SQL99 features for security

Hi,

I am a graduate student working on my course paper. I had read Jim Melton's paper "SQL: 1999, formerly known as SQL3". It is said SQL99 enhanced security, probably introduced the "role" model. I would like to know some detail about it, including:

• user level, what syntax or keyword provided
• implement level, what is the difficult part, is