ANALYSIS OF USE CASE POINTS MODELS FOR SOFTWARE COST ESTIMATION

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1 Farhad S. Gharehchopogh, A. Talebi, I. Maleki. Analysis of use case points models for software cost estimation. International Journal of Academic Research Part A; 2014; 6(3), DOI: / /6-3/A.16 Library of Congress Classification: TK ANALYSIS OF USE CASE POINTS MODELS FOR SOFTWARE COST ESTIMATION Farhad Soleimanian Gharehchopogh, Akbar Talebi, Isa Maleki Department of Computer Engineering, Science and Research Branch, Islamic Azad University, West Azerbaijan (IRAN) s: ABSTRACT DOI: / /6-3/A.16 Received: 11 Jan, 2014 Accepted: 07 May, 2014 Software projects development is inherently complex and in the project implementation process large resources must already be estimated. Also, many software companies try to increase software project quality and to lower software development costs. The most influential factors in Software Cost Estimation (SCE) are time, working environment, risk, size, and complexity of software and manpower resources in the project. Software projects are of sophisticated software engineering products that contain a lot of resources and the amount of each of them must be exact so that the project do not fails. So SCE as an important part of software engineering is considered in the success of software development projects. Use Cases consider SCE factors with respect to the smallest details. Use Case is one of the best ways of software modeling before production and development which does not describe the software process but will provide the exact knowledge of the software. In this paper, we review the software effort and cost estimation based on Use Case Points (UCP) that is used as a method to estimate the project cost. Key words: Software Cost Estimation, Use Case, Use Case Points 1. INTRODUCTION Today, software is considered as the most expensive member of any computer system. Much of the decision-making of managers at the start of a software project is discussion about cost and time. The successful software project is a project to achieve certain predetermined purposes in terms of cost and time. Excessive costs for a software maker can be harmful. Cost estimation was the problem of systems analysts, project managers and software engineers in the decades. Identify the true costs of software projects helps managers to accurately estimate the real price of software [1]. In software projects, must begin by analyzing the previous projects and those are being marketed as a product. Calculation of software cost is usually tricky. Software projects were not understandable early and always themes and ideas that are in the customer's mind and the minds of managers may differ. With the gradual growth in size and importance of applicable programs of costs of creating software began to grow as that excessive increase of costs for software planner will be disastrous. In previous years, various methods are presented for estimating software project cost [2, 3, 4 and 5]. Also among algorithmic models, COCOMO Model [6, 7] is used based on the number of lines of code. With the increase of the size of the project, time, human and financial costs will be raise. Customers have only one goal at the beginning of their work that to do their work easily and accurately with the software. Most software projects customers can not define all expectations at the beginning. On the other hand, the size of estimate is an important factor affects software cost. Several methods are used for software size that the most important one can be Function Point (FP). Complexity is an important factor that must be considered in the SCE. Project complexity can be measured by the project's factors [8]. This point should be regarded in mind that the complexity factors are not the same on projects. Small projects may be much more complex than large-scale projects. For example, programming a three-dimensional modeling is more complex than writing a text editor. The complexity can also be a relative factor, for example writing a web commercial project for someone who already has not have experience in such work may seem very complicated. This factor is based on customer demand, it means that if the customer wants the delivery of project outputs would be on time, the number of employees must be increased and more effort is required. The reason is that the task force will spend more time for communicating and defining the interface between developed system's sections. The structure of the paper is as follows: in Section2, we will describe UCP models for SCE; in Section 3, we will discuss the UCP models and finally in Section 4, we will explain conclusions and future works. 118 PART A. APPLIED AND NATURAL SCIENCES

