Element Definitions:
|
eml-constraint
|
|
Tooltip:
|
Relational integrity constraint descriptors
|
|
Summary:
|
Describes the relational integrity constraints of a relational
database.
|
|
Description:
|
Describes the relational integrity constraints of a relational
database. This includes primary keys, foreign keys, unique keys, etc.
|
|
Example:
|
|
|
identifier
|
|
Tooltip:
|
Unique identifier
|
|
Summary:
|
The unique identifier of this metadata file or object.
|
|
Description:
|
The identifier field provides a unique identifier for this
metadata documentation. It will most likely be part of a
sequence of numbers or letters that are meaningful in a
larger context, such as a metadata catalog. That larger
system can be identified in the "system" attribute. Multiple
identifiers can be listed corresponding to different catalog
systems.
|
|
Example:
|
<identifier system="metacat">nceas.3.2</identifier>
|
|
constraint
|
|
Tooltip:
|
Integrity constraint
|
|
Summary:
|
Information about the integrity constraint being defined.
|
|
Description:
|
Complete information needed to reconstruct this integrity
constraint for enforcement in a system such as a relational
database management system.
|
|
Example:
|
|
|
constraintType
|
|
Tooltip:
|
type of constraint
|
|
Summary:
|
the type of constraint being defined
|
|
Description:
|
the type of constraint being defined. This is
what kind of constraint this is.
|
|
Example:
|
PrimaryKey, ForeignKey, UniqueKey
|
|
constraintName
|
|
Tooltip:
|
constraint name
|
|
Summary:
|
name of the field that this constraint is tied to
|
|
Description:
|
name of the field that this constraint is tied to. This
could also be the name of an independent constraint such
as a trigger or an autonumber generator.
|
|
Example:
|
LocationID, TABLE1_NUMBER_GEN1
|
|
constraintDescription
|
|
Tooltip:
|
constraint description
|
|
Summary:
|
description of the constraint
|
|
Description:
|
description of the constraint. Any additional
information that may be needed to fully understand
the constraint.
|
|
Example:
|
|
|
entityId
|
|
Tooltip:
|
table to which this constraint is tied
|
|
Summary:
|
table to which this constraint is tied
|
|
Description:
|
table to which this constraint is tied. In the instance
of a key, it is the name of the table in which it is
defined.
|
|
Example:
|
site_properties
|
|
key
|
|
Tooltip:
|
Key |
|
Summary:
|
The set of attributes to which this constraint applies.
|
|
Description:
|
The set of attributes to which this constraint applies.
For a primary key or a unique key, the set of attributes must be
identifying. For a foreign key, the set of attributes must match
an identifying key in the referenced entity. For a not null
constraint, the key indicates the attribute which should not
be null.
|
|
Example:
|
|
|
referencedEntityId
|
|
Tooltip:
|
Referenced Entity ID |
|
Summary:
|
The id of the parent-entity in a foreign key constraint.
|
|
Description:
|
This field contains the id of the entity to which a foreign key
refers, otherwise known as the parent-entity or parent-table.
|
|
Example:
|
site_properties
|
|
referencedKey
|
|
Tooltip:
|
Key |
|
Summary:
|
The set of attributes to which a foreign key constraint refers.
|
|
Description:
|
The set of attributes to which a foreign key constraint refers.
If the key refers to the primary key in the referenced entity,
then the "referencedKey" is optional. For a foreign key, the
set of attributes must match an identifying key in the
referenced entity.
|
|
Example:
|
|
|
cardinality
|
|
Tooltip:
|
Constrint Cardinality |
|
Summary:
|
The cardinality of a foreign key constraint. |
|
Description:
|
Indicates the cardinality (zero, one, many) of a foreign key constraint.
|
|
Example:
|
|
|
checkCondition
|
|
Tooltip:
|
Check Condition |
|
Summary:
|
An SQL statement to be used as the condition for a check constraint.
|
|
Description:
|
A SQL statement to be used as the condition for a check constraint.
Generally this provides a means for constraining the values within
and among entities.
|
|
Example:
|
(year > 1900 and year < 1990) |
|
Attribute Definitions:
|
system
|
|
Tooltip:
|
Catalog system
|
|
Summary:
|
The catalog system in which this identifier is used.
|
|
Description:
|
This element gives the name of the catalog system in which
this identifier is used. It is useful to determine the
scope of the identifier, and to determine the semantics
of the various subparts of the identifier. Unresolved issue:
can or should this be a URI/URL pointing to the catalog
system, or just the name?
|
|
Example:
|
<identifier system="metacat">nceas.3.2</identifier> |
|