Lean software development
Encyclopedia
Lean software development is a translation of Lean manufacturing
and Lean IT
principles and practices to the software development
domain. Adapted from the Toyota Production System
, a pro-lean subculture is emerging from within the Agile
community.
community, including talks at several Agile conferences has resulted in such concepts being more widely accepted within the Agile community.
In order to be able to eliminate waste, one should be able to recognize and see it. If some activity could be bypassed or the result could be achieved without it, it is waste. Partially done coding eventually abandoned during the development process
is waste. Extra processes and features not often used by customers are waste. Waiting for other activities, teams, processes is waste. Defects and lower quality are waste. Managerial overhead not producing real value is waste. A value stream mapping
technique is used to distinguish and recognize waste. The second step is to point out sources of waste and eliminate them. The same should be done iteratively until even essential-seeming processes and procedures are liquidated.
The learning process is sped up by usage of short iteration cycles – each one coupled with refactoring and integration testing. Increasing feedback via short feedback sessions with customers helps when determining the current phase of development and adjusting efforts for future improvements. During those short sessions both customer representative
s and the development team learn more about the domain problem and figure out possible solutions for further development. Thus the customers better understand their needs, based on the existing result of development efforts, and the developers learn how to better satisfy those needs. Another idea in the communication and learning process with a customer is set-based development – this concentrates on communicating the constraints of the future solution and not the possible solutions, thus promoting the birth of the solution via dialog with the customer.
is always associated with some uncertainty, better results should be achieved with an options-based approach, delaying decisions as much as possible until they can be made based on facts and not on uncertain assumptions and predictions. The more complex a system is, the more capacity for change should be built into it, thus enabling the delay of important and crucial commitments. The iterative approach promotes this principle – the ability to adapt to changes and correct mistakes, which might be very costly if discovered after the release of the system.
An agile software development
approach can move the building of options earlier for customers, thus delaying certain crucial decisions until customers have realized their needs better. This also allows later adaptation to changes and the prevention of costly earlier technology-bounded decisions. This does not mean that no planning should be involved – on the contrary, planning activities should be concentrated on the different options and adapting to the current situation, as well as clarifying confusing situations by establishing patterns for rapid action. Evaluating different options is effective as soon as it is realized that they are not free, but provide the needed flexibility for late decision making.
. The shorter the iterations, the better the learning and communication within the team. Without speed, decisions cannot be delayed. Speed assures the fulfilling of the customer's present needs and not what they required yesterday. This gives them the opportunity to delay making up their minds about what they really require until they gain better knowledge. Customers value rapid delivery of a quality product.
The Just-in-Time production ideology could be applied to software development
, recognizing its specific requirements and environment. This is achieved by presenting the needed result and letting the team organize itself and divide the tasks for accomplishing the needed result for a specific iteration. At the beginning, the customer provides the needed input. This could be simply presented in small cards or stories
– the developers estimate the time needed for the implementation
of each card. Thus the work organization changes into self-pulling system – each morning during a stand-up meeting
, each member of the team reviews what has been done yesterday, what is to be done today and tomorrow, and prompts for any inputs needed from colleagues or the customer. This requires transparency of the process, which is also beneficial for team communication.
Another key idea in Toyota's Product Development System is set-based design. If a new brake system is needed for a car, for example, three teams may design solutions to the same problem. Each team learns about the problem space and designs a potential solution. As a solution is deemed unreasonable, it is cut. At the end of a period, the surviving designs are compared and one is chosen, perhaps with some modifications based on learning from the others - a great example of deferring commitment until the last possible moment. Software decisions could also benefit from this practice to minimize the risk brought on by big up-front design.
, so they can explain better what actions might be taken, as well as provide suggestions for improvements. The lean approach favors the aphorism "find good people and let them do their own job," encouraging progress, catching errors, and removing impediments, but not micro-managing.
Another mistaken belief has been the consideration of people as resources. People might be resources from the point of view of a statistical data sheet, but in software development
, as well as any organisational business, people do need something more than just the list of tasks and the assurance that they will not be disturbed during the completion of the tasks. People need motivation and a higher purpose to work for – purpose within the reachable reality, with the assurance that the team might choose its own commitments. The developers should be given access to customer; the team leader
should provide support and help in difficult situations, as well as make sure that skepticism does not ruin the team’s spirit.
