1 Systems Analysis & Design System Analysis Overview IS 431: Lecture 3 CSUN Information Systems...

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Systems Analysis & Design

System Analysis Overview

IS 431: Lecture 3

CSUN Information Systems

http://www.csun.edu/~dn58412/IS431/IS431_SP15.htm

IS 431 : Lecture 3 2

Systems Analysis Overview

Systems Analysis vs. Systems DesignSystems Analysis Approaches Systems Analysis Phases (purposes,

participants, inputs, outputs, techniques, and steps)– Scope Definition– Problem Analysis– Requirements Analysis– Logical Design– Decision Analysis

User Requirements Discovery


System Development


System Analysis


Systems Analysis vs. Systems Design

Systems Analysis: development phases in a project that primarily focus on the business problems, i.e., WHAT the system must do in terms of Data, Processes, and Interfaces, independent of any technology that can or will be used to implement a solution to that problem.Systems Design: development phases focus on the technical construction and implementation of the system (HOW technology will be used in the system.)


Context of System Analysis


Model-Driven Analysis

Model-driven Analysis emphasizes the drawing of graphical system models to document and validate both existing and/or proposed systems. Ultimately, the system model becomes the blueprint for designing and constructing an improved system.


Model-Driven Methods

Structured Analysis (Waterfall) : a model-driven, PROCESS-centered technique to analyze an existing system and define business requirements for a new system.

The models illustrate the system’s components: processes (functions, tasks) and their associated inputs, outputs, and files.


A Simple Process Model


Model-Driven Methods…

Information Engineering (IE):a model-driven and DATA-centered, but process-sensitive (context specific) technique to plan, analyze, and design information systems.

IE illustrate and synchronize the system’s data and processes.


A Simple Data Model


Model-Driven Methods…

Object-oriented Analysis (OOA): a model-driven technique that integrates data and process concerns into constructs called OBJECTS.

OOA illustrate the system’s objects from various perspectives such as structure and behavior.


A Simple Object Model

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Accelerated Systems Analysis

• Accelerated Systems Analysis approaches emphasize the construction of prototypes to more rapidly identify business and user requirements for a new system. Discovery Prototyping Rapid Architected Analysis :derive system models from

existing systems or discovery prototypes.


Discovery Prototyping

Discovery Prototyping – a technique used to identify the users’ business requirements by having them react to a quick-and-dirty implementation of those requirements.– Advantages

Prototypes cater to the “I’ll know what I want when I see it” way of thinking that is characteristic of many users and managers.

– Disadvantages Can become preoccupied with final “look and feel” prematurely Can encourage a premature focus on, and commitment to, design Users can be misled to believe that the completed system can be

built rapidly using prototyping tools


Agile MethodsAgile Method – the integration of various approaches

of systems analysis and design for applications as deemed appropriate to the problem being solved and the system being developed.– Most commercial methodologies do not impose a single

approach (structured analysis, IE, OOA) on systems analysts.– Instead, they integrate all popular approaches into a

collection of agile methods.– System developers are given the flexibility to select from a

variety of tools and techniques to best accomplish the tasks at hand,

Agile Methods …

Agile methodology aims for customer satisfaction through early and continuous delivery of useful application software components developed by an iterative process using the bare minimum requirements

Iterative development – Consists of a series of tiny projects


Extreme Programming

Extreme Programming (XP) – Breaks a project into tiny phases, and developers cannot continue on to the next phase until the first phase is complete


Rational Unified Process (RUP)

Rational Unified Process (RUP) – Provides a framework for breaking down the development of software into four gates

– Gate One: Inception

– Gate Two: Elaboration

– Gate Three: Construction

– Gate Four: Transition


SCRUM

SCRUM – Uses small teams to produce small pieces of deliverable software using sprints, or 30-day intervals, to achieve an appointed goal

Under this methodology, each day ends or begins with a stand-up meeting to monitor and control the development effort



Classic Systems Analysis Phases

Scope Definition Phase– Is the project worth looking at, for WHAT?

Problem Analysis Phase– Is a new system worth building, for WHAT?

Requirements Analysis Phase– WHAT do the users need and want from the new system?

Logical Design Phase– WHAT must the new system do?

Decision Analysis Phase– WHAT is the best solution among others?


Systems Analysis Phases

Scope Definition Phase : WHAT PROBLEM– Is the project worth looking at to solve problem?

Problem Analysis Phase: WHAT ISSUES– Is the new system worthwhile to build?

Requirements Analysis Phase: WHAT REQUIREMENTS– What do users need and want from the new system?

Logical Design Phase: WHAT TO DO– What the new system must do to satisfy user’s needs?

Decision Analysis Phase: WHAT SOLUTION– What is the best available solution for the business?


Scope Definition Phase


Scope Definition Tasks


1. Scope Definition Phase

• Task 1.1: Identify Problems, Opportunities, and Directives (POD)

•Input: Request for System Service (Fig 5.7)

•Deliverable: Preliminary Problem Statement (Fig 5.8)

•Urgency, Visibility, Benefits, Priority, Possible Solutions


System Improvement Objectives

• Objective – a measure of success. It is something (measurable) that we expect to achieve, if given sufficient resources.

