What is Vertical Slicing and its Application in Project Management
A Deep Dive into Vertical Slicing - The Agile Approach to Deliver Value Faster
Vertical slicing is an agile software development technique that allows teams to deliver value faster by prioritizing user stories and incrementally building thin vertical slices of a product in each sprint. This approach differs from traditional horizontal slicing where teams build feature-by-feature and layer-by-layer.
In this comprehensive guide, we will explore what vertical slicing is, its key principles, benefits, and how it enables agile teams to iteratively deliver value and gather feedback. We will also look at how vertical slicing complements other agile practices like user stories and helps project managers plan and manage software projects. By the end, you will have a clear understanding of this important agile concept and how to leverage it for your projects.
What is Vertical Slicing?
Vertical slicing is an agile software development technique where software is built in thin vertical slices that cut through the traditional system layers of UI, business logic, and data access. These vertical slices deliver a thin thread of end-to-end business value that stretches over every layer.
Some key principles of vertical slicing include:
Building in small vertical slices or increments rather than horizontal layers
Ensuring each slice or increment offers end-to-end business value
Prioritizing user stories based on business value
Refining user stories into small enough vertical slices to fit in a single sprint
Working on all layers of the system - UI, business logic, data - for each slice
To understand vertical slicing, let's use the analogy of slicing a cake. In traditional horizontal slicing, you would cut layers of the cake first - icing, cake, filling. With vertical slicing, you would cut vertically through the cake to get a slice with some icing, cake, and filling in each slice.
In software development, horizontal slicing means completing UI screens first, then business logic, then data access layers. Vertical slicing means in each increment we build a thin slice of UI, business logic, and data access to deliver end-to-end value.
For example, for a simple login user story, horizontal slicing would first build all the login UI screens. Vertical slicing would include a simple UI, basic validation logic, and ability to check credentials in the database in one increment.
Vertical slicing focuses on cutting user stories for incremental delivery rather than traditional system layers. This enables value to be delivered incrementally versus waiting for all components of a layer to be built.
How Does Vertical Slicing Differ from Horizontal Slicing?
In traditional horizontal slicing, software is built layer-by-layer with all UI first, then business logic, then data access. This waterfall approach leads to big batch handoffs and delays delivering value.
For example, the UI team might spend months building pixel-perfect screens before handing off to the business logic team. Only after the backend was done would an end-to-end piece of value be delivered.
This horizontal approach causes several issues:
Big batches and delays before value is delivered
Harder to refine user stories based on each layer
Lack of visibility into progress from an end-user perspective
Key feedback comes much later in the process
Hard to coordinate priorities across layers
Difficulty estimating work
Testing and QA is complex
In contrast, vertical slicing builds a thin thread of functionality across all layers in an increment. This cross-sectional approach allows value to be delivered in small pieces and offers end-to-end system feedback.
With vertical slicing the team collectively owns delivering end-to-end value. This improves communication, accountability, and agility.
Horizontal slicing also makes it hard to refine user stories, estimate work, and collaborate across skills. The traditional layered approach encourages "tossing work over the wall" to other teams vs. shared ownership.
Vertical slicing breaks down user stories into smaller, more manageable pieces for the team. This makes planning, coordinating, and delivering together more manageable.
In summary, traditional horizontal slicing delays value delivery while vertical slicing enables incremental value delivery by cutting across layers.
Key Benefits of Vertical Slicing
There are several key benefits teams gain from vertical slicing:
Faster Feedback
Vertical slices allow functional increments to be demonstrated early and feedback gathered from stakeholders after each increment. This facilitates the build-measure-learn feedback loop crucial for agile projects.
Rather than waiting months for an entire layer like the UI to be built, vertical slicing provides a thin slice to demo after a sprint or two. This means faster feedback on what is being built before more work continues.
For example, the first vertical slice could be a simple working login screen with placeholder content. This provides feedback on the general look and flow from stakeholders.
The iterative approach makes it easier to incorporate feedback more frequently than traditional approaches. This reduces overall project risk and improves stakeholder satisfaction.
Focused on Business Value
Each vertical slice delivers a thin thread of end-to-end business value rather than just output. This keeps the focus of agile teams on delivering value vs. just finishing requirements or outputs.
For example, a team building an e-commerce site might first focus on allowing users to search and view products before building advanced recommendation algorithms. This focuses on user and business value first.
Vertical slicing avoids '100% complete' syndrome where teams build substantial functionality with minimal actual value. By tying each increment to value, it keeps agile teams focused on what matters most.
Better Estimation
Thin vertical slices make it easier for agile teams to estimate work for a sprint or iteration. Estimating large requirements in horizontal layers is quite difficult.
But estimating a thin vertical slice through UI, logic, and data is simpler. The slices represent tangible end-to-end deliverables versus nebulous layers.
This makes sprint planning more accurate when based on small vertical slices. Teams have greater confidence in what they can complete within a sprint.
Greater Flexibility
With traditional horizontal slicing, major reprioritization is difficult once an entire layer is underway. But with vertical slicing, the product backlog can be reprioritized without disrupting half-done work across layers.
For example, if UI screens were 50% done but priorities changed, this would require substantial rework. But with vertical slicing, any backlog item can be reprioritized since slices are thin and focused on value.
This flexibility allows agile teams to easily adapt to changing stakeholder needs. Minimal rework is required when priorities change.
Encourages Collaboration
Since vertical slicing requires working across UI, business logic, and data access in an increment, it encourages collaboration across disciplines. Rather than siloed teams, vertical slicing promotes shared ownership and accountability.
Developers, testers, UX designers, etc. must tightly collaborate to ensure each vertical slice meets requirements. This frequent synchronization improves communication and working relationships within agile teams.
By removing hand-offs between layers, it reduces misalignments across teams. It also provides improved visibility since all disciplines own value delivery together.
Vertical Slicing Enables Key Agile Practices
Vertical slicing complements other agile practices and ceremonies:
Refining User Stories
Vertical slicing helps agile teams refine user stories into small vertical slices that can be delivered within a sprint increment.
Traditionally, large requirements span multiple layers. But vertical slicing requires breaking these down into thin end-to-end slices representing tangible value.
This makes it easier to create vertical stories suitable for sprint planning. The emphasis shifts from delivering outputs and layers to delivering value.
Sprint Increments
The thin vertical slices align well with sprint increments in agile. Sprint increments should produce a potentially releasable increment of value.
Vertical slices map to this goal since each slice entails end-to-end function that offers value. Agile teams can deliver a complete slice within a single sprint.
So vertical slicing enables teams to work incrementally and deliver value in each sprint. This provides tangible progress inspection points during the sprint review.
Focus on Business Value
Since vertical slices provide end-to-end value, they naturally align with the focus on business value in agile.
When agile teams vertically slice user stories for prioritization, the emphasis remains on which slices offer the most value. This takes priority over output-focused requirements.
It encourages product owners and teams to evaluate what brings the most business benefit when planning sprints and releases.
Enables Iterative Development
Agile methods rely on iterative development as opposed to big, serial phases. Vertical slicing supports this well.
Vertical slices are small enough to build within a sprint iteration. This facilitates the incremental, iterative approach.
Rather than waiting for entire layers to be built before feedback, vertical slicing provides quick iterative loops for evaluation and adaptation.
This iterative approach based on vertical slicing helps teams continuously refine and steer value delivery in the right direction.
Facilitates the Feedback Loop
The fast feedback cycles enabled by vertical slicing are critical for agile success.
Agile methods leverage regular inspection and adaptation driven by stakeholder feedback. Vertical slices provide thin value increments to collect feedback on quickly.
This facilitates the empirical, iterative nature of agile development guided by constant feedback. Teams can gather feedback sprint-by-sprint and incorporate learnings moving forward.
So vertical slicing is an important enabler of rapid feedback loops by delivering value increments frequently. This allows teams to regularly inspect and adapt.
In summary, vertical slicing complements and enables many core agile and lean principles. It aligns well with the fast, empirical approach of delivering value and leveraging feedback.
How Does Vertical Slicing Help Project Managers?
Vertical slicing offers several benefits for agile project managers:
Planning and Tracking Increments
Vertical slicing provides natural increments that can be planned and tracked in agile projects. Since each slice represents an end-to-end function, it serves as a tangible increment of work.
This gives project managers more predictable units of work to plan sprints and milestones around. It also offers clear inspection points to assess progress.
Estimating Work
As mentioned earlier, estimating large requirements spanning multiple layers is difficult. But thin vertical slices are much easier to estimate.
Project managers can use vertical slices as the basis of work estimation for agile projects. This improves accuracy which translates to better sprint planning and tracking.
Flexibility in Prioritization
Project managers need the flexibility to reprioritize the backlog as stakeholder needs change. Vertical slicing enables this by avoiding partial work across layers.
With thin slices focused on value delivery, backlog items can be rearranged without substantial rework. This allows agile PMs to easily adapt scope based on evolving needs.
Feedback Loops
The fast feedback loops enabled by vertical slicing provide project managers greater visibility into value delivery and stakeholder sentiment.
The slice demonstrations from each sprint offer regular touchpoints for the PM to inspect progress and get feedback. This helps validate that work aligns to customer needs.
Predictability of Delivery
The combination of reliable estimation, planning, prioritization, and feedback ultimately provides more predictable value delivery.
Project managers gain confidence that vertical slices scoped for each sprint will complete as planned. This results in more dependable agile delivery.
