Logical Design Tools are used during analysis to represent what is required of an information system represent (i.e. its specifications) but does not try to say how the specifications will be constructed. They lay out what the system's features and abilities will be. They include

Context Diagrams
Data Dictionaries
Hierarchy Charts / Org charts
Decision Trees

Physical design tools for PSM design

Physical Design Tools - describe how a system will be physically implemented (like a blueprint). They include:

Data Flow Diagrams
Storyboards
Flow Charts, N-S charts
Structure Charts
IPO charts
Layout diagrams / mockups
Pseudocode

Logical Design Tools - used during PSM analysis phase

CONTEXT DIAGRAMS - please go to this page

HIERARCHY DIAGRAM

A Hierarchy Diagram shows the inter-relationship of modules or sub-programs. It looks like a corporate organisational chart.

ORGANISATIONAL CHART ("Org chart")

An organisational chart graphically shows the parts of an organisation and their relationships to each other (e.g. which part is a subsidiary of another). They are especially useful in large organisations with many parts, such as the United Nations (click here for their org chart), government departments etc.

CHECKLIST

A checklist is simply a list of items or actions that need to be addressed - like a shopping list or a "To Do" list. It helps you remember to do things.

DECISION TREES, DECISION TABLES

Decision trees and tables are a set of rules for what to do in certain conditions. e.g. If this happens, do that otherwise go to this step. They can be used to enforce strict compliance with local procedures, and avoid improper behaviour, especially in complex procedures or life-and-death situations.

e.g. If the photocopier breaks down, call Alex. If Alex is not available, call Bert. If Bert is away, ring Sally.

They are valuable when setting out how the system should behave, and what conditions it will need to be able to cope with.

A decision tree showing decisions and actions required of a software system

Physical Design Tools - used during PSM design phase

IPO charts - please see this page

In brief - when you want to calculate some information, an IPO chart sets out the data needed and the logic of the necessary calculation (algorithm).

e.g.

INPUT	PROCESSING	OUTPUT
Date of birth Current date	(Current Date - Date of Birth) / 365.25	Age
Date Borrowed Date Now	if (Datenow - Date Borrowed) >7, show Datenow - Date Borrowed and "days" else show "Not overdue"	How long overdue

DATA DICTIONARY - please see this page

In brief - a data dictionary is a blueprint of how a database table should be built, including its field names, field types, validation rules etc.

PSEUDOCODE - also known as STRUCTURED ENGLISH - see this page

In brief - pseudocode describes algorithms (calculation strategies) with an expression that is halfway between normal language and programming language what allows very rapid planning of ideas and methods without getting bogged down in 100% accurate program coding.

STORY BOARDS

Ususally used for animations, film making and webpages, story boards are a graphical outline of what a presentation will look like. They show "key frames" of a presentation and include information on camera positions, sound effects, lighting, fade ins and fade outs, captions, movements, scripts: everything a director needs to visualise the finished product.

Note: the old VCAA IT Glossary defined a storyboard as "A method of representing the design of a multimedia solution. Not to be confused with a film storyboard, multimedia storyboarding refers to drawing a structure chart identifying each page and indicating the links between pages (whether one-way or two-way). A layout diagram may accompany this."

If you see the term used in the exam, it will probably be referring to the definition given above (even if it's not in the 2011-2014 study design), but most people in the world use "storyboard" in the sense I described. That type of storyboard is still a valuable multimedia design tool.

TEMPLATES

A template is simply a document with structure but no detail. For example, if you were writing a textbook, you could create a Word document with some dummy text that has been formatted the way you want it to be. It could have standard sections in it (with dummy text) so you when you create a new chapter, you just have to load the template and replace the dummy text with real text. The pre-defined headings remind you of what to include, and since the text is already formatted, it saves time and ensures each chapter looks similar.

These web pages are all based on the same template.htm file: every time I start a new page, I load 'template.htm', add the text and save it with a new name. The formatting, date codes, heading styles, colouring etc are already done for me!

DATA FLOW DIAGRAM - details are here

In brief - shows how data and information flow into, within and out from an organisation. For example, it shows who processes data, passes it onto another person to do something else with it.

DFD details are here

Important note: A DFD is a physical design tool) and is a detailed version of a context diagram (which is a logical design tool).

The context diagram is an overview of how data flows between the system and its external entities. It has few or no details of the inner workings of the system. That's why it's called a context diagram, because it shows the system in the context of its surroundings.

The DFD is similar, but goes into much more detail and describes how processes within the organisation work.

DATA STRUCTURE CHARTS and TABLES and DIAGRAMS

Visually shows the structure of data – fields, records, tables etc.

DATA STRUCTURE TABLE

The table summarises field information (similar to defining fields in ‘Access’)

DATA STRUCTURE DIAGRAM

This diagram shows the relationships between tables in a database

Though many people consider the diagram below to be an ERD, we now will call it a data structure diagram...

FLOWCHART - details are here

NASSI-SHNEIDERMAN (N-S) CHART

N-S charts are similar to flowcharts, but are more concise and have built-in support for common operations like decisions and loops. N-S charts are named after I. Nassi and B. Shneiderman, who published this technique in 1982. Note: there is no "c" in Shneiderman!

N-S Chart tutorial

Entity Relationship Diagram (ERD)

See the new ERD theory slideshow for 2011

There are three basic elements in ER models:

Entities are the "things" about which we want to store information.
Attributes are the properties or data we collect about the entities.
Relationships provide the structure needed to draw information from multiple entities. In a database ERD they show how two entities share information in the database structure.

They are often used to illustrate the logical structure of databases. e.g.

2011 - VCAA has decided that the pink chart above is not actually an ERD: it's a data structure diagram. They have decided that an ERD looks like this

Here's anothe ERD from the same place that inspired the VCAA sample ERD... Note the underlined primary keys and indicators of cardinality (e.g. 1:1 , 1:many , many:many)

*Unless you print it in black and white, that is.

Several pictures were taken from IT@Work by Andersen, Christophersen and Timmer-Arends, pub. VCTA / MacMillan.

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Last changed: November 23, 2011 12:19 PM

VCE IT Lecture notes (c) Mark Kelly, McKinnon Secondary College

Analysis and Design Documentation Tools

Categories of Design Tools: logical and physical

Logical design tools for PSM analysis