Unified Modeling Language (UML)

Most UML diagram types can also be represented using plain ASCII text.

Class diagram in plain text

+----------------------------+
|          Order             |
+----------------------------+
| - orderId: int             |
| - date: Date               |
+----------------------------+
| + calculateTotal(): float  |
+----------------------------+
              |
              |
              v
+----------------------------+
|         Customer           |
+----------------------------+
| - customerId: int          |
| - name: String             |
+----------------------------+
| + getContactInfo(): String |
+----------------------------+