Reduce the number of uncollectible customer accounts by 50 percent within the next year.

Increase by 25 percent the number of loan applications that can be processed during an eight-hour shift.

Decrease by 50 percent the time required to reschedule a production lot when a workstation malfunctions.

• Constraint – something that will limit our flexibility in defining a solution to our objectives. Essentially, constraints cannot be changed.

The new system must be operational by April 15. The new system cannot cost more than $350,000. The new system must be web-enabled. The new system must bill customers every 15 days.


Problem Statement


1. Scope Definition Phase ...

• Task 1.2: Negotiate Preliminary Scope

•Deliverable: Statement of Project Scope (boundary of the project)

•What types of DATA to be studied

•What business PROCESSES to be included

•How the system INTERFACE with users, locations, and other systems

•Note: if later the scope changes, the budget and schedule should be changed accordingly


1. Scope Definition Phase …

• Task 1.3: Assess Project Worthiness

•“Is this project worth looking at ?”

•Cost/benefit analysis

•Decision

•Approve project

•Cancel project

•Renegotiate the scope of project (with adjusted budget and schedule)



• Task 1.4: Schedule and Budget Plan for Project

•Deliverables: Project Charter

•Master plan for the whole project: schedule and resource assignments

•Detail plan and schedule for completing the next phase



• Task 1.5: Present the Project and Plan

•Present and defend the project and plan before steering committee

•Formally launch the project and announce the project, goals, and schedule

•Deliverable: Project Charter (participants, problems, scope, methodology, statement of work to be completed, deliverables, quality standards, schedule, budget)


Problem Analysis Phase


Problem Analysis Tasks


2. Problem Analysis Phase

• Task 2.1: Study the Problem Domain

•Understanding of the problem domain and business vocabulary

•DATA: currently stored data, their business terms

•PROCESSES: current business events

•INTERFACES: current locations and users

•Deliverables: definition of system domain / models of Current System


2. Problem Analysis Phase …

• Task 2.2: Analyze Problems and Opportunities

•Study causes and effects of each problem (Note: an effect may be the cause of other problems)

•Deliverables: updated problem statements and the cause-effect analyses for each problem and opportunities (Fig 5.11)



• Task 2.3: Analyze Business Processes (for BPR)

•Measure the value added or subtracted by each process as it relates to the total organization

•Volume of throughput, response time, bottlenecks, cost, value added, consequences of eliminating or streamline of the process

•Deliverable: current business process models



• Task 2.4: Establish System Improvement Objectives

•Define specific system improvement objectives and constraints for each problem

•Objectives to be precise, measurable

•Constraints in terms of schedule, cost, technology, policy

•Deliverable: System Improvement Objectives and Recommendations Report


PROBLEMS, OPPORTUNITIES, OBJECTIVES, AND CONSTRAINTS MATRIX



• Task 2.5: Update the Project Plan

•Update project:

•Reduce the scope to keep only higher priority objectives to meet a deadline/budget

•Expanse the scope and adjust schedule and budget accordingly

•Deliverable: updated project plan



• Task 2.6: Present Findings and Recommendations

•Deliverable: system improvement objectives

•Decision: continue/adjust/cancel current project


Requirements Analysis Phase


Requirements Analysis Tasks


3. Requirements Analysis Phase

• Task 3.1: Identify System Requirements

• Functional requirements: activities and services providing by a system: business functions, inputs, outputs, stored data.

• Nonfunctional requirements: features, characteristics defining a satisfactory system: performance, documentation, budget, ease of use and learn, cost saving, time saving, security

•Deliverable: draft functional and nonfunctional requirements: improvement objectives and related input, output, processes, stored data to fulfill the objectives


3. Requirements Analysis Phase …

• Task 3.2: Prioritize Requirements

• Mandatory vs. desirable requirements

• Time boxing: deliver the system in a set of subsequent versions in a time frame. The first version satisfies essential and highest prioritized requirements.


3. Requirements Analysis Phase …


•If requirements exceed original vision: reduce the scope or increase the budget

•Deliverable: consolidated system requirements (completed requirements and priorities)


Logical Design Phase


Logical Design Tasks


4. Logical Modeling Phase

• Task 4.1: Analyze Functional Requirements

•Logical systems models: WHAT the system must do (not HOW)

•Separation of business concerns from technical solutions will help considering many different ways for business processes improvement and alternative technical solutions

•Build prototypes to establish user interface requirements

•Deliverables: Data models (ERD), Process models (DFD), Interfaces models (Context diagram, Use case diagram), Object models (UML diagrams) of the Proposed System.


4. Logical Modeling Phase …

• Task 4.2: Validate Functional Requirements

•Completeness check, revisit, make changes and additions to system models and prototypes to assure that requirements are adequately defined.

