Cocomo (Constructive Cost Model) is a regression model based on LOC, i.e number of Lines of Code. It is a procedural cost estimate model for software projects and often used as a process of reliably predicting the various parameters associated with making a project such as size, effort, cost, time and quality. It was proposed by Barry Boehm in 1970 and is based on the study of 63 projects, which make it one of the best-documented models.
The key parameters which define the quality of any software products, which are also an outcome of the Cocomo are primarily Effort & Schedule:
Apr 13, 2018 Cocomo (Constructive Cost Model) is a regression model based on LOC, i.e number of Lines of Code.It is a procedural cost estimate model for software projects and often used as a process of reliably predicting the various parameters associated with making a. The theoretical model is referred to as COCOMO II. The USC-CSE software implementation of the model is referred to as USC COCOMO II, to distinguish it from other academic or commercial implementations of the model. Here are several available Tools which support COCOMO II itself or its extensions.
- Effort: Amount of labor that will be required to complete a task. It is measured in person-months units.
- Schedule: Simply means the amount of time required for the completion of the job, which is, of course, proportional to the effort put. It is measured in the units of time such as weeks, months.
Different models of Cocomo have been proposed to predict the cost estimation at different levels, based on the amount of accuracy and correctness required. All of these models can be applied to a variety of projects, whose characteristics determine the value of constant to be used in subsequent calculations. These characteristics pertaining to different system types are mentioned below.
![Proshow producer software Proshow producer software](/uploads/1/2/5/3/125303944/293118436.png)
Boehm’s definition of organic, semidetached, and embedded systems:
- Organic – A software project is said to be an organic type if the team size required is adequately small, the problem is well understood and has been solved in the past and also the team members have a nominal experience regarding the problem.
- Semi-detached – A software project is said to be a Semi-detached type if the vital characteristics such as team-size, experience, knowledge of the various programming environment lie in between that of organic and Embedded. The projects classified as Semi-Detached are comparatively less familiar and difficult to develop compared to the organic ones and require more experience and better guidance and creativity. Eg: Compilers or different Embedded Systems can be considered of Semi-Detached type.
- Embedded – A software project with requiring the highest level of complexity, creativity, and experience requirement fall under this category. Such software requires a larger team size than the other two models and also the developers need to be sufficiently experienced and creative to develop such complex models.
- Basic COCOMO Model
- Intermediate COCOMO Model
- Detailed COCOMO Model
- Basic Model –The above formula is used for the cost estimation of for the basic COCOMO model, and also is used in the subsequent models. The constant values a and b for the Basic Model for the different categories of system:
Software Projects a b Organic 2.4 1.05 Semi Detached 3.0 1.12 Embedded 3.6 1.20 The effort is measured in Person-Months and as evident from the formula is dependent on Kilo-Lines of code. These formulas are used as such in the Basic Model calculations, as not much consideration of different factors such as reliability, expertise is taken into account, henceforth the estimate is rough. - Intermediate Model –The basic Cocomo model assumes that the effort is only a function of the number of lines of code and some constants evaluated according to the different software system. However, in reality, no system’s effort and schedule can be solely calculated on the basis of Lines of Code. For that, various other factors such as reliability, experience, Capability. These factors are known as Cost Drivers and the Intermediate Model utilizes 15 such drivers for cost estimation.Classification of Cost Drivers and their attributes:(i) Product attributes –
- Required software reliability extent
- Size of the application database
- The complexity of the product
(ii) Hardware attributes –- Run-time performance constraints
- Memory constraints
- The volatility of the virtual machine environment
- Required turnabout time
(iii) Personnel attributes –- Analyst capability
- Software engineering capability
- Applications experience
- Virtual machine experience
- Programming language experience
(iv) Project attributes –- Use of software tools
- Application of software engineering methods
- Required development schedule
;Cost Drivers Very Low Low Nominal High Very High Product Attributes Required Software Reliability 0.75 0.88 1.00 1.15 1.40 Size of Application Database 0.94 1.00 1.08 1.16 Complexity of The Product 0.70 0.85 1.00 1.15 1.30 Hardware Attributes Runtime Performance Constraints 1.00 1.11 1.30 Memory Constraints 1.00 1.06 1.21 Volatility of the virtual machine environment 0.87 1.00 1.15 1.30 Required turnabout time 0.94 1.00 1.07 1.15 Personnel attributes Analyst capability 1.46 1.19 1.00 0.86 0.71 Applications experience 1.29 1.13 1.00 0.91 0.82 Software engineer capability 1.42 1.17 1.00 0.86 0.70 Virtual machine experience 1.21 1.10 1.00 0.90 Programming language experience 1.14 1.07 1.00 0.95 Project Attributes Application of software engineering methods 1.24 1.10 1.00 0.91 0.82 Use of software tools 1.24 1.10 1.00 0.91 0.83 Required development schedule 1.23 1.08 1.00 1.04 1.10 The project manager is to rate these 15 different parameters for a particular project on a scale of one to three. Then, depending on these ratings, appropriate cost driver values are taken from the above table. These 15 values are then multiplied to calculate the EAF (Effort Adjustment Factor). The Intermediate COCOMO formula now takes the form:The values of a and b in case of the intermediate model are as follows:Software Projects a b Organic 3.2 1.05 Semi Detached 3.0 1.12 Embeddedc 2.8 1.20 - Detailed Model –
Detailed COCOMO incorporates all characteristics of the intermediate version with an assessment of the cost driver’s impact on each step of the software engineering process. The detailed model uses different effort multipliers for each cost driver attribute. In detailed cocomo, the whole software is divided into different modules and then we apply COCOMO in different modules to estimate effort and then sum the effort.The Six phases of detailed COCOMO are:- Planning and requirements
- System design
- Detailed design
- Module code and test
- Integration and test
- Cost Constructive model
The effort is calculated as a function of program size and a set of cost drivers are given according to each phase of the software lifecycle.
