Schema Extensions can be defined in two different ways that are breaking reuse.

## What are the schemas that are affected by the issue
The extensions/aem and extensions/ims schemas include the schema they are extending, so they are like a pre-extended (or pre-merged) schema.
## What are examples of products that are impacted by the issue
Experience Cloud.

There are two different ways to express extensions.
1. The way /extensions/adobe/experience schemas do it which use the meta:extends syntax and allows multi composition of schemas, which is very important for implementation that require expression of highly varied data.
2. The fully contained extensions like /extensions/aem or /extensions/ims which pre-include the schemas they are extending.

The latter approach limits the ability for schema processors to automate the construction of schemas with ease.

Can we avoid using the second option?