We should provide a way to filter the index using a regular expression. For example, only index nodes that contain a reference to another node. (Not a JCR reference, but a reference within the value itself). For example, index a node if one of the properties contains:
- <html...> <a href="/content/abc">
- and so on
This will allow to run a query to find if /content/abc is referenced. The index and the query will probably need to use a tag, and the cost of the index needs to be high. Otherwise the query engine can't know when this index should be used.