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Quality attributes in software architecture
- 1. Quality Attributes in Software Architecture
- 2. QualityAttributes in SoftwareArchitecture Nov 2011 Gang Tao
- 3. Confidential Levels of RequirementBusiness Requirements Vision and Scope Documents User Requirements Quality Attributes Other Nonfunctional Requirements Use Cases Functional Requirements Software Requirements Specification
- 6. Confidential 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.
- 8. Confidential Responsiveness • All Operations Must Be Responsive Click Me Under normal IO load, any operation must return to the user within 3 seconds.
- 9. Confidential A Case Study • getVersion() methods cause serious performance downgrade.
- 10. Confidential What causes the performance issue? • Complexity • Indirection • Repetitions • Bad Design • I/O • … …
- 11. Confidential Price of Optimization • Loss Readability • Increase Complexity • Hard to maintain and extend • Introduce conflict • … …
- 13. Scalability
- 14. Confidential 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
- 15. Confidential Scale Up VS Scale Out
- 16. Confidential Scalability Considerations • Increased Managed Content Must Scale Appropriately • Maintain Viability as System Resources Decrease • UI Data Presentation Scaling • Load Sharing Considerations
- 17. Usability
- 19. Confidential 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.
- 20. Confidential 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
- 21. Confidential 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?
- 22. Confidential Rule One – Don’t Make Me Think
- 23. Confidential Rule Two - Know Your Users
- 24. Confidential Rule Three – Be Consistent • Be Consistent • Things that look the same should act the same. • Things that look different should act different.
- 25. Confidential Usability VS. User Experiences • Free Discussion
- 26. Confidential Case Study & Samples
- 27. Confidential Some References of Usability • [1]《Designing Interfaces》，中文版名为《Designing Interfaces中文版》 • [2]《Usability Engineering》，中文版名为《可用性工程》 • [3]《The Design of Everyday Things》，中文版名为《设计心理学》 • [4]《About Face 3》，中文版名为《交互设计精髓》 • [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 Design》，中文版名为《设计沟通十器》 • [8]《Don’t Make Me Think》，中文版名为《点石成金：访客至上的网页设计秘笈》 • [9]《Designing From Both Sides of the Screen》，内外兼修的设计，尚未出版文版 • [10]《UI Design for Programmers》，程序员之用户界面设计，尚未出版中文版 • [11]《The 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》
- 28. Security
- 29. Confidential Security • Security is defined as being protected against danger or loss
- 31. Confidential Refereneces • OWASP Top Ten • Seven Pernicious Kingdoms • Sans Top 25 • Common Weakness Enumerations
- 32. Accessibility
- 33. Confidential Accessibility • “accessibility“ refers to the possibility for everyone, including and especially people with disabilities, to access and use technology and information products.
- 34. Confidential Case Study : Choose the right color
- 35. Serviceability
- 36. Confidential 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.
- 37. Confidential 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.
- 38. Confidential 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.
- 39. Confidential Cost of Service Customer Self Service Web Remote Support, BBS/MSN Phone/Email Support On Site Support
- 40. Extensibility
- 41. Confidential Extensibility • With extensibility, the design and implementation takes into consideration future growth.
- 42. Confidential 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
- 43. Distributability
- 44. Confidential 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.
- 45. Confidential 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.
- 46. Confidential Distributed Architecture • Web Service • CORBA
- 47. Maintainability
- 48. Confidential 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.
- 49. Confidential Maintainability Tips • Adhere to Coding Standards • Avoid duplication • Story Telling with your code • Keep your code simple
- 50. Portability
- 51. Confidential 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.
- 52. Reliability
- 53. Confidential 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.
- 54. Confidential Availability MTBF – Mean Time Between Failure MTTR – Mean Time to Recovery Availability= MTBF/(MTBF+MTTR)
- 55. Confidential 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
- 56. Testability
- 57. Confidential 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.
- 58. Confidential 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
- 59. Confidential Testability of Requirements • consistent • complete • unambiguous • quantitative • verifiable in practice
- 60. Compatibility
- 62. Summary
- 63. Confidential Quality Attributes Relationship Matrix Responsive ness ReliabilitySecurityUsability Extensibility Reliability Security Extensibility Usability Responsive ness Negative Impact No Impact Positive Impact
- 64. Confidential Quality Model • McCall/GE Quality Model • ISO 9126
- 65. Confidential Business Qualities • Time to Market • Cost and Benefit • Project Lifetime • Target Market • Rollout schedule • Integration with Legacy System
- 66. Confidential 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.