Architecture Learnings Part #11 {COCOMO Model in Modern Software Architecture}

Introduction

In the ever-evolving landscape of software architecture, where new methodologies and tools emerge seemingly every day, it's essential to revisit and assess the relevance of time-tested models. One such model that has stood the test of time is the Constructive Cost Model (COCOMO). In this article, we'll explore whether the COCOMO model remains relevant in modern software architecture and why it continues to be a valuable asset for software development teams.

COCOMO - A Brief Overview

The COCOMO model, developed by Dr. Barry Boehm in the late 1970s, is a parametric estimation model that helps software teams estimate the cost, effort, and schedule of a project. It provides a structured framework for understanding the factors that influence software development, making it easier to plan, budget, and execute projects effectively.

Is COCOMO Still Relevant?

In an era where Agile, DevOps, and other modern methodologies have gained significant traction, it's natural to question whether a decades-old model like COCOMO still has a place in the software architecture world. Here are some reasons why it remains relevant:

1. Baseline for Estimations: COCOMO provides a valuable baseline for estimating project parameters like size, effort, and schedule. Modern methodologies can benefit from this structured approach when initial project estimates are needed.

2. Historical Data: Many organizations have a wealth of historical data from past projects. COCOMO can be used alongside this data to refine and improve estimations. It helps in avoiding the "gut feeling" estimates that can lead to cost overruns and project delays.

3. Complex Projects: While modern methodologies excel in flexibility and adaptability, they can be challenging to apply to large and complex projects. COCOMO's scalability allows it to handle projects of varying sizes and complexities.

4. Risk Assessment: COCOMO encourages a thorough analysis of various project factors, including risks. This can be especially valuable in projects where risk management is a critical concern.

5. Resource Allocation: Even in Agile environments, resource allocation remains a significant concern. COCOMO aids in identifying resource requirements, which can be critical for project planning.

Let's walk through an example of using the COCOMO (Constructive Cost Model) to estimate the effort and cost for a software development project.

Scenario: Imagine a software development team is tasked with building a mobile app for a small startup. The project involves developing a basic mobile app for both iOS and Android platforms. The team needs to estimate the effort and cost for this project using the COCOMO model.

Step 1: Define Project Size

In COCOMO, project size is typically measured in thousands of lines of code (KLOC) or function points. For this example, let's estimate the project size in KLOC.

- Total Lines of Code (LOC) for both iOS and Android: 60 KLOC (30 KLOC for each platform)

Step 2: Select COCOMO Mode

There are three COCOMO modes:

• Basic,
• Intermediate, and
• Detailed.

For this example, we'll use the Intermediate COCOMO model, as it's suitable for projects with moderate complexity and requirements.

Step 3: Determine Scale Factors

Scale factors are used to adjust the estimation based on project-specific characteristics. These factors include Product, Hardware, Personnel, Project, and more. Rate each factor on a scale from "Very Low" to "Extra High." For this example, we'll assume the following ratings:

- Product Complexity: Low

- Hardware Constraints: Low

- Personnel Capability: High

- Project Flexibility: High

- Process Maturity: Medium

Step 4: Calculate the Effort Adjustment Factor (EAF)

The Effort Adjustment Factor (EAF) is calculated based on the scale factors. The EAF formula depends on the specific version of COCOMO you're using, but it generally involves multiplying the ratings of the scale factors. In our example, the EAF is calculated as follows:

EAF = Product Hardware Personnel Project Process

EAF = Low Low High High Medium = 0.1

Step 5: Estimate Effort

Now, you can estimate the effort (in Person-Months) using the COCOMO formula:

Effort (PM) = a (Size)^b EAF

For the Intermediate COCOMO model, the constants 'a' and 'b' are typically defined as follows:

- a = 3.0 (for projects with high personnel capability)

- b = 1.12

Let's calculate the effort:

Effort (PM) = 3.0 (60 KLOC)^1.12 0.1

Effort (PM) ≈ 27.03 Person-Months

Step 6: Estimate Schedule

Once you have the effort, you can estimate the project schedule in months. The schedule is often calculated based on historical data for the organization. For this example, let's assume the team's historical data suggests an average productivity of 2 Person-Months per month.

Schedule (Months) = Effort (PM) / Productivity

Schedule (Months) ≈ 27.03 PM / 2 PM per month ≈ 13.51 months

Step 7: Estimate Cost

Finally, estimate the project cost using the schedule and the team's monthly cost. Let's assume the average team cost is $10,000 per Person-Month.

Cost ($) = Effort (PM) * Monthly Cost

Cost ($) ≈ 27.03 PM * $10,000 ≈ $270,300

So, based on the Intermediate COCOMO model, the estimated effort for building the mobile app is approximately 27.03 Person-Months, with an estimated cost of around $270,300.

Please note that this is a simplified example, and real-world projects may have additional complexities and factors to consider. COCOMO is a valuable tool, but it's important to use it in conjunction with other estimation methods and expert judgment to arrive at more accurate estimates for software development projects.

Modernizing COCOMO

To make COCOMO more compatible with contemporary software development practices, consider the following adaptations:

1. Agile Integration: Incorporate COCOMO estimations into Agile practices by using them as a starting point for iteration planning and sprint backlogs.

2. Continuous Improvement: Leverage COCOMO's historical data analysis to continually improve estimations and adapt to changing project dynamics.

3. Use in Parallel: Use COCOMO in parallel with Agile methods to provide a comprehensive view of project planning and budgeting.

Conclusion

The COCOMO model, though developed in an earlier era of software development, continues to be a relevant and valuable tool in modern software architecture. It complements modern methodologies by providing a structured approach to project estimation and management. By leveraging the strengths of both COCOMO and contemporary practices, software development teams can achieve more accurate estimates, better resource allocation, and ultimately, greater project success.

In the fast-paced world of software architecture, embracing the best of both old and new can be the key to delivering successful projects on time and within budget. All about attaching a $ value to your architecture proposal.

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