1. UNIT III Design Engineering
- Prof. Prasad Mahale

2. THE DESIGN PROCESS Software Quality Guidelines and Attributes
A design should exhibit an architecture that
has been created using recognizable architectural styles or patterns,
is composed of components that exhibit good design characteristics , and
can be implemented in an evolutionary fashion, thereby facilitating implementation and testing.
A design should be modular;
A design should contain representations of data, architecture, interfaces, and components.

3. A design should lead to components that exhibit independent functional characteristics.
A design should lead to interfaces that reduce the complexity of connections between components and with the external environment.
A design should be derived using a repeatable method that is driven by information obtained during software requirements analysis.
A design should be represented using a notation that effectively communicates its meaning.

4. Functionality (capability, delivered, security)
Quality Attributes
Functionality (capability, delivered, security)
Usability (human factor, consistency, documentation)
Reliability (severity, accuracy, recover, predictability)
Performance (speed, response time, throughput, efficiency)
Supportability (extensibility, adaptability, serviceability, testability, compatibility)

5. DESIGN CONCEPTS Abstraction Architecture Patterns
Separation of concern
Functional Independence
Refinement

6. DESIGN CONCEPTS Modularity Information Hiding Aspects
Object-Oriented Design Concepts

7. 1. Abstraction
A solution is stated in large terms using the language of the problem environment at the highest level abstraction.
The lower level of abstraction provides a more detail description of the solution.
A sequence of instruction that contain a specific and limited function refers in a procedural abstraction.
A collection of data that describes a data object is a data abstraction.
2. Architecture
The complete structure of the software is known as software architecture.
Structure provides conceptual integrity for a system in a number of ways.
The architecture is the structure of program modules where they interact with each other in a specialized way.
The components use the structure of data.
The aim of the software design is to obtain an architectural framework of a system.
The more detailed design activities are conducted from the framework.

8. 3. Patterns
A design pattern describes a design structure and that structure solves a particular design problem in a specified content.
4. Modularity
A software is separately divided into name and addressable components. Sometime they are called as modules which integrate to satisfy the problem requirements.
Modularity is the single attribute of a software that permits a program to be managed easily.
5. Information hiding
Modules must be specified and designed so that the information like algorithm and data presented in a module is not accessible for other modules not requiring that information.

9. 6. Functional independence
The functional independence is the concept of separation and related to the concept of modularity, abstraction and information hiding.
The functional independence is accessed using two criteria i.e Cohesion and coupling.
Cohesion
Cohesion is an extension of the information hiding concept.
A cohesive module performs a single task and it requires a small interaction with the other components in other parts of the program.
Coupling
Coupling is an indication of interconnection between modules in a structure of software.

10. 7. Refinement
Refinement is a top-down design approach.
It is a process of elaboration.
A program is established for refining levels of procedural details.
A hierarchy is established by decomposing a statement of  function in a stepwise manner till the programming language statement are reached.
8. Refactoring
It is a reorganization technique which simplifies the design of components without changing its function behavior.
Refactoring is the process of changing the software system in a way that it does not change the external behavior of the code still improves its internal structure.
9. Design classes
The model of software is defined as a set of design classes.
Every class describes the elements of problem domain and that focus on features of the problem which are user visible.

11. THE DESIGN MODEL

12. THE DESIGN MODEL Data Design Elements Architectural Design Elements
High level of abstraction
Structure of data
Data warehouse
Architectural Design Elements
Floor plan gives us an overall view of house
Information about Application
Specific Requirement
Availability of Architectural styles

13. 1) UI 2) external interface 3) internal interface
Interface Design Elements
Detailed Drawing
Design element for software into flow
1) UI 2) external interface 3) internal interface

14. Component-Level Design Elements
It describe internal detail of each software component
Component is represented in UML diagrammatical form
Pseudo code (programming language)
diagrammatical form (flowchart or box diagram)

15. Deployment-Level Design Elements
S/w functionality & subsystem allocate within the physical computing environment
External access subsystem designed to manage.
Elaborate to indicate components.
It shows computing environment but does not explicate indicate configuration detail.

16. ARCHITECTURAL DESIGN

17. SOFTWARE ARCHITECTURAL
Architecture:-
Analyze effectiveness of design
Consider architecture alternative
Reduce risk associates
Importance of Architecture:-
Representation of software architecture enables for communication
Design decision will profound impact
The system structured & how its components work together.
Description:-
Different things to different peoples
Variety of different stakeholders
Infrastructure to ensure its profitability

18. ARCHITECTURAL STYLES 1. A Brief classification of Architectural Styles
Data-centered architectures

19. Data-flow architectures

20. Call and return architectures
Main program/subprogram architectures
Remote procedure call architectures

21. Object-oriented architectures
Layered architectures

22. ARCHITECTURAL STYLES 2. Architectural Patterns
3. Organization and Refinement
Control
Data

23. ARCHITECTURAL DESIGN
Representing the System in Context

26. ARCHITECTURAL DESIGN Defining Archetypes
For example-an archetype for a car: wheels, doors, seats, engine

27. ARCHITECTURAL DESIGN Refining the Architecture into Components
Memory management components, communication components, database components, task management

28. USER INTERFACE DESIGN

29. THE GOLDEN RULES Place the User in Control
Define interaction modes in a way that does not force a user into unnecessary or undesired actions
Provide for flexible interaction
Allow user interaction to be interruptible and undoable
Streamline interaction as skill levels advance and allow the interaction to be customized
Hide technical internals from the casual user
Design for direct interaction with objects that appear on the screen