Overall, vertical slicing gives project managers several leverages like reliable increments and feedback cycles to plan and track agile projects effectively.
Common Challenges with Adopting Vertical Slicing
While vertical slicing offers many benefits, teams also face some adoption challenges:
Prioritizing User Stories
Transitioning to prioritizing user stories and backlog items based on vertical slices is a mindset shift for teams.
Traditionally, requirements focus on outputs and layers. But vertical slicing requires a value-focused perspective when prioritizing and planning.
This takes some adjustments for product owners and teams to think at the vertical level vs. horizontal layers. Time should be spent educating teams on the principles.
Synchronizing Work
Delivering vertical slices requires strong coordination across disciplines like developers, QA, UX, etc. Everyone must come together to deliver a thin but complete slice.
If work across teams falls out of sync, the end-to-end thread breaks and vertical slicing stalls. Teams must proactively communicate blockers and synchronize frequently.
Daily standups and maybe additional integration meetings help identify and resolve bottlenecks early. A mindset of shared ownership is critical.
Testing Approach
Testing strategies may need to adjust to focus on validating vertical slices. Often testing is organized around system layers and components.
But with vertical slicing, testing needs to confirm that the end-to-end functionality works for the increment. This may require tweaking processes and tools.
Automated testing and test-driven development are highly compatible with vertical slicing to validate slices.
Requirements Detail
Product owners must provide well-detailed requirements for vertical slices, splitting stories effectively. Enough details must exist for the slice while retaining flexibility for implementation.
This level of analysis requires some practice and collaboration between the product owner and team. But it yields big benefits in small batch delivery of value.
Making Vertical Slicing Work
Here are some tips to help teams implement vertical slicing effectively:
Provide education and training on vertical slicing so the team understands the principles and benefits
Involve developers, testers, UX designers etc. in user story refinement to define thin vertical slices
Identify dependencies across slices and system components to coordinate work across sprints
Establish cadences for integration and testing to validate slices across disciplines
Encourage conversations between team members to proactively identify bottlenecks
Adjust testing strategies and infrastructure to validate full vertical slices
Re-orient product roadmaps and backlogs around delivery of end-to-end value
Provide visibility using boards and charts to unblock dependencies between teams
Celebrate successes delivering end-to-end value increments with the team
Key Takeaways and Summary
Vertical slicing delivers end-to-end value increments across system layers versus handing off layers.
Key principles are small thin slices, focus on value, and working incrementally.
It enables faster feedback, flexibility, collaboration and complements agile practices.
Project managers benefit from improved planning, estimation, tracking, and predictability.
Adopting vertical slicing requires teams to shift perspectives and synchronize work.
In summary, vertical slicing is a powerful agile technique to deliver value faster. While it requires some adjustment, the benefits are well worth it for most software teams. By providing end-to-end value increments, it enables the frequent feedback so crucial to agile development success.
Vertical slicing is a modern, versatile approach that helps software teams focus their efforts on delivering value early and often. When combined with agile principles, vertical slicing can transform how teams build products and drastically improve outcomes. This guide provided a comprehensive overview of vertical slicing and how to leverage it; teams can use these insights to implement vertical slicing in their projects and reap the speed and quality benefits.
What is Vertical Slicing and its Application in Project Management
A Deep Dive into Vertical Slicing - The Agile Approach to Deliver Value Faster
Vertical slicing is an agile software development technique that allows teams to deliver value faster by prioritizing user stories and incrementally building thin vertical slices of a product in each sprint. This approach differs from traditional horizontal slicing where teams build feature-by-feature and layer-by-layer.
In this comprehensive guide, we will explore what vertical slicing is, its key principles, benefits, and how it enables agile teams to iteratively deliver value and gather feedback. We will also look at how vertical slicing complements other agile practices like user stories and helps project managers plan and manage software projects. By the end, you will have a clear understanding of this important agile concept and how to leverage it for your projects.
What is Vertical Slicing?
Vertical slicing is an agile software development technique where software is built in thin vertical slices that cut through the traditional system layers of UI, business logic, and data access. These vertical slices deliver a thin thread of end-to-end business value that stretches over every layer.
Some key principles of vertical slicing include:
Building in small vertical slices or increments rather than horizontal layers
Ensuring each slice or increment offers end-to-end business value
Prioritizing user stories based on business value
Refining user stories into small enough vertical slices to fit in a single sprint
Working on all layers of the system - UI, business logic, data - for each slice
To understand vertical slicing, let's use the analogy of slicing a cake. In traditional horizontal slicing, you would cut layers of the cake first - icing, cake, filling. With vertical slicing, you would cut vertically through the cake to get a slice with some icing, cake, and filling in each slice.
In software development, horizontal slicing means completing UI screens first, then business logic, then data access layers. Vertical slicing means in each increment we build a thin slice of UI, business logic, and data access to deliver end-to-end value.
