* Reading*:

- Greetings and felicitations!
- Expressive power
- HRU vs. SPM
- Multiparent joint creates in HRU
- Adding multiparent joint creates to SPM (giving ESPM)
- Simulation of multiparent joint creates by 2-parent joint creates
- Monotonic ESPM, monotonic HRU equivalent
- Safety question in ESPM decidable if acyclic attenuating scheme

- Comparing Expressive Power of Models
- Graph representation
- Go through 3-parent joint create as simulated by 2-parent joint create
- Correspondence between two schemes in terms of graph representation
- Formal definition of scheme
*A*simulating scheme*B* - Model expressive power
- Result: monotonic 1-parent models less expressive than monotonic multiparent models (so ESPM more expressive than SPM)

- Typed Access Matrix Model
- Add notion of type for entities—set of types
*T*, set of subject types*TS*⊆*T* - New create rules: specify subject/object type
- In command, child type if something of that type created; otherwise, a parent type
- Show type graph and cycles in it
- Safety decidable for systems with acyclic MTAM schemes

- Add notion of type for entities—set of types

Version of April 10, 2006 at 9:55 PM

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