1. Application of a Data Visualization Technique Based on Trees to Aid Prioritization
of Requirements in Agile Projects
Fabio Abrantes Diniz1, Thiago Reis da Silva2, Diego Grosmann3, Ithalo Bruno Gregório de Moura4,
Francisco Milton Mendes Neto5, Pedro Fernandes Ribeiro Neto6
Abstract  The practice of requirements prioritization Therefore, this work used a data viewing technique
involves the recovery analysis of each requirement by based on "TreeMap" [4]. This technique aims to show new
customers and requirements selection that will be ways of data viewing more intuitive and effective, which
implemented in a specific version of the system. Wrong helps in the analysis of the results obtained by the
choices during requirements prioritization may affect the requirements prioritization practice that is based on Kano
system quality and thus its acceptance by customers. Within technique.
this context, some practices of requirements prioritization
have been addressed in agile projects to improve the SCRUM – AN AGILE SOFTWARE DEVELOPMENT
requirements prioritization stage. Among them, there is a METHODOLOGY
practice based on Kano technique, which uses the agile
development methodology Scrum in software projects. The agile methodology Scrum has come up proposing to
However, the resulting data from Kano practice produces “debureaucratize” the software development process,
much textual information, which is difficult to be viewed and allowing teams to be more adaptables, rapidly responding to
analyzed in order to determine the real importance of each constant changes in software projects. According to their
requirement. Therefore, this paper proposes a data evangelizers, the customer becomes more satisfied, because
visualization technique based on "TreeMaps" in order to there are constantly deliveries of developed features, and the
assist in the viewing results o the Kano technique. customer actively participates in the project bringing
knowledge about the business.
Index Terms  Agile Projects. Prioritizing Requirements. Kano. Scrum stands out from other processes for being a
method interactive, incremental and agile for projects
INTRODUCTION management [10. Like any other methodology, it has roles
and responsibilities. There are three roles: Product Owner,
The requirements prioritization is a challenging activity Team Member and Scrum Master. Product Owner could be
in software development [6]. This practice involves the the sponsor or the person interested in the project and is in
Stakeholders analysis of each requirement and the charge to represent the interests of all users of the system.
requirements selection that will be developed in a specific The Team Member is composed by a people group in charge
version of the system. Wrong choices on which requirements to develop the project taking into account all of the features
should be prioritize and may affect the system quality and, needed. And finally, the Scrum Master, which the main
then, be accepted by customers. characteristic is the project leadership, the Product Owner
In agile methodologies, with reference to the Scrum interests management and the conflicts management faced
agile methodology, some practices of requirements by the Team Member.
prioritization have been addressed in agile projects to Scrum works with incremental development, where
improve the requirements prioritization stage. Among them, each iteration is called Sprint. The process must start from
there is a practice based on Kano technique [1]. the requirements organization of the project in a
The Kano technique enables the product developers requirements list named Product Backlog. This list is
transform the information obtained by research into real organized in descending order of priority. From Product
improvements in order to achieve the customer satisfaction Backlog, the team selects parts of the requirements
[5]. However, the Kano technique produces a lot information according to priorities in order to Sprint be performed,
with textual presentation by means of tables and reports, forming the Sprint Backlog (Sprint task list) [10].
which interfere in viewing of such, making the responsible During a Sprint, the team has autonomy to decide how
ones spend a lot of time processing large data volumes. the tasks will be implemented and ensures that the most
important requirements are developed first. In addition, there
1
Fábio Abrantes Diniz, Master in Computer Science at the Graduate Program in Computer Science – UERN/UFERSA, fabio.abrantes.diniz@gmail.com
2
Thiago Reis da Silva, Master in Computer Science at the Graduate Program in Computer Science – UERN/UFERSA, trsilva.si@gmail.com
3
Íthalo Bruno Grigório de Moura, Master in Computer Science at the Graduate Program in Computer Science – UERN/UFERSA, ithalobgm@gmail.com
4
Diego Grosmann, Master in Computer Science at the Graduate Program in Computer Science – UERN/UFERSA, diegogrosmann@gmail.com
5
Francisco Milton Mendes Neto, Teacher Graduate Program in Computer Science – UERN/UFERSA, miltonmendes@ufersa.edu.br
6
Pedro Fernandes Ribeiro Neto, Teacher Graduate Program in Computer Science – UERN/UFERSA, pedrofernandes@uern.br
© 2013 ICECE March 03 - 06, 2013, Luanda, ANGOLA
VIII International Conference on Engineering and Computer Education
81

2. are short daily meetings always at the same time with the TABLE I
Scrum Master, which is charge of project management and ANSWERS TO THE FUNCTIONL AND NON-FUNCTIONAL
QUESTIONS AND RESULTS FOR EACH COMBINATION
group leadership. In these meetings, it is discussed the work
progress in which every team member presents results of
their tasks and what should be done after conclusion [10].
