Notation
In the following chapters, tables with the description of attributes can be found. Attributes can be marked in the following way:
| Marker | Denotation | Description |
|---|---|---|
| + | Key information | A key is the unique identification of one instance of an entity. Use key information that is familiar to the user. Some entities have so called “composite keys” (aka “compound keys”), which means that every single key field is just a part of the complete key information of the entity. In this case more than one field is marked by the + sign. This kind of key information must not be omitted. |
| (+) | Alternate key | There is more than one key field and only one of the fields can contain the key information. All other alternate key fields of the same instance are left blank. |
| * | Mandatory | This attribute cannot be left blank or omitted. |