system design

System DesignSystem Analysis And Design

By:12BS(CS)02

17th October 2014

Computer Science Department , QUEST

April 13, 20232

Overview

12bs(cs)02 System Analysis And Design

System Design Physical and Logical Design Designing Database Designing Form and Report Designing Interface and Dialogue

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Physical And Logical DesignPhysical Design is a graphical representation of a system showing the system’s internal and external entities, and the flows of data into and out of these entities.An internal entity is an entity (person, place, or thing) within the system that transforms data. Internal entities include, for example, accounting clerks (persons), departments (places), and computers (things). Whereas, an external entity is an entity (person, place, or thing) outside the system that transforms data.


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Cont…The physical portion of systems design can generally be broken down into three sub-tasks User Interface Design is concerned with how users add information to the system and with how the system presents information back to them.Data Design is concerned with how the data is represented and stored within the system.Process Design is concerned with how data moves through the system, and with how and where it is validated, secured and/or transformed as it flows into, through and out of the system. 12bs(cs)02 System Analysis And

Design

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Cont…Logical Design is a graphical representation of a system showing the system’s processes and the flows of data into and out of the processes. We use logical design to document information systems because we can represent the logical nature of a system-what tasks the system is doing, without having to specify how, where or by whom the tasks are accomplished. To represent the logical design of a system we can use different diagrams like Entity- Relationship Diagram.


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Database Design


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Database Design


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The database design phase is divided into three steps:1)conceptual database design2) logical database design3) physical database designConceptual Database DesignOnce all the requirements have been collected and analyzed, the next step is to create a conceptual schema for the database, using a high level conceptual data model.The result of this phase is an Entity-Relationship (ER) diagram or UML class diagram.It describes how different entities (objects, items) are related to each other. It also describes what attributes (features) each entity has. It includes the definitions of all the concepts (entities, attributes) of the application area.


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Database DesignLogical Database DesignThe result of the logical design phase (or data model mapping phase) is a set of relation schemas. The ER diagram or class diagram is the basis for these relation schemas.There are rules how the ER model or class diagram is transferred to relation schemas.The relation schemas are the basis for table definitions. In this phase (if not done in previous phase) the primary keys and foreign keys are defined.


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Database DesignNormalizationNormalization is the last part of the logical design. The goal of normalization is to eliminate redundancy and potential update anomalies.

Redundancy means that the same data is saved more than once in a database. Update anomaly is a consequence of redundancy. If a piece of data is saved in more than one place, the same data must be updated in more than one place.

Normalization is a technique by which one can modify the relation schema to reduce the redundancy.


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Physical Database Design The goal of the last phase of database design, physical design, is to implement the database. At this phase one must know which database management system (DBMS) is used. For example, different DBMS's have different names for data types and have different data types.The SQL clauses to create the database are written. The indexes, the integrity constraints (rules) and the users‘ access rights are defined.

Designing Database


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Designing DatabaseApplication Design In the application design phase, the design of the user interface and the application programs that use and process the database are defined and designed. PrototypingThe purpose of a prototype is to allow the users to use the prototype to identify the features of the system using the computerThere are horizontal and vertical prototypes. A horizontal prototype has many features (e.g. user interfaces) but they are not working. A vertical prototype has very few features but they are working.


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ImplementationDuring the implementation phase, the physical realization of the database and application designs are to be done. This is the programming phase of the systems development.Data Conversion and LoadingThis phase is needed when a new database is replacing an old system. During this phase the existing data will be transferred into the new database. TestingBefore the new system is going to live, it should be thoroughly tested. The goal of testing is to find errors! The goal is not to prove the software is working well.

Designing Database


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Designing Database Operational MaintenanceThe operational maintenance is the process of monitoring and maintaining the database system.Monitoring means that the performance of the system is observed. If the performance of the system falls below an acceptable level, tuning or reorganization of the database may be required.Maintaining and upgrading the database system means that, when new requirements arise, the new development lifecycle will be done.


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Designing Forms and Reports


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Designing Forms and Reports(Cont…Form

A business document that contains some predefined data and may include some areas where additional data are to be filled in

An instance of a form is typically based on one database record

Report A business document that contains only

predefined data. A passive document for reading or viewing data. Typically contains data from many database

records or transactions.


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Is user-focused activity that follows a prototyping approach

First steps are to gain an understanding of the intended user and task objectives by collecting initial requirements during requirements determination

Requirement Determination Who will use the form or report? What is the purpose of the form or report? When is the report needed or used? Where does the form or report need to be delivered and

used? How many people need to use or view the form or report?

Designing Forms and Reports(Cont…


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Formatting for Form and Report Design

Meaningful titles: clear, specific, version information, current date

Meaningful information– include only necessary information, with no need to modify

Balanced layout: adequate spacing, margins, and clear labels

Easy navigation system: show how to move forward and backward, and where you are currently


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A better form design

A poor form design

Formatting for Form and Report Design


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Highlighting Information Notify users of errors in data entry or processing Provide warnings regarding possible problems Draw attention to keywords, commands, high-

priority messages, unusual data valuesMethods For Highlighting

Highlighting can include use of upper case, font size differences, bold , italics , underline , boxing,blinking , reverse video ,audible tones , offsetting nonstandard information and other approaches.


