2 What Is An Information System? An information system is a collection of interrelated components that collect, process, store, and provide as output the information needed to complete a business task.
3 Examples of Information Systems Course registration systemOnline order systemOnline banking system
4 What Is System Analysis About? Understanding the goals and strategies of the business.Defining the information requirements that support those goals and strategies.It is not about programming.
5 System Analysis vs. System Design Investigation of the problem and requirement rather than solution.System Design:A conceptual solution that fulfills the requirements, rather than implementation.
6 System AnalystA business professional who uses analysis and design techniques to solve business problems using information technology.
7 The Role of a System Analyst Investigate, analyze, design, develop, install, evaluate, and maintain a company’s information systems.Business knowledge.Business problem solver.Help translate business requirements into IT projects.
8 Traditional System Development Life Cycle (SDLC)
9 Traditional System Development life Cycle (SDLC) Project planning – initiate, ensure feasibility, plan schedule, obtain approval for projectAnalysis – understand business needs and processing requirementsDesign – define solution system based on requirements and analysis decisionsImplementation – construct, test, train users, and install new systemSupport – keep system running and improve it
10 Two Approaches to System Development Traditional (Structured) approachAlso called structured system developmentStructured analysis and design technique (SADT)Includes information engineering (IE)Object-oriented approachAlso called OOA, OOD, and OOPViews information system as collection of interacting objects that work together to accomplish tasks
11 Structured System Development Structure ProgrammingTop-down ProgrammingStructured DesignStructured Analysis
12 Object-Oriented Approach Completely different approach to information systemsViews information system as collection of interacting objects that work together to accomplish tasksObjects – things in computer system that can respond to messagesConceptually, no processes, programs, data entities, or files are defined – just objectsOO languages: Java, C++, C# .NET, VB .NET
13 Object-oriented Analysis and design (OOAD) OOAD essential for creating well-designed,& maintainable software systemAll Software Analysis and Design is preceded by the analysis of requirements.Analysis models the “real-world” requirements, independent of the implementation environment.Design applies object-oriented concepts to develop and communicate the architecture and details of how to meet requirements.
14 Unified Modeling Language (UML) UML (Unified Modeling Language) is a graphical language that is suit-able to express software or system requirements, architecture, and design.UML used for both database and software modelingUML modeling also supports multiple views of the same system.use case diagram shows the purposes of the system (use cases) and the users (actors).
15 UML diagrams Can be categorized as the fallowing: Structural diagrams: to show the building blocks of your system—features that don’t change with time.Ex: Class diagramBehavioral diagrams:to show how your system responds to requests or otherwise evolves over time.Ex: Use case diagramInteraction diagrams:Is a type of behavioral diagram.To depict the exchange of messages within a collaboration (a group of cooperating objects).Ex: Sequence diagram & Collaboration diagram
16 UML Diagrams Another way of categorizing UML diagram: Static diagrams to show the static features of the system. (no change)Dynamic diagramsto show how your system evolves over time.Functional diagrams:to show the details of behaviors and algorithms.
17 Object-oriented analysis (OOA) Trying to figure out what the users and customers of a software effort want the System to do.Builds a “real-world” model from requirementsclient interviews, domain knowledge, real-world experience collected in use cases and other simple notationsOOA models address three aspects of the system (its objects)class structure and relationshipssequencing of interactions and eventsdata transformations and computations
18 Models of Object-Oriented Analysis (UML) Structural Model (Data-Oriented)static featureswhat objects are in the system?how are they related?Dynamic Model (Action-Oriented)behavioral aspectswhat events occur in the systemwhen do they occur and in what order?Functional Model (Both Data and Actions)data transformations“what” does the system do
20 Ex: Use Case (Analysis) Start from requirementsDescribe response of system to eventsNormal flow of actionError and exception handlingCan implement tests to check use cases
21 OOD: Object Oriented Design Emphasizes a conceptual solution that fulfils the requirements specified in the analysis.Need to define software objects and how they collaborate to fulfill the requirements.For example, in the Library Information System, a Book object may have a title attribute and a display() method.Designs are implemented in a programming language.In the example, we will have a Book class in Java.
22 ObjectsIn an OO approach, a system consist of a collection of interacting objects.An object is a computational entity which Provide services with which other entities mayinteract○Typically, the services consumer sends a message( requesting the service) to the provides object○PossessesSate-Information that the object holds , called (attributes)Behaviour-Operation it can perform , called (method)
23 MessagesInteraction is achieved by one object sending a message to anotherMessage hasA senderA receiverMessage contents :A reference to an operation of the receiverPossible additional information (parameters)Some messages return information to the sender
24 Why Objects? Encapsulation Message-based Invocation Data Hiding Helps to organize data & behavior into meaningful associations.Message-based InvocationHelps to make code adaptable and reusableData HidingHelps to manage complexity, since programmer can control the data that objects are allowed to do manipulate
25 Classes A Class Describes a set of equivalent objects ○Hence, operates like a data type of objects○Typically, every object in a system belongs to a classProvides a useful way of representing and implementing the shared state and behavior of the objects that it describes
26 Why Class Inheritance Polymorphism a form of reuse means same operation may behave differently on different classes.