For example, for a simple login user story, horizontal slicing would first build all the login UI screens. Vertical slicing would include a simple UI, basic validation logic, and ability to check credentials in the database in one increment.
Vertical slicing focuses on cutting user stories for incremental delivery rather than traditional system layers. This enables value to be delivered incrementally versus waiting for all components of a layer to be built.
How Does Vertical Slicing Differ from Horizontal Slicing?
In traditional horizontal slicing, software is built layer-by-layer with all UI first, then business logic, then data access. This waterfall approach leads to big batch handoffs and delays delivering value.
For example, the UI team might spend months building pixel-perfect screens before handing off to the business logic team. Only after the backend was done would an end-to-end piece of value be delivered.
This horizontal approach causes several issues:
Big batches and delays before value is delivered
Harder to refine user stories based on each layer
Lack of visibility into progress from an end-user perspective
Key feedback comes much later in the process
Hard to coordinate priorities across layers
Difficulty estimating work
Testing and QA is complex
In contrast, vertical slicing builds a thin thread of functionality across all layers in an increment. This cross-sectional approach allows value to be delivered in small pieces and offers end-to-end system feedback.
With vertical slicing the team collectively owns delivering end-to-end value. This improves communication, accountability, and agility.
Horizontal slicing also makes it hard to refine user stories, estimate work, and collaborate across skills. The traditional layered approach encourages "tossing work over the wall" to other teams vs. shared ownership.
Vertical slicing breaks down user stories into smaller, more manageable pieces for the team. This makes planning, coordinating, and delivering together more manageable.
In summary, traditional horizontal slicing delays value delivery while vertical slicing enables incremental value delivery by cutting across layers.
Key Benefits of Vertical Slicing
There are several key benefits teams gain from vertical slicing:
Faster Feedback
Vertical slices allow functional increments to be demonstrated early and feedback gathered from stakeholders after each increment. This facilitates the build-measure-learn feedback loop crucial for agile projects.
Rather than waiting months for an entire layer like the UI to be built, vertical slicing provides a thin slice to demo after a sprint or two. This means faster feedback on what is being built before more work continues.
For example, the first vertical slice could be a simple working login screen with placeholder content. This provides feedback on the general look and flow from stakeholders.
The iterative approach makes it easier to incorporate feedback more frequently than traditional approaches. This reduces overall project risk and improves stakeholder satisfaction.
Focused on Business Value
Each vertical slice delivers a thin thread of end-to-end business value rather than just output. This keeps the focus of agile teams on delivering value vs. just finishing requirements or outputs.
For example, a team building an e-commerce site might first focus on allowing users to search and view products before building advanced recommendation algorithms. This focuses on user and business value first.
Vertical slicing avoids '100% complete' syndrome where teams build substantial functionality with minimal actual value. By tying each increment to value, it keeps agile teams focused on what matters most.
Better Estimation
Thin vertical slices make it easier for agile teams to estimate work for a sprint or iteration. Estimating large requirements in horizontal layers is quite difficult.
But estimating a thin vertical slice through UI, logic, and data is simpler. The slices represent tangible end-to-end deliverables versus nebulous layers.
This makes sprint planning more accurate when based on small vertical slices. Teams have greater confidence in what they can complete within a sprint.
Greater Flexibility
With traditional horizontal slicing, major reprioritization is difficult once an entire layer is underway. But with vertical slicing, the product backlog can be reprioritized without disrupting half-done work across layers.
For example, if UI screens were 50% done but priorities changed, this would require substantial rework. But with vertical slicing, any backlog item can be reprioritized since slices are thin and focused on value.
This flexibility allows agile teams to easily adapt to changing stakeholder needs. Minimal rework is required when priorities change.
Encourages Collaboration
Since vertical slicing requires working across UI, business logic, and data access in an increment, it encourages collaboration across disciplines. Rather than siloed teams, vertical slicing promotes shared ownership and accountability.
Developers, testers, UX designers, etc. must tightly collaborate to ensure each vertical slice meets requirements. This frequent synchronization improves communication and working relationships within agile teams.
By removing hand-offs between layers, it reduces misalignments across teams. It also provides improved visibility since all disciplines own value delivery together.
Vertical Slicing Enables Key Agile Practices
Vertical slicing complements other agile practices and ceremonies:
Refining User Stories
Vertical slicing helps agile teams refine user stories into small vertical slices that can be delivered within a sprint increment.
Traditionally, large requirements span multiple layers. But vertical slicing requires breaking these down into thin end-to-end slices representing tangible value.
This makes it easier to create vertical stories suitable for sprint planning. The emphasis shifts from delivering outputs and layers to delivering value.
