`<onetoone>`

The <onetoone> element defines a single-valued association to another entity that has a one-to-one cardinality. Guidewire defines this element in the data model metadata files as the <onetoone> XML subelement. A one-to-one element functions in a similar manner to a foreign key in that it makes a reference to another entity. However, its purpose is to provide a reverse pointer to an entity or object that is pointing at the <onetoone> entity, through the use of a foreign key.

For example, entity A has a foreign key to entity B. You can associate an instance of B with at most one instance of A. Perhaps, there is a unique index on the foreign key column. This then defines a one-to-one relationship between A and B. You can then declare the <onetoone> element on B, to provide simple access to the associated A. In essence, using a one-to-one element creates an array-of-one, with, at most, one element. Zero elements are also possible.

Note: PolicyCenter labels one-to-one elements in the Guidewire Data Dictionary as foreign keys. You access these elements in Gosu code in the same manner as you access foreign keys.

Attributes of `<onetoone>`

The <onetoone> element contains the following attributes.

`<onetoone>` attribute	Description	Default
`cascadeDelete`	If `true`, then PolicyCenter deletes the entity to which the `<onetoone>` element points if you delete this entity.	`false`
`deprecated`	If `true`, then PolicyCenter marks the item as deprecated in the Data Dictionary and places a `Deprecated` annotation on it in the Guidewire Studio API Reference. If you deprecate an item, use the description to explain why. For more information, see Data entity subelements.	`false`
`desc`	A description of the purpose and use of the field.	None
`exportable`	Unused.
`fkentity`	Required. The entity to which this foreign key points.	None
`getterScriptability`	See Data objects and scriptability for information.	`all`
`ignoreForEvents`	This attribute has complex, non-intuitive interactions with data entity relationships. See Interactions of ignoreForEvents attribute with data entity relationships for information on how to use and configure it. Important: Do not confuse the definition of the ignoreForEvents attribute for the <onetoone> element with the definition of the attribute of the same namesake in <entity> and <array> elements. Although they share the same name, the two ignoreForEvents attributes are near opposites in effect.	`false`
`linkField`	Optional. Specifies the foreign key field that points back to this object.	None
`name`	Required. Specifies the name property on the entity.	None
`nullok`	Whether the field can contain `null` values.	`true`
`owner`	If `true`, this entity owns the linked object (the object to which the `<onetoone>` element points): If you delete the owning object, then PolicyCenter deletes the linked object as well. If you update the object pointed to by the `<onetoone>` element, then PolicyCenter considers the owning object updated as well.	`false`
`setterScriptability`	See Data objects and scriptability for information.	`all`
`triggersValidation`	Whether changes to the entity pointed to by this entity trigger validation.	`false`

Subelements of `<onetoone>`

The <onetoone> element contains the following subelements.

`<onetoone>` subelement	Description	Default
`fulldescription`	See <fulldescription>.	None
`tag`	See <tag>.	None

<onetoone>

Attributes of <onetoone>

Subelements of <onetoone>

`<onetoone>`

Attributes of `<onetoone>`

Subelements of `<onetoone>`