Agile Software Development PDF

Agile Software Development  Agile methods  Agile development techniques  Agile project management  Scaling agile methods Dr. Noha Adly CSE 322 - Agile Software Development 1 Rapid software development ...

Agile Software Development  Agile methods  Agile development techniques  Agile project management  Scaling agile methods Dr. Noha Adly CSE 322 - Agile Software Development 1 Rapid software development  Rapid development and delivery is now often the most important requirement for software systems  Businesses operate in a fast –changing requirement and it is practically impossible to produce a set of stable software requirements  Software has to evolve quickly to reflect changing business needs.  Plan-driven development is essential for some types of system but does not meet these business needs.  Agile development methods emerged in the late 1990s whose aim was to radically reduce the delivery time for working software systems Dr. Noha Adly CSE 322 - Agile Software Development 2 What is “Agility”?  Effective (rapid and adaptive) response to change  Effective communication among all stakeholders  Drawing the customer onto the team  Organizing a team so that it is in control of the work performed Yielding …  Rapid, incremental delivery of software Dr. Noha Adly CSE 322 - Agile Software Development 3  Why Agile?  Traditional software processes have the following problems:  Lengthy development times (typical 1-5 years): For many companies, especially, this is too long and not appropriate. In three years, companies will have changed their focus or products. So, if the project is successful by traditional standards, it may be too late.  Inability to cope with changing requirements: Often, the environment changes very rapidly, forcing the business to adapt and change. Traditional software development methods do not handle changing requirements well. They assume that the later a change is made, the more expensive it will be.  Assumption that requirements are completely understood before the project begins: Most users are not capable of expressing their requirements in clear and unambiguous language. In spite of the valiant efforts of many systems analysts, the requirements will be incomplete, and many times incorrect. Dr. Noha Adly CSE 322 - Agile Software Development 4 Agility and the Cost of Change Dr. Noha Adly CSE 322 - Agile Software Development 5 Agile manifesto 2001 Dr. Noha Adly CSE 322 - Agile Software Development 6  Agile Principles  The Agile Manifesto is based on 12 principles: 1. Customer satisfaction by rapid delivery of useful software. 2. Welcome changing requirements, even late in development. 3. Working software is delivered frequently (weeks rather than months). 4. Close, daily cooperation between business people and developers. 5. Projects are built around motivated individuals, who should be trusted. 6. Face-to-face conversation is the best form of communication (colocation). 7. Working software is the principal measure of progress. 8. Sustainable development, able to maintain a constant pace. 9. Continuous attention to technical excellence and good design. 10.Simplicity - the art of maximizing the amount of work not done - is essential 11.Self-organizing teams. 12.Regular adaptation to changing circumstances. Dr. Noha Adly CSE 322 - Agile Software Development 7 Agile development  Is driven by customer descriptions of what is required (scenarios)  Recognizes that plans are short-lived  Develops software iteratively  Program specification, design and implementation are inter-leaved  The system is developed as a series of versions or increments with stakeholders involved in version specification and evaluation  Frequent delivery of multiple ‘software increments’ for evaluation  Adapts as changes occur  Extensive tool support (e.g. automated testing tools) used to support development.  Minimal documentation – focus on working code Dr. Noha Adly CSE 322 - Agile Software Development 8 Plan-driven and agile development  Plan-driven development  A plan-driven approach to software engineering is based around separate development stages with the outputs to be produced at each of these stages planned in advance.  Not necessarily waterfall model – plan-driven, incremental development is possible  Iteration occurs within activities.  Agile development  Specification, design, implementation and testing are inter- leaved and the outputs from the development process are decided through a process of negotiation during the software development process. Dr. Noha Adly CSE 322 - Agile Software Development 9 Plan-driven and agile development Dr. Noha Adly CSE 322 - Agile Software Development 10  Agile methods Dr. Noha Adly CSE 322 - Agile Software Development 11 The principles of agile methods Principle Description Customer Customers should be closely involved throughout the involvement development process. Their role is provide and prioritize new system requirements and to evaluate the iterations of the system. Incremental delivery The software is developed in increments with the customer specifying the requirements to be included in each increment. People not process The skills of the development team should be recognized and exploited. Team members should be left to develop their own ways of working without prescriptive processes. Embrace change Expect the system requirements to change and so design the system to accommodate these changes. Maintain simplicity Focus on simplicity in both the software being developed and in the development process. Wherever possible, actively work to eliminate complexity from the system. Dr. Noha Adly CSE 322 - Agile Software Development 13 Agile method applicability  Product development where a software company is developing a small or medium-sized product for sale.  