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A Tool to use when ER Modeling using Crows Feet Notation

November 25, 2012

Hi all,

We have been looking at Crows Feet Notation in my Advanced Database Systems module. I think that Crows Feet notation is a great notation to use as it uses minimal room and is easy to read. Its array of participation and cardinality symbols provide clear and understandable notation to understand what the diagram is modelling.

Notation for a Mandatory One Relationship

Notation for a Mandatory One RelationshipNotation for a Optional One RelationshipNotation for a Optional One RelationshipNotation for a Mandatory Many RelationshipNotation for a Mandatory Many RelationshipNotation for a Optional Many RelationshipNotation for a Optional Many Relationship

In the diagram these will be double ended to show the relationship between two entities like shown in the example below.

Simple Diagram

Simple Diagram showing the relationship between Student & Result and Module & Result

The tool I use for ER Modelling using Crows Feet Notation is Dia. Dia is a german diagramming tool that supports all sorts of diagrams including cisco networks, flowcharts, chemical engineering , and electical. The applicaton started off its life in the linux enviroment as a gnome project. It has seen been ported into a windows version which is available at http://dia-installer.de/ . Dia also supports UML and Database diagramming. A basic ER diagram does not show attributes, it only show the relations between the entities. Below I show how to create the diagram above using Dia. First select the UML sheet from dropdown list that shows Assorted by default. Then select the first icon which contains a 3 tier box with xxx in the top line.

Dia UML Toolbox with Class Selected (blue background)

Click on the diagram space to the right to create a blank class. By default the class will have space for attributes and operations. To hide these right click on the object and select properties. Untick ‘Attributes visible’ and ‘Operations Visible’ and press OK.

Dia Class Properties Dialog Box (You also use this properties box to edit the entity name)

Right click the class and press copy, then paste into white area of the diagram. Repeat this action once more. Then rename using the properties dialog to create a the three classes Student, Module and Result.

Now use the generic line tool from the top toolbox (two green dots with a connecting black line) and draw a line from Student to Result. Right click the line created and select properties. You can use this dialog to set the symbols at each end. Set the start arrow to two straight lines and the end arrow to one straight line and three outreaching lines. To achieve this use the more arrows menu from the dropdown. I usally also alter the size to 0.9 * 0.7. You will need to unlink the two first by pressing the little chain icon. You should have the following in the properties window.

Completed relationship properties window

You now have a relationship between the two entities. Now create the second entity between result and module on your own.

Look out for my next post on how to show generalization when modelling using Crows Feet Notation.

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