Conceptual integrity means that the system’s separate components work well together as a whole with balance between flexibility, maintainability, efficiency, and responsiveness. This could be achieved by understanding the problem domain and solving it at the same time, not sequentially. The needed information is received in small batch pieces – not in one vast chunk with preferable face-to-face communication and not any written documentation. The information flow should be constant in both directions – from customer to developers and back, thus avoiding the large stressful amount of information after long development in isolation.
One of the healthy ways towards integral architecture is refactoring
. The more features are added to the System, the more loose the starting code base for further improvements. As described above in the XP agile method refactoring is about keeping simplicity, clarity, minimum amount of features in the code. Repetitions in the code are signs for bad code designs and should be avoided. The complete and automated building process should be accompanied by a complete and automated suite of developer and customer tests, having the same versioning, synchronization and semantics as the current state of the System. At the end the integrity should be verified with thorough testing, thus ensuring the System does what the customer expects it to. Automated tests are also considered part of the production process, and therefore if they do not add value they should be considered waste. Automated testing should not be a goal, but rather a means to an end, specifically the reduction of defects.
Lean thinking has to be understood well by all members of a project, before implementing in a concrete, real-life situation. “Think big, act small, fail fast; learn rapidly” – these slogans summarize the importance of understanding the field and the suitability of implementing lean principles along the whole software development process. Only when all of the lean principles are implemented together, combined with strong “common sense” with respect to the working environment, is there a basis for success in software development
.
, but there are parallels. Examples of such practices include:
Some of the tools map quite easily to agile methods. Lean Workcell
s, for example are expressed in Agile methods as cross-functional team
s.
Lean manufacturing
Lean manufacturing, lean enterprise, or lean production, often simply, "Lean," is a production practice that considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination...
and Lean IT
Lean IT
Lean IT is the extension of lean manufacturing and lean services principles to the development and management of information technology products and services...
principles and practices to the software development
Software development
Software development is the development of a software product...
domain. Adapted from the Toyota Production System
Toyota Production System
The Toyota Production System is an integrated socio-technical system, developed by Toyota, that comprises its management philosophy and practices. The TPS organizes manufacturing and logistics for the automobile manufacturer, including interaction with suppliers and customers...
, a pro-lean subculture is emerging from within the Agile
Agile software development
Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams...
community.
Origin
The term Lean Software Development originated in a book by the same name, written by Mary Poppendieck and Tom Poppendieck. The book presents the traditional Lean principles in a modified form, as well as a set of 22 tools and compares the tools to agile practices. Mary and Tom's involvement in the Agile software developmentAgile software development
Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams...
community, including talks at several Agile conferences has resulted in such concepts being more widely accepted within the Agile community.
Lean principles
Lean development can be summarized by seven principles, very close in concept to lean manufacturing principles:- Eliminate waste
- Amplify learning
- Decide as late as possible
- Deliver as fast as possible
- Empower the team
- Build integrity in
- See the whole
Eliminate waste
Everything not adding value to the customer is considered to be waste (muda). This includes:- unnecessary code and functionality
- delay in the software development processSoftware development processA software development process, also known as a software development life cycle , is a structure imposed on the development of a software product. Similar terms include software life cycle and software process. It is often considered a subset of systems development life cycle...
- unclear requirements
- insufficient testing, leading to avoidable process repetition
- bureaucracyBureaucracyA bureaucracy is an organization of non-elected officials of a governmental or organization who implement the rules, laws, and functions of their institution, and are occasionally characterized by officialism and red tape.-Weberian bureaucracy:...