30. Reduce the User’s Memory Load
Reduce demand on short-term memory
Establish meaningful defaults
Define shortcuts that are intuitive
The visual layout of the interface should be based on a real-world metaphor
Disclose information in a progressive fashion

31. THE GOLDEN RULES Make the Interface Consistent
Allow the user to put the current task into a meaningful context (window titles, graphics icons, consistent color coding )
Maintain consistency across a family of applications
If past interactive models have created user expectations, do not make changes unless there is a compelling reason to do so (Ctrl+S)

32. USER INTERFACE ANALYSIS AND DESIGN
1. Interface Analysis and Design Models
user model
design model
mental model or the system perception
implementation model
users can be categorized as:
Novices
Knowledgeable, intermittent users
Knowledgeable, frequent users

33. USER INTERFACE ANALYSIS AND DESIGN
2. The Process
ability to i/f, task variation, user requirements
Skill level, business understanding,
requirement, identified, describe, elaborate
Interface object & actions
Defines task,
Creation of prototype,
construction of i/f

34. INTERFACE ANALYSIS 1. User Analysis User Interviews Sales input
Marketing input
Support input

35. Task Analysis and Modeling
Use cases
Task elaboration
Object elaboration
Workflow analysis
Hierarchical representation
Analysis of Display Content
Analysis of the Work Environment

36. Interface Design Steps
Applying interface design steps
User interface design patterns

37. Design issues Response time Help facilities Error handling
Menu and command labelling
Application accessibility

38. PATTERN-BASED DESIGN

39. DESIGN PATTERNS Kinds of Patterns
Architectural patterns describe design problems that are solved using a structural approach.
Data patterns describe recurring data-oriented problems and the data modeling solutions that can be used to solve them.
Component patterns address problems associated with the development of subsystems and components, the manner in which they communicate with one another, and their placement within a larger architecture.

40. Interface design patterns describe common user interface problems and their solution that includes the specific characteristics of end users.
WebApp patterns address a problem set that is encountered when building WebApps.
Creational patterns focus on the “creation, composition, and representation” of objects.
Structural patterns focus on problems and solutions associated with how classes and objects are organized and integrated to build a larger structure.
Behavioral patterns address problems associated with the assignment of responsibility between objects and the manner in which communication is effected between objects.

41. DESIGN PATTERNS Frameworks
In some cases it may be necessary to provide an implementation-specific skeletal infrastructure, called a framework, for design work.
That is, you can select a “reusable mini architecture that provides the generic structure and behavior for a family of software

42. Pattern language and repositories
Describing a pattern
How do u find patterns that fit your needs?
Effective communication
Standard form of template
Represented characteristics of pattern
Pattern language and repositories
Languages
Communicate ideas
Collection of pattern
Pattern languages

43. Component level design patterns
AdvancedSearch. Users must find a specific item in a large collection of items.
HelpWizard. Users need help on a certain topic related to the website or when they need to find a specific page within the site.
SearchArea. Users must find a page.
SearchTips. Users need to know how to control the search engine.
SearchResults. Users have to process a list of search results.
SearchBox. Users have to find an item or specific information.
For SafeHomeAssured.com the number of products is not particularly large,

44. User Interface design patterns
Whole UI. Provide design guidance for top-level structure and navigation throughout the entire interface.
Pattern: TopLevelNavigation
Brief description: Used when a site or application implements a number of major functions. Provides a top-level menu, often coupled with a logo or major functions.
Details: Major functions (generally limited to between four and seven function names) are listed across the top of the display (vertical column formats are also possible) in a horizontal line of text. Each name provides a link to the appropriate function or information source. Often used with the
BreadCrumbs pattern discussed later.
Navigation elements: Each function/content name represents a link to the appropriate function or content.
Page layout. Address the general organization of pages (for websites) or distinct screen displays (for interactive applications).

52. WEBAPP DESIGN PATTERNS
Design Focus
Information architecture patterns relate to the overall structure of the information space, and the ways in which users will interact with the information.
Navigation patterns define navigation link structures, such as hierarchies, rings, tours, and so on.
WEBAPP DESIGN PATTERNS

53. Interaction patterns
contribute to the design of the user interface. Patterns in this category address how the interface informs the user of the consequences of a specific action, how a user expands content based on usage context and user desires, how to best describe the destination that is implied by a link, how to inform the user about the status of an ongoing interaction, and interface-related issues.
Presentation patterns in this category address how to organize user interface control functions for better usability, how to show the relationship between an interface action and the content objects it affects, and how to establish effective content hierarchies.
Functional patterns define the workflows, behaviors, processing, communication, and other algorithmic elements within a WebApp.

54. WEBAPP DESIGN PATTERNS
Design Granularity
Architectural patterns.-
This level of abstraction will typically relate to patterns that define the overall structure of the WebApp, indicate the relationships among different components or increments, and define the rules for specifying relationships among the elements (pages, packages, components, subsystems) of the architecture.

55. Design patterns. These address a specific element of the design such as an aggregation of components to solve some design problem, relationships among elements on a page, or the mechanisms for effecting component-to component communication.
Component patterns. This level of abstraction relates to individual small scale elements of a WebApp. Examples include individual interaction elements (e.g., radio buttons), navigation items (e.g., how might you format links?) or functional elements (e.g., specific algorithms).

56. Introduction to UML Diagrams