Unformatted text preview: Software Engineering: A Practitioner’s Approach, 7/e Chapter 3
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Any other reproduction or use is expressly prohibited. Coming up: The Manifesto for Agile Software Development 1 The Manifesto for Agile Software Development “We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: •Individuals and interactions over processes and tools •Working software over comprehensive documentation •Customer collaboration over contract negotiation •Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more.”
Kent Beck et al Coming up: What is “Agility”? 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 Coming up: An Agile Process 3 An Agile Process Is driven by customer descriptions of what is required (scenarios)
Recognizes that plans are shortlived
Develops software iteratively with a heavy emphasis on construction activities
Delivers multiple ‘software increments’
Adapts as changes occur Coming up: Extreme Programming (XP) 4 Extreme Programming (XP) The second most widely used agile process, originally proposed by Kent Beck
XP Planning Begins with the creation of “user stories”
Agile team assesses each story and assigns a cost
Stories are grouped to form 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 Coming up: Extreme Programming (XP) 5 Extreme Programming (XP) XP Design XP Coding Follows the KIS principle
Encourage the use of CRC cards (see Chapter 8)
For difficult design problems, suggests the creation of “spike solutions”—a design prototype
Encourages “refactoring”—an iterative refinement of the internal program design
Recommends the construction of a unit test for a store before coding commences
Encourages “pair programming” XP Testing All unit tests are executed daily
“Acceptance tests” are defined by the customer and executed to assess customer visible functionality Coming up: Extreme Programming (XP) 6 Dynamic Systems Development Method Promoted by the DSDM Consortium (www.dsdm.org)
DSDM—distinguishing features Similar in most respects to XP Nine guiding principles Active user involvement is imperative. DSDM teams must be empowered to make decisions.
The focus is on frequent delivery of products. Fitness for business purpose is the essential criterion for acceptance of deliverables.
Iterative and incremental development is necessary to converge on an accurate business solution.
All changes during development are reversible. (configuration management)
Requirements are baselined at a high level
Testing is integrated throughout the lifecycle. Coming up: Dynamic Systems Development Method 7 DSDM
DSDM An agile approach
A focus on frequent delivery of products deliver something "goodenough" earlier is always better than to deliver everything "perfectly" in the end When should we not use it? Cases where there is no “good enough” ultradependable/safety critical software
What else? These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 8 Scrum Originally proposed by Schwaber and Beedle
Scrum—distinguishing features Development work is partitioned into “packets”
Testing and documentation are ongoing 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 timebox allocated Currently seems to have overtaken XP as most popular Coming up: Scrum 9 Scrum Coming up: Others 10 Agile Idea
Agile Idea Frequent idea: Fix time, not features
Functionality FIXED Time Resources Agile
Time Resources VARIABLE Functionality 11 Criticisms
Criticisms Lack of structure and necessary documentation
Only works with seniorlevel developers
Incorporates insufficient software design
Requires meetings at frequent intervals at enormous expense to customers
Requires too much cultural change to adopt
Can lead to more difficult contractual negotiations
Can be very inefficient— maybe code things multiple times as they change if the requirements for one area of code change through various iterations, the same programming may need to be done several times over. Whereas if a plan were there to be followed, a single area of code is expected to be written once.
Hard to develop realistic estimates of work effort because at the beginning of the project no one knows the entire scope/requirements
Agile is feature driven, nonfunctional quality attributes are hard to be placed as user stories
Can increase the risk of scope creep due to lack of detailed requirements
Source: Wikipedia 12 ...
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- agile process, Dynamic Systems Development