QuickNotes

System Analysis and Design

System

A system is an inter-related set of components with an identifiable boundary, working together for some purpose.

Information System

An information system is defined as the software that helps organize and analyze data. So, the purpose of an information system is to turn raw data into useful information that can be used for decision making in an organization.

Information Technology

Information technology can be broadly defined as integration of computer with telecommunication equipment for storing, retrieving, manipulating and storage of data.

Systems Analysis

It is a process of collecting and interpreting facts, identifying the problems, and decomposition of a system into its components.

Systems Design

It is a process of planning a new business system or replacing an existing system by defining its components or modules to satisfy the specific requirements.

SDLC

Software Development Life Cycle is a process used by software industry to design, develop and test high quality softwares. 

Context Diagram

The Context Diagram shows the system under consideration as a single high-level process and then shows the relationship that the system has with other external entities (systems, organizational groups, external data stores, etc.). 

DFD

A Data-Flow Diagram (DFD) is a graphical visualization of the movement of data through an information system. 

SRS

A Software requirements specification document describes the intended purpose, requirements and nature of a software to be developed. It also includes the yield and cost of the software.

Functional requirements: 

Specify what the information system must do or Functionality or services that the system is expected to provide.

Non-Functional requirements

Specify a property / quality the system must have or These are constraints  on the services or functions offered by the system.

Feasibility Study

The measure of how beneficial an information system will be to an organization.

Types of Feasibility

Technical Feasibility, Economical Feasibility, Operational Feasibility, Legal Feasibility, Scheduling Feasibility

UML

The Unified Modeling Language (UML) is a graphical language for OOAD that gives a standard way to write a software system’s blueprint. It helps to visualize, specify, construct, and document the artifacts of an object-oriented system.

Spiral Model

The spiral model, also known as the spiral lifecycle model, is a systems development method (SDM) used in information technology (IT). This model of development combines the features of the prototyping model and the systems development life cycle (SDLC).

Waterfall Model

Waterfall approach was first SDLC Model to be used widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of software development is divided into separate phases.

Prototype 

A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and software programming. 

Prototyping Model

The prototyping model is a systems development method in which a prototype is built, tested and then reworked as necessary until an acceptable outcome is achieved from which the complete system or product can be developed.

Class Diagram

The class diagram is the main building block of object-oriented modeling. It is used for general conceptual modeling of the structure of the application, and for detailed modeling translating the models into programming code.

Use Case Diagram

A use case diagram at its simplest is a representation of a user's interaction with the system that shows the relationship between the user and the different use cases in which the user is involved.

Activity Diagram

An activity diagram visually presents a series of actions or flow of control in a system similar to a flowchart or a data flow diagram. Activity diagrams are often used in business process modeling. They can also describe the steps in a use case diagram.

Sequence Diagram

A sequence diagram is a type of interaction diagram because it describes how—and in what order—a group of objects works together. These diagrams are used by software developers and business professionals to understand requirements for a new system or to document an existing process.

Database System 

Database

A database is an organized collection of data. The data is typically organized to model aspects of reality in a way that supports processes requiring information.

DBMS

Database Management Systems are computer software applications that interact with the user, other applications, and the database itself to capture and analyze data.

Ex: MySQL, PostgreSQL, Microsoft SQL Server, Oracle, Sybase and IBM DB2.

Database Model

A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. 

Ex:  Hierarchical Data Model, Relational Model, Network Model, and Object-oriented Data Model

Data Independence

Data independence refers characteristic of being able to modify the schema at one level of the database system without altering the schema at the next higher level.

Logical Data Independence

Logical data independence refers characteristic of being able to change the conceptual schema without having to change the external schema.

Physical Data Independence

Physical data independence can be defined as the capacity to change the internal schema without having to change the conceptual schema.

Database Schema

A database schema is the skeleton structure that represents the logical view of the entire database. It defines how the data is organized and how the relations among them are associated. It formulates all the constraints that are to be applied on the data.

Data Dictionary

A data dictionary contains metadata i.e data about the database. The data dictionary is very important as it contains information such as what is in the database, who is allowed to access it, where is the database physically stored etc.

Database view

A database view is a searchable object in a database that is defined by a query. Though a view doesn't store data, some refer to a views as “virtual tables,” you can query a view like you can a table. A view can combine data from two or more table, using joins, and also just contain a subset of information.

Relational Algebra

Relational algebra is a procedural query language. It gives a step by step process to obtain the result of the query. It uses operators to perform queries.

Primary key

A primary key is a key in a relational database that is unique for each record. It is a unique identifier, such as a driver license number, telephone number, employee number. A relational database must always have one and only one primary key.

Foreign key

A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. It acts as a cross-reference between tables because it references the primary key of another table, thereby establishing a link between them.

Composite key

In database design, a composite key is a candidate key that consists of two or more attributes (table columns) that together uniquely identify an entity occurrence (table row).

Constraints

Every relation has some conditions that must hold for it to be a valid relation. These conditions are called Relational Integrity Constraints. There are three main integrity constraints −

• Key constraints
• Domain constraints
• Referential integrity constraints

Referential integrity Constraints

Referential integrity constraints work on the concept of Foreign Keys. A foreign key is a key attribute of a relation that can be referred in other relation.

Conceptual data model

A conceptual data model identifies the highest-level relationships between the different entities.

Logical data model

A logical data model describes the data in as much detail as possible, without regard to how they will be physical implemented in the database.

Physical data model

Physical data model represents how the model will be built in the database. A physical database model shows all table structures, including column name, column data type, column constraints, primary key, foreign key, and relationships between tables.

SQL

Structure Query Language (SQL) is a programming language used for storing and managing data in RDBMS.

Data Normalization

Normalization is a database design technique that reduces data redundancy and eliminates undesirable characteristics like Insertion, Update and Deletion Anomalies.