2 2. SCE BASED ON THE UCP In UCP method, each Use Case includes scenario or scenarios that can be regarded costs need to be estimated in their implementing [9]. Use Cases are associated with the outside world through system interfaces that their design and implementation requires a considerable amount of cost. So the first step is to define the Use Cases and to describe their scenarios. If identifying and describing the Use Cases process can be done more accurately, it will express estimate of the cost more realistically. Use Cases as a model of system activities was quite abstract and based on class, Use Cases can different. So, in the cost estimates, must paid much attention in the number of UCP, then it is better abstract surfaces to obey from fixed process. Otherwise, abstract class coefficient should be regarded in the process and interactions related to UCP. UCP to directly for measuring and counting up the number of scenarios weight that can occur on some events [9]. The main purpose of the event can occur between actors is that an event in all cases performed wholly or did not take place at all. Figure (1) shows the Use Case use for order processing system. Fig. 1. System of customer order based on use case 2.1. Models of UCP Use Case model defines operating range of a system. Use Case features are steps to measure the complexity and functionality of software projects. Using UCP and with developing FP can analyze Environment Factors (EF). Users who are more familiar with the Object programming, EF operating will be very important for them. UCP can be classified in three groups which changes should be considered in any project, that these three groups include [9]: Unadjusted UCP (UUCP) Technical Complexity Factor (TCF) Environment Complexity Factor (ECF) In addition to mentioned cases, it can be regarded the production time as a coefficient which expresses time to estimate the number of hours needed to complete the project accomplishment. For estimating UCP factors which are defined according to equation (1) the factor of Productivity Factor (PF) should also be considered [9]. UCP=UUCP*TCF*ECF*PF (1) UUCP Effort estimation based on UUCP is performed as the following steps: Unadjusted Use Case Weight (UUCW): In UUCW, the estimation is based on the total number of activities with the existence steps in the Use Cases scenarios [9, 10]. Algebraic sum of system's Use Case values can be calculated after categorizing them and before multiplying them in complexity factors. Use Cases are placed in three categories: simple, medium and complex. Each Use Case is expressed by a number of scenario steps. A number of steps in the UUCW scenarios lead to decrease of UCP with the emergence of simplicity and to increase of UCPs with the emergence of complexity. Sometimes a lot of steps can be reduced without any impact on business processes. Use Cases complexity is determined by the mass of the changes and events. So, the simplest methods for doing the events in Use Case model are interviews and event counting. There is no standard for writing activities that the developer can freely send several use interaction in a number of events using natural language. Several guidelines for writing event in Use Case for Creating a Successful scenario are proposed. We refer to two of the guidelines for a successful scenario. Using of simple instruction that subject is easily understood and easily uses expressions. It includes a set of logical steps that play effective role in making changes in Use Cases. In the case that no trace of event in the Use Case does exist, at that time, the complexity rate is measured in terms of experience. The experience of data includes information about Use Cases and Use Cases development in software projects in the past. Actors in UCP model are considered to be simple, medium and complex. Weight, actors and UUCW results is shown in Table (1) that finally the actor s weights are calculated by adding these values. Baku, Azerbaijan 119

3 Table 1. UUCW model factors [9] Complexity Definition weight Actors Results Simple Medium Complex There is only a database that has three or fewer scenarios and transaction its implementation includes 5 or less class There are 2 databases that have 4 to 7 scenarios and transaction, its implementation includes between 5 to 10 classes it includes 3 or more databases that has more than 7 scenarios and transaction, its implementation includes more than 10 class Sum of UUCW 185 UUCW calculation is done according to equation (2) [9]. In equation (2) w is the weight of the casts and f is the values of the parameters. UUCW use case* wf (2) Unadjusted Actor Weight (UAW): it is the Algebra sum of actors' values after categorizing them and before multiplying them in the system's operating complexity. The first step is actors packaging that the Use Case numbers in this way are derived of three categories [11]: simple, medium and complex. Under this decision, a number of events and interactions occur in a Use Case. For this reason, an event is as an overall set of activities that are either completely done or not done at all in the condition that extending Use Case should not be considered. Table (2) shows classification of cast in UAW model. Table 2. UAW model factors [9] Complexity Definition Weight Actors Results Simple Medium Actors who are associated with the system via API. Software programming interface actors Actors who are associated with the system via HTTP and FTP protocols. Actors have kept the data Complex Actors communicate via GUI Sum of UAW 14 UAW calculated according to equation (3) [9]. In equation (3) w is the weight of the cast and f is the values of the parameters. UUCW actor* wf (3) UUCP: UUCP is calculated by adding the total weight of the actors to the total sum of the Use Cases. The sum of UAW and UUCW is computed according to equation (4) [9]: UUCW UUCW UAW (4) TCF TCF factors are dedicated a value of complexity by development team and programming [12]. Development team will determine the complexity of the TCF project. TCF considers different rates for almost every function which routinely removes some of the factors. TCF is for identifying and measuring parameters of the technical factors which includes 13 identified factors and these are able to increase. Weight of factors is different based on the experience of objects in projects. In this paper we have added three items to the previous factors [12]. Those three are the T14, T15, and T16 which in the Table (3), the total of the projects technical factors will determine complexity of the project. 120 PART A. APPLIED AND NATURAL SCIENCES

