The theory looks very promising. Separations of tags and roles and the ability to decide who can grant what looks very flexible (at least if I compare it to som

The theory looks very promising. Separations of tags and roles and the ability to decide who can grant what looks very flexible (at least if I compare it to some systems that I worked on). But I think that there is one implmentation detail that will make or break system with such powerfull security model. And it is the performance cost. Has anybody seen any real implementations of this model that are applied on the lowest possible level and still meets performance requirements for whole system? I'm asking because I have seen few simpler ACL system, which when applied to Full Text Search Systems with power users enabled to define and modify security schemas, brought the system to its knees. I think the problem is that reading search results from any kind of search engine with dynamic read (entry visibility) rules applied on top seems like very hard problem to solve in performant way (while preserving theoretical flexibility).