Key Concepts in System Analysis and Design

logical models

Logical models show WHAT the system must do, regardless of physical implementation.

physical models

Physical models describe HOW the system will be constructed.

data store

Used in DFD to represent data that the system stores because one or more processes needs to use the data.

black box

Inputs, outputs and functions are known but logic and details are hidden.

blackhole

Has an input but no output.

grayhole

Has at least one input and output.

terminators

DFD entries are called this because they are data origins or final decisions.

Data Flow Diagram in order

Customer, order system, warehouses, sales rep, bank, accounting.

leveling/decomposing

Leveling is the process of drawing a series of increasingly detailed diagrams until all function; primitives are identified.

balancing

Balancing maintains consistency among a set of DFDs by ensuring that input and output data flows align properly.

data dictionary

Central storehouse of information about the systems data.

field

The smallest piece of data within a system that has meaning.

record

A meaningful combination of related data.

type length

Max number of characters. Type refers to whether there are letters, numbers or other characters in the data.

process description

Documents the details of a functional primitive and represents specific steps.

Modularity

Grouping similar types of functions into their own files and libraries, and splitting out related helper functions into their own files.

selection

The completion of one of two or more process steps based on the results of a test or condition.

structured english

Subset of standard English that describes logical processes.

Decision Table

A logical structure that shows every combo of conditions and outcomes.

object oriented analysis

System analysis by identifying objects.

attribute

Characteristics that describe an object.

method

Tasks or functions that the object performs.

encapsulation

All data and objects are self contained.

subclass

More specific categories within a class.

relationships

Enable objects to communicate and react with one another.

use case

Steps in a specific business process or function.

Cardinality

How instances of one class relate to instances of another.

activity diagram

Resembles a horizontal flow chart, shows actions and events as they occur.

User Interface

Screens, commands, controls, and features that enables a user to interact with the system.

outsourcing

Using an outside firm for IT needs for a fee.

usage model

Charges a variable fee based on volume of operations performed in a system.

Structure Service

Model of software in which apps are hosted as a service. Reduces need for maintenance, operation and support.

Return on investment

Profit made outweighs the cost to implement the system.

evaluation model

Uses common yardsticks to measure and compare vendor ratings.

benchmarking

Measures the time a package takes to process a transaction.

software license

Bought that gives the purchaser the ability to use software.

GUI

Graphical interface that facilitates user interaction.

usability metrics

Using software that can record and measure user interaction.

natural language

Feature that allows users to type commands or request normal text phrases.

dialogue box

Explains what is required through text.

input mask

Template or pattern that restricts data entry and prevents errors.

data validation

Improves input quality by testing the data and rejecting any entry that fails to meet conditions.

combination check

Performed on two or more fields, ensures consistency or reasonableness.

audit trails

Log every instance of data entry and changes.

summary report

Condenses information into a high-level overview, focusing on key points and conclusions.

VARS

Value added reseller, adds custom features and configs software to specific markets.