All the above system types utilize different values of the constants used in Effort Calculations.
Types of Models: COCOMO consists of a hierarchy of three increasingly detailed and accurate forms. Any of the three forms can be adopted according to our requirements. These are types of COCOMO model:
The first level, Basic COCOMO can be used for quick and slightly rough calculations of Software Costs. Its accuracy is somewhat restricted due to the absence of sufficient factor considerations.
Intermediate COCOMO takes these Cost Drivers into account and Detailed COCOMO additionally accounts for the influence of individual project phases, i.e in case of Detailed it accounts for both these cost drivers and also calculations are performed phase wise henceforth producing a more accurate result. These two models are further discussed below.
Estimation of Effort: Calculations –
Also read: Classical Waterfall Model, Iterative Waterfall Model, Prototyping Model, Spiral Model
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The job pattern of an IT company engaged in software development can be seen split in two parts:
- Software Creation
- Software Project Management
A project is well-defined task, which is a collection of several operations done in order to achieve a goal (for example, software development and delivery). A Project can be characterized as:
- Every project may has a unique and distinct goal.
- Project is not routine activity or day-to-day operations.
- Project comes with a start time and end time.
- Project ends when its goal is achieved hence it is a temporary phase in the lifetime of an organization.
- Project needs adequate resources in terms of time, manpower, finance, material and knowledge-bank.
Software Project
A Software Project is the complete procedure of software development from requirement gathering to testing and maintenance, carried out according to the execution methodologies, in a specified period of time to achieve intended software product.
Need of software project management
Software is said to be an intangible product. Software development is a kind of all new stream in world business and there’s very little experience in building software products. Most software products are tailor made to fit client’s requirements. The most important is that the underlying technology changes and advances so frequently and rapidly that experience of one product may not be applied to the other one. All such business and environmental constraints bring risk in software development hence it is essential to manage software projects efficiently.
The image above shows triple constraints for software projects. It is an essential part of software organization to deliver quality product, keeping the cost within client’s budget constrain and deliver the project as per scheduled. There are several factors, both internal and external, which may impact this triple constrain triangle. Any of three factor can severely impact the other two.
Therefore, software project management is essential to incorporate user requirements along with budget and time constraints.
Software Project Manager
A software project manager is a person who undertakes the responsibility of executing the software project. Software project manager is thoroughly aware of all the phases of SDLC that the software would go through. Project manager may never directly involve in producing the end product but he controls and manages the activities involved in production.
A project manager closely monitors the development process, prepares and executes various plans, arranges necessary and adequate resources, maintains communication among all team members in order to address issues of cost, budget, resources, time, quality and customer satisfaction.
Let us see few responsibilities that a project manager shoulders -
Managing People
- Act as project leader
- Liaison with stakeholders
- Managing human resources
- Setting up reporting hierarchy etc.
Managing Project
- Defining and setting up project scope
- Managing project management activities
- Monitoring progress and performance
- Risk analysis at every phase
- Take necessary step to avoid or come out of problems
- Act as project spokesperson
Software Management Activities
Software project management comprises of a number of activities, which contains planning of project, deciding scope of software product, estimation of cost in various terms, scheduling of tasks and events, and resource management. Project management activities may include:
- Project Planning
- Scope Management
- Project Estimation
Project Planning
Software project planning is task, which is performed before the production of software actually starts. It is there for the software production but involves no concrete activity that has any direction connection with software production; rather it is a set of multiple processes, which facilitates software production. Project planning may include the following:
Scope Management
It defines the scope of project; this includes all the activities, process need to be done in order to make a deliverable software product. Scope management is essential because it creates boundaries of the project by clearly defining what would be done in the project and what would not be done. This makes project to contain limited and quantifiable tasks, which can easily be documented and in turn avoids cost and time overrun.