The Sprint output is a set of features 100% developed,
which shall be approved by Product Owner (in charge for
project definition, definition and prioritization of
requirements) and delivered to the customer. At the end of
each iteration, the whole team participates in a Sprint The category I (indifferent) in Table I is used when the
retrospective. After the Sprint conclusion, the cycle restarts, user shows that has no real need for this feature, i.e. it does
removing the next slice of Product Backlog for the next not matter if is satisfied or not. The category M (mandatory
Sprint [10]. or indispensable) means that if the requirement is not met,
In view of the facts presented, it is possible to notice the customer will be not satisfied. For the customer, the
the reason why Scrum is one of the agile methodologies requirements of category M are already embedded in the
most used by software development companies, because it is products offered, and are therefore a prerequisite. That put
a process that builds software incrementally in complex the Mandatory requirements will not make the customer
environments, where the requirements are not clear or happier, however, without them the system does not work
change very frequently. and the customer does not acquire the product.
Category D (desired) means that these requirements
KANO TECHNIQUE IN REQUIREMENTS provide great satisfaction to the customer when they are
PRIORITIZATION FOR AGILE PROJECTS present, but do not represent dissatisfaction in case they are
not present. The category L (linear or important) means that
Using Kano technique in requirements prioritization
the customer satisfaction is proportional to the completion
process for agile projects proposed by [1] facilitates the
level of these requirements, i.e., the higher the completion of
requirements prioritization for the customer. The customer
level, the higher will be the customer satisfaction. The
has difficulty in saying what requirement is the most
category R (reverse) means that, if that requirement is
important in a system, because for the customer, all
developed, could cause a rejection to the software or certain
requirements are interesting and indispensable for the
feature. The category Q (questionable) means that the user
product. In Scrum methodology, this happens in many cases.
does not understand the questions or that he is not
The customer puts many requirements with maximum
corresponding with the truth [1]. According to the analysis
business value making it clear that the costumer has no idea
of the proposed work by Asfora [1], shows that the order of
which requirements are really important.
prioritization of requirements that would bring a very large
The application of Kano technique in the prioritization
value if they are treated is respectively: Mandatory, after the
process for agile projects based on Scrum methodology is
important or linear and, finally, desirable.
performed before the Product Owner sends the Product
According to Table II, the combinations of the
Backlog to the development team in order to the
responses from Kano table for the two questions generate a
requirements can be prioritized. The technique is to make a
result for each requirement. It is seen that the requirement 1
couple of questions for each requirement. A functional
(Req 1) has the largest percentage (43.8 %) for classification
question and other non-functional. According to [1] the
as linear or important. The requirement 3 (Req 3) was
importance of Kano technique in these questions is to show
classified as mandatory and desired because both have close
the parallel between what makes the customer very satisfied
results. Therefore, leaving the following descending order of
and what it does not, this helps to understand the real need
prioritization: Requirement 2, requirement 1 and finally
for each requirement. If the parallel mentioned is not present
Requirement 3.
in the next prototype delivery, it is very important to have
the real need relation for each requirement. It is natural that
TABLE II
always be responded that such very important requirement RESULTS SUMMARIZING
must be done, because the user wants a great amount of
activities performed by a software. In these cases, it is
interesting include the dissatisfaction criterion to notice what
really makes him unsatisfied if it is not developed.