•Associate nonfunctional requirements with functional requirements


Consolidated Requirements Statement


Decision Analysis Phase


Decision Analysis Tasks


5. Decision Analysis Phase

• Task 5.1: Identify Candidate Solutions

•Identify all possible candidate solutions

•Deliverable: candidate systems (solutions) matrix (Fig 5.19)


Candidate Systems Matrix


Candidate Systems Matrix..


5. Decision Analysis Phase …

• Task 5.2: Analyze Candidate Solutions

•Feasibility analysis is performed on each individual candidate without regard to the feasibility of other candidates

•Technical, operational, economic, schedule feasibilities (TOES)


Feasibility Analyses

Technical feasibility. Is the solution technically practical? Does our staff have the technical expertise to design and build this solution?

Operational feasibility. Will the solution fulfill the users’ requirements? To what degree? How will the solution change the users’ work environment? How do users feel about such a solution?

Economic feasibility. Is the solution cost-effective?

Schedule feasibility. Can the solution be designed and implemented within an acceptable time period?



• Task 5.3: Compare Candidate Solutions

•Select the candidate solution having the “best overall” combination of technical, operational, economic, and schedule feasibilities

•Feasibility matrix (Fig 5.20)

•Deliverable: recommended solution


Feasibility Matrix




•Input: recommended solution

•Review and update the latest project schedule and resource assignments

•Deliverable: updated project plan



• Task 5.5: Recommend a Solution

•Deliverable: System Proposal


The Importance of Requirements Discovery

System requirement (business requirement) is a description of the needs and desires for an information system. A requirement may describe functions, features (attributes), and constraints.Functional requirements: functions or features that must be included in an information system in order to satisfy the business need and be acceptable to the users. Nonfunctional requirements: features, characteristics, and attributes of the system as well as any constraints that may limit the boundaries of the proposed solution. Use PIECES framework for classification.


PIECES Classification of System Requirements


Results of Incorrect Requirements

The system may cost more than projected.The system may be delivered later than promised.The system may not meet the users’ expectations

and that dissatisfaction may cause them not to use it.Once in production, the costs of maintaining and

enhancing the system may be excessively high.The system may be unreliable and prone to errors

and downtime.The reputation of the IT staff on the team is

tarnished because any failure, regardless of who is at fault, will be perceived as a mistake by the team.


Relative Cost to Fix an Error


Criteria to Define System Requirements

Consistent – requirements are not conflicting or ambiguous.Complete – requirements describe all possible system inputs

and responses.Feasible – requirements can be satisfied based on the

available resources and constraints.Required – requirements are truly needed and fulfill the

purpose of the system.Accurate – requirements are stated correctly.Traceable – requirements directly map to the functions and

features of the system.Verifiable – requirements are defined so they can be

demonstrated during testing.


The Process of Requirements Discovery

Problem discovery and analysis Requirements discovery Documenting and analyzing requirements Requirements management to handle

changes


Ishikawa Diagram

The Ishikawa diagram: graphical tool to identify, explore, and depict problems, causes and effects of those problems. (Also called a cause-and-effect diagram or a fishbone diagram.)


Ishikawa Diagram …

Four M’s:– Materials, Machines, Manpower, and Methods

Four P’s:– Places, Procedures, Policies, and People

Four S’s:– Surroundings, Suppliers, Systems, and Skills


USER

TASK TOOL

Context of Requirements for an Information System

SYSTEM

ORGANIZATION


Analyzing Requirements

Analyzing requirements to resolve problems of:– Missing requirements

– Conflicting requirements

– Infeasible requirements

– Overlapping requirements

– Ambiguous requirements

Formalizing requirements– Requirements definition document

– Communicated to stakeholders or steering body


Documenting Requirements

A requirements definition document should consist of the following:– The functions and services that the system should provide.– Nonfunctional requirements including the system’s

features, characteristics, and attributes.– The constraints that restrict the development of the system

or under which the system must operate.– Information about other systems that the system must

interface with.


Requirements Management

Requirements management - the process of managing change to the requirements. – Over the lifetime of the project it is very common for

new requirements to emerge and existing requirements to change.

– Studies have shown that over the life of a project as much as 50 percent or more of the requirements will change before the system is put into production.


Fact-Finding Methods

Sampling of existing documentation, forms, and databases.

Research and site visits. Observation of the work environment. Questionnaires. Interviews. Prototyping. Joint requirements planning (JRP).


Discovery Prototyping

Discovery prototyping – the act of building a small-scale, representative or working model of the users’ requirements in order to discover or verify those requirements. – Advantages

– Disadvantages


Joint Requirements Planning

Joint requirements planning (JRP) – a process whereby highly structured group meetings (having defined agenda, key representatives) are conducted for the purpose of analyzing problems and defining requirements. – JRP is a subset of a more comprehensive joint application

development or JAD technique that encompasses the entire systems development process.


Benefits of JRP

JRP actively involves users and management in the development project (encouraging them to take “ownership” in the project).

JRP reduces the amount of time required to develop systems.

JRP incorporates the benefits of prototyping as a means for confirming requirements and obtaining design approvals.

1 Systems Analysis & Design System Analysis Overview IS 431: Lecture 3 CSUN Information Systems...

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