Quality Attributes in Software Architecture

2021-09-03 83浏览

  • 1. Quality Attributes in Software Architecture
  • 2. Quality Attributes in Software Architecture Nov 2011 Gang Tao
  • 3. Levels of Requirement Business Requirements Vision and Scope Documents User Requirements Use Cases Functional Requirements Quality Attributes Other Nonfunctional Requirements Software Requirements Specification Confidential
  • 4. Quality Attributes Confidential
  • 5. Responsiveness
  • 6. Responsiveness • Responsiveness is defined as how quickly a system responds to user input. • Long delays can be a major cause of user frustration, or let the user believe the system is broken or that a command or input has been ignored. • Responsiveness is not same as performance. Confidential
  • 7. Responsive Matters Confidential
  • 8. Responsiveness • All Operations Must Be Responsive Click Me Under normal IO load, any operation must return to the user within 3 seconds. Confidential
  • 9. A Case Study • getVersion() methods cause serious performance downgrade. Confidential
  • 10. What causes the performance issue? • Complexity • Indirection • Repetitions • Bad Design • I/O • … … Confidential
  • 11. Price of Optimization • Loss Readability • Increase Complexity • Hard to maintain and extend • Introduce conflict • … … Confidential
  • 12. SAP Standard Reference Confidential
  • 13. Scalability
  • 14. Scalability • Scalability refers to a systems ability to handle increased adversity in its environment in a manner that is graceful and predictable. • Adversity comes in two dimensions: • Increased managed content • Decreased system resources Confidential
  • 15. Scale Up VS Scale Out Confidential
  • 16. Scalability Considerations • Increased Managed Content Must Scale Appropriately • Maintain Viability as System Resources Decrease • UI Data Presentation Scaling • Load Sharing Considerations Confidential
  • 17. Usability
  • 18. Usability Confidential
  • 19. Usability • Usability is the customer’s ability to get work done with the system in an efficient and pleasing manner. • A usable system should build on skills a user already has and not require new or unique knowledge to use the system. • Each new function the user encounters should follow a similar pattern so that once a user has learned one function others are intuitive to learn. Confidential
  • 20. Usability Notions • More efficient to use—takes less time to accomplish a particular task • Easier to learn—operation can be learned by observing the object • More satisfying to use Confidential
  • 21. Usability Composition • Learnability • How easy is it for users to accomplish basic tasks the first time they encounter the design? • Efficiency • Once users have learned the design, how quickly can they perform tasks? • Memorability • When users return to the design after a period of not using it, how easily can they re establish proficiency? • Errors • How many errors do users make, how severe are these errors, and how easily can they recover from the errors? • Satisfaction • How pleasant is it to use the design? Confidential
  • 22. Rule One – Don’t Make Me Think Confidential
  • 23. Rule Two - Know Your Users Confidential
  • 24. Rule Three – Be Consistent • Be Consistent • Things that look the same should act the same. • Things that look different should act different. Confidential
  • 25. Usability VS. User Experiences • Free Discussion Confidential
  • 26. Case Study & Samples Confidential
  • 27. Some References of Usability • [1] 《Designing • [2] 《Usability • [3] 《The • [4] 《About • [5] 《Designing Web Interfaces》，中文版名为《Web界面设计》 • [6] 《Designing the Obvious》，中文版名为《一目了然——Web软件显性设计之路》 • [7] 《Communicating • [8] 《Don’t • [9] 《Designing • [10] 《UI • [11] 《The Interfaces》，中文版名为《Designing Interfaces中文版》 Engineering》，中文版名为《可用性工程》 Design of Everyday Things》，中文版名为《设计心理学》 Face 3》，中文版名为《交互设计精髓》 Design》，中文版名为《设计沟通十器》 Make Me Think》，中文版名为《点石成金：访客至上的网页设计秘笈》 From Both Sides of the Screen》，内外兼修的设计，尚未出版文版 Design for Programmers》，程序员之用户界面设计，尚未出版中文版 Inmates are Running the Asylum》，中文版名为《交互设计之路——让高科 技产品回归人性》 Confidential
  • 28. Security
  • 29. Security • Security is defined as being protected against danger or loss Confidential
  • 30. Security Model Authentication Authorization Audit Encryption Confidential
  • 31. Refereneces • OWASP Top Ten • Seven Pernicious Kingdoms • Sans Top 25 • Common Weakness Enumerations Confidential
  • 32. Accessibility
  • 33. Accessibility • “accessibility“ refers to the possibility for everyone, including and especially people with disabilities, to access and use technology and information products. Confidential
  • 34. Case Study : Choose the right color Confidential
  • 35. Serviceability
  • 36. Serviceability • Serviceability refers to the ability to monitor systems, identify issues, perform root cause analysis, and provide maintenance in order to solve a problem and restore the system to a functioning state. Confidential
  • 37. Serviceability • Diagnostic Infrastructure Should Not Be Intrusive • Issues that arise on a customer site that require engineering involvement should be able to be diagnosed without requiring that the affected system gets taken off line, new binaries get installed, or a debugger gets installed. Confidential