Questions are formed as follows: (a) how would you
feel if Requirement X was in the next release? (B) How
would you feel if Requirement X was not in the next Kano technique is very efficient regarding its use and
release? The answer options are specified in Table I. the data types obtained. However, concerning viewing
results, it is very unsatisfactory due to the fact of already
© 2013 ICECE March 03 - 06, 2013, Luanda, ANGOLA
VIII International Conference on Engineering and Computer Education
82

3. know which requirements will be prioritized. And it is really TreeSolutions were: Slice and Dice, Squarified TreeMap and
difficult to make a decision. For example, in Table II, how to Ordered TreeMap [11] [4]. These algorithms represent a
know which requirements (between Req 2 and Req 3) must hierarchical data structure by rectangles recursive division.
firstly be implemented? Both appears as mandatory. In agile This recursion determines the layout by calculating the
projects, the team makes fast decisions and it may happen rectangle area filling them in their respective locations.
the team does not understand the Kano technique results [1]. There are many different characteristics among these
Thus, it was adapted to the Kano technique the use of TreeMaps algorithms. These algorithms, when applied to the
data viewing resource from "TreeMaps" method, because TreeSolutions tool, have their respective characteristics,
only the table view that is indicating the percentage that presenting variations, advantages and disadvantages among
were most voted by the users, it is not enough to make the them. It is interesting to make a comparative analysis among
items prioritization. them to be used in certain moments of data viewing. This
helps the making decision process becomes faster in order to
TREEMAP – A DATA VIEWING TECHNIQUE assist in the requirements prioritization process, so that to
BASED ON TREE choose which requirements have more priorities to be
developed in early versions of the prototypes. Table III
TreeMap is a viewing technique that explores compares these algorithms through metrics:
ergonomics basic concepts, making human being initially • Aspect ratio: (ratio between length and width of
focus their gaze on large figures to then look at small figures the rectangle;
[11]. This feature can be used in viewing of items from the • Stability: checks the data stability in terms of size
Product Backlog, aiming to display the requirements and position of the rectangles when processing data
hierarchy that have more priority to be developed. changes;
Some advantages are evident using TreeMap, such as: • Ordering: evaluates the original order of data when
efficiently uses the whole screen viewing; preserves the processing data changes;
general information context; quick navigation among nodes;
• Suitability for reading: verifies the performance
allows the user a scope overview and is very useful in
of the visualization of data regarding structures.
displaying data quantitative variables [11] [4]. It has been
used in multiple applications due to its ease of viewing that
TABLE III
provides to users the comparative analysis of a large amount COMPARISON OF TREEMAPS ALGORITHMS
of information. Nowadays, it is used in computer file system
applications, geographical maps, complex databases (IBGE),
industrial applications (stocks), educational systems,
artificial intelligent systems, headlines news, marketing,
among others [11].
The TreeMap divides the screen in a nested rectangles
sequence corresponding to attributes of a data set. Each
rectangle has an area and color which are defined by the According to Table III, the positive sign (+) indicates a
values previously set. Therefor, it has properties that must be positive result that brings the metric to the specific
taken into consideration, and according to [11] and [4], the algorithm, since the minus sign (-) indicates a negative result
properties are: or metric in the absence of specific algorithm. Looking at
Table III, the Squarified and the Ordered TreeMap
• A weight (requirement classification) will
algorithms were the most viable for the TreeSolutions tool,
determine the size of each rectangle in the
because they have characteristics focused on stability and
structure;
ability to represent an amount of information without
• The color is used to represent the user's satisfaction
generating a TreeMap, which is uncomfortable for the
in having the requirement in the system [5]. The
interaction with the user and show suitability for reading and
lighter colors will represent the requirements most
data analysis.
desired, while the darker colors will represent the
less desired. This work implements a color scale TREESOLUTIONS
that assigns unique values for each color in order to
differentiate them; Based on the TreeMap concepts, the TreeSolutions was
• Using pop-ups to show requirement information designed to meet the Product Owner in the requirements
when hover the mouse over an interest area of prioritization stage of Scrum methodology that uses the
rectangle. Kano technique. It helps the Product Owner in decision
Another strong point in the TreeMap construction is the making to determine the business value of Product Backlog
algorithm definition to be used in the rectangles creation. requirements so that it can be delivered faster to the
The rectangles layouts are dependent on the division developers team.
algorithm used. Some of the algorithms used in
© 2013 ICECE March 03 - 06, 2013, Luanda, ANGOLA
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4. The system is open source and developed in the Java. allocated according to the their characteristics contexts and
Tests were performed with the existent data in case studies analyzed tests during development. The questionable
found in the work produced by [1] and according to the category and the reverse received negative values, because
results analysis, it was observed that, using TreeMap they categorized the requirements that do not bring
technique made data viewing more efficient, consistent, satisfaction to the users [1].
