Task decomposition is the process of breaking down a complex task or project into smaller, manageable, and understandable subtasks. This approach simplifies task execution, structures it better, and reduces the stress associated with completing it.
Task decomposition can be performed both during the planning stage of a new sprint and throughout the sprint's execution by breaking down requirements for subsequent iterations. However, the latter approach is generally more preferable. It is advisable not to tie decomposition to a specific sprint, in order to come to its planning with a prepared backlog divided into user stories.
In such a situation, having a reserve of decomposed requirements offers the following advantages:
- Firstly, we do not limit ourselves in choosing tasks for the sprint (we can work only with those tasks that have already been decomposed).
- Secondly, during planning, we do not need to spend time on breakdown, allowing the team to focus on forming the sprint considering all priorities, discussing dependencies, and details of the requirements' implementation.
- Thirdly, the meeting will be more productive, and all team members will be actively engaged. Remember that meetings should be effective and positive, so the team looks forward to them rather than perceives them as a boring routine.
Two Main Approaches to Decomposition
There are two basic approaches to decomposing large tasks into user stories: "horizontal" and "vertical" decomposition.
- In the so-called "horizontal" decomposition, tasks are divided based on the type of work (functions) performed and the components used. In this approach, a large task is broken down into parts where a developer takes on one share of responsibilities, a tester takes another, a technical writer another, and so on. It is important to note that each of these parts does not lead to a completed result on its own; successful delivery of the finished functionality requires collaborative execution of all interrelated tasks by all process participants.
- On the other hand, the "vertical" approach to decomposition focuses on identifying smaller tasks, functions, and features so that each user story can be implemented and completed independently of others. In this case, various roles may be involved in the development process, and several modules and systems may be utilized, providing greater flexibility and speed in implementing functionality.
The vertical decomposition approach aligns more closely with Agile principles and is much more effective for several key reasons:
When using the "vertical" approach to decomposition, each task becomes available for implementation, testing, and demonstration to clients or users, making it understandable and measurable, unlike the more abstract "technical" tasks that arise from "horizontal" decomposition.
Within the "vertical" decomposition framework, each final user story has explicit business value, simplifying the process of comparing and prioritizing such tasks.
Since solving tasks organized by the "vertical" principle involves specialists with different roles, they can more easily identify potential problems, dependencies, and risks that may arise during the work's execution.
Techniques for Decomposing Requirements
Method 1: Stage-wise Breakdown of Business Processes
This approach suggests breaking down a large task related to a business process into smaller, independent components and stages. For this method to be effective, it is important to identify sequential steps that can be performed independently. For example, if there is a requirement in the backlog to implement an online purchasing function, the stages could include:
- Logging into the personal account
- Viewing items in the "cart"
- Generating an invoice
- Sending the invoice by email
- Payment via various methods: credit card, transfer, etc.
- Each of these stages can be formatted as a separate user story. Thus, we break down an extensive business process into components, allowing us to set priorities and better understand the process as a whole, including possible dependencies between stages.
Method 2: Separation into Positive and Negative Scenarios
Every functionality involves a primary use case that leads to the expected outcome, but deviations leading to negative consequences are also possible. This method suggests identifying scenarios that can lead to a successful or unsuccessful result. For example, for the online store purchase function:
- Positive scenario: the user logs in and successfully completes the purchase.
- Negative scenario 1: attempt to purchase without logging in.
- Negative scenario 2: insufficient funds in the account to complete the transaction.
- Negative scenario 3: account locked after several failed password attempts.
- This approach allows for the proactive identification and planning of how to handle possible errors and exceptions.
Method 3: Breakdown by Rules and Conditions
In contrast to the previous method, this method emphasizes logical branches of the process based on various rules. For example, for the purchase function, rules might include:
- Minimum purchase amount.
- Additional payment options for exceeding a certain amount.
- Automatic order cancellation after 2 days without payment.
- Each of these conditions can be formatted as a separate task, helping to identify important constraints and simplifying the implementation process.
Method 4: Separation by Types of Operations
Many functional requirements correspond to standard operations such as create, read, update, and delete (CRUD). For example, for managing product cards in an online store, we can identify:
- Create: adding a new product.
- Read: viewing product descriptions.
- Update: editing product information.
- Delete: removing a product from the store.
- This breakdown allows for a clear definition of necessary operations and their priorities.
Method 5: Decomposition by Platforms and Operating Systems
This method involves breaking down requirements based on the platform or operating system. For example, for the payment function in a web application, tasks can be identified for various devices:
- Personal computers
- Tablets
- Smartphones
- Different operating systems: Windows, iOS, Android.
- This approach helps to define priority development directions.
Method 6: Separation by Data Types and Parameters
Some functions may handle various types of data or parameters. For example, for the search function in an online store, we can identify:
- Search by product name.
- Search by product number.
- Search using regular expressions.
- This decomposition allows for a clear definition of acceptable parameters and easy management of requirements.
Method 7: Separation by Roles and Access Rights
Different user groups may have different access rights and perform various functions. For example, in an online store, these may include:
- Owner: create and delete products.
- Administrator: edit descriptions and interact with customers.
- Customer: view and purchase products. This breakdown helps understand what functionalities are necessary for each role and prioritize their implementation.
Method 8: Decomposition by Test Scenarios
This method breaks down functionality based on test cases that need to be verified to check the successful operation of functions. For example, for the function of adding a product to the "cart," the following test scenarios might be identified:
- The product is available for purchase.
- The product is reserved by another user.
- The product is out of stock. This approach allows for the integration of various decomposition techniques and creates clear tasks for development and testing.
Each of these decomposition methods helps to better structure requirements and contributes to more effective development in an Agile environment.
Advantages of Task Decomposition:
Improved Understanding: Breaking down large tasks (or user stories) into smaller parts allows the team to better understand what exactly needs to be done. Smaller tasks are easier to conceive and discuss.
Better Estimation: The team can more accurately estimate the time and effort required to complete smaller tasks, improving planning and resource management (ensures great Planning Meetings using Fibonacci numbers or T-Shirt Sizes).
Manageability: Smaller tasks are easier to plan and control. The team can more accurately estimate the time and labor resources needed to complete each task.
Increased Transparency: When tasks are broken down into smaller parts, it becomes easier to track progress and identify issues at early stages. This allows the team to respond quickly to changes.
Enhanced Flexibility: In Scrum, changes in requirements often occur, and task decomposition allows the team to adapt more flexibly to these changes by adjusting their plans and priorities.
Improved Quality: Smaller tasks enable the team to focus on the quality of each individual part, which can lead to a higher quality final product.
Encouragement of Collaboration: Task decomposition can foster more active collaboration within the team, as participants can work on different parts of the same task simultaneously.
Gradual Integration: Breaking tasks down into smaller parts allows the team to integrate and test functionality in stages, reducing risks and improving stability.
I hope this information is useful to you! If you have any questions or suggestions, please leave comments. I would be happy to assist you with personal advice on IT, business analysis, Scrum, or project management!
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