  • 38. Serviceability • Solutions Must Support a Customer-Centric Service Model • Common issues are able to be root-caused and addressed by customers or entry level technical service representatives over the phone. • Meaningful log messages, alerts, and trouble-shooting trees all must be considered to be mandatory and complementary components for servicing a system. Confidential
  • 39. Cost of Service Customer Self Service Web Remote Support, BBS/MSN Phone/Email Support On Site Support Confidential
  • 40. Extensibility
  • 41. Extensibility • With extensibility, the design and implementation takes into consideration future growth. Confidential
  • 42. Extensibility Considerations • Design and Implement With Scale in Mind • Producers of Interfaces Must Support the Ability to Minimize the Amount of Data Returned to a Client • Clients Should Minimize Data Traffic and Network Requests • Business Logic Must Be Centralized • Revision Compatibility Focus Confidential
  • 43. Distributability
  • 44. Distributability • Distributability is defined as the ability to manage a group of systems as one unit and to perform management from any location in the network. • Decide whether a component will run in process, in a separate process on the same machine, or on a remote machine. Confidential
  • 45. Layers and Tiers • Layers are a means of logical separation, and are an architectural pattern to separate concerns • Tiers are the physical separation of an application. Confidential
  • 46. Distributed Architecture • Web Service • CORBA Confidential
  • 47. Maintainability
  • 48. Maintainability • Maintainability means the ease with which a system can be modified in order to correct defects, meet new functionality, make maintenance easier, or cope with a changing environment. Confidential
  • 49. Maintainability Tips • Adhere to Coding Standards • Avoid duplication • Story Telling with your code • Keep your code simple Confidential
  • 50. Portability
  • 51. Portability • Portability is defined as the ability to reuse features and utility source code, across multiple Operating systems. • By having an OS abstraction layer that implements platform specific utilities, such as locks and shared memory. • Can also be achieved by compiling different segments of code, depending on the platform the software is to be run on. Confidential
  • 52. Reliability
  • 53. Reliability (Availability) • Reliability is defined as the ability of a system, to function correctly, under any reasonable circumstance. • Reasonable can include adverse situations, in which unexpected (but supported) usage occurs. • For Storage systems, this includes putting extreme I/O load on the system, but expecting the system to be manageable. Confidential
  • 54. Availability MTBF – Mean Time Between Failure MTTR – Mean Time to Recovery Availability= MTBF/(MTBF+MTTR) Confidential
  • 55. Reliability Consideration • All errors must be handled in a graceful manner • The Storage System must be manageable, without external dependencies. • There should be NO single point of failure Confidential
  • 56. Testability
  • 57. Testability • Software testability is the degree to which a software artifact (i.e. a software system, software module, requirements- or design document) supports testing in a given test context. Confidential
  • 58. Testability of Software Components • Controllability: The degree to which it is possible to control the state of the component under test (CUT) as required for testing. • Observability: The degree to which it is possible to observe (intermediate and final) test results. • Isolateability: The degree to which the component under test (CUT) can be tested in isolation. • Separation of concerns: The degree to which the component under test has a single, well defined responsibility. • Understandability: The degree to which the component under test is documented or self-explaining. • Automatability: The degree to which it is possible to automate testing of the component under test. • Heterogeneity: The degree to which the use of diverse technologies requires to use diverse test methods and tools in paralle Confidential
  • 59. Testability of Requirements • consistent • complete • unambiguous • quantitative • verifiable in practice Confidential
  • 60. Compatibility
  • 61. Compatibility • Backward • Forward Confidential
  • 62. Summary
  • 63. Quality Attributes Relationship Matrix Negative Impact Responsive ness No Impact Positive Impact Usability Extensibility Security Reliability Responsive ness Usability Extensibility Security Reliability Confidential
  • 64. Quality Model • McCall/GE Quality Model • ISO 9126 Confidential
  • 65. Business Qualities • Time to Market • Cost and Benefit • Project Lifetime • Target Market • Rollout schedule • Integration with Legacy System Confidential
  • 66. Symptoms of Bad Architecture • Rigidity • the system is hard to change because every change forces many other changes. • Fragility • changes cause the system to break in conceptually unrelated places. • Immobility • it’s hard to disentangle the system into reusable components. • Viscosity • doing things correctly is harder than doing things incorrectly. • Opacity • the code is hard to read and understand. It does not express its intent well. Confidential