robust and agile. Next, it will be described the TreeSolutions In addition to presenting to the user the requirements
system with the features and the result obtained by TreeMap viewing in rectangle shape, the system has the pop-up
with a case study data of [1]. resource, which presents the requirement information when
hover the mouse over the area that represents a requirement,
TreeSolutions System Implementation such as: rectangle size are, color value, and the requirement
TreeSolutions consists of a desktop system developed attributes with its values received from the Kano table result.
in Java. However, there is a beta version for Web. System Results
TreeSolutions is subdivided into two main modules
implementation: TreeMap Module and Interface Module. The test of TreeSolutions system was performed based
In the Interface module, the Product Owner has access to a on data collected in [1]. The data acquired involve a case
graphical interface with information about its Product study of the (CESAR), short for Centro de Estudos e
Backlog containing the requirements. This interface allows Sistemas Avançados do Recife (English: Recife Center
insertion of the Product Backlog. In addition, the for Advanced Studies and Systems). They were originated of
information coming from the Kano table are inserted, such the SEPG project - group of improvement of the internal
as: the categories percentage values of all requirements software development process [1]. Some of these data are
(mandatory, linear, desired, questionable, reverse or presented in Table IV, which contains 15 requirements with
indifferent). They could be imported and exported into a file their results from applying of Kano technique.
in XML (Extensible Markup Language). The TreeMap resulting is from data entry in Table IV,
In the TreeMap module is implemented the viewing which is shown in Figure 1. According to the results
technique named TreeMap. We used the Java TreeMap class analysis, it was observed that using the TreeMap technique
that offers additional features to associate the order to the made the data viewing more efficient and robust for the list
collection elements. The algorithms mentioned in Section 5 preparation of requirements prioritized.
were developed and implemented in this module to represent
the rectangles areas and were implemented the color TABLE IV
providers, which import the color models RGB (Red, Green RESPONSE PERCENTAGE GENERATED BY KANO TECHNIQUE [1].
and Blue), HSB (Hue, Saturation and Brightness) and its
variations for colors reproduction in the rectangles areas of
the TreeMap.
According to the system implementation context, it was
given the rectangle area as an attribute more significant than
the color, since the area represents indispensable and
important requirements, i.e., they are requirements which
without them, the system does not work. The rectangle color
represents the user satisfaction in having the requirement in
the system. Then, the clearer is the color in the colors scale,
the greater is the user satisfaction having the requirement in
the system. The rectangle area indicates the presence degree, As is shown in Figure 1, the viewing screen has a
i.e., rectangles of greater area represent the requirements that choice field of the viewing strategy (a) in which you choose
must be in the system. Therefor, the larger is the area and the the algorithm used in the TreeMap construction and has the
greater is the color in the colors scale, this indicates that this rectangles color scale that can be changed according to
requirement has higher priority and should be implemented user's wish (d, e). The central part (c) shows the
first. requirements list of the project selected (f). Finally, when
To calculate the size of the rectangle area due its you hover the mouse over one of the rectangles, appears a
function of serve to "measure the presence degree in the pop-up showing the requirement details (b).
system", it was made a weighted average with the data As is shown in Figure 1, the viewing screen has a
inputs of the Mandatory and Linear categories, with their choice field of the viewing strategy (a) in which you choose
respective weights, such as: data entry or by a standard the algorithm used in the TreeMap construction and has the
default of the chosen system. The default values are: rectangles color scale that can be changed according to
Mandatory = 10, Linear = 5, Desired = 2, Indifferent = 0, user's wish (d, e). The central part (c) shows the
Questionable = -1, Reverse = -2. These values were requirements list of the project selected (f). Finally, when
© 2013 ICECE March 03 - 06, 2013, Luanda, ANGOLA
VIII International Conference on Engineering and Computer Education
84

5. you hover the mouse over one of the rectangles, appears a applying of technique proposed. Compared to the results
pop-up showing the requirement details (b). viewing process of textual form, it is clearly observed the
improvement that this tool provides to the user regarding to
the decision-making process.
The proposed tool proved to be efficient in conducting
a quick feedback on the data analysis, generating less
documentation and less effort in requirements prioritization.
In addition, it is more users friendly and easily understood.
Thus, TreeSolutions supports the Product Owner to
prioritize the Product Backlog in a manner more efficient
and robust. As a result, the developers teams can estimate
and develop the requirements faster. As future work, we
intend to add Kano table into the tool, so that the entries
could be made faster for the TreeMap. This will generate
information viewing directly from the table. It is also
intended to implement other data viewing techniques.
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© 2013 ICECE March 03 - 06, 2013, Luanda, ANGOLA
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