1. Software engineering (cs3529) target classes: cs14: A,B
Lecturer:
Eng. Mohamed Adam Isak
PH.D Researcher in CS
M.Sc. and B.Sc. of Information Technology Engineering,
Lecturer in University of Somalia and Mogadishu university
Tell:
February – July 2016

2. Chapter 3 – Agile Software Development

3. Topics covered Plan-driven and agile development
The principles of agile methods
Technical, human, organizational issues
Extreme programming
Scrum approach
Agile project management
Scrum approach and scrum processes
Chapter 3 Agile software development

4. 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.
Although there are many approaches to rapid software development, they share these three fundamental characteristics:
The processes of Specification, design and implementation are inter-leaved.
The system is developed as a series of versions with stakeholder’s feedback.
User interfaces are often developed using an interactive development system that allows the interface design to be quickly.
Chapter 3 Agile software development

5. Agile methods
Dissatisfaction with the overheads involved in software design methods of the 1980s and 1990s led to the creation of agile methods. These methods:
Focus on the code rather than the design
Are based on an iterative approach to software development
Are intended to deliver working software quickly and evolve this quickly to meet changing requirements.
The aim of agile methods is to reduce overheads in the software process (e.g. by limiting documentation) and to be able to respond quickly to changing requirements without excessive rework.
Chapter 3 Agile software development

6. The principles of agile methods
Although agile methods are all based around incremental development and delivery, they propose different processes to achieve this, however, they share a set of principles.
Principle
Description
Customer involvement
Customers should be closely involved throughout the 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.
Chapter 3 Agile software development

7. Agile methods applicability
Agile methods have been very successful for some types of system development:
Product development where a software company is developing a small or medium- sized product for sale.
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 not a lot of external rules and regulations that affect the software.
Because of their focus on small, tightly-integrated teams, there are problems in scaling agile methods to large systems.
Chapter 3 Agile software development

8. Problems with agile methods
It can be difficult to keep the interest of customers who are involved in the process.
Team members may be unsuited to the intense involvement that characterizes agile methods.
Prioritizing changes can be difficult where there are multiple stakeholders.
Maintaining simplicity requires extra work.
Chapter 3 Agile software development

9. Plan-driven VS 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.
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.
Chapter 3 Agile software development

10. Technical, human, organizational issues
In fact, most software projects include practices from plan-driven and agile approaches. To decide on the balance between a plan-based and an agile approach, you have to answer a range of technical, human, and organizational questions:
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.
Chapter 3 Agile software development

11. Technical, human, organizational issues
What type of system is being developed?
Plan-driven approaches may be required for systems that require a lot of analysis before implementation (e.g. real-time system with complex timing requirements).
What is the expected system lifetime?
Long-lifetime systems may require more design documentation to communicate the original intentions of the system developers to the support team.
What technologies are available to support system development?
Agile methods rely on good tools to keep track of an evolving design
How is the development team organized?
If the development team is distributed or if part of the development is being outsourced, then you may need to develop design documents to communicate across the development teams.
Chapter 3 Agile software development

12. Technical, human, organizational issues
Are there cultural or organizational issues that may affect the system development?
Traditional engineering organizations have a culture of plan-based development, as this is the norm in engineering.
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
Is the system subject to external regulation?
If a system has to be approved by an external regulator then you will probably be required to produce detailed documentation as part of the system safety case.
Chapter 3 Agile software development

13. Extreme programming (XP model)
Extreme programming (XP) is perhaps the best known and most widely used of the agile methods.
The name was coined by Beck (2000) because the approach was developed by pushing recognized good practice, such as iterative development, to ‘extreme’ levels.
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 2 weeks;
All tests must be run for every build and the build is only accepted if tests run successfully.
In an XP process, customers are involved in specifying and prioritizing requirements.
in XP, the new versions may be developed by different programmers in different locations.
Requirements in eXtreme Programming (XP) Called: scenarios or user stories
Chapter 3 Agile software development

14. The extreme programming release cycle (Phases of xp model)
Chapter 3 Agile software development

15. Extreme programming practices (1/2)
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’.
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.
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.
Chapter 3 Agile software development

16. Extreme programming practices (2/2)
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 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.
On-site customer
The customer should be available full time with the XP team. He is responsible for specifying system requirements.
Chapter 3 Agile software development

17. XP and change
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 solves problem of changing using constant code improvement (refactoring) which is responsible for making changes easier when they have to be implemented.
Refactoring is a process of software improvement. Examples of refactoring include the reorganization of a class hierarchy to remove duplicate code, the tidying up and renaming of attributes and methods, and the replacement of code with calls to methods defined in a program library.
Chapter 3 Agile software development

18. The characteristics of testing in xp
The three important characteristics of extreme programming are:
Requirements expressed as scenarios,
Pair programming,
Test-first development. Means When a system feature is identified, the tests of the code implementing that feature are written before the code. Tests are automated and all tests are run when a new increment is added to the system.
The possible problems of test-first development are:
Programmers may take short-cuts when developing tests so that the system tests are incomplete.
Some tests can be difficult to write incrementally. It is difficult to estimate the completeness of a test set.
Chapter 3 Agile software development

19. Advantages of pair programming
The use of pair programming has a number of advantages:
It supports the idea of collective ownership and responsibility for the system.
It acts as an informal review process because each line of code is looked at by at least two people.
It helps support refactoring, which is a process of software improvement.
Chapter 3 Agile software development

20. 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. They supervise the work of software engineers and monitor how well the software development is progressing
The standard approach to project management is plan-driven
Like every other professional software development process, agile development has to be managed so that the best use is made of the time and resources available to the team. This requires a different approach to project management, which is adapted to incremental development and the particular strengths of agile methods.
SCRUM is one of the usable approaches to manage agile development.
Chapter 3 Agile software development

21. Scrum approach and scrum processes
The Scrum approach is a general agile method but its focus is on managing iterative development rather than specific technical approaches to agile software engineering.
A Scrum sprint is a planning unit in which the work to be done is assessed, features are selected for development, and the software is implemented. At the end of a sprint, the completed functionality is delivered to stakeholders.
Chapter 3 Agile software development

22. Scaling agile methods
Agile methods were developed for use by small programming teams who could work together in the same room and communicate informally.
It is difficult to introduce agile methods into large companies for a number of reasons:
Project managers who do not have experience of agile methods may be reluctant to accept the risk of a new approach, as they do not know how this will affect their particular projects
Large organizations often have quality procedures and standards that all projects are expected to follow
Agile methods seem to work best when team members have a relatively high skill level
There may be cultural resistance to agile methods, especially in those organizations that have a long history of using conventional systems engineering processes.
Chapter 3 Agile software development

23. Key points
Agile methods are incremental development methods that focus on rapid development, frequent releases of the software, reducing process overheads and producing high-quality code. They involve the customer directly in the development process.
The decision on whether to use an agile or a plan-driven approach to development should depend on the type of software being developed, the capabilities of the development team and the culture of the company developing the system.
Extreme programming is a well-known agile method that integrates a range of good programming practices such as frequent releases of the software, continuous software improvement and customer participation in the development team.
Chapter 3 Agile software development