Virtually lots software products and apps are now developed using an agile approach  Custom system development within an organization, where there is a clear commitment from the customer to become involved in the development process and where there are few external rules and regulations that affect the software. Dr. Noha Adly CSE 322 - Agile Software Development 14 Agile development techniques  Adaptive Software Development (ASD)  Agile Unified Process (AUP)  Crystal family Methods (Crystal Clear, Crystal Orange)  Disciplined Agile Delivery  Dynamic Systems Development Method (DSDM)  Extreme Programming (XP)  Feature Driven Development (FDD)  Lean software development  Scrum  ………. Dr. Noha Adly CSE 322 - Agile Software Development 16 Extreme programming  A very influential agile method, developed in the late 1990s, that introduced a range of agile development techniques.  The most widely used agile process, originally proposed by Kent Beck  Extreme Programming (XP) takes an ‘extreme’ approach to iterative development.  New versions may be built several times per day;  Increments are delivered to customers every two weeks;  All tests must be run for every build and the build is only accepted if tests run successfully. Dr. Noha Adly CSE 322 - Agile Software Development 17 Extreme Programming Planning Begins with the creation of “user stories” Agile team assesses each story and assigns a cost Stories are grouped for a deliverable increment A commitment is made on delivery date After the first increment “project velocity” is used to help define subsequent delivery dates for other increments Dr. Noha Adly CSE 322 - Agile Software Development 18 The extreme programming release cycle Dr. Noha Adly CSE 322 - Agile Software Development 19 Extreme programming practices (a) Principle or practice Description Incremental planning Requirements are recorded on story cards and the stories to be included in a release are determined by the time available and their relative priority. The developers break these stories into development ‘Tasks’. See examples later Small releases The minimal useful set of functionality that provides business value is developed first. Releases of the system are frequent and incrementally add functionality to the first release. Simple design Enough design is carried out to meet the current requirements and no more. Test-first development An automated unit test framework is used to write tests for a new piece of functionality before that functionality itself is implemented. Refactoring All developers are expected to refactor the code continuously as soon as possible code improvements are found. This keeps the code simple and maintainable. Dr. Noha Adly CSE 322 - Agile Software Development 20 Extreme programming practices (b) Pair programming Developers work in pairs, checking each other’s work and providing the support to always do a good job. Collective ownership The pairs of developers work on all areas of the system, so that no islands of expertise develop and all the developers take responsibility for all of the code. Anyone can change anything. Continuous integration As soon as the work on a task is complete, it is integrated into the whole system. After any such integration, all the unit tests in the system must pass. Sustainable pace Large amounts of overtime are not considered acceptable as the net effect is often to reduce code quality and medium term productivity On-site customer A representative of the end-user of the system (the customer) should be available full time for the use of the XP team. In an extreme programming process, the customer is a member of the development team and is responsible for bringing system requirements to the team for implementation. Dr. Noha Adly CSE 322 - Agile Software Development 21 XP and agile principles  XP practices reflects the principles of the agile manifesto:  Incremental development is supported through small, frequent system releases.  Customer involvement means full-time customer engagement with the team.  People not process is supported through pair programming, collective ownership and a process that avoids long working hours.  Change is supported through regular system releases.  Maintaining simplicity through constant refactoring of code. Dr. Noha Adly CSE 322 - Agile Software Development 22 Influential XP practices  Extreme programming has a technical focus and is not easy to integrate with management practice in most organizations.  Consequently, companies pick and choose XP practices suitable for their way of working  Practices are used in conjunction with a management focused agile method such as Scrum  Key practices  User stories for specification  Refactoring  Test-first development  Pair programming Dr. Noha Adly CSE 322 - Agile Software Development 23 User stories for requirements  In XP, a customer or user is part of the XP team and is responsible for making decisions on requirements.  User requirements are expressed as user stories or scenarios.  These are written on cards and the development team break them down into implementation tasks. These tasks are the basis of schedule and cost estimates.  