1. Conceptual Data Model

Create a new model in Logical mode

In the New Model dialog:

• Model Type: Logical (we'll switch back and forth later)
• Database: leave empty for now (we'll set it in the Physical lesson)
• Notation: IE (Information Engineering) — the default, used by most enterprises

Click OK. You'll see a blank canvas.

Place your first entity

In the toolbox, click the Entity icon (looks like a rounded rectangle). Then click anywhere on the canvas to drop one. A new entity called "E/1" appears.

Press F2 (or just type) and rename it to Customer. Click anywhere to deselect.

Place the rest of the entities

Repeat for the other four entities: Order, Product, Category, Address. Position them on the canvas so they're not overlapping.

Don't worry about layout aesthetics — ERWIN has auto-layout (Diagram → Layout → Auto Layout) that you can run later.

At this point your canvas should look something like:

Add your first relationship

In the toolbox, click the Identifying Relationship icon (solid line) — this represents a strong dependency. (We'll discuss non-identifying soon.)

Then:

• Click on Customer (the parent — the "one" side)
• Then click on Order (the child — the "many" side)

A line appears connecting them, with a dot on the Order side. The dot represents "many" — so this reads as "one Customer places many Orders."

Set cardinality on the relationship

Right-click the relationship line and choose Relationship Properties (or double-click it).

You'll see a dialog with options for Cardinality:

• One or many (default) — parent has zero or many children. Most common.
• One or zero — parent has zero or exactly one child (1:1 optional)
• Exactly one — parent has exactly one child (1:1 mandatory — rare)
• Many (P) — parent has one or many (NOT zero) children

For Customer → Order, "One or many" is correct: a customer can have zero orders (just signed up) or many.

Also set the Verb Phrase — this is the human-readable description of the relationship. From Customer's side, type "places". From Order's side, type "is placed by".

Identifying vs Non-identifying relationships

ERWIN has two styles for parent-child relationships:

For Customer → Order, use a non-identifying relationship (dashed line). An Order has its own OrderID and could conceptually exist without being tied to a specific Customer (e.g., guest checkouts).

To convert: right-click the line → Relationship Properties → Type → Non-identifying.

Add the remaining relationships

Add these one by one (non-identifying for all):

• Customer → Address ("has" / "belongs to") — one customer, many addresses
• Order → Address ("ships to" / "is shipping address for") — one order, one address
• Category → Product ("contains" / "belongs to") — one category, many products

Handle the many-to-many: Order ↔ Product

An order can contain many products, and a product can appear in many orders. This is a many-to-many (M:N) relationship.

In the toolbox, click the Many-to-Many relationship icon, then click Order, then Product. You'll see a line with a dot at both ends.

Right now this is allowed in the CDM. But when we move to logical/physical, ERWIN will force us to resolve it by inserting a bridge entity (we'll call it OrderLine).

Document the entities

Even though a CDM has no attributes, you can still document what each entity means — and you absolutely should.

Double-click any entity (e.g., Customer). In the Property Editor:

• Click the Definition tab
• Type a clear description: "A person or business that has placed an order or has a registered account. Includes prospects who registered but haven't yet placed an order."
• Click OK

This definition will travel with the model into Logical and Physical, and gets included when you generate documentation. It's how you settle "what counts as a Customer" debates years from now.

Auto-layout and save

Run auto-layout to clean up the diagram:

Save your model:

Take a screenshot or export as image — you've completed your first Conceptual Data Model.