Object Role Modeling (ORM) uses graphics to illustrate a system and supplies the accompanying textual documentation.
ORM facts are represented for both current elements and the system's desired content.
Often facts for the conceptual model are derived from inputs, outputs, and reports used in the current system. You might have to derive facts from interviews.
As a quality check, make sure objects are well defined and appropriately split and/or combined.
Uniqueness, mandatory role, value, set-comparison, subtype, and ring constraints can play a part in any system.
When indicating the relationship between entities, you show both cardinality and optionality.
Uniqueness constraints indicate that entries occur only once and check parity/cardinality of the fact types.
Add mandatory role constraints and check for logical derivations.
Business rules are often implemented as objects in the diagram process.
Value constraints or constraints over a range of values, set-comparison constraints that examine multiple values, and subtype constraints are used to apply data rules.
A set-comparison constraint specifies a subset, an equality, or an exclusion and is applied between compatible roles or sequences of compatible roles.
Ring constraints in the system are put in place to mandate or prevent cyclical situations.