The customer chooses the stories for inclusion in the next release based on their priorities and the schedule estimates. Dr. Noha Adly CSE 322 - Agile Software Development 24 A ‘prescribing medication’ story Dr. Noha Adly CSE 322 - Agile Software Development 25 Examples of task cards for prescribing medication Dr. Noha Adly CSE 322 - Agile Software Development 26 Refactoring  Conventional wisdom in software engineering is to design for change. It is worth spending time and effort anticipating changes as this reduces costs later in the life cycle.  XP, however, maintains that this is not worthwhile as changes cannot be reliably anticipated.  Rather, it proposes constant code improvement (refactoring) to make changes easier when they have to be implemented. Dr. Noha Adly CSE 322 - Agile Software Development 27 Refactoring  Programming team look for possible software improvements and make these improvements even where there is no immediate need for them.  This improves the understandability of the software and so reduces the need for documentation.  Changes are easier to make because the code is well- structured and clear.  However, some changes requires architecture refactoring and this is much more expensive. Dr. Noha Adly CSE 322 - Agile Software Development 28 Examples of refactoring  Re-organization of a class hierarchy to remove duplicate code.  Tidying up and renaming attributes and methods to make them easier to understand.  The replacement of inline code with calls to methods that have been included in a program library. Dr. Noha Adly CSE 322 - Agile Software Development 29 Test-first development  Testing is central to XP and XP has developed an approach where the program is tested after every change has been made.  XP testing features:  Test-first development.  Incremental test development from scenarios.  User involvement in test development and validation.  Automated test harnesses are used to run all component tests each time that a new release is built. Dr. Noha Adly CSE 322 - Agile Software Development 30 Test-driven development  Writing tests before code clarifies the requirements to be implemented.  Tests are written as programs rather than data so that they can be executed automatically. The test includes a check that it has executed correctly.  Usually relies on a testing framework such as Junit.  All previous and new tests are run automatically when new functionality is added, thus checking that the new functionality has not introduced errors. Dr. Noha Adly CSE 322 - Agile Software Development 31 Customer involvement  The role of the customer in the testing process is to help develop acceptance tests for the stories that are to be implemented in the next release of the system.  The customer who is part of the team writes tests as development proceeds. All new code is therefore validated to ensure that it is what the customer needs.  Cons: However, people adopting the customer role have limited time available and so cannot work full-time with the development team. They may feel that providing the requirements was enough of a contribution and so may be reluctant to get involved in the testing process. Dr. Noha Adly CSE 322 - Agile Software Development 32 Test case description for dose checking Dr. Noha Adly CSE 322 - Agile Software Development 33 Test automation  Test automation means that tests are written as executable components before the task is implemented  These testing components should be stand-alone, should simulate the submission of input to be tested and should check that the result meets the output specification.  An automated test framework (e.g. Junit) is a system that makes it easy to write executable tests and submit a set of tests for execution.  As testing is automated, there is always a set of tests that can be quickly and easily executed  Whenever any functionality is added to the system, the tests can be run and problems that the new code has introduced can be caught immediately. Dr. Noha Adly CSE 322 - Agile Software Development 34 Problems with test-first development  Programmers prefer programming to testing and sometimes they take short cuts when writing tests. For example, they may write incomplete tests that do not check for all possible exceptions that may occur.  Some tests can be very difficult to write incrementally. For example, in a complex user interface, it is often difficult to write unit tests for the code that implements the ‘display logic’ and workflow between screens.  It difficult to judge the completeness of a set of tests. Although you may have a lot of system tests, your test set may not provide complete coverage. Dr. Noha Adly CSE 322 - Agile Software Development 35 Pair programming  Pair programming involves programmers working in pairs, developing code together.  This helps  develop common ownership of code, and  spreads knowledge across the team.  It serves as an informal review process as each line of code is looked at by more than 1 person.  It encourages refactoring as the whole team can benefit from improving the system code. Dr. Noha Adly CSE 322 - Agile Software Development 36 Pair programming  In pair programming, programmers sit together at the same computer to develop the software.  Pairs are created dynamically so that all team members work with each other during the development process.  The sharing of knowledge that happens during pair programming is very important as it reduces the overall risks to a project when team members leave.  Should be used with care: Studying the value of pair- programming led to mixed results  Productivity is comparable to two individual programmers in case of beginners  In case of experienced programmers it led to loss of productivity Dr. Noha Adly CSE 322 - Agile Software Development 37  Agile project management Dr. Noha Adly CSE 322 - Agile Software Development 39 Agile project management  The principal responsibility of software project managers is to manage the project so that the software is delivered on time and within the planned budget for the project.  The standard approach to project management is plan- driven:  Managers draw up a plan for the project showing what should be delivered, when it should be delivered and who will work on the development of the project deliverables.  Agile project management requires a different approach, which is adapted to incremental development and the practices used in agile methods. Dr. Noha Adly CSE 322 - Agile Software Development 40 Scrum  Scrum is an agile method that provides a project management framework; focusing on managing iterative development rather than specific agile practices.  There are three phases in Scrum.  The initial phase is an outline planning phase where you establish the general objectives for the project and design the software architecture.  This is followed by a series of sprint cycles, where each cycle develops an increment of the system.  The project closure phase wraps up the project, completes required documentation such as system help frames and user manuals and assesses the lessons learned from the project. Dr. Noha Adly CSE 322 - Agile Software Development 41 The Scrum process Dr. Noha Adly CSE 322 - Agile Software Development 42 Scrum terminology (a) Scrum term Definition Development team A self-organizing group of software developers, which should be no more than 7 people. They are responsible for developing the software and other essential project documents. Potentially The software increment that is delivered from a sprint. The idea is shippable product that this should be ‘potentially shippable’; that it is in a finished state increment and no further work, such as testing, is needed to incorporate it into the final product. In practice, this is not always achievable. Product backlog This is a list of ‘to do’ items which the Scrum team must tackle. They may be feature definitions for the software, software requirements, user stories or descriptions of supplementary tasks that are needed, e.g. architecture definition or user documentation. Product owner An individual (or possibly a small group) whose job is to identify product features or requirements, prioritize these for development and continuously review the product backlog to ensure that the project continues to meet critical business needs. The Product Owner can be a customer but might also be a product manager in a software company or other stakeholder representative. Dr. Noha Adly CSE 322 - Agile Software Development 43  Scrum terminology (b) Scrum term Definition Scrum A daily meeting of the Scrum team that reviews progress and prioritizes work to be done that day. Ideally, this should be a short face-to-face meeting that includes the whole team. ScrumMaster The ScrumMaster is responsible for ensuring that the Scrum process is followed and guides the team in the effective use of Scrum. He or she is responsible for interfacing with the rest of the company and for ensuring that the Scrum team is not diverted by outside interference. The Scrum developers are adamant that the ScrumMaster should not be thought of as a project manager. Others, however, may not always find it easy to see the difference. Sprint A development iteration. Sprints are usually 2-4 weeks long. Velocity An estimate of how much product backlog effort that a team can cover in a single sprint. Understanding a team’s velocity helps them estimate what can be covered in a sprint and provides a basis for measuring improving performance. Dr. Noha Adly CSE 322 - Agile Software Development 44 The Scrum sprint cycle  Sprints are fixed length, normally 2–4 weeks.  The starting point for planning is the product backlog, which is the list of work to be done on the project.  The selection phase involves all of the project team who work with the customer to select the features and functionality from the product backlog to be developed during the sprint.  Once these are agreed, the team organize themselves to develop the software.  The team is isolated from the customer and the organization, with all communications channelled through the ‘Scrum master’.  The role of the Scrum master is to protect the development team from external distractions.  At the end of the sprint, the work done is reviewed and presented to stakeholders. The next sprint cycle then begins. Dr. Noha Adly CSE 322 - Agile Software Development 45 Scrum sprint cycle Dr. Noha Adly CSE 322 - Agile Software Development 46 Scrum  Originally proposed by Schwaber and Beedle  Terminology derived from the Rugby game  Scrum—distinguishing features  Development work is partitioned into chunks  Testing and documentation are on-going as the product is constructed  Work occurs in “sprints” and is derived from a “backlog” of existing requirements  Meetings are very short and sometimes conducted without chairs  “demos” are delivered to the customer with the time-box allocated The Scrum framework consists of roles, events, artifacts, and rules. Dr. Noha Adly CSE 322 - Agile Software Development 47 Scrum Roles  Sprints are basic units of development of the total software product.  They are short in duration (2-4 weeks)  Time-boxed (duration is fixed, but scope may be adjusted if needed).  Ideally, a potentially shippable product is produced at the end of each sprint.  Scrum Roles: A Scrum project defines three core roles  The Product Owner, who represents the voice of the customer and ensures that the team delivers value to the business  The development team, who actually produce the software  A Scrum Master, who keeps the team on track and ensures Scrum is followed.  There are also two additional ancillary roles: the stakeholders and the managers. Dr. Noha Adly CSE 322 - Agile Software Development 48 Teamwork in Scrum  The ‘Scrum master’ is a facilitator who arranges daily meetings, tracks the backlog of work to be done, records decisions, measures progress against the backlog and communicates with customers and management outside of the team.  The whole team attends short daily meetings (Scrums) where all team members share information, describe their progress since the last meeting, problems that have arisen and what is planned for the following day.  This means that everyone on the team knows what is going on and, if problems arise, can re-plan short-term work to cope with them. Dr. Noha Adly CSE 322 - Agile Software Development 49 Scrum Artifacts and Rules  Scrum Artifacts: Artifacts to be used for controlling the project:  The product backlog, an ordered list of all the remaining requirements or stories for a product. Everybody can see what still needs to be done overall (although developers focus mostly on the sprint backlog).  The sprint backlog is the ordered list of tasks need to be done for the current sprint. Tasks here are broken down to be small (4 to 16 hours usually), so developers know exactly what to do. Developers choose their next task based on the sprint backlog and their particular skills.  The increment : the sum of all requirements implemented in this sprint and all previous sprints. This should be a shippable (albeit not feature-complete) project.  Scrum Rules: Based on three "pillar" concepts: 1. Transparency: Making the process visible and having a common definition of when an item is completed so developers, the product owner, and the Scrum Master can agree on whether an item is finished. 2. Inspection (of artifacts and progress), and 3. Adaptation (whenever a significant deviation is detected, correct it). Dr. Noha Adly CSE 322 - Agile Software Development 50 Scrum Events  Scrum Events: The Scrum process is defined as three sequential events: 1. The sprint planning meeting, in which the product owner and the team decide on what will be implemented during that sprint. 2. The daily Scrum, a very short (15 minutes or less) meeting in which team members synchronize, make sure they are on-track, and ask for help if needed. Oftentimes all participants are standing instead of sitting, to ensure meetings are short. 3. The sprint review, held at the end of the sprint, to inspect its products and adapt the product backlog if needed. During this review the product owner identifies what has been done and discusses the product backlog. The development team demonstrates the work it has done answers questions, and discusses what went well, what problems they faced, and how they solved them. Finally the entire team collaborates on what to do next (which is input for the sprint planning for the next sprint). Dr. Noha Adly CSE 322 - Agile Software Development 51 Scrum benefits  The product is broken down into a set of manageable and understandable chunks.  Unstable requirements do not hold up progress.  The whole team have visibility of everything and consequently team communication is improved.  Customers see on-time delivery of increments and gain feedback on how the product works.  Trust between customers and developers is established and a positive culture is created in which everyone expects the project to succeed. Dr. Noha Adly CSE 322 - Agile Software Development 52 Practical problems with agile methods  The informality of agile development is incompatible with the legal approach to contract definition that is commonly used in large companies.  Agile methods are most appropriate for new software development rather than software maintenance. Yet the majority of software costs in large companies come from maintaining their existing software systems.  Agile methods are designed for small co-located teams yet much software development now involves worldwide distributed teams. Dr. Noha Adly CSE 322 - Agile Software Development 53 Contractual issues  Most software contracts for custom systems are based around a specification and deliverables which sets out what has to be implemented by the system developer for the system customer.  However, this precludes interleaving specification and development as is the norm in agile development.  A contract that pays for developer time rather than functionality is required.  However, this is seen as a high risk by many legal departments because what has to be delivered cannot be guaranteed. Dr. Noha Adly CSE 322 - Agile Software Development 54 Agile methods and software maintenance  Most organizations spend more on maintaining existing software than they do on new software development. So, if agile methods are to be successful, they have to support maintenance as well as original development.  