| Name | Meta_Link |
|---|---|
| Entity Type | External |
| Description | Relationships are defined via the Meta_Link table. |
| Submodel | Meta |
| Entity Scope | Meta |
| Primary Key | Entity , Link |
| Natural Key | Entity , Link |
| Generalizations | |
| Specializations |
| Name | Value Domain | Property / Storage Unit | Description | Required / Default | Type |
|---|---|---|---|---|---|
| Attribute_Nr |
|
Physical definition order of entitys attributes, links and inverses. Automatically populated by the meta-system.Not currently exploited. | No |
NUMBER(3) | |
| Composite |
|
Private system property that records whether the link is a simple relationship (single attribute) or a composite relationship with multi-part keys. 0 = simple, 1 = composite (default = 0) | No 0 |
NUMBER(2) | |
| Description |
|
Long description of Relationship. Primary purpose is for documentation in Web Report. | No |
VARCHAR2(2000) | |
| Distance |
|
Private system property that records depth in IsA hierarchy in order to manage specialization of relationships. It is computed by the system. | No |
NUMBER(1) | |
| Entity | Meta_Entity |
|
Foreign Key to Meta_Entity | Yes |
VARCHAR2(25) |
| Entity_Domain |
|
This specifies the type of Entity that is referenced. Foreign Key to Meta_Entity. | No |
VARCHAR2(25) | |
| Implementation_Technique |
|
Specifies how the relationship is implemented. Enumeration Values: Cascade (Child): Classical relational technique that deletes Child entry when Parent entry is deleted. Nullify (Child): Classical relational technique that nullifies reference in Child entry when Parent entry is deleted. Restrict (Parent): Classical relational technique that prevents Control (Parent): Parent cannot be deleted directly. Deletion of Child entry triggers deletion of Parent entry. Assoc: The relationship is implemented via private association table. The cardinality can be more than one. Composition: A special case of Cascade in which the Child is defined to be an extension table of the Parent. Link default value is Restrict. Delete semantics for Cascade, Restrict, and Nullify are implemented by referential integrity services in the database. Delete semantics for Control, Assoc are implemented via triggers. | No |
VARCHAR2(32) | |
| Join_Rule |
|
This property is being phased out. The new technique is to specify Implementation_Technique = Composition and to specify Max_Child to distinguish 1-1 and 1-MANY relationship. This is the only way to specify the assembly of an object. Enumeration Values: ONE: link is a one to one relationship from extension table to a base table. MANY: link is a many to one relationship from extension table to a base table. A value of ONE or MANY causes current entity to be an extension table of the referenced base entity. | No |
VARCHAR2(10) | |
| Link |
|
Name of relationship property. Actual implementation for Link to Entity XYZ is XYZ_Id. Abstract relationships require XYZ_Type. | Yes |
VARCHAR2(30) | |
| Mandatory |
|
Is this property mandatory? That is, must this child have a parent of the given type? 1 => TRUE and 0 => FALSE. This property will grow up to be Min_Parent. Except for Assoc relationship type, this value must be 0 or 1. Currently values greater than 1 will be squashed to 1. | No |
NUMBER(1) | |
| Max_Child |
|
Max_Child specifies the maximum number of children that the parent type can have. Value of 1 implies a one-one relationship. All other values imply a one-many relationship. Default value of -1 stands for MANY (sigh). This cardinality is not enforced by Seabed system. | No |
NUMBER(4) | |
| Max_Parent |
|
This specifies the maximum number of parent instances to which this link refers. Except for Assoc relationship type, this value must be 1. Value of -1 stands for MANY (sigh). Default value is 1 except for Assoc in which case the default is -1. This cardinality is not enforced by Seabed system. | No |
NUMBER(4) | |
| Min_Child |
|
The Link describes the relationship from a child to a parent type. Min_Child specifies the minimum number of children that the parent type can have. Value of 0 implies parent optionally has children. All other values imply parent must have children. Default value is 0. This cardinality is not enforced by Seabed system. | No |
NUMBER(4) |
| Link | To Entity | Description | Implementation Technique | Required |
|---|---|---|---|---|
| Entity | Meta_Entity | Foreign Key to Meta_Entity | Restrict | Yes |