Content Architecture

CAUTION

AEM 6.4 has reached the end of extended support and this documentation is no longer updated. For further details, see our technical support periods. Find the supported versions here.

Follow David’s Model

David’s Model was written by David Nuescheler years ago, but the ideas hold true today. The main tenets of David’s Model are as follows:

Data comes first, structure later. Maybe.
Drive the content hierarchy, don’t let it happen.
Workspaces are for clone(), merge(), and update().
Beware of same name siblings.
References are considered harmful.
Files are files are files.
IDs are evil.

David’s Model can be found on the Jackrabbit wiki at https://wiki.apache.org/jackrabbit/DavidsModel.

Everything is content

Everything should be stored in the repository rather than relying on separate third party data sources such as databases. This applies to authored content, binary data like images, code, configurations, etc. This allows us to use one set of APIs to manage all content and to manage the promotion of this content through replication. We also gain a single source of backup, logging, etc.

Use the “content model first” design principle

When building a new feature, always start by designing the JCR content structure first, and then look into reading and writing your content using the default Sling servlets. This will allow you to ensure that your implementation works well with out of the box access control mechanisms and allow you to avoid generating unnecessary CRUD-style servlets.

Be RESTful

Servlets should be defined based on resourceTypes instead of paths. This makes it possible to use JCR access controls, adhere to REST principles, and use the resource and resource resolver that are provided to us in the request. This also allows us to change the scripts that render URLs on the server side without needing to change any URLs from the client side, while hiding server-side implementation details from the client for added security.

Avoid defining new node types

Node types work at a low level in the infrastructure layer and most requirements can be met by using a sling:resourceType assigned to an nt:unstructured, oak:Unstructured, sling:Folder or cq:Page node type. Node types equate to schema in the repository and changing node types can be very expensive down the road.

Adhere to naming conventions in the JCR

Adhering to naming conventions will add consistency to your code base, lowering the incidence rate of defects and increasing the velocity of developers working in the system. The following conventions are used by Adobe in developing AEM: