Logical System Design

• Computing
• Further Education (Key Stage 5)

Logical System Design

Unit 11: System Analysis and Design

Objectives for this week

1. Identify the key components of a system

2. Analyse the input and output requirements

3. Develop a process flow diagram

4. Create a logical data model

5. Map the data flow between different components of the system.

Unified Modelling Language (UML)

UML produces a series of diagrams to represent a system.

Each type of diagram shows a different aspect of the system model and has its own purpose.

Logical system design

What is a logical design and why is it necessary in system design?

Logical system design

• A logical design looks at how a system is structured; for example, its entities and the relationships between those entities.
• It can identify inputs, outputs and processes

Logical system design

• Logical design does not require the platform (Operating system) to be identified.
• When analysing and producing the inputs, outputs, entities etc. It does not matter what platform the system is to be produced on.
• The actions will be the same; the platform only affects the physical design and how the system will actually be built.

Logical Design - Inputs

• The inputs to the system need to be identified and listed.

• When identifying the inputs, the type of data and any validation rules that are needed can also be listed.
• The logical design of the inputs does not identify how these are input, or what the method of input looks like, it is only concerned with what is being input.

Logical Design - Outputs

• The outputs of the system also need identified, as well as their format and contents.
• In the logical stage, the actual layout and appearance is not considered, as with the inputs.
• For example the wages system scenario, the output is the payslip.

Logical Design - Data

• Any data to be stored within, or by, the system needs to be identified.
• For example, in the wages system scenario, the tables within the database could be identified as Staff, PayRecord.
• Then the data in each of these could be listed to identify the data and data type using a tabular format.

Task

• In your groups using the flipchart pages and markers provided, create a logical design poster for the scenario assigned to your group. (15 minutes)
• Identify the key components of the system including input and output requirements.
• Designate 1 person from your group to present the poster to the class. (10 minutes)

What three key concepts did you learn today about logical design?

Logical Design - Summary

Logical design is the process of creating a conceptual model of a system, which defines its overall structure, behaviour and functionality.

Overall, the goal of logical system design is to create a clear, concise and comprehensive representation of the system that can be used as a blueprint for its implementation.

Lesson - objectives review

1. Identify the key components of a system

2. Analyse the input and output requirements

3. Develop a process flow diagram

4. Create a logical data model

5. Map the data flow between different components of the system.