If its what I think it is it is describing the links between you tables eg
1 – many
0 – many
many – many
You need to read a database design book for more details
————– kccrosser ——-
The values seem to be a mixture of regular expression terms and fragments of UML cardinality relationships:
1* and 0* are usually used in regular expressions:
1* usually means the thing associated occurs “1 or more times”
0* usually means the thing associated occurs “0 or more times”
The other items are UML cardinality expressions, and these are left-right order dependent:
1..1 usually means that when the item on the left exists, there must be exactly one item on the right to which it is linked, and vice versa.
1..* usually means that when the item on the left exists, there MAY be one or more items on the right to which it is linked. Items on the right are linked to exactly one item on the left.
0..* usually means that the relationship is many-to-many in both directions AND optional – i.e., if an item on the left exists, it MAY have 0 or more links to items on the right, and vice versa.
There are lots of variations on the above, for example (these examples may not be very useful for anything other than illustrating possible cardinalities):
1..3* – anything on the left must be linked to at least three things on the right, but the things on the right must each be linked to exactly one item on the left.
Consider an Accounts Receivable database with tables for Customers, Invoices, Items. Relationships might be represented as:
Invoices 0..1* Items (If an Invoice exists, it must include at least one item, but items may associate to 0 or more invoices)
Customers 1..* Invoices (If a Customer exists, it MAY associate with 0 or more Invoices, but any Invoice MUST associate to exactly one customer)