IS 385 - System Analysis & Design (Mohammad)

Computer Application

a computer software program that executes on a computing device to carryout a specific set of functions

Information System

a set of interrelated components that collects, processes, stores, and provides as output the information needed to complete business tasks

System Analysis is an...

activity that enable a person to understand and specify what an information system should accomplish

System design is an...

Activity that enable a person to define and describe in detail the system that solves a need

Steps for a System Analysis

1. Understand the need

2. Capture the vision

3. Define a solution

4. Communicate the vision and solution

5. Direct others in building the solution

6. Confirm that the solution meets the need

7. Launch/deploy the solution system

System Development Life Cycle (SDLC)

The overall process for developing information systems from planning and analysis through implementation and maintenance

SDCL order

research, build, deploy, and (often) maintain an information system

Six core processes for SDLC

1. Identify the problem or need and obtain approval

2. Plan and monitor the project

3. Discover and understand the details of the problem or need

4. Design the system components that solve the problem

5. Build, test, and integrate system components

6. Complete system tests and then deploy the solution

Ian's Pet Uncovered Dinosaur Bones in the Chairman's Desk

I(dentify), P(lan and monitor, UN(derstand details), D(esign solution), B(uild and integrate), C(omplete tests), DE(ploy)

Waterfall Model

Non-iterative; an SDLC approach that assumes the phases can be completed sequentially w/o overlap

Agile Development

SDLC approach that emphasizes flexibility to anticipate new requirements during development

Iterative Development

the SDLC approach in which the system is developed piece by piece through multiple iterations; complete "small-projects" then repeat processes to refine and add more

Advantage of Agile development

Fast on feet; responsive to change

Advantages of Waterfall

faster and cheaper if you get it right the first time

Disadvantages of agile

no set deadlines

Most processess/methodologies now use ___ and ___ development

agile; iterative

Semi-waterfall

lower risk if business market and taste did not change

what has to be involved in a system vision document

Problem description; system capabilities; benefits

System analysis activities

1. Gather detailed information

2. define requirements

3. prioritize requirements

4. develop user-interface dialogs

5. evaluate requirements w/ users

Gerald's Dad Prepares Dinner Everyday

G(ather info)

D(efine reqs)

PR(ioritize reqs)

D(envelop user-interface)

EV(aluate reqs)

Functional Reqs.

system MUST perform; business uses, functions the users carry out

Non-functional Reqs.

other system characteristics; constraints and performance goals

"F. U. R. P. S." accronym

Functional reqs.

Usability reqs.

Reliability reqs.

Performance reqs.

Security reqs.

Non functional reqs include

Usability, reliability, performance, security

Example of functional reqs.

business rule & processes

Example of usability reqs.

user interface, ease of use

Example of reliability reqs.

failure rate, recovery methods

Example of performance reqs.

response time, throughput

Example of security reqs.

access control, encryption

Stakeholder

persons who have an interest in the successful implementation of the system

Internal stakeholder

persons within the organization

external stakeholder

persons outside the organization

operational stakeholder

persons who regularly interact with the system

executive stakeholders

persons who don't directly interact, but use the information or have financial interest

Central tendency

occurs when respondents rate everything as average

How to avoid central tendency

Adjust the strength of the descriptors and create a scale with more points

Halo Effects

When the impression formed in one requestion carries into the next question

How to solve halo effect

place one trait and several items on each page

Model is a...

a representation of some aspect of the system being built

types of models

Textual, graphical, mathematical

textual models are...

written down, described

graphical models are...

diagrams, schematic

mathematical models are...

formulas, statistics, algorithms

Unified Modeling Language (UML) is...