During Project Scope management, it is necessary to -
![Cocomo model pdf download Cocomo model pdf download](/uploads/1/2/5/3/125303944/209614558.gif)
- Define the scope
- Decide its verification and control
- Divide the project into various smaller parts for ease of management.
- Verify the scope
- Control the scope by incorporating changes to the scope
Project Estimation
For an effective management accurate estimation of various measures is a must. With correct estimation managers can manage and control the project more efficiently and effectively.
Project estimation may involve the following:
- Software size estimationSoftware size may be estimated either in terms of KLOC (Kilo Line of Code) or by calculating number of function points in the software. Lines of code depend upon coding practices and Function points vary according to the user or software requirement.
- Effort estimationThe managers estimate efforts in terms of personnel requirement and man-hour required to produce the software. For effort estimation software size should be known. This can either be derived by managers’ experience, organization’s historical data or software size can be converted into efforts by using some standard formulae.
- Time estimationOnce size and efforts are estimated, the time required to produce the software can be estimated. Efforts required is segregated into sub categories as per the requirement specifications and interdependency of various components of software. Software tasks are divided into smaller tasks, activities or events by Work Breakthrough Structure (WBS). The tasks are scheduled on day-to-day basis or in calendar months.The sum of time required to complete all tasks in hours or days is the total time invested to complete the project.
- Cost estimationThis might be considered as the most difficult of all because it depends on more elements than any of the previous ones. For estimating project cost, it is required to consider -
- Size of software
- Software quality
- Hardware
- Additional software or tools, licenses etc.
- Skilled personnel with task-specific skills
- Travel involved
- Communication
- Training and support
Project Estimation Techniques
We discussed various parameters involving project estimation such as size, effort, time and cost.
Project manager can estimate the listed factors using two broadly recognized techniques –
Decomposition Technique
This technique assumes the software as a product of various compositions.
There are two main models -
- Line of Code Estimation is done on behalf of number of line of codes in the software product.
- Function Points Estimation is done on behalf of number of function points in the software product.
Empirical Estimation Technique
This technique uses empirically derived formulae to make estimation.These formulae are based on LOC or FPs.
![Cocomo Cocomo](/uploads/1/2/5/3/125303944/137554472.png)
- Putnam ModelThis model is made by Lawrence H. Putnam, which is based on Norden’s frequency distribution (Rayleigh curve). Putnam model maps time and efforts required with software size.
- COCOMOCOCOMO stands for COnstructive COst MOdel, developed by Barry W. Boehm. It divides the software product into three categories of software: organic, semi-detached and embedded.
Project Scheduling
Project Scheduling in a project refers to roadmap of all activities to be done with specified order and within time slot allotted to each activity. Project managers tend to define various tasks, and project milestones and them arrange them keeping various factors in mind. They look for tasks lie in critical path in the schedule, which are necessary to complete in specific manner (because of task interdependency) and strictly within the time allocated. Arrangement of tasks which lies out of critical path are less likely to impact over all schedule of the project.
For scheduling a project, it is necessary to -
- Break down the project tasks into smaller, manageable form
- Find out various tasks and correlate them
- Estimate time frame required for each task
- Divide time into work-units
- Assign adequate number of work-units for each task
- Calculate total time required for the project from start to finish
Resource management
All elements used to develop a software product may be assumed as resource for that project. This may include human resource, productive tools and software libraries.
The resources are available in limited quantity and stay in the organization as a pool of assets. The shortage of resources hampers the development of project and it can lag behind the schedule. Allocating extra resources increases development cost in the end. It is therefore necessary to estimate and allocate adequate resources for the project.
Resource management includes -
- Defining proper organization project by creating a project team and allocating responsibilities to each team member
- Determining resources required at a particular stage and their availability
- Manage Resources by generating resource request when they are required and de-allocating them when they are no more needed.
Project Risk Management
Risk management involves all activities pertaining to identification, analyzing and making provision for predictable and non-predictable risks in the project. Risk may include the following:
- Experienced staff leaving the project and new staff coming in.
- Change in organizational management.
- Requirement change or misinterpreting requirement.
- Under-estimation of required time and resources.
- Technological changes, environmental changes, business competition.
Risk Management Process
There are following activities involved in risk management process:
- Identification - Make note of all possible risks, which may occur in the project.
- Categorize - Categorize known risks into high, medium and low risk intensity as per their possible impact on the project.
- Manage - Analyze the probability of occurrence of risks at various phases. Make plan to avoid or face risks. Attempt to minimize their side-effects.
- Monitor - Closely monitor the potential risks and their early symptoms. Also monitor the effects of steps taken to mitigate or avoid them.
