Software quality extends beyond mere bug fixes; it's about delivering reliable, secure, and efficient software that truly meets customer needs. Software quality issues can result in financial losses, security breaches, and dissatisfaction among customers. This is where structured software quality models come in.
Using quality models, you can assess and improve software by setting clear criteria for functionality, performance, security, and maintainability. Instead of relying on intuition or ad hoc testing, developers and testers use these models to build software that works as expected, scales efficiently, and has longevity.
In this guide, we’ll explore the most widely used software quality models, how they work, and why they matter.
Software quality is an indicator of the extent to which a software product meets its specified requirements and user expectations. It’s not just about removing any bugs; it’s about ensuring that the software is efficient, secure, user-friendly, and maintainable for all users. Building high-quality software minimizes errors, reduces security risks, and enhances user satisfaction. Poor-quality software leads to frustrated users, increased maintenance costs, and business failures that can affect your business overall.
Here are a few key reasons why ensuring software quality is critical:
Software quality is mainly categorized based on three primary dimensions:
The first one is functional quality, which refers to how well the software meets functional requirements for the main software tasks it’s designed to perform. This functional quality ensures:
Even if a software product functions correctly, its underlying structure plays an important role in long-term performance. In structural quality it mainly focuses on:
Process quality ensures that software is developed using best practices, standardized workflows, and proper testing methodologies. It includes:
You can understand these key dimensions of software quality, and developers and businesses can take a structured approach to building reliable software.
But how do we systematically measure and maintain software quality? This is where software quality models come from, which we will discuss in the next section.
Software quality isn’t just about writing good code, it is about making sure that the final product meets user expectations, performs reliably, and remains maintainable over time.
So, software teams measure and maintain quality across different projects with software quality models.
The models provide a structured framework for assessing software quality, helping the QA teams to identify errors and improve efficiency. To maximize the effectiveness of your testing strategy, check out this detailed guide on essential testing reports for QA teams.
There are many benefits of software quality models:
In the early days of software development, quality was largely subjective, with developers depending on experience, intuition, and trial-and-error to enhance software reliability. However, as software systems became more complex and widely used, this approach proved inefficient and led to costly failures.
To address these challenges, industry experts and organizations introduced software quality models and structured methodologies that:
Understanding various software quality models is crucial for developing reliable and efficient software. Each model offers a unique perspective on assessing and enhancing software quality. Below is an overview of some of the most recognized software quality models:
McCalls Quality Model was introduced in 1977 as a groundbreaking model for software quality. This Model aimed to cover the gap between users and developers by specifying a structured way to understand and measure software quality. It's about how well the software performs, adapts, and integrates with the expectations of both the users and the developers.
The Model is mainly classified into two quality attributes that are Quality Factors and Quality Criteria.
Quality factors are the high level of quality matters that can be accessed directly and these are externals. This level of attributes is given more importance by the users and managers. Quality criteria are lower-level, internal attributes that can be assessed subjectively or objectively.
To better organize these quality factors, McCall's Model further classifies them into 11 distinct factors, each representing an important factor of software performance.
These 11 factors are then organized into three key categories of software quality:
Product operation includes 5 types of software quality factors. This category focuses on the software's behaviour during its operational phase for daily use, performance, convenience, and ease of usage.
Product revision includes three factors crucial for software testing and maintenance.
Product transition includes three key factors focusing on the software's adaptability to new environments and its ability to integrate with other systems.
Boehm’s Quality Model, developed by Barry W. Boehm in 1978, defines a comprehensive and hierarchical structure for evaluating software quality. It adds human engineering and testability as key considerations, reflecting a broader perspective on software quality.
This hierarchical structure gives a more organized and thorough assessment of software quality throughout the development process. It is an important tool for building high-quality software that excels in reliability, usability, and adaptability in real-world usage. The model categorizes quality attributes into three levels: High-Level Characteristics (Primary Uses), Mid-Level Characteristics (Intermediate Constructs), and Primitive Characteristics (Primitive Constructs).
These characteristics represent the overall quality of the software from a user's perspective. The primary uses are:
These characteristics contribute to the high-level characteristics and are more focused on the software's internal qualities and development aspects. They include:
These are the detailed, technical attributes that contribute to the mid-level characteristics:
By organizing quality attributes in this hierarchical way, Boehm's model provides a comprehensive framework for evaluating and improving software quality.
The FURPS model, introduced in 1987, proposes a practical and comprehensive framework for classifying and managing software quality attributes. It offers a structured method to ensure all key aspects of software quality are addressed during development and testing. This model is widely used in the software industry and emphasizes functionality, usability, reliability, performance, and supportability.
Feature sets, capabilities, and security. (What the software does)
This includes human factors, user interface design, and documentation. (How easy it is to use)
Frequency and severity of failures, recoverability, predictability, accuracy, and mean time between failures. (How dependable it is)
Speed, efficiency, resource consumption, throughput, availability and response time. (How well it performs)
Testability, extensibility, adaptability, maintainability, compatibility, configurability, serviceability, installability, and localizability. (How easy it is to maintain and support)
The model is proposed by Geoff Dromey and it takes a unique approach to software quality by emphasizing the relationship between measurable software product properties and higher-level quality attributes. It provides a structured method for predicting potential defects and improving overall software quality by focusing on the underlying properties that influence quality.