Standard graphical modeling symbols/terminology used for information systems

Reasons for modeling

1. communicating w/ other development team members and with a variety of users & stakeholders

2. remembering all the details

3. learning from the modeling process

4. documenting what was done for future maintenance/enhancement

5. reducing complexity by abstraction

CO-RE LEA-D-eR

Co(mmunicating)

Re(membering details)

LEA(rning)

D(ocumenting)

R(educing complexity)

workflow

a sequence of processing steps that completely handles one business transaction or customer reqst.

activity diagram

describes user or system activities, the person doing them, and their sequential flow

Use story

one-sentence description of a work-related task done by a user to achieve some goal or result

acceptance criteria

identify the features that must be present at the completion of the task

Use case

an activity that the system performs in response to a request by a user

what defines functional reqs.

use cases

techniques for identifying use cases

user goal technique and event decomposition technique

user goal (UG) steps

1. identify all the potential users

2. classify users of the system

3. interview and ask them to describe the tasks the computer can help w/

In-CL-INeD

I(dentify users)

Cl(assify users)

IN(terview users) and ask to D(escribe the tasks desired)

objective of user goal

Identify what the system could do to improve users' performance & productivity

benefits of user-goal technique

simple and effective

most common technique to identify use cases

user goal

Event decomposition (ED) technique

Using events to define functional reqs.

Difference between ED and UG.

ED is more comprehensive and complete

Event

something that occurs at a specific time and place, can be described, and should be remembered by the system

External event

an event that occurs outside the system, usually initiated by an external agent

Temporal event

an event that occurs as a result of reaching a point in time

State event

an event that occurs when something happens inside the system that triggers some process

Techniques for identifying problem domain

Brainstorming technique and noun technique

Brainstorming technique

use a checklist of all of the usual types of things typically found and brainstorm to identify domain classes of each type

Noun technique

identify all the nouns that come up when the system is described and determine if each is a domain class, an attribute, or not something we need to remember

the most popular technique for identifying problem domain

noun technique

attribute

describes one piece of information about each instance

identifier or key

One attribute uniquely identifies an instance of the class. Required for data entities, optional for domain classes.

compound attribute

Two or more attributes combined into one structure to simplify the model. Sometimes an identifier or key is a compound attribute.

Association

UML for a naturally occurring link between classes

Relationship

ERD for a naturally occurring link between classes

multiplicity

UML for number of associations between classes

cardinality

ERD for number of relationships between classes

Unary association

associations between two things of the same types

Binary Association

associations between two different types of things

ternary association

associations between three different types of things

Data entities

terms for things in ERD

Difference between ERD and UML

ERD is not as expressive as UML

Semantic Net

a graphical representation of an individual data entity and its relationship w/ other individual entities

Domain class

describes objects in the problem domain

class diagram

A UML diagram that shows classes with attributes and associations

domain model class diagram

a class diagram that only includes classes from the problem domain

Camelback notation example

"custNumber"; use upper-case to separate words

Association class

An association that is treated as a class in a M:N association because it has attributes that need to be remembered

Difference between association class and association

No real difference; it's just a class that is part of an association

Generalization/Specialization

A hierarchical relationship where subordinate classes are special types of the superior classes. Often called an Inheritance Hierarchy

Superclass

superior or more general class in a generalization/specialization hierarchy

Subclass

the subordinate or more specialized class in a generalization/specialization relationship

inheritance

the concept that subclasses inherit characteristics of the more general superclass

aggregation

a whole part relationship where the component part exists separately and can be removed and replaced

composition

a whole part relationship where the parts cannot be removed

types of relationships

association, whole-part, generalization/specialization

state

condition during an object's life when it satisfies some criterion, performs an action, or waits for an event

transition

movement of an object from one state to another

state machine diagram

a diagram showing the life of an object in states and transitions

origin state

the original state of an object before it begins a transition

destination state

the state to which an object moves after completing a transition

pseudostate

the starting point of a state machine diagram, indicated by a black circle

action-expression

some activity that must be completed as part of a transition

guard-condition

a true/false test to see whether a transition can fire

concurrent states

when an object is in one or more states at the same time

path

sequential set of connected states and transition