Key problems are:  Lack of product documentation  Keeping customers involved in the development process  Maintaining the continuity of the development team Agile development relies on the development team knowing and understanding what has to be done. For long-lifetime systems, this is a real problem as the original developers will not always work on the system. Dr. Noha Adly CSE 322 - Agile Software Development 55 Organizational issues  Traditional engineering organizations have a culture of plan-based development, as this is the norm in engineering - There may be cultural resistance to agile methods  Is it standard organizational practice to develop a detailed system specification?  Can informal agile development fit into the organizational culture of detailed documentation?  Will customer representatives be available to provide feedback of system increments?  Project managers who do not have experience of agile methods may be reluctant to accept the risk of a new approach.  Large organizations often have quality procedures and standards that all projects are expected to follow and, because of their bureaucratic nature, these are likely to be incompatible with agile methods Dr. Noha Adly CSE 322 - Agile Software Development 56 Agile principles and organizational problems Principle Practice Customer This depends on having a customer who is willing and able to spend time with involvement the development team and who can represent all system stakeholders. Often, customer representatives have other demands on their time and cannot play a full part in the software development. Where there are external stakeholders, such as regulators, it is difficult to represent their views to the agile team. Embrace change Prioritizing changes can be extremely difficult, especially in systems for which there are many stakeholders. Typically, each stakeholder gives different priorities to different changes. Incremental delivery Rapid iterations and short-term planning for development does not always fit in with the longer-term planning cycles of business planning and marketing. Marketing managers may need to know what product features several months in advance to prepare an effective marketing campaign. Maintain simplicity Under pressure from delivery schedules, team members may not have time to carry out desirable system simplifications - refactoring People not process Individual team members may not have suitable personalities for the intense involvement that is typical of agile methods, and therefore may not interact well with other team members. Dr. Noha Adly CSE 322 - Agile Software Development 57  Scaling agile methods Dr. Noha Adly CSE 322 - Agile Software Development 58 Scaling agile methods  Agile methods have proved to be successful for small and medium sized projects that can be developed by a small co-located team.  It is sometimes argued that the success of these methods comes because of improved communications which is possible when everyone is working together.  Scaling up agile methods involves changing these to cope with larger, longer projects where there are multiple development teams, perhaps working in different locations.  When scaling agile methods it is important to maintain agile fundamentals:  Flexible planning  frequent system releases  continuous integration  test-driven development and  good team communications Dr. Noha Adly CSE 322 - Agile Software Development 59 Factors affecting Agile methods in large systems Dr. Noha Adly CSE 322 - Agile Software Development 60 Factors affecting Agile methods for large systems  Large systems are usually collections of separate, communicating systems, where separate teams develop each system.  Frequently, these teams are working in different places, sometimes in different time zones.  Large systems are ‘brownfield systems’, that is they include and interact with a number of existing systems. Many of the system requirements are concerned with this interaction and so don’t really lend themselves to flexibility and incremental development.  Where several systems are integrated to create a system, a significant fraction of the development is concerned with system configuration rather than original code development. Dr. Noha Adly CSE 322 - Agile Software Development 61 Factors affecting Agile methods for large systems  Large systems and their development processes are often constrained by external rules and regulations limiting the way that they can be developed.  Large systems have a long procurement and development time. It is difficult to maintain coherent teams who know about the system over that period as, inevitably, people move on to other jobs and projects.  Large systems usually have a diverse set of stakeholders. It is practically impossible to involve all of these different stakeholders in the development process. Dr. Noha Adly CSE 322 - Agile Software Development 62 Distributed Scrum Dr. Noha Adly CSE 322 - Agile Software Development 63 Scaling up to large systems  A completely incremental approach to requirements engineering is impossible.  There cannot be a single product owner or customer representative.  For large systems development, it is not possible to focus only on the code of the system.  Cross-team communication mechanisms have to be designed and used.  