Sprint Increments
The thin vertical slices align well with sprint increments in agile. Sprint increments should produce a potentially releasable increment of value.
Vertical slices map to this goal since each slice entails end-to-end function that offers value. Agile teams can deliver a complete slice within a single sprint.
So vertical slicing enables teams to work incrementally and deliver value in each sprint. This provides tangible progress inspection points during the sprint review.
Focus on Business Value
Since vertical slices provide end-to-end value, they naturally align with the focus on business value in agile.
When agile teams vertically slice user stories for prioritization, the emphasis remains on which slices offer the most value. This takes priority over output-focused requirements.
It encourages product owners and teams to evaluate what brings the most business benefit when planning sprints and releases.
Enables Iterative Development
Agile methods rely on iterative development as opposed to big, serial phases. Vertical slicing supports this well.
Vertical slices are small enough to build within a sprint iteration. This facilitates the incremental, iterative approach.
Rather than waiting for entire layers to be built before feedback, vertical slicing provides quick iterative loops for evaluation and adaptation.
This iterative approach based on vertical slicing helps teams continuously refine and steer value delivery in the right direction.
Facilitates the Feedback Loop
The fast feedback cycles enabled by vertical slicing are critical for agile success.
Agile methods leverage regular inspection and adaptation driven by stakeholder feedback. Vertical slices provide thin value increments to collect feedback on quickly.
This facilitates the empirical, iterative nature of agile development guided by constant feedback. Teams can gather feedback sprint-by-sprint and incorporate learnings moving forward.
So vertical slicing is an important enabler of rapid feedback loops by delivering value increments frequently. This allows teams to regularly inspect and adapt.
In summary, vertical slicing complements and enables many core agile and lean principles. It aligns well with the fast, empirical approach of delivering value and leveraging feedback.
How Does Vertical Slicing Help Project Managers?
Vertical slicing offers several benefits for agile project managers:
Planning and Tracking Increments
Vertical slicing provides natural increments that can be planned and tracked in agile projects. Since each slice represents an end-to-end function, it serves as a tangible increment of work.
This gives project managers more predictable units of work to plan sprints and milestones around. It also offers clear inspection points to assess progress.
Estimating Work
As mentioned earlier, estimating large requirements spanning multiple layers is difficult. But thin vertical slices are much easier to estimate.
Project managers can use vertical slices as the basis of work estimation for agile projects. This improves accuracy which translates to better sprint planning and tracking.
Flexibility in Prioritization
Project managers need the flexibility to reprioritize the backlog as stakeholder needs change. Vertical slicing enables this by avoiding partial work across layers.
With thin slices focused on value delivery, backlog items can be rearranged without substantial rework. This allows agile PMs to easily adapt scope based on evolving needs.
Feedback Loops
The fast feedback loops enabled by vertical slicing provide project managers greater visibility into value delivery and stakeholder sentiment.
The slice demonstrations from each sprint offer regular touchpoints for the PM to inspect progress and get feedback. This helps validate that work aligns to customer needs.
Predictability of Delivery
The combination of reliable estimation, planning, prioritization, and feedback ultimately provides more predictable value delivery.
Project managers gain confidence that vertical slices scoped for each sprint will complete as planned. This results in more dependable agile delivery.
Overall, vertical slicing gives project managers several leverages like reliable increments and feedback cycles to plan and track agile projects effectively.
Common Challenges with Adopting Vertical Slicing
While vertical slicing offers many benefits, teams also face some adoption challenges:
Prioritizing User Stories
Transitioning to prioritizing user stories and backlog items based on vertical slices is a mindset shift for teams.
Traditionally, requirements focus on outputs and layers. But vertical slicing requires a value-focused perspective when prioritizing and planning.
This takes some adjustments for product owners and teams to think at the vertical level vs. horizontal layers. Time should be spent educating teams on the principles.
Synchronizing Work
Delivering vertical slices requires strong coordination across disciplines like developers, QA, UX, etc. Everyone must come together to deliver a thin but complete slice.
If work across teams falls out of sync, the end-to-end thread breaks and vertical slicing stalls. Teams must proactively communicate blockers and synchronize frequently.
Daily standups and maybe additional integration meetings help identify and resolve bottlenecks early. A mindset of shared ownership is critical.
Testing Approach
Testing strategies may need to adjust to focus on validating vertical slices. Often testing is organized around system layers and components.
But with vertical slicing, testing needs to confirm that the end-to-end functionality works for the increment. This may require tweaking processes and tools.
Automated testing and test-driven development are highly compatible with vertical slicing to validate slices.
Requirements Detail
Product owners must provide well-detailed requirements for vertical slices, splitting stories effectively. Enough details must exist for the slice while retaining flexibility for implementation.
This level of analysis requires some practice and collaboration between the product owner and team. But it yields big benefits in small batch delivery of value.
