System Development Life Cycle (SDLC) - Part II


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The second part of SDLC talks about various types of life cycles - Waterfall, Prototype, Spiral, V Model and Incremental. Special focus provided for Agile. Good number of case studies are provided to understand which life cycle to choose during what type of project. The slide deck concludes with detailed description of Requirement Engineering and Sytem modelling.

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System Development Life Cycle (SDLC) - Part II

  1. 1. System Development Life Cycle (SDLC) Day-2 Team Emertxe
  2. 2. Course span-out
  3. 3. SDLC models
  4. 4. Models  Waterfall  V Shape  Prototype  Spiral  Incremental
  5. 5. Waterfall model
  6. 6. Waterfall model
  7. 7. Strengths  Easy to understand, easy to use  Provides structure to inexperienced staff  Milestones are well understood  Sets requirements stability  Good for management control (plan, staff, track)  Works well when quality is more important than cost or schedule
  8. 8. Weakness  All requirements must be known upfront  Inhibits flexibility  Can give a false impression of progress  Does not reflect problem-solving nature of software development  Integration is one big bang at the end  Little opportunity for customer to preview
  9. 9. When to use?  Requirements are very well known  Product definition is stable  Technology is understood  New version of an existing product  Porting an existing product to a new platform
  10. 10. V model
  11. 11. V model
  12. 12. Strengths  Emphasize planning for verification and validation  Each deliverable must be testable  Project management can track progress by milestones  Easy to use
  13. 13. Weakness  Does not easily handle concurrent events  Does not handle iterations or phases  Does not easily handle dynamic changes in requirements  Does not contain risk analysis activities
  14. 14. When to use?  Excellent choice for systems requiring high reliability  All requirements are known up-front  Solution and technology are known
  15. 15. Prototype model
  16. 16. Prototype model
  17. 17. Strengths  Customers can “see” the system requirements  Developers learn from customers  A more accurate end product  Unexpected requirements accommodated  Allows for flexible design and development  Steady, visible signs of progress produced  Interaction with the prototype stimulates awareness of additional needed functionality
  18. 18. Weakness  Tendency to abandon structured program development for “code-and-fix” development  Bad reputation for “quick-and-dirty” methods  Overall maintainability may be overlooked  The customer may want the prototype delivered.  Process may continue forever (scope creep)
  19. 19. When to use?  Requirements are unstable or have to be clarified  As the requirements clarification stage of a waterfall model  Develop user interfaces  Short-lived demonstrations  New, original development
  20. 20. Spiral model
  21. 21. Spiral model
  22. 22. Strengths  Provides early indication of risks  Users see the system early because of rapid prototyping tools  Critical high-risk functions are developed first  The design does not have to be perfect  Users can be closely tied to all lifecycle steps  Early and frequent feedback from users  Cumulative costs assessed frequently
  23. 23. Weakness  Time spent for evaluating risks too large  Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive  The model is complex  Risk assessment expertise is required  Spiral may continue indefinitely  Developers must be reassigned
  24. 24. When to use?  When creation of a prototype is appropriate  When costs and risk evaluation is important  For medium to high-risk projects  Long-term project commitment unwise because of potential changes to economic priorities  Users are unsure of their needs  Requirements are complex  New product line  Significant changes are expected (research and exploration)
  25. 25. Incremental model
  26. 26. Incremental model
  27. 27. Strengths  Develop high-risk or major functions first  Each release delivers an operational product  Customer can respond to each build  Uses “divide and conquer” breakdown of tasks  Lowers initial delivery cost  Initial product delivery is faster  Customers get important functionality early  Risk of changing requirements is reduced
  28. 28. Weakness  Requires good planning and design  Requires early definition of a complete system  Well-defined module interfaces are required  Total cost of the complete system is not lower
  29. 29. When to use?  Risk, funding, schedule, program complexity, or need for early realization of benefits.  Most of the requirements are known up-front but are expected to evolve over time  A need to get basic functionality to the market early  On projects which have lengthy development schedules  On a project with new technology
  30. 30. Case studies
  31. 31. Product line p40  Product line p40 is already existing in the market, successfully used by customers  In order to enhance performance requirements a new ASIC got taped out  p40 firmware to be ported to new ASIC, with enhanced performance requirements  Other functionality should work as expected  Customers have given go ahead for upgraded version • Life cycle • Main list of activities • Specific focus areas • Risks • Dependencies
  32. 32. Product line a400  A400 is a high-availability telecom platform with 99.999% requirement  There are certain new features addition to meet network requirements as a401  Security patches application to address latest vulnerabilities  Live upgrade in the network with 3 million users • Life cycle • Main list of activities • Specific focus areas • Risks • Dependencies
  33. 33. Product PL v1.0  PL v1.0 is a warehouse automation product priced at 40$ by ABC corporation  ABC want to bring down cost to 30$ with new design  R & D team is not sure about achieving this price-point  ABC is not ready to compromise on established PL v1.0 functionality • Life cycle • Main list of activities • Specific focus areas • Risks • Dependencies
