completeness
Is the concern defined clearly? Yes
Are there missing details or anything forgotten? No
Is there any association with other concerns or requirements? Yes
Does it include all the necessary information to make an architectural decision and design it? Yes
Is there enough information to develop a test case for the concern? Yes
Concern consistency
Is the successful scenario of each concern written in clear language? Yes
Is the description written so that it won’t lead to misinterpretation? Yes
Are there any parts of the concern repeated in other concerns? Yes
Are there any conflicts with other concerns or requirements? Yes
Is the concern traceable to its origins and stakeholder? Yes

36
Table 11. Logged aspectual requirement description template
Aspectual Requirement Document
ID Theme_a
Name Logged
Concerns Crosscuts all system concerns
Description This aspect shall record each functionality of the system.
Priority High
Pre-condition The influenced concerns by this aspect must be executed and valid in terms of
process.
Reference List of requirements in requirements documents, Table 7, Table 8 and Table 9
Table 12. Logged aspectual requirements validation template
Aspectual requirement validation Aspect ID: theme_a Review
count: 2
Does the aspect describe the solution concept for the problem? Yes
Does the aspect define the process in accurate description and understandable language? Yes
Does the aspect contain all the related parts of the crosscutting concerns? Yes
Have the areas of intersection with other requirements or concerns have been identified and
specified within the scope of the aspect?
Yes
Are the requirements and concerns affected by the aspect identified and represented clearly? Yes
5. DISCUSSION AND RESULTS
In this article, we have conducted two experiments on AORE approaches, i.e., AORE with
ArCaDe and Theme/Doc. Theme/doc [5] represents functional concerns more effectively since
they are associated with action verbs. In addition, the Theme view is a powerful tool to capture
the relationship between concerns using lexical analysis of the requirements as for the non-
functional concerns; the requirement documented may require being re-written. The non-
functional concerns are challenging in terms of capturing the representation using Theme/doc.
Using ValFAR on the concerns resulted from Theme/doc, the non-functional artefacts have gone
through several iterations of refinement to avoid inconsistency of combing them with functional
concerns. However, from a functional perspective, no iterations of refinement are needed to
improve their granularity. Furthermore, the identified aspectual requirements in Theme/doc are
not specified clearly in terms of SRS structure. Thus, we have to improve some of the themes for
validation.
The Theme/Doc tool relies on lexical analysis and defining the action words to capture the
relationship between base-themes, i.e., concerns, and crosscutting-themes. Moreover, the
requirements must be written and documented before analysts can use the Theme/doc tool to
identify the base-themes and action words that are shared with requirements to identify the
crosscutting-themes, i.e., potential aspects.
However, we have found that concerns and requirements extracted using this method are more
coherent and do not require any decomposition mechanism. In addition, there have been few
inconsistencies describing the process of the shared requirement between the base-theme and the
crosscutting-theme. This was handled by modeling the base-theme and relating it to the
crosscutting-theme, which then is passed through validation for consistency and completeness to
ensure the validity of the crosscutting relationship.
AORE with ArCaDe [6] uses the XML schema to store the aspect and its requirements. It
represents an aspect as a concern encapsulated in XML schema, which contains the related

37
requirements with their sub-requirements and the composition rules for the aspectual
requirements. This method is effective when modularizing of aspectual requirements is highly
demanded, but the treatment of concern is not efficient in terms of clarity and decomposition. By
applying the ValFAR method, we discovered that requirements in the XML schema needed to be
decomposed in order to validate the concerns and the aspectual requirements. This decomposition
helped to achieve better granularity for each artefact. As a result, the new decomposed sub-
concerns had to be analyzed and validated to maintain the cohesive structure of the schema. The
decomposition rules we provided, showed that there are tangled descriptions of requirements in at
least two concerns, which are identified and documented using the viewpoint approach.
6. CONCLUSIONS
This paper introduced a Validation Framework for Aspectual Requirements (ValFAR) and
included the critical artefacts of the framework. The ValFAR method validates AORE artefacts in
three phases. Each phase has its own set of activities to be performed to achieve the best results.
The ValFAR enables requirements engineers to perform validation on two levels, i.e., high-level
and low-level validation. The high-level validation is to validate the concerns with stakeholders
and the low-level validation validates the aspectual requirement by developers using a checklist.
The framework has been used to conduct an experimental study to ensure the effectiveness of the
method. The experiment was conducted on the resulted artefacts of the requirements engineering
phase of each approach. The results have been discussed briefly and the artefacts of ValFAR
have been explained in detail. The proposed solution has shown that the results obtained from the
experiments are encouraging. Furthermore, the investigation into the problem of aspect validation
has shown that aspectual requirements are not specified in structured format as the regular
requirements. As a result, developers document the aspects to the best of their knowledge without
fully grasping the concepts of crosscutting concerns and aspects. To conclude, the approaches
discussed in the related work showed that the existing approaches specify concerns and aspects to
their satisfaction. Each approach describes and specifies aspects differently from other
approaches. Thus, a standard and formal specification of aspects are desired to cope with this
issue.
The proposed solution treats each viewpoint and theme as a concern, which facilitates the process
of concern decomposition to validate the crosscutting relationship by inspecting each concern
individually. This benefits in determining the correctness and consistency of crosscutting
relationship components. The resulted aspectual requirements are validated with a checklist,
which aims at defining what aspect should be in the requirements phase. The evaluation of the
proposed solution on the different approaches has shown that the resulting aspectual requirement
requires more refinement and a deep understanding of the nature of each one to validate them.
We have demonstrated the ValFAR method with two different AORE approaches step by step.
This presents a limitation to the work we conducted. Furthermore, we believe that our work
might be carried out with other approaches, which produce different AORE artefacts. The main
idea is to handle each artefact as a crosscutting concern, i.e., aspectual requirements. Thus, we
encourage conducting more case studies using ValFAR.
Finally, we are working on validating the integrity and the correctness of the proposed solution
with formal methods. Formalizing the framework would ensure its correctness and accuracy as
well as testing it for shortcomings. On the other hand, the demonstration of the work in this paper
is presented manually, and therefore, requirements engineers and analysts have to pay attention to
every little detail along the process. Moreover, future work is concentrating on automating this
framework in a software tool to increase time and effort productivity for ease of use.

38
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