Making Vertical Slicing Work
Here are some tips to help teams implement vertical slicing effectively:
Provide education and training on vertical slicing so the team understands the principles and benefits
Involve developers, testers, UX designers etc. in user story refinement to define thin vertical slices
Identify dependencies across slices and system components to coordinate work across sprints
Establish cadences for integration and testing to validate slices across disciplines
Encourage conversations between team members to proactively identify bottlenecks
Adjust testing strategies and infrastructure to validate full vertical slices
Re-orient product roadmaps and backlogs around delivery of end-to-end value
Provide visibility using boards and charts to unblock dependencies between teams
Celebrate successes delivering end-to-end value increments with the team
Key Takeaways and Summary
Vertical slicing delivers end-to-end value increments across system layers versus handing off layers.
Key principles are small thin slices, focus on value, and working incrementally.
It enables faster feedback, flexibility, collaboration and complements agile practices.
Project managers benefit from improved planning, estimation, tracking, and predictability.
Adopting vertical slicing requires teams to shift perspectives and synchronize work.
In summary, vertical slicing is a powerful agile technique to deliver value faster. While it requires some adjustment, the benefits are well worth it for most software teams. By providing end-to-end value increments, it enables the frequent feedback so crucial to agile development success.
Vertical slicing is a modern, versatile approach that helps software teams focus their efforts on delivering value early and often. When combined with agile principles, vertical slicing can transform how teams build products and drastically improve outcomes. This guide provided a comprehensive overview of vertical slicing and how to leverage it; teams can use these insights to implement vertical slicing in their projects and reap the speed and quality benefits.
What is Vertical Slicing and its Application in Project Management
A Deep Dive into Vertical Slicing - The Agile Approach to Deliver Value Faster
Vertical slicing is an agile software development technique that allows teams to deliver value faster by prioritizing user stories and incrementally building thin vertical slices of a product in each sprint. This approach differs from traditional horizontal slicing where teams build feature-by-feature and layer-by-layer.
In this comprehensive guide, we will explore what vertical slicing is, its key principles, benefits, and how it enables agile teams to iteratively deliver value and gather feedback. We will also look at how vertical slicing complements other agile practices like user stories and helps project managers plan and manage software projects. By the end, you will have a clear understanding of this important agile concept and how to leverage it for your projects.
What is Vertical Slicing?
Vertical slicing is an agile software development technique where software is built in thin vertical slices that cut through the traditional system layers of UI, business logic, and data access. These vertical slices deliver a thin thread of end-to-end business value that stretches over every layer.
Some key principles of vertical slicing include:
Building in small vertical slices or increments rather than horizontal layers
Ensuring each slice or increment offers end-to-end business value
Prioritizing user stories based on business value
Refining user stories into small enough vertical slices to fit in a single sprint
Working on all layers of the system - UI, business logic, data - for each slice
To understand vertical slicing, let's use the analogy of slicing a cake. In traditional horizontal slicing, you would cut layers of the cake first - icing, cake, filling. With vertical slicing, you would cut vertically through the cake to get a slice with some icing, cake, and filling in each slice.
In software development, horizontal slicing means completing UI screens first, then business logic, then data access layers. Vertical slicing means in each increment we build a thin slice of UI, business logic, and data access to deliver end-to-end value.
For example, for a simple login user story, horizontal slicing would first build all the login UI screens. Vertical slicing would include a simple UI, basic validation logic, and ability to check credentials in the database in one increment.
Vertical slicing focuses on cutting user stories for incremental delivery rather than traditional system layers. This enables value to be delivered incrementally versus waiting for all components of a layer to be built.
How Does Vertical Slicing Differ from Horizontal Slicing?
In traditional horizontal slicing, software is built layer-by-layer with all UI first, then business logic, then data access. This waterfall approach leads to big batch handoffs and delays delivering value.
For example, the UI team might spend months building pixel-perfect screens before handing off to the business logic team. Only after the backend was done would an end-to-end piece of value be delivered.
This horizontal approach causes several issues:
Big batches and delays before value is delivered
Harder to refine user stories based on each layer
Lack of visibility into progress from an end-user perspective
Key feedback comes much later in the process
Hard to coordinate priorities across layers
Difficulty estimating work
Testing and QA is complex
In contrast, vertical slicing builds a thin thread of functionality across all layers in an increment. This cross-sectional approach allows value to be delivered in small pieces and offers end-to-end system feedback.
With vertical slicing the team collectively owns delivering end-to-end value. This improves communication, accountability, and agility.
Horizontal slicing also makes it hard to refine user stories, estimate work, and collaborate across skills. The traditional layered approach encourages "tossing work over the wall" to other teams vs. shared ownership.
Vertical slicing breaks down user stories into smaller, more manageable pieces for the team. This makes planning, coordinating, and delivering together more manageable.