- slow internal communication
In order to be able to eliminate waste, one should be able to recognize and see it. If some activity could be bypassed or the result could be achieved without it, it is waste. Partially done coding eventually abandoned during the development process
Software development process
A software development process, also known as a software development life cycle , is a structure imposed on the development of a software product. Similar terms include software life cycle and software process. It is often considered a subset of systems development life cycle...
is waste. Extra processes and features not often used by customers are waste. Waiting for other activities, teams, processes is waste. Defects and lower quality are waste. Managerial overhead not producing real value is waste. A value stream mapping
Value Stream Mapping
Value stream mapping is a lean manufacturing technique used to analyze and design the flow of materials and information required to bring a product or service to a consumer. At Toyota, where the technique originated, it is known as "material and information flow mapping"...
technique is used to distinguish and recognize waste. The second step is to point out sources of waste and eliminate them. The same should be done iteratively until even essential-seeming processes and procedures are liquidated.
Amplify learning
Software development is a continuous learning process with the additional challenge of development teams and end product sizes. The best approach for improving a software development environment is to amplify learning. The accumulation of defects should be prevented by running tests as soon as the code is written. Instead of adding more documentation or detailed planning, different ideas could be tried by writing code and building. The process of user requirements gathering could be simplified by presenting screens to the end-users and getting their input.The learning process is sped up by usage of short iteration cycles – each one coupled with refactoring and integration testing. Increasing feedback via short feedback sessions with customers helps when determining the current phase of development and adjusting efforts for future improvements. During those short sessions both customer representative
Customer representative
A customer representative is an individual who represents a community that intends to purchase a product. The term is most often applied to a representative of a company who works closely with a producer or developer to clarify specifications for a product or service. The term is used in software...
s and the development team learn more about the domain problem and figure out possible solutions for further development. Thus the customers better understand their needs, based on the existing result of development efforts, and the developers learn how to better satisfy those needs. Another idea in the communication and learning process with a customer is set-based development – this concentrates on communicating the constraints of the future solution and not the possible solutions, thus promoting the birth of the solution via dialog with the customer.
Decide as late as possible
As software developmentSoftware development
Software development is the development of a software product...
is always associated with some uncertainty, better results should be achieved with an options-based approach, delaying decisions as much as possible until they can be made based on facts and not on uncertain assumptions and predictions. The more complex a system is, the more capacity for change should be built into it, thus enabling the delay of important and crucial commitments. The iterative approach promotes this principle – the ability to adapt to changes and correct mistakes, which might be very costly if discovered after the release of the system.
An agile software development
Agile software development
Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams...
approach can move the building of options earlier for customers, thus delaying certain crucial decisions until customers have realized their needs better. This also allows later adaptation to changes and the prevention of costly earlier technology-bounded decisions. This does not mean that no planning should be involved – on the contrary, planning activities should be concentrated on the different options and adapting to the current situation, as well as clarifying confusing situations by establishing patterns for rapid action. Evaluating different options is effective as soon as it is realized that they are not free, but provide the needed flexibility for late decision making.
Deliver as fast as possible
In the era of rapid technology evolution, it is not the biggest that survives, but the fastest. The sooner the end product is delivered without considerable defect, the sooner feedback can be received, and incorporated into the next iterationIteration
Iteration means the act of repeating a process usually with the aim of approaching a desired goal or target or result. Each repetition of the process is also called an "iteration," and the results of one iteration are used as the starting point for the next iteration.-Mathematics:Iteration in...
. The shorter the iterations, the better the learning and communication within the team. Without speed, decisions cannot be delayed. Speed assures the fulfilling of the customer's present needs and not what they required yesterday. This gives them the opportunity to delay making up their minds about what they really require until they gain better knowledge. Customers value rapid delivery of a quality product.
The Just-in-Time production ideology could be applied to software development
Software development
Software development is the development of a software product...
, recognizing its specific requirements and environment. This is achieved by presenting the needed result and letting the team organize itself and divide the tasks for accomplishing the needed result for a specific iteration. At the beginning, the customer provides the needed input. This could be simply presented in small cards or stories
User story
In computer programming a user story is one or more sentences in the everyday or business language of the end user that captures what the user wants to achieve. User stories are used with Agile software development methodologies for the basis of what features that can be implemented...
– the developers estimate the time needed for the implementation
Implementation
Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy.-Computer Science:...
of each card. Thus the work organization changes into self-pulling system – each morning during a stand-up meeting
Stand-up meeting
A stand-up meeting is a daily team meeting held to provide a status update to the team members. The 'semi-real-time' status allows participants to know about potential challenges as well as coordinate efforts to resolve difficult and/or time-consuming issues...
