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Design Model & User Interface Design in Software Engineering
- 1. TOPIC : DESIGN MODEL PRESENTEDBY: SAJAN SINGH (MCA/25019/18) MEGHAJ KUMAR MALLICK (MCA/25017/18)
- 2. Software designis an iterative process through which requirements are translated into a blueprintfor constructing the software. Initially, the blueprint depicts a holistic view of software i.e. the design is represented at a high- level of abstraction.
- 4. GOALS OF THEDESIGN PROCESS: 1) The design must implement all of the explicit requirements contained in the analysis model and it must accommodate all of the implicit requirements desired by the customer. 2) The design must be a readable, understandable guide for those who generate code and for those who test and subsequently support the software. 3) The design should address the data, functional and behavioral domains from an implementation perspective
- 5. Data Design: ◦ Transforms information domain model into data structures required to implement software Architectural Design : ◦ Defines relationship among the major structural elements of a software Interface Design : ◦ Describes how the software communicates with systems that interact with it and with humans. Procedural Design/ Component-level design : ◦ Transforms structural elements of the architecture into a procedural description of software components. DESIGN MODEL
- 7. A designmethodology combines a systematic set of rules for creating a program design with diagramming tools needed to represent it. Procedural design is best used to model programs that have an obvious flow of data from input to output. It represents the architecture of a program as a set of interacting processes that pass data from one to another.
- 8. There aretwo component for design tool are following: Data Flow Diagram: Adataflowdiagram(orDFD)isatooltohelpyoudiscoveranddocumentthe program’smajor processes.Thefollowingtableshowsthesymbolsusedandwhat each represents. Structure Chart : A structure chart is a tool to help you derive and document the program’s architecture. It is similar to an organization chart
- 15. USER INTERFACE DESIGN Designing effective interfaces for software systems
- 16. To suggestsome general design principles for user interface design To explain different interaction styles To introduce styles of information presentation To describe the user support which should be built-in to user interfaces To introduce usability attributes and system approaches to system evaluation
- 17. System usersoften judge a system by its interface rather than its functionality A poorly designed interface can cause a user to make catastrophic errors Poor user interface design is the reason why so many software systems are never used
- 18. Most usersof business systems interact with these systems through graphical interfaces although, in some cases, legacy text-based interfaces are still used
- 19. Characteristic Description Windows Multiplewindows allow different information to be displayed simultaneously on the user’s screen. Icons Icons different types of information. On some systems, icons represent files; on others, icons represent processes. Menus Commands are selected from a menu rather than typed in a command language. Pointing A pointing device such as a mouse is used for selecting choices from a menu or indicating items of interest in a window. Graphics Graphical elements can be mixed with text on the same display.
- 20. They areeasy to learn and use. • Users without experience can learn to use the system quickly. The user may switch quickly from one task to another and can interact with several different applications. • Information remains visible in its own window when attention is switched. Fast, full-screen interaction is possible with immediate access to anywhere on the screen
- 21. The aimof this chapter is to sensitise software engineers to key issues underlying the design rather than the implementation of user interfaces User-centred design is an approach to UI design where the needs of the user are paramount and where the user is involved in the design process UI design always involves the development of prototype interfaces
- 22. Executable prototype Design prototype Produce paper- based design prototype Produce dynamicdesign prototype Evaluate design with end-users Implement final user interface Evaluate design with end-users Analyse and understand user activities
- 23. UI designmust take account of the needs, experience and capabilities of the system users Designers should be aware of people’s physical and mental limitations (e.g. limited short-term memory) and should recognise that people make mistakes UI design principles underlie interface designs although not all principles are applicable to all designs
- 24. DescriptionPrinciple User familiarity Consistency The interfaceshould use terms and concepts which are drawn from the experience of the people who will make most use of the system. The interface should be consistent in that, wherever possible, comparable operations should be activated in the same way. Users should never be surprised by the behaviour of a system. Minimal surprise Recoverability The interface should include mechanisms to allow users to recover from errors. User guidance User diversity The interface should provide meaningful feedback when errors occur and provide context-sensitive user help facilities. The interface should provide appropriate interaction facilities for different types of system user.
- 25. Users feelin control of the computer and are less likely to be intimidated by it User learning time is relatively short Users get immediate feedback on their actions so mistakes can be quickly detected and corrected
- 26. Users neednot remember command names as they are always presented with a list of valid commands Typing effort is minimal User errors are trapped by the interface Context-dependent help can be provided. The user’s context is indicated by the current menu selection
- 27. Concerned withtechniques for displaying large amounts of information Visualisation can reveal relationships between entities and trends in the data Possible data visualisations are: • Weather information collected from a number of sources • The state of a telephone network as a linked set of nodes • Chemical plant visualised by showing pressures and temperatures in a linked set of tanks and pipes • A model of a molecule displayed in 3 dimensions • Web pages displayed as a hyperbolic tree
- 29. Data designis the first design activity, which results in less complex, modular and efficient program structure. The information domain model developed during analysis phase is transformed into data structures needed for implementing the software. The data objects, attributes, and relationships depicted in entity relationship diagrams and the information stored in data dictionary provide a base for data design activity.