In summary, traditional horizontal slicing delays value delivery while vertical slicing enables incremental value delivery by cutting across layers.
Key Benefits of Vertical Slicing
There are several key benefits teams gain from vertical slicing:
Faster Feedback
Vertical slices allow functional increments to be demonstrated early and feedback gathered from stakeholders after each increment. This facilitates the build-measure-learn feedback loop crucial for agile projects.
Rather than waiting months for an entire layer like the UI to be built, vertical slicing provides a thin slice to demo after a sprint or two. This means faster feedback on what is being built before more work continues.
For example, the first vertical slice could be a simple working login screen with placeholder content. This provides feedback on the general look and flow from stakeholders.
The iterative approach makes it easier to incorporate feedback more frequently than traditional approaches. This reduces overall project risk and improves stakeholder satisfaction.
Focused on Business Value
Each vertical slice delivers a thin thread of end-to-end business value rather than just output. This keeps the focus of agile teams on delivering value vs. just finishing requirements or outputs.
For example, a team building an e-commerce site might first focus on allowing users to search and view products before building advanced recommendation algorithms. This focuses on user and business value first.
Vertical slicing avoids '100% complete' syndrome where teams build substantial functionality with minimal actual value. By tying each increment to value, it keeps agile teams focused on what matters most.
Better Estimation
Thin vertical slices make it easier for agile teams to estimate work for a sprint or iteration. Estimating large requirements in horizontal layers is quite difficult.
But estimating a thin vertical slice through UI, logic, and data is simpler. The slices represent tangible end-to-end deliverables versus nebulous layers.
This makes sprint planning more accurate when based on small vertical slices. Teams have greater confidence in what they can complete within a sprint.
Greater Flexibility
With traditional horizontal slicing, major reprioritization is difficult once an entire layer is underway. But with vertical slicing, the product backlog can be reprioritized without disrupting half-done work across layers.
For example, if UI screens were 50% done but priorities changed, this would require substantial rework. But with vertical slicing, any backlog item can be reprioritized since slices are thin and focused on value.
This flexibility allows agile teams to easily adapt to changing stakeholder needs. Minimal rework is required when priorities change.
Encourages Collaboration
Since vertical slicing requires working across UI, business logic, and data access in an increment, it encourages collaboration across disciplines. Rather than siloed teams, vertical slicing promotes shared ownership and accountability.
Developers, testers, UX designers, etc. must tightly collaborate to ensure each vertical slice meets requirements. This frequent synchronization improves communication and working relationships within agile teams.
By removing hand-offs between layers, it reduces misalignments across teams. It also provides improved visibility since all disciplines own value delivery together.
Vertical Slicing Enables Key Agile Practices
Vertical slicing complements other agile practices and ceremonies:
Refining User Stories
Vertical slicing helps agile teams refine user stories into small vertical slices that can be delivered within a sprint increment.
Traditionally, large requirements span multiple layers. But vertical slicing requires breaking these down into thin end-to-end slices representing tangible value.
This makes it easier to create vertical stories suitable for sprint planning. The emphasis shifts from delivering outputs and layers to delivering value.
Sprint Increments
The thin vertical slices align well with sprint increments in agile. Sprint increments should produce a potentially releasable increment of value.
Vertical slices map to this goal since each slice entails end-to-end function that offers value. Agile teams can deliver a complete slice within a single sprint.
So vertical slicing enables teams to work incrementally and deliver value in each sprint. This provides tangible progress inspection points during the sprint review.
Focus on Business Value
Since vertical slices provide end-to-end value, they naturally align with the focus on business value in agile.
When agile teams vertically slice user stories for prioritization, the emphasis remains on which slices offer the most value. This takes priority over output-focused requirements.
It encourages product owners and teams to evaluate what brings the most business benefit when planning sprints and releases.
Enables Iterative Development
Agile methods rely on iterative development as opposed to big, serial phases. Vertical slicing supports this well.
Vertical slices are small enough to build within a sprint iteration. This facilitates the incremental, iterative approach.
Rather than waiting for entire layers to be built before feedback, vertical slicing provides quick iterative loops for evaluation and adaptation.
This iterative approach based on vertical slicing helps teams continuously refine and steer value delivery in the right direction.
Facilitates the Feedback Loop
The fast feedback cycles enabled by vertical slicing are critical for agile success.
Agile methods leverage regular inspection and adaptation driven by stakeholder feedback. Vertical slices provide thin value increments to collect feedback on quickly.
This facilitates the empirical, iterative nature of agile development guided by constant feedback. Teams can gather feedback sprint-by-sprint and incorporate learnings moving forward.
So vertical slicing is an important enabler of rapid feedback loops by delivering value increments frequently. This allows teams to regularly inspect and adapt.
