Chapter 9 Working with Data Models
The following CDM/LDM model checks are made on relationships:
| Check | Description and Correction |
|---|---|
| Relationship name and code uniqueness | Relationship names and codes must be unique in the model.
Manual correction: Modify the duplicate name/code Automatic correction: Appends a number to the duplicate name/code. |
| Reflexive dependency | A dependency means that one entity is defined through a relationship with another. A dependent relationship cannot therefore be reflexive.
Manual correction: Change or delete the reflexive dependency. Automatic correction: None. |
| Reflexive mandatory | A reflexive mandatory relationship exists.
Manual correction: Deselect the Mandatory check boxes for the relationship to be non-mandatory. Automatic correction: None. |
| Bijective relationship between two entities | There is a bijective relationship between two entities when there is a two-way one to one relationship between the entities. This is equivalent to a merge of two entities.
Manual correction: Merge the entities or modify the relationship. Automatic correction: None. |
| Name uniqueness constraint for many to many relationships and entities | A many-to-many relationship and an entity cannot have the same name or code.
Manual correction: Change the name or code of the many-to-many relationship or the name or code of the entity. If you do not, PDM generation will rename the generated table. Automatic correction: None. |
| Consistency between dominant and dependent relationships | A dependent relationship between entities cannot also be a dominant relationship.
Manual correction: Select the Dominant check box on the other (correct) side of the relationship. Automatic correction: None. |
| Relationship with child shortcut | External shortcut could be generated as child table. An entity that is at the "many" end of a one-to-many relationship or which is non-dominant should not be an external shortcut as the reference will not be generated during the generation of a PDM.
Manual correction: Change the cardinality of the relationship cardinality or the entity, which should not be an external shortcut. Automatic correction: None. |
| 'Many-many' relationships | [LDM only] 'Many-to-many' relationships are not permitted.
Manual correction: Create an intermediary entity, which contains the primary identifiers of the previous 'many-to-many' entities. Automatic correction: None. |
| Copyright (C) 2008. Sybase Inc. All rights reserved. |
| |