- 30. For specifying anddesigning efficient data structures, some principles should be followed. These principles are listed below. 1) The data structures needed for implementing the software as well-as the operations that can be applied on them should be identified. 2) A data dictionary should be developed to depict how different data objects interact with each other and what constraints are to be imposed o the elements of data structure. 3) Stepwise refinement should be used in data design process and detaile design decisions should be made later in the process. 4) Only those modules that need to access data stored in a data structure directly should be aware of the representation of the data structure.
- 31. 5) A librarycontaining the set of useful data structures along with the operations that can be performed on them should be maintained. 6)Language used for developing the system should support abstract data types. The structure of data can be viewed at three levels, namely, program component level, application level, and business level.
- 32. At theprogram component level, the design of data structures and the algorithms required to manipulate them is necessary, if high-quality software is desired. At the application level, it is crucial to convert the data model into a database so that the specific business objectives of a system could be achieved. At the business level, the collection of information stored in different databases should be reorganized into data warehouse, which enables data mining that has an influential impact on the business.
- 33. Requirements ofthe software should be transformed into an architecture that describes the software's top-level structure and identifies its components. Architectural design (also called system design), which acts as a preliminary 'blueprint' from which software can be developed.
- 34. IEEE definesarchitectural design as 'the process of defining a collection of hardware and software components and their interfaces to establish the framework for the development of a computer system.' An architectural design performs the following functions. 1) It defines an abstraction level at which the designers can specify the functional and performance behaviour of the system. 2) It acts as a guideline for enhancing the system (when ever required) by describing those features of the system that can be modified easily without affecting the system integrity. 3) It evaluates all top-level designs.
- 35. 4) It developsand documents top-level design for the external and internal interfaces. 5) It develops preliminary versions of user documentation. 6) It defines and documents preliminary test requirements and the schedule for software integration. 7) The sources of architectural design are listed below.
- 36. 8) Information regardingthe application domain for the software to be developed. 9) Using data-flow diagrams 10) Availability of architectural patterns and architectural styles. Architectural design is of crucial importance in software engineering during which the essential requirements like reliability, cost, and performance are dealt with.
- 37. ARCHITECTURAL DESIGN REPRESENTATION Architectural designcan be represented using the following models. Structural model: Illustrates architecture as an ordered collection of program components Dynamic model: Specifies the behavioral aspect of the software architecture and indicates how the structure or system configuration changes as the function changes due to change in the external environment
- 38. Process model: Focuseson the design of the business or technical process, which must be implemented in the system. Functional model: Represents the functional hierarchy of a system. Framework model: Attempts to identify repeatable architectural design patterns encountered in similar types of application. This leads to an increase in the level of abstraction.
- 39. The architecturaldesign process results in an Architectural Design Document (ADD). Architectural design document gives the developers a solution to the problem stated in the Software Requirements Specification (SRS). Note that it considers only those requirements in detail that affect the program structure. In addition to ADD, other outputs of the architectural design are listed below : 1. Various reports including audit report, progress report, and configuration status accounts report
- 40. 2) Various plansfor detailed design phase, which include the following 3) Software verification and validation plan. 4) Software configuration management plan. 5) Software quality assurance plan. 6) Software project management plan.
- 41. Architectural stylesdefine a group of interlinked systems that share structural and semantic properties. In short, the objective of using architectural styles is to establish a structure for all the components present in a system.
- 42. 1. DATA-FLOW ARCHITECTURE Data-flowarchitecture is mainly used in the systems that accept some inputs and transform it into the desired outputs by applying a series o transformations. Each component, known as filter, transforms the data and sends this transformed data to other filters for further processing using the connector, known as pipe. Most of the times, the data-flow architecture degenerates a batch sequential system.
- 44. ADVANTAGES ASSOCIATED WITHTHE DATA-FLOW ARCHITECTURE: It supports reusability. It is maintainable and modifiable. It supports concurrent execution. DISADVANTAGES ASSOCIATED WITH THE DATA- FLOW ARCHITECTURE: It often degenerates to batch sequential system. It does not provide enough support for applications requires user interaction. It is difficult to synchronize two different but related streams.
- 45. In object-orientedarchitectural style, components of a system encapsulate data and operations, which are applied to manipulate the data. In this style, components are represented as objects and they interact with each other through methods (connectors). Two important characteristics: 1) Objects maintain the integrity of the system. 2) An object is not aware of the representation of other objects.
- 46. ADVANTAGES OBJECT-ORIENTED ARCHITECTURE Itallows designers to decompose a problem into a collection of independent objects. The implementation detail of objects is hidden from each other and hence, they can be changed without affecting other objects.
- 47. One commonexample of this architectural style is OSI-ISO (Open Systems Interconnection-International Organization for Standardization) communication system.
- 48. A data-centeredarchitecture has two distinct components: a central data structure or data store (central repository) and a collection of client software. The data store (for example, a database or a file) represents the current state of the data and the client software performs several operations like add, delete, update, etc., on the data stored in the data store.
- 49. ADVANTAGES OF THEDATA- CENTERED ARCHITECTURE 1) Clients operate independently of one another. 2) Data repository is independent of the clients. 3) It adds scalability (that is, new clients can be added easily). 4) It supports modifiability. 5) It achieves data integration in component-based development using blackboard.