In summary, vertical slicing complements and enables many core agile and lean principles. It aligns well with the fast, empirical approach of delivering value and leveraging feedback.
How Does Vertical Slicing Help Project Managers?
Vertical slicing offers several benefits for agile project managers:
Planning and Tracking Increments
Vertical slicing provides natural increments that can be planned and tracked in agile projects. Since each slice represents an end-to-end function, it serves as a tangible increment of work.
This gives project managers more predictable units of work to plan sprints and milestones around. It also offers clear inspection points to assess progress.
Estimating Work
As mentioned earlier, estimating large requirements spanning multiple layers is difficult. But thin vertical slices are much easier to estimate.
Project managers can use vertical slices as the basis of work estimation for agile projects. This improves accuracy which translates to better sprint planning and tracking.
Flexibility in Prioritization
Project managers need the flexibility to reprioritize the backlog as stakeholder needs change. Vertical slicing enables this by avoiding partial work across layers.
With thin slices focused on value delivery, backlog items can be rearranged without substantial rework. This allows agile PMs to easily adapt scope based on evolving needs.
Feedback Loops
The fast feedback loops enabled by vertical slicing provide project managers greater visibility into value delivery and stakeholder sentiment.
The slice demonstrations from each sprint offer regular touchpoints for the PM to inspect progress and get feedback. This helps validate that work aligns to customer needs.
Predictability of Delivery
The combination of reliable estimation, planning, prioritization, and feedback ultimately provides more predictable value delivery.
Project managers gain confidence that vertical slices scoped for each sprint will complete as planned. This results in more dependable agile delivery.
Overall, vertical slicing gives project managers several leverages like reliable increments and feedback cycles to plan and track agile projects effectively.
Common Challenges with Adopting Vertical Slicing
While vertical slicing offers many benefits, teams also face some adoption challenges:
Prioritizing User Stories
Transitioning to prioritizing user stories and backlog items based on vertical slices is a mindset shift for teams.
Traditionally, requirements focus on outputs and layers. But vertical slicing requires a value-focused perspective when prioritizing and planning.
This takes some adjustments for product owners and teams to think at the vertical level vs. horizontal layers. Time should be spent educating teams on the principles.
Synchronizing Work
Delivering vertical slices requires strong coordination across disciplines like developers, QA, UX, etc. Everyone must come together to deliver a thin but complete slice.
If work across teams falls out of sync, the end-to-end thread breaks and vertical slicing stalls. Teams must proactively communicate blockers and synchronize frequently.
Daily standups and maybe additional integration meetings help identify and resolve bottlenecks early. A mindset of shared ownership is critical.
Testing Approach
Testing strategies may need to adjust to focus on validating vertical slices. Often testing is organized around system layers and components.
But with vertical slicing, testing needs to confirm that the end-to-end functionality works for the increment. This may require tweaking processes and tools.
Automated testing and test-driven development are highly compatible with vertical slicing to validate slices.
Requirements Detail
Product owners must provide well-detailed requirements for vertical slices, splitting stories effectively. Enough details must exist for the slice while retaining flexibility for implementation.
This level of analysis requires some practice and collaboration between the product owner and team. But it yields big benefits in small batch delivery of value.
Making Vertical Slicing Work
Here are some tips to help teams implement vertical slicing effectively:
Provide education and training on vertical slicing so the team understands the principles and benefits
Involve developers, testers, UX designers etc. in user story refinement to define thin vertical slices
Identify dependencies across slices and system components to coordinate work across sprints
Establish cadences for integration and testing to validate slices across disciplines
Encourage conversations between team members to proactively identify bottlenecks
Adjust testing strategies and infrastructure to validate full vertical slices
Re-orient product roadmaps and backlogs around delivery of end-to-end value
Provide visibility using boards and charts to unblock dependencies between teams
Celebrate successes delivering end-to-end value increments with the team
Key Takeaways and Summary
Vertical slicing delivers end-to-end value increments across system layers versus handing off layers.
Key principles are small thin slices, focus on value, and working incrementally.
It enables faster feedback, flexibility, collaboration and complements agile practices.
Project managers benefit from improved planning, estimation, tracking, and predictability.
Adopting vertical slicing requires teams to shift perspectives and synchronize work.
In summary, vertical slicing is a powerful agile technique to deliver value faster. While it requires some adjustment, the benefits are well worth it for most software teams. By providing end-to-end value increments, it enables the frequent feedback so crucial to agile development success.
Vertical slicing is a modern, versatile approach that helps software teams focus their efforts on delivering value early and often. When combined with agile principles, vertical slicing can transform how teams build products and drastically improve outcomes. This guide provided a comprehensive overview of vertical slicing and how to leverage it; teams can use these insights to implement vertical slicing in their projects and reap the speed and quality benefits.