Schema changes and inheritance
The graph server provides an in-memory model of entity data, as well as fast ancestor traversal and content retrieval. It contains:
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An Elasticsearch graph worker, which creates denormalized search service documents that activate after any change to the entity data model.
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A business audit graph worker, which creates audit entries from any event in the system, including those not affecting the entity data model.
The following sections explain the different schema change types in Sitecore Content Hub, and the inheritance model. Changes to entity items, entity definitions, validation rules, or rules that represent the entity model impact the graph server and how it behaves.
Changing entity definitions also changes the structure of the data. Be careful when changing existing entity definitions. You can only delete an entity definition when there are no relations or taxonomies linked to the definition itself. All entities created under the entity definition you are deleting are lost.
Schema change types
|
Change type |
Description |
Includes |
|---|---|---|
|
Content |
Changes to entity definitions that can be directly represented by the entity model, such as alteration of relation flags, inheritance, new or removed members, and so on. |
Changes that: Affect descendants. This applies to most changes, because of numerous relations between entities. Do not affect descendants. For example, the addition of a property that is not included in full-text content, or the addition of a relation that does not provide any inheritance. |
|
Validation |
Changes to the rules that are enforced on the entity definition. |
Changes to: Entity definition member mandatory flags. Mandatory member conditions. Mandatory validation cultures. Regular expressions or validation expressions of the property definition. Mandatory rules and conditions of a parent or a child. |
|
Representation |
Changes to rules representing the entity model using external APIs, for example, the REST API. These rules are not essential to the existing entity model. |
Changes to the list of nested properties and to the following flags: allow updates allow navigation is nested nested permissions is rendition relation |
|
Entity |
Changes to entity items. |
Changes to the: Value of system properties, for example, the modified on or is locked flag. Value of properties. Linked entities via the relations in the form of a difference set. Entity relation properties, for example, the inherit security flag. |
Inheritance and dependency
The Content Hub data model can be represented as a directed graph, which allows multiple forms of inheritance:
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Taxonomy inheritance - the entity has a taxonomy hierarchy attached to it and can be searched for using this taxonomy as a facet.
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Path inheritance - the full path is available on path-enabled entities.
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Topology inheritance - the entity inherits directly from its parents.
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Content inheritance - the entity inherits the full-text content of its ancestors.
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Completion inheritance - the entity inherits all content from the parent and ancestor entities.
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Security inheritance - the entity inherits security settings from its ancestors, determining access to that entity.
We recommend that you turn off the Inherits security switch to improve performance when there are more than two levels of inheritance. You can find this switch in the Technical group on the entity detail page.
This model creates various change configurations, including:
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Entity content changed - a change requiring an update of the entity and any descendants that inherit from the entity.
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Entity locked - a change requiring an update of the relations for the entity.
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Entity removed from the system - a change requiring an update to descendants connected through relations and inheritance.
Any change to the entity or the relation information, which is visible to the entity or to a descendant of the entity by inheritance, needs to be propagated so that none of the related entities in the system contain outdated information.
The concept of inheritance creates a natural order in the entities – for example, ancestors, parents, children, descendants – and in the entity definitions. For example, there is a flow of data from asset definition entities to file definition entities, but not the other way around.
This concept represents dependencies of several objects towards one another. Entities and entity definitions with few dependencies are called high-hierarchy, whereas those with many dependencies are called low-hierarchy.