  34. 34. Cloud enabling  Product line 6500 series is a standalone consumer electronic device  First time upgrade functionality is planned to be introduced for connecting it with cloud services  This has high risk as small failure might make the device unusable  User experience should be smooth during upgrade, which involves user testing  Cost & risk to be assessed now • Life cycle • Main list of activities • Specific focus areas • Risks • Dependencies
  35. 35. Online services  KKT organization wants to launch a new online services to customers  They have decent understanding of the market but not sure how they will receive the product  To test waters first they would like to release the product to market with Minimal Viable Product (MVP) with one complete user flow working  They would subsequently do a alpha testing with enthusiasts and subsequently improve the product • Life cycle • Main list of activities • Specific focus areas • Risks • Dependencies
  36. 36. Agile
  37. 37. What is Agile?
  38. 38. Agile - A mindset • Learn through Discovery • Collaboration • Failing Early • Seeking Feedback for learning • Strive for Continuous Delivery • Focus on Value A mindset is the established set of attitudes held by someone
  39. 39. Defined by 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 • Agile manifesto • Formed by experts
  40. 40. Agile principles
  41. 41. Agile Practices
  42. 42. Flavors Flavor Characteristics Scrum “Reference Implementation” of Agile. Time boxed. Kanban Focus of understanding how work flows, visualizing the work. Limit WIP. SAFe: Agile @ Scale Handles integrating multiples teams with program and portfolio layers Extreme Programming (XP) Technical focus on development practices. Prescribes practices that are commonly needed to make Scrum deliver high quality. Time Boxed.
  43. 43. Requirement Engineering
  44. 44. Engineering Requirements  The process of establishing the services that the customer requires from a system  Understanding constraints  Requirements themselves are generated by engineering the whole process  Singular documented physical and functional need that a particular product or service must be or perform  Statement that identifies a necessary attribute, capability, characteristic, or quality of a system for it to have value and utility to a user Having Requirement Analysis (RA) document captures customer‟s needs by following a Engineering process
  45. 45. Types  User requirements • Statements in natural language plus diagrams of the services the system provides and its operational constraints. Written for customers  System requirements • A structured document setting out detailed descriptions of the system‟s functions, services and operational constraints  Functional requirements • Statements of services the system should provide, how the system should react to particular inputs and how the system should behave in particular situations.  Non Functional requirements • Security, Scalability, Environment, Organizational, Compliance
  46. 46. Expectations  Complete • They should include description of all facilities required  Consistent • There should be no conflicts or uncertainties in the descriptions of the system facilities In practice, it is very difficult to produce a complete and consistent requirement document
  47. 47. Elicitation process  Interviewing and questionnaires  Requirements workshops (Brain storming)  Storyboards  Prototyping  Voice of Customer
  48. 48. Why challenging?  Ideal system vs. possibility building it good  Expectations  Scope/boundary of the system  Old, rusted demands and wishes  Resistance to change  Aiming at a moving target  „Wicked problems‟ – More than one good solution  Functional vs. Technical solutions  Completeness  Nice-to-have vs. critical functionality
  49. 49. Stakeholder issues  Users don't have a clear idea of their requirements  Will not commit to a set of written requirements  Scope creep after cost and schedule have been fixed  Communication gaps  Users often do not participate in reviews  Technically unsophisticated  Don‟t understand the development process  Don‟t know about present technology
  50. 50. Engineer issues  Technical personnel and end users may have different vocabularies  Engineers and developers may try to make the requirements fit an existing system  Taking technical view of people's needs
  51. 51. Requirement spec  A complete description of the behavior of a system to be developed and may include a set of use cases that describe interactions the users will have with the software  In addition to a description of the software functions, the SRS also contains non-functional requirements  Process of checking that a software system meets specifications and that it fulfils its intended purpose  Validation: “Am I building the right product?”  Verification: “Am I building the product right?” Both development and test engineers will have Requirement Spec as the common point of building product. But their views are different to ensure customer requirements are met or exceeded.
  52. 52. System modeling
  53. 53. Use case model  A use case diagram depicts the interactions various external entities in the customer's environment will have with they system being modeled  A use case identifies an interaction that must be supported between a given external entity, known as an actor, and the system  A use case is typically labeled as a verb since it is identifying system behavior  An actor is labeled as a noun and is the entity that is requesting some service from the system Example: Microwave oven and its functionality
  54. 54. Use case modeling
  55. 55. Data flow model  A Data Flow Mode describes how data is processed by the system under development.  The Flow of Data from one stage of processing to the next is shown in this model
  56. 56. Data flow model
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