CORE 1:PROJECTMANAGEMENTDesigning

This stage is where the actual solution is designed and built.

This includes describing information processes and specifying system resources (participants, data/info, IT) to perform these processes.

DESIGNING

DESIGNING

System Tools for understanding, Explaining and documenting the operation of a system

Information processes are the link between a systems resources which will operate the new system. Describing the detail of these processes is critical and as such we use a number of detailed models to do so. The following ‘design’ tools are typically used…

• Context Diagrams• Data Dictionaries • Data Flow Diagrams• Decision Tree’s and Decision Tables• Storyboards

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In small groups (2-3) read one of the following

• Context Diagrams (p65-66)• Data Dictionaries (p66-67)• Data Flow Diagrams (p68-70)• Decision Tree’s and Decision Tables (p71-

72)• Storyboards (p73-74)

Create a single A4 summary poster that provides the following:

• Clear Heading “Design Tools: ___________”• Definition• Example • Key Terms

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Context Diagram

Context Diagrams represent the entire system as a single process. They don’t attempt to describe IP’s rather they identify:

• Data Entering the system• Information Leaving the system• Sources• Destination (sink)

The sources and sinks are called “external entities”. Context diagrams are really top level data flow diagrams and are often referred to as level 0 data flow diagrams.

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Context Diagram

Squares are used to represent each of the external entities. Commonly users, other organizations or systems. These entities are not part of the system and do not perform any information processes.

The entire system is represented using a circle. The system collects or receives data from each source entity and displays or transmits information to each sink entity.

Labeled data flow arrows describe the data and its direction of flow between the system and its entities.

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Example Context Diagram from the text.

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Context Diagram

Think about a student using a swipe on card to record attendance at school in the morning. What might the context diagram look like?

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Student

Sign in Proces

s

Student barcode

Collected

Sign in confirmation

Displayed

Student

Data Dictionaries

Data dictionaries are used to detail each of the data items used by the system. They are made up of tables, where each row describes particular item, and eachcolumn describes a detail or attribute of the item. The name or identificationof the item has to be included, along with the data type, storage size, description, etc.Data dictionaries are most commonly associated with Databases, documenting details of each field, but we can use them as a design tool to specify details for each data item in a system.

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DESIGNING

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Data Flow Diagrams

The aim of a DFD is to represent a system by describing the changes in data as it passes through processes. This is done in an illustrative fashion.

An example is a computer that is summing a series of numbers. Rather than explain the step-by-step process of how they are summed, a DFD would focus on where the numbers came from and where their output lies.

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Data Flow Diagrams

As well as the symbols used in a context diagram (level 0 data flow diagram) we also represent data stores as open sided rectangles.

A data store is where data is maintained prior to and after

is has been processed.

Additionally circles now represent processes rather than the entire system.

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Entity

Process

Data Movement

Data Store

Data Flow Diagrams

We have already said that a context diagram is a level 0 DF diagram, representing the complete system as a single process.

A level 1 DF diagram expands this single process into multiple processes.

A series of level 2 DF diagrams are drawn to expand each level 1 process into further processes.

Level 3 DFD’s similarly expand each level 2 process and so on.

This process is called “top-down design”.

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Data Flow DiagramsDESIGNING

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Decision Tables

Decision tables are tools for documenting the logic upon which decisions are made; they describe a strict set of rules where each rule leads to a particular decision alternative or action.  Each rule is composed of one or more conditions that must be satisfied for the rule to be true.

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Decision Tables

For example, if you are an Australian citizen and you 18 years or older then you can vote. This rule contains two conditions namely; “Australian citizen” and “18 years or older” and the single action “can vote”.  In this rule both conditions must be true for the action to take place. We could produce further rules for when either or both conditions are false, which would result in the action “can NOT vote”.

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Decision Trees

A decision tree is a decision support tool that uses a tree-like graph or model of decisions and their possible consequences, including outcomes, resource costs and utility. Used in operations research specifically decision analysis to identify a strategy most likely to reach a goal. They describe a strict set of rules where each rule leads to a particular decision alternative or action.

With a decision tree each condition is split into two parts, the first being a variable written above the tree and the second being the value (or range of values) for that variable within the tree.

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Decision Tree vs. Decision Table

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For the above example of data which do you think would be the best tool for describing this decision situation? Tree or Table?

Create the model using either a decision table or a decision tree…

Storyboard

A storyboard is a part of graphic organisers that shows the layout of each step or stage in a document or project. They are often hand drawn sketches or diagrams and have notes and ideas on the side. They are used in many types of ways such as in comics, film, theatre, business, novels and interactive media. They benefit in allowing easy changes to the project and helps with visual thinking and brainstorming bigger and better ideas. Storyboards can be created using either dedicated software or pencil and paper.

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StoryboardDESIGNING

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Designing the Information Technology

Having used design tools to model the systems treatment of data into information it is now important to choose the Information Technology that will be involved. The ability of a system’s hardware and software to perform information processing is crucial and so the following should be considered.

• Are spare parts available for hardware now and into the future?

• Is the software user friendly?• Is the software human centered or machine

centered?• Can it be customized to meet new

requirements?• Is it maintainable and upgradeable?

DESIGNING