Continuous integration is practically impossible. However, it is essential to maintain frequent system builds and regular releases of the system. Dr. Noha Adly CSE 322 - Agile Software Development 65 Multi-team Scrum – Key characteritics  Role replication  Each team has a Product Owner for their work component and ScrumMaster.  Product architects  Each team chooses a product architect and these architects collaborate to design and evolve the overall system architecture.  Release alignment  The dates of product releases from each team are aligned so that a demonstrable and complete system is produced.  Scrum of Scrums  There is a daily Scrum of Scrums where representatives from each team meet to discuss progress and plan work to be done. Dr. Noha Adly CSE 322 - Agile Software Development 66  Agile vs Plan-Driven Dr. Noha Adly CSE 322 - Agile Software Development 67 Agile versus Plan-based factors Dr. Noha Adly CSE 322 - Agile Software Development 68 System issues  Scale: How large is the system being developed?  Agile methods are most effective a relatively small co-located team who can communicate informally.  Type: What type of system is being developed?  Systems that require a lot of analysis before implementation need a fairly detailed design to carry out this analysis.  Lifetime: What is the expected system lifetime?  Long-lifetime systems require documentation to communicate the intentions of the system developers to the support team.  Regulation: Is the system subject to external regulation?  If a system is regulated you will probably be required to produce detailed documentation as part of the system safety case. Dr. Noha Adly CSE 322 - Agile Software Development 69 People and teams  Competence: How good are the designers and programmers in the development team?  It is sometimes argued that agile methods require higher skill levels than plan-based approaches in which programmers simply translate a detailed design into code.  However, within large organizations, there are likely to be a wide range of skills and abilities  Distribution: How is the development team organized?  Design documents may be required if the team is distributed.  Technology: What support technologies are available?  IDE support for visualisation and program analysis is essential if design documentation is not available. Dr. Noha Adly CSE 322 - Agile Software Development 70 Agile and plan-driven methods  Most projects include elements of plan-driven and agile processes. Deciding on the balance depends on:  Is it important to have a very detailed specification and design before moving to implementation? If so, you probably need to use a plan-driven approach.  Is an incremental delivery strategy, where you deliver the software to customers and get rapid feedback from them, realistic? If so, consider using agile methods.  How large is the system that is being developed? Agile methods are most effective when the system can be developed with a small co-located team who can communicate informally. This may not be possible for large systems that require larger development teams so a plan-driven approach may have to be used. Dr. Noha Adly CSE 322 - Agile Software Development 71  Agile and plan-driven methods Principle Agile Plan Driven Requirements Assumes they will change; requirements are Assumes they will not change during the collected informally at the beginning of the project. A complete, detailed formal project, and then at the beginning of each requirements document is necessary for iteration. Uses constant user interaction success. Any changes in requirements after instead of formal requirements. the design or implementation has started will be costly. Design Informal and iterative Formal and done up front, after all requirements are known. User involvement Crucial, frequent, throughout the whole Required only at the beginning process (requirements solicitation and analysis) and at the end (acceptance testing). Communication Done informally, throughout the project. Relies mainly on documents and formal memos and meetings Process complexity Relatively low High. RUP (2002) describes more than 100 artifacts, 9 disciplines, 30 roles, and 4 phases. Documentation Minimal, only what is necessary; relies on Requires heavy, formal documentation of source code as the ultimate documentation. every phase of the project. Overhead Low. Relatively high Dr. Noha Adly CSE 322 - Agile Software Development 72  Selection of Development Process - Guidlines Principle Agile Plan Driven Scope/size Small; limited to 1 team of up to 10 Better suited to larger projects; scales up people. to the largest projects; can be scaled down for smaller projects. Criticality Relatively low; not suitable for life- Can be used for mission-critical systems critical systems without adaptation (maybe with minimal modifications). People More suitable for team players, "good Defines many roles, which can be citizens" who can do design and appropriate for most kinds of people; programming adequately. Agile doesn't require tight team playing; almost requires strict adherence to certain any personality will work, as long as the practices. team member can follow rules. Company Better suited for small co-located Better suited for larger companies with culture companies with relaxed cultures. possibly geographically remote sites and more formal cultures. Stability Copes easily with changes in Less suited to cope with changes. Assumes requirements or environment a relatively stable environment where requirements don't change much. Can be Dr. Noha Adly adapted. CSE 322 - Agile Software Development 73