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Guidelines for Displaying Text

Case: mixed upper and lower case, use conventional punctuation

Spacing: double spacing if possible, otherwise blank lines between paragraphs

Justification: left justify text, ragged right margins

Hyphenation: no hyphenated words between lines

Abbreviations: only when widely understood and significantly shorter than full text


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Guidelines for Displaying Text

A poor help screen design

A better help screen design


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Labels All columns and rows should have meaningful labels. Labels should be separated from other information by

using highlighting. Redisplay labels when the data extend beyond a

single screen or page.

Formatting columns, rows and text Sort in a meaningful order. Place a blank line between every five rows in long

columns. Similar information displayed in multiple columns should

be sorted vertically. Columns should have at least two spaces between

them.

Guidelines for Tables and Lists


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Guidelines for Tables and Lists (cont.) Allow white space on printed reports for user

to write notes. Use same family of typefaces within and

across displays and reports. Avoid overly fancy fonts.

Formatting numeric, textual and alphanumeric data

Right justify numeric data and align columns by decimal points or other delimiter.

Left justify textual data. Use short line length, usually 30 to 40 characters per line.

Break long sequences of alphanumeric data into small groups of three to four characters each.


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A poor table design A better table design

Guidelines for Tables and Lists (cont.)


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UsabilityOverall evaluation of how a system performs in supporting a particular user for a particular taskThere are three characteristics Speed Accuracy SatisfactionGuidelines for Maximizing Usability Consistency: of terminology, formatting, titles, navigation,

response time Efficiency: minimize required user actions Ease: self-explanatory outputs and labels Format: appropriate display of data and symbols Flexibility: maximize user options for data input according

to preference12bs(cs)02 System Analysis And

Design

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Designing Interface And Dialog


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Designing Interface And DialogueInterface design An interface is a method by which users interact with information systems.Dialogue design A dialogue reflects the sequence of interaction between a user and a system . The design of interface and dialogues is the

process ofdefining the manner in which human and computersexchange information. Similar to designing f&r, the process of designing I&d is user focused activity To design usable i&d you must answer the same

who,what, when, where and how


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Methods of Interacting

Command Language Interaction Users enter explicit statements into a system to invoke operationsExample from MS DOS:COPY C:PAPER.DOC A:PAPER.DOCThis copies a file from C: drive to A: driveMenu interactionList of system options is provided and a specific command is invoked by user selection of a menu option.Pop-up menu: menu placed near the current cursor position.


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Drop-down menu: a menu-positioning method that places the access point of the menu near the top line of the display.

Methods of Interacting(cont…)


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Pop-up menu


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Drop-down menu


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Wording: meaningful titles, clear command verbs, mixed upper/lower case.

Organization: consistent organizing principle. Length: all choices fit within screen length. Selection: consistent, clear and easy selection

methods. Highlighting: only for selected options or

unavailable options.

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Contrasting Menu Designs


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Methods of Interacting(cont…)Form interaction: data fields are formatted in a manner similar to paper-based forms.Allows users to fill in the blanks when working with a system.Measures of an effective design: Self-explanatory title and field headings Fields organized into logical groupings Distinctive boundaries Default values Displays appropriate field lengths Minimizes the need to scroll windows


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Methods of Interacting(cont…)


Object-based interaction: symbols are used to represent commands or functions.

Icons graphical pictures that represent specific functions within a system.

Use little screen space and are easily understood by users.

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Methods of Interacting(cont…)Natural language interactionInputs to and outputs from a computer-based application are in a conventional spoken language such as English.Both keyboard and voice entry


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Designing InterfacesUse standard formats similar to paper-based forms and reports.Left-to-right, top-to-bottom navigation.Flexibility and consistency:

Free movement between fields No permanent data storage until the user requests Each key and command assigned to one function


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Structuring Data Entry


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Controlling Data InputObjective: reduce data entry errors.Common sources data entry errors in a field:

Appending: adding additional characters Truncating: losing characters Transcripting : entering invalid data Transposing: reversing sequence of characters


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Providing Feedback & HelpThree types of system feedback:

Status information: keep user informed of what’s going on, helpful when user has to wait for response

Prompting cues: tell user when input is needed, and how to provide the input

Error or warning messages: inform user that something is wrong, either with data entry or system operation

Place yourself in user’s place when designing help.Guidelines for designing usable help:

Simplicity - Help messages should be short and to the point.

Organize - Information in help messages should be easily absorbed by users

Show - It is useful to explicitly show users how to perform an operation.


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Designing DialoguesDialogues: the sequence of interaction between a user and a system. Dialogue design involves:

Designing a dialogue sequence Building a prototype Assessing usabilityGuidelines for Dialgoue Design

Consistency (same terminology on all screens) Shortcuts and Sequence (special keys can be used for advanced

users) Error Handling(errors should be detected and reported) Reversal (reverse action) Feedback (for very user action, eg: record is added) Closure (e.g.: indication of first or last screen) Control (consistent response time) Ease (e.g.: transitions to first and last screen)


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Designing DialoguesDialogue diagramming is a formal method for designing and representing human computer dialogues using box and line diagramThe three section of the box are used :


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Designing Interfaces and Dialogues inGraphical EnvironmentsTwo rules repeatedly emerge as comprising the first step to becoming an effective GUI designer : Become an expert user of the GUI environment Understand the available resources and how they can

be used.Common properties of Windows and forms in GUI environment that can be active or inactive : Modality Resizable Movable Minimize Maximize System menu


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Opening new browser window Breaking or slowing down the back button Complex URLs Orphan pages Scrolling navigation pages Lack of navigation support Hidden links Links that don’t provide enough information Buttons that provide no click feedback


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THANKYOU


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