A key idea in Dromey's model is that the quality of a software depends on the properties of its individual components. These 'quality-carrying properties' include things like how complex a component is, how tightly it's connected to others, how well its parts work together, and how data moves through it. These factors directly affect qualities like how easy to maintain the software product is.
This model is structured into four main categories: Correctness, Internal, Contextual, and Descriptive. Each category addresses different facets of software quality, ensuring a proper evaluation of a system.
At the top level of the hierarchy, correctness includes key factors like Functionality and Reliability, ensuring that the software meets its intended purpose and operates without failure.
This category focuses on the internal aspects of the software, such as Maintainability, Efficiency, and Reliability. It looks at how well the system can be maintained, how efficiently it operates, and how stable and consistent it is over time.
The contextual level emphasizes the software's adaptability and fit within its environment. Attributes such as Maintainability, Reusability, Portability, and Reliability ensure that the software can be effectively used in various contexts and can adapt to different requirements or environments.
At this level, Dromey's model evaluates attributes like Efficiency, Reliability, and Usability, all of which are crucial for ensuring that the software is not only functional but also user-friendly and efficient in its real-world application.
The ISO 9126-1 standard, introduced in 1993, was a significant international effort to evaluate software quality, offering a structured framework for defining, measuring, and assessing various software quality attributes. While the model was influenced by earlier frameworks, such as McCall’s factor criteria metric model, it aimed to establish a global consensus on software quality.
In 2011, the ISO/IEC 25010 standard succeeded ISO 9126-1, expanding on its principles and refining the categories of software quality. While ISO/IEC 25010 is now the current standard, many of the concepts from ISO 9126-1 remain relevant, and the newer model builds on the original attributes with additions like Security and more specific sub-characteristics.
The ISO/IEC 25010 standard is the current international standard for software quality assessment. The ISO/IEC 25010 model is widely adopted across industries and focuses on both functional and non-functional attributes of software.
This model was designed to accommodate the growing complexity of software systems, especially with the increasing need for interoperability, security, and performance optimization in modern software. The ISO/IEC 25010 quality model comes with nine qualities that are mainly for evaluating software quality across its lifecycle.
Assesses how effectively the software meets the specified requirements and serves its intended purpose. This includes functionality like functional correctness, functional completeness, and functional appropriateness for the user’s needs. It ensures that the software does what it is supposed to do without defects.
It refers to the software’s ability to perform its tasks under various conditions while minimizing resource usage. This includes time behaviour (response time, processing time), resource utilization (CPU, memory, network bandwidth), and capacity (how well the software handles increased loads or data).
It's the ability of the software to work in conjunction with other systems or software within various environments. This includes the software's interoperability, co-existence with other systems with standards.
It refers to how easy and intuitive the software is for end users to learn, understand, and interact with. This includes understandability, learnability, operability, user assistance, self descriptiveness, user error protection and attractiveness of the user interface (UI).
It's the software product to perform consistently and recover gracefully from failures. It includes faultlessness, fault tolerance, recoverability, and availability (uptime and accessibility).
The software product ability to protect against unauthorized access and make sure the data confidentiality, integrity, and availability. It includes confidentiality, integrity, non-repudiation, accountability, resistance and authenticity of the software and its data.
It measures how easily the software can be modified to correct defects, meet new requirements, or enhance performance. This includes modularity, reusability, analysability, modifiability and testability making the software easy to maintain and upgrade over time.
The ability to be easily transferred between different environments, including various hardware, operating systems, and platforms. This includes adaptability, installability and replaceability allowing the software to be moved or replicated across different environments or configurations.
The best model for your project depends on factors such as project size, complexity, industry standards, and development methodology.
Below are key factors to consider when selecting a software quality model and when combining multiple models might be the best approach.
The scale and complexity of a project influence the type of quality assurance practices needed.
Certain industries impose strict regulatory and compliance requirements that directly impact software quality decisions.
The choice of software development methodology significantly influences the approach to quality assurance.
The objectives of the organization influence the level of quality assurance investment.
The level of acceptable risk determines how stringent the quality processes need to be.
The budget and expertise available for quality assurance determine the feasibility of certain approaches.
Implementing these quality models leads to early detection of defects, better alignment with user requirements, and overall proper software performance. To effectively apply these models, integrating advanced AI testing tools can be transformative.
AIO Tests is an all-in-one QA testing and test management app for Jira designed to streamline end-to-end testing processes. It offers features such as AI-assisted test creation, integration with Jira requirements, traceability across test cases and defects, defect tracking, and execution management that help teams deliver high-quality releases faster.
You can learn more about AIO Tests' capabilities and features by checking out the website or book a demo.
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