System Development Life Cycle (SDLC) Day-2 Team Emertxe

Transcription

1 System Development Life Cycle (SDLC) Day-2 Team Emertxe

2 Course span-out

3 SDLC models

4 Models Waterfall V Shape Prototype Spiral Incremental

5 Waterfall model

6 Waterfall model

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 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 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 V model

11 V model

12 Strengths Emphasize planning for verification and validation Each deliverable must be testable Project management can track progress by milestones Easy to use

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 When to use? Excellent choice for systems requiring high reliability All requirements are known up-front Solution and technology are known

15 Prototype model

16 Prototype model

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 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 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 Spiral model

21 Spiral model

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 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 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 Incremental model

26 Incremental model

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 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 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 Case studies

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 Product line a400 A400 is a high-availability telecom platform with % 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 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 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 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 Agile

37 What is Agile?

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 Defined by value Agile manifesto Formed by experts Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan

40 Agile principles

41 Agile Practices

42 Flavors Flavor Scrum Kanban SAFe: Scale Extreme Programming (XP) Characteristics Reference Implementation of Agile. Time boxed. Focus of understanding how work flows, visualizing the work. Limit WIP. Handles integrating multiples teams with program and portfolio layers Technical focus on development practices. Prescribes practices that are commonly needed to make Scrum deliver high quality. Time Boxed.

43 Requirement Engineering

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 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 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 Elicitation process Interviewing and questionnaires Requirements workshops (Brain storming) Storyboards Prototyping Voice of Customer

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 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 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 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 System modeling

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 Use case modeling

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 Data flow model

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