4 Table 3. TCF model factors Factors Defining and Determining the Describing the Factor Weight Complexity Results Factors T1 [12] distributed system Does system use a distributed architecture? Does client or company needs a broadband system? Which the response T2 [12] response time time of the system is of important points. T3 [12] end performance How is the performance and functionality for end users? Is the process complicated? Complex computations in a system should be T4 [12] complex process considered. Such as accounting calculations T5 [12] reusable codes Does the cods is reusable? Which is very complicated T6 [12] easy installation Is the installation easy for the customer? Or there are vary methods for installation, at installation time has control to system components T7 [12] easy use should window that the pages used in the system be easy and high priority T8 [12] movable and transferable Is the customer looking for implementation and execution environment? T9 [12] easy changes must system have the ability to change in the future from the customer point T10 [12] T11 T12 simultaneously security Accessible to private companies. of view? This increases the designing architect Do users use system simultaneous and distributed? That makes sophisticated architecture and design Will customer want to create on the system more security? For example, data encryption Did system link to control of a third-party company or mechanized systems? T13 Users' training Is software hard from the perspective of the client? That needs to be trained. The ability to must system has the ability to publish in intranet and extensive context of T spread internet? That be able to control remotely and be applicable T15 support Does the system need support after delivery and at the time of facing with a problem? T16 Hardware capabilities what hardware specification and hardware facilities system need to run Sum of TCF 27.5 Equation (5) multiplies the sum obtained by the complexity of the project to achieve the project's level of complexity. Each technical factor has a weight that determines its effect extent. Each TCF factors can be assigned values from 0 to 5. Usually for the most important and valuable factors it is better to be assigned the value 3.TCF calculation is defined according to equation (5) [9, 12]: 16 TCF (5) C1 C2 W F 1 In equation (5) C1 and C2 are constant values and their values are respectively 0.6 and 0.1. Parameter W is factors' weights and parameter F is equals to the perceived complex factor ECF The experienced teams have a greater impact on UCP than less experienced teams. The software development team distinguishes the effect of each factor based on the understanding that factor and to the success of the project. Factors that will have a direct effect on the timing and costs of project must be considered. UCP model with ECF is helped to evaluate the functioning of the project [12]. This factor includes 8 factors that can be significantly increased. In this paper we have added two cases including E9, E10 to the previous factors. In Table (4) ECF model factors is shown. ECF calculation is defined according to equation (6) [9, 12]: 10 W EF (6) C1 C2 F 1 In equation (6) C1 and C2 are constant values and their values are respectively 1.4 and The parameter W is the weighting factor and the parameter F against perceived complex factor. Baku, Azerbaijan 121