, each member of the team reviews what has been done yesterday, what is to be done today and tomorrow, and prompts for any inputs needed from colleagues or the customer. This requires transparency of the process, which is also beneficial for team communication.
Another key idea in Toyota's Product Development System is set-based design. If a new brake system is needed for a car, for example, three teams may design solutions to the same problem. Each team learns about the problem space and designs a potential solution. As a solution is deemed unreasonable, it is cut. At the end of a period, the surviving designs are compared and one is chosen, perhaps with some modifications based on learning from the others - a great example of deferring commitment until the last possible moment. Software decisions could also benefit from this practice to minimize the risk brought on by big up-front design.
Empower the team
There has been a traditional belief in most businesses about the decision-making in the organization – the managers tell the workers how to do their own job. In a Work-Out technique, the roles are turned – the managers are taught how to listen to the developersSoftware developer
A software developer is a person concerned with facets of the software development process. Their work includes researching, designing, developing, and testing software. A software developer may take part in design, computer programming, or software project management...
, so they can explain better what actions might be taken, as well as provide suggestions for improvements. The lean approach favors the aphorism "find good people and let them do their own job," encouraging progress, catching errors, and removing impediments, but not micro-managing.
Another mistaken belief has been the consideration of people as resources. People might be resources from the point of view of a statistical data sheet, but in software development
Software development
Software development is the development of a software product...
, as well as any organisational business, people do need something more than just the list of tasks and the assurance that they will not be disturbed during the completion of the tasks. People need motivation and a higher purpose to work for – purpose within the reachable reality, with the assurance that the team might choose its own commitments. The developers should be given access to customer; the team leader
Team leader
A team leader or team lead is someone who provides guidance, instruction, direction, leadership to a group of other individuals for the purpose of achieving a key result or group of aligned results. The team lead reports to a project manager...
should provide support and help in difficult situations, as well as make sure that skepticism does not ruin the team’s spirit.
Build integrity in
The customer needs to have an overall experience of the System – this is the so called perceived integrity: how it is being advertised, delivered, deployed, accessed, how intuitive its use is, price and how well it solves problems.Conceptual integrity means that the system’s separate components work well together as a whole with balance between flexibility, maintainability, efficiency, and responsiveness. This could be achieved by understanding the problem domain and solving it at the same time, not sequentially. The needed information is received in small batch pieces – not in one vast chunk with preferable face-to-face communication and not any written documentation. The information flow should be constant in both directions – from customer to developers and back, thus avoiding the large stressful amount of information after long development in isolation.
One of the healthy ways towards integral architecture is refactoring
Refactoring
Code refactoring is "disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior", undertaken in order to improve some of the nonfunctional attributes of the software....
. The more features are added to the System, the more loose the starting code base for further improvements. As described above in the XP agile method refactoring is about keeping simplicity, clarity, minimum amount of features in the code. Repetitions in the code are signs for bad code designs and should be avoided. The complete and automated building process should be accompanied by a complete and automated suite of developer and customer tests, having the same versioning, synchronization and semantics as the current state of the System. At the end the integrity should be verified with thorough testing, thus ensuring the System does what the customer expects it to. Automated tests are also considered part of the production process, and therefore if they do not add value they should be considered waste. Automated testing should not be a goal, but rather a means to an end, specifically the reduction of defects.
See the whole
Software systems nowadays are not simply the sum of their parts, but also the product of their interactions. Defects in software tend to accumulate during the development process – by decomposing the big tasks into smaller tasks, and by standardizing different stages of development, the root causes of defects should be found and eliminated. The larger the system, the more organisations that are involved in its development and the more parts are developed by different teams, the greater the importance of having well defined relationships between different vendors, in order to produce a system with smoothly interacting components. During a longer period of development, a stronger sub- contractor network is far more beneficial than short-term profit optimizing, which does not enable win-win relationships.Lean thinking has to be understood well by all members of a project, before implementing in a concrete, real-life situation. “Think big, act small, fail fast; learn rapidly” – these slogans summarize the importance of understanding the field and the suitability of implementing lean principles along the whole software development process. Only when all of the lean principles are implemented together, combined with strong “common sense” with respect to the working environment, is there a basis for success in software development
Software development
Software development is the development of a software product...