Project Execution & Monitoring
In this phase, the tasks described in project plans are executed according to their schedules.
Execution needs monitoring in order to check whether everything is going according to the plan. Monitoring is observing to check the probability of risk and taking measures to address the risk or report the status of various tasks.
These measures include -
- Activity Monitoring - All activities scheduled within some task can be monitored on day-to-day basis. When all activities in a task are completed, it is considered as complete.
- Status Reports - The reports contain status of activities and tasks completed within a given time frame, generally a week. Status can be marked as finished, pending or work-in-progress etc.
- Milestones Checklist - Every project is divided into multiple phases where major tasks are performed (milestones) based on the phases of SDLC. This milestone checklist is prepared once every few weeks and reports the status of milestones.
Cocomo Model Example
Project Communication Management
Effective communication plays vital role in the success of a project. It bridges gaps between client and the organization, among the team members as well as other stake holders in the project such as hardware suppliers.
Communication can be oral or written. Communication management process may have the following steps:
- Planning - This step includes the identifications of all the stakeholders in the project and the mode of communication among them. It also considers if any additional communication facilities are required.
- Sharing - After determining various aspects of planning, manager focuses on sharing correct information with the correct person on correct time. This keeps every one involved the project up to date with project progress and its status.
- Feedback - Project managers use various measures and feedback mechanism and create status and performance reports. This mechanism ensures that input from various stakeholders is coming to the project manager as their feedback.
- Closure - At the end of each major event, end of a phase of SDLC or end of the project itself, administrative closure is formally announced to update every stakeholder by sending email, by distributing a hardcopy of document or by other mean of effective communication.
After closure, the team moves to next phase or project.
Configuration Management
Configuration management is a process of tracking and controlling the changes in software in terms of the requirements, design, functions and development of the product.
IEEE defines it as “the process of identifying and defining the items in the system, controlling the change of these items throughout their life cycle, recording and reporting the status of items and change requests, and verifying the completeness and correctness of items”.
Generally, once the SRS is finalized there is less chance of requirement of changes from user. If they occur, the changes are addressed only with prior approval of higher management, as there is a possibility of cost and time overrun.
Baseline
A phase of SDLC is assumed over if it baselined, i.e. baseline is a measurement that defines completeness of a phase. A phase is baselined when all activities pertaining to it are finished and well documented. If it was not the final phase, its output would be used in next immediate phase.
Configuration management is a discipline of organization administration, which takes care of occurrence of any change (process, requirement, technological, strategical etc.) after a phase is baselined. CM keeps check on any changes done in software.
Change Control
Change control is function of configuration management, which ensures that all changes made to software system are consistent and made as per organizational rules and regulations.
A change in the configuration of product goes through following steps -
- Identification - A change request arrives from either internal or external source. When change request is identified formally, it is properly documented.
- Validation - Validity of the change request is checked and its handling procedure is confirmed.
- Analysis - The impact of change request is analyzed in terms of schedule, cost and required efforts. Overall impact of the prospective change on system is analyzed.
- Control - If the prospective change either impacts too many entities in the system or it is unavoidable, it is mandatory to take approval of high authorities before change is incorporated into the system. It is decided if the change is worth incorporation or not. If it is not, change request is refused formally.
- Execution - If the previous phase determines to execute the change request, this phase take appropriate actions to execute the change, does a thorough revision if necessary.
- Close request - The change is verified for correct implementation and merging with the rest of the system. This newly incorporated change in the software is documented properly and the request is formally is closed.
Project Management Tools
The risk and uncertainty rises multifold with respect to the size of the project, even when the project is developed according to set methodologies.
There are tools available, which aid for effective project management. A few are described -
Gantt Chart
Gantt charts was devised by Henry Gantt (1917). It represents project schedule with respect to time periods. It is a horizontal bar chart with bars representing activities and time scheduled for the project activities.
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PERT Chart
PERT (Program Evaluation & Review Technique) chart is a tool that depicts project as network diagram. It is capable of graphically representing main events of project in both parallel and consecutive way. Events, which occur one after another, show dependency of the later event over the previous one.
Events are shown as numbered nodes. They are connected by labeled arrows depicting sequence of tasks in the project.
Resource Histogram
Cocomo Model Example
This is a graphical tool that contains bar or chart representing number of resources (usually skilled staff) required over time for a project event (or phase). Resource Histogram is an effective tool for staff planning and coordination.
Critical Path Analysis
This tools is useful in recognizing interdependent tasks in the project. It also helps to find out the shortest path or critical path to complete the project successfully. Like PERT diagram, each event is allotted a specific time frame. This tool shows dependency of event assuming an event can proceed to next only if the previous one is completed.
Detailed Cocomo Model Pdf
The events are arranged according to their earliest possible start time. Path between start and end node is critical path which cannot be further reduced and all events require to be executed in same order.