5 Table 4. ECF model factors Factors E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 Environmental Factor Familiarity with project Team's experience object-oriented Experience Conductivity of the analyst Motivation Constancy of system's needs Part-time member Programming language Team's member System's stability Factor's Description Weight Complexity Results Are all members of the project familiar with technical systems and its procedures? Otherwise, they will spend much time getting to know How much experience has team in producing software? Since the use cases are sources to design, so the team should have enough and basic familiarity with the object-oriented software engineering. Are analyst or systems analyst familiar enough with the systems? Does team have an incentive to work on the project? How is the marketing department and software production?. what will customer or user well know? Users' needs are the most important factor of constancy of the system's requirements. Variability will increase complexity Are part-time and casual people in the project Which programming language is used for implementation? will team members for performance and implementation of the project be fixed or if someone is out of team, there will be the possibility of compensation for members of the team. To what extent does the system is stable and has not continuous change Sum of ECF DISCUSSION UCP model is a documented approach for estimating software development. When the size of a system is estimated, it also can be calculated effort to be done on the system. It can be estimated using the evidence obtained from the system and ECF factors and environmental influences. In Figure (2) UCP different models is shown. Fig. 2. Use Case basic concepts in the project cost estimates In Use Case model, estimating the effort is completed by adding supplemental classes such as (hours of project management, testing and integration). Use Cases weights are determined by some of different events of Use Cases interacting with the actors in the system. Figure (3) shows the processing of UUCP and UCP factors for SCE. 122 PART A. APPLIED AND NATURAL SCIENCES

6 Fig. 3. Processing of UUCP and UCP factors One important factor in the teams and programming companies is human resources. Usually one person do this work for small projects that need less effort but for big projects which are developed from size and complexity aspect should use some expert and familiar to job environment and programming persons. Estimating the effort required for developing a software systems and overall cost of the project and estimating time to design and prepare software and time development required for personnel will be the responsibility of the project manager. Dividing effort needed to develop the project is not a good indication of the number of people required for the project team members. In general, only a small number of people at the beginning of a project are required for the initial design. So, project managers need to avoid adding too many project staff early in the project. 4. CONCLUSION AND FUTURE WORKS Nowadays, one of the most important challenges faced by software project managers is careful selection of cost estimation method to improve tracking of projects status and their monitoring. Facing with the constraints of cost, they also need reliable and frequent estimates of the cost. In general, any factor that increases the duration of the software projects and creates the delay in the projects will affect the projects' cost in the completion point and will encounter them with increase. Therefore, it is necessary to use a method to determine created time offset and delay in any project. In this paper we estimate the software projects' cost based on the Use Case discussed. Software producing in the context of predicted software cost is one of the main goals of the Use Case. One of the benefits of creating Use Case is that it divides software systems into well-defined subsystems based on the needs and behaviors of the final system. We hope in the future with presenting this paper to offer new models based on UCP for SCE. REFERENCES 1. M.O. Elish, T. Helmy, M.I. Hussain, Empirical Study of Homogeneous and Heterogeneous Ensemble Models for Software Development Effort Estimation, Mathematical Problems in Engineering, pp. 1-2, F.S. Gharehchopogh, I. Maleki, S.R. Khaze, A Novel Particle Swarm Optimization Approach for Software Effort Estimation, International Journal of Academic Research, Part A, Vol. 6. No. 2, pp , I. Maleki, A. Ghaffari, M. Masdari, A New Approach for Software Cost Estimation with Hybrid Genetic Algorithm and Ant Colony Optimization, International Journal of Innovation and Applied Studies, Vol. 5, No. 1, pp , F.S. Gharehchopogh, Neural Networks Application in Software Cost Estimation: A Case Study, 2011 International Symposium on Innovations in Intelligent Systems and Applications (INISTA 2011), pp , IEEE, Istanbul, Turkey, June Z.A. Khalifelu, F.S. Gharehchopogh, Comparison and Evaluation Data Mining Techniques with Algorithmic Models in Software Cost Estimation, Elsevier, Procedia-Technology Journal, Vol. 1, pp , B.W. Boehm, Software Engineering Economics, Prentice-Hall, Englewood Cliffs, New Jersy, B.W. Boehm, Software Cost Estimation with COCOMO II, Prentice Hall PTR, Englewood Cliffs, New Jersy, Baku, Azerbaijan 123

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