.
Lean software practices
Lean software development practices, or what the Poppendiecks call "tools" are expressed slightly differently from their equivalents in agile software developmentAgile software development
Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams...
, but there are parallels. Examples of such practices include:
- Seeing waste
- Value stream mappingValue Stream MappingValue stream mapping is a lean manufacturing technique used to analyze and design the flow of materials and information required to bring a product or service to a consumer. At Toyota, where the technique originated, it is known as "material and information flow mapping"...
- Set-based developmentTheory of ConstraintsThe theory of constraints adopts the common idiom "A chain is no stronger than its weakest link" as a new management paradigm. This means that processes, organizations, etc., are vulnerable because the weakest person or part can always damage or break them or at least adversely affect the...
- Pull systems
- Queuing theory
- MotivationMotivationMotivation is the driving force by which humans achieve their goals. Motivation is said to be intrinsic or extrinsic. The term is generally used for humans but it can also be used to describe the causes for animal behavior as well. This article refers to human motivation...
- Measurements
Some of the tools map quite easily to agile methods. Lean Workcell
Workcell
A workcell is an arrangement of resources in a manufacturing environment to improve the quality, speed and cost of the process. Workcells are designed to improve these by improving process flow and eliminating waste...
s, for example are expressed in Agile methods as cross-functional team
Cross-functional team
A cross-functional team is a group of people with different functional expertise working toward a common goal. It may include people from finance, marketing, operations, and human resources departments. Typically, it includes employees from all levels of an organization...
s.
See also
- Scrum (development)Scrum (development)Scrum is an iterative, incremental framework for project management often seen in agile software development, a type of software engineering....
- Kanban (development)Kanban (development)Kanban is a method for developing products with an emphasis on just-in-time delivery while not overloading the developers. It emphasizes that developers pull work from a queue, and the process, from definition of a task to its delivery to the customer, is displayed for participants to see.Kanban...
- Lean IntegrationLean IntegrationLean Integration is a management system that emphasizes creating value for customers, continuous improvement, and eliminating waste as a sustainable data integration and system integration practice. Lean Integration has parallels with other lean disciplines such as Lean Manufacturing, Lean IT, and...
- Lean ServicesLean servicesLean services is the application of the lean manufacturing concept to service operations. It is distinct in that Lean services are not concerned with the making of ‘hard’ products....
External links
- Interview with Mary Poppendieck
- Mary Poppendieck, Tom Poppendieck Lean Software Development: An Agile Toolkit for Software Development Managers
- Lean-Agile Straight Talk A podcast hosted by author Jim Trott and featuring author Alan Shalloway about Lean Software Development and Agile Software Development.
- Lean Software Institute
- Lean Integration A white paperWhite paperA white paper is an authoritative report or guide that helps solve a problem. White papers are used to educate readers and help people make decisions, and are often requested and used in politics, policy, business, and technical fields. In commercial use, the term has also come to refer to...
from the Integration ConsortiumIntegration ConsortiumThe Integration Consortium is a global non-profit community that shares knowledge and best practices related to enterprise application integration...
on the use of Lean methods in systems and data integration. - Improving Agile through Lean, or The Essence of Lean Software Development Insights into Lean Software Development from projects, and implementation notes around extending Agile through Lean.
- InfoQ.com / Agile (includes Lean) - Tracking change and innovation in the enterprise software development community (News, Articles, Books, Video)
- Lean-Agile-Scrum - a discussion group for those interested in how Lean, Agility, and Scrum work together
- Lean Thinking Blog
- Lean Programming - a discussion group for those interested in programming in Lean Software Development environments
- Article: Lean Primer: Introduction
- Lean Startup Business Model Pattern - Lean software development principles applied to business models and entrepreneurship
- Startup Lesson Learnt 2011 - Lean development - Complete sum up of the Startup Lesson Learnt conference on Lean Development in San Francisco, may, 23rd, 2011