Performing data modeling with ERD

1. Study the following extract from a website which describe the instructions of performing an online purchase.

   Instructions Add items to your shopping cart. When finished, click on Check Out. Fill in customer information. Click 'OK' to verify the payment being made. You can optionally print out the receipt.

2. We are going to model the data involved in the online purchase process as described above. Start Business Process Visual ARCHITECT.
3. Create a new project by selecting File > New Project from the main menu. Name the project as Online Purchase and click Create Blank Project to continue.
   
4. Create an entity relationship diagram by right clicking on Entity Relationships Diagram in Diagram Navigator and selecting New Entity Relationship Diagram from the popup menu.
   
   On the top right of diagram, select Conceptual Model and click on the diagram background to confirm the selection.
   
5. We use ERD to help visualize the entities of a business process, which are the data required/provided by a process, the participants that act upon the data, their structure as well as inter-relationship. By study the instruction of online purchase, we can collect the following items as entities.

   Item

   Shopping Cart

   Customer Information

   Payment

   Receipt

   
   As you can see entities are usually noun-phrase.
6. Now, draw the entities on diagram. Select Entity from the diagram toolbar. Click on the diagram to create an entity and name it as Item.
   
7. Repeat the previous step to create the other entities as listed above.
   
8. There are properties in each entity. We call them columns. For example, Customer Information has columns like name, postal address, telephone number. Now, create columns in entity Item. Right click on Item and select New Column from the popup menu. Name it as product name.
   
9. Press Enter to create another column. Name it as quantity. Press Enter to confirm and press Esc to exit from creating columns.
   
10. Repeat the previous steps to add columns to other entities.

    Entity	Columns
    Shopping Cart	N/A
    Customer Information	name, postal address, telephone number
    Payment	id, date, total price
    Receipt	id, date

    
    So you obtain a diagram like this:
    
11. As said before, ERD not only visualize the entities, but also how that relate with each other. Take the online purchase process as example, entity Shopping Cart is related with Item as 'shopping cart contains the items to be paid'.
    Now, draw the relationships between entities. Move the mouse pointer to Shopping Cart. Select and press on the resource icon One-To-Many-Relationship -> Entity. Drag to entity Item and release the mouse button.
    
12. Similarly, add relationships between other entities through the use of resource-centric interface.

    From	To	Relationship	Description
    Payment	Item	one-to-many	A payment contains a number of items to be paid
    Payment	Customer Information	one-to-one	A payment is paid by a customer
    Receipt	Payment	one-to-one	A receipt prints the payment information

    
    Tidy up the diagram a little bit. You should obtain a diagram like this:
    
    This is the end of the tutorial.

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