Software Design Lecture Notes PDF

Lecture 8&9 Software design - Requirements -> architecture and design -> code - Requirements -> design -> implementation -> verification -> maintenance - goals/activities - Making system-wide decisions - Architecture, languages, libraries, platforms...

Lecture 8&9 Software design - Requirements -> architecture and design -> code - Requirements -> design -> implementation -> verification -> maintenance - goals/activities - Making system-wide decisions - Architecture, languages, libraries, platforms - Making lower-level decisions in an iterative manner - Studying problem, identifying solutions, creating abstractions, evaluating Approaches to software design - Software architecture - Functional decomposition - Breaks down complex process, system or task into smaller and more manageable parts/functions - Improves clarity, manageability and maintainability - - Relational database design - Process of structuring database to store and manage data efficiently by organizing it into tables that represent real world entities and their relationships - - Object oriented design and UML (left photo) - Object contains both data and methods - Class is blueprint for making objects - - UI design (photo on left) - Process of creating interfaces in software or computerized devices that focus on maximizing usability and user experience - Encompasses look and feel of product as well as user interaction - Sketching (lec 8) Purpose of designs/models  - To think, talk, prescribe - Designs are developed iteratively Abstraction - Abstractions are formed by removing irrelevant information and retaining/highlighting relevant information - Every design notation supports certain kind of abstraction - Software engineering is all about constructing and elaborating abstractions/models Summary - Design phase of software engineering - How to what of requirements - Architecture, functional decomp……. - Purpose of design - Software engineering is all about constructing and elaborating….. Design notations - By relieving brain of all unnecessary work, good notation sets it free to concentrate on more advanced problems and in effect increase mental power of race Software development languages - Different languages are used at different stages - Requirements (english) -> design (diagrams/UML) -> coding/testing (java,python) - Design notations = diagrams/UML UML (unified modeling language) - Industry standard for software design/modeling - Different types of UML diagrams are used to represent different aspects (structure, behavior, interactions) of a system - Class diagrams, activity diagrams, use case, sequence diagrams, etc - Used in decomposing system into modules known as classes - Typically used to - Model domain concepts - Create a detailed object oriented design of code Relationships between classes - Inheritance - Allows class (subclass or derived class) to inherit properties and behaviors from another class - Establishes hierarchy between classes, enabling code reuse/establish structure - Association - Defines relationship between two or more classes that indicates how objects of those classes interact with each other - Multiplicity: specifies how many instances of one class can be associated with instances of another class in an association - Whole part (aggregation and composition) - Aggregation: one object contains set of other objects - Relationships are transitive (having or containing a direct object) and asymmetric - Composition: variant of aggregation which adds property of existence dependency How to create classes? - Set of nouns in description of problem -> classes, attributes - Set of verbs in description of problem -> operations, associations - Go through more detailed use cases to further flash out flow and objects necessary - UI mockups, a bit of programming?, refer/add to/revise design as necessary - Example: amazon - Other diagram pictures - Lec8, pt2: UML activity, UML sequence, UML use case - Lec 8,pt3: User interface mockups, pseudocode, entity relationship, Architecture, storyboard, sketches What is software engineering - Process of building a set of related models that represent the system-to-be Design principles - High cohesion/low coupling - Effects: changes don't propagate; reuse is facilitated - High: grouping related functionality - Low: ungrouping unrelated functionality/reducing interdependency - - Information hiding - Hide design decisions that are most likely to change, thereby protecting other parts of the program from change if the design decision is changed - Showing details to outside world that are necessary and other detailed are hidden Summary - Every design notation supports an abstraction - A design diagram is a statement in a language that has a syntax - UML diagrams,UI mockups, pseudo code, ER diagrams, storyboard,sketches - Software engineering -> process of building set related models that represent system to be Usability is important! - hope…change..test! User centered design works (UCD) - Simple, inexpensive, higher sales, higher satisfaction, higher efficiency - Benefit will shift from conversion (first-time customers) to loyalty (repeat customers) - But sometimes NOT USED! Usability fail - Office space printer scene on youtube - Picture examples (lec9,pt1) - Pc warnings, ATM, security warning (office disabled contents)’ - False missile alert (hawaii missile threat notification on phone) Usability & first impression matters! - User interface is well-designed when the program behaves exactly how user thought it would work - GUI should provide GUIdance - Focus on user and all else will follow Why is usability engineering so hard? - Usability design based on: - Psychology, art, cognitive science, aesthetics - Software engineers generally not audience of software they develop Summary - We use HCI/UCD methods for good reasons - Sales/performance doubles, traffic counts increase, frustration decreases - It's all about the user! User centered/oriented methods (*****look at lec9 pt2 for more examples/pictures of each*****) - Interviews and observations - Personas - Scenarios - Storyboard - Wireframe and mockups  - Design guidelines - Heuristic evaluation - Using principles based on research to evaluate and improve usability of system - Process: - Select task, someone plays user, evaluators focus on aspect, someone takes notes - Nielsen - Visibility of system status - Match system worlds to real world - User control and freedom - Consistency and standards - Error prevention - Recognition rather than recall - Accelerators - Minimalist design - Principles: contrast, repetition, alignment, proximity - Help users recognize and recover from errors - Help and documentation - User testing - Improve designs and interfaces before showing users - Checklists, heuristic evaluation - Cognitive walkthrough - Planning user testing - Subjects, system, tasks, session, measures taken - Formal: testing facilities -> professional usability labs - Less formal user testing Online readings (posted on week 5-6 roadmap) https://medium.com/the-u-s-digital-service/introducing-u-s-web-design-standards-aff21383afd6 https://www.nngroup.com/articles/ux-learn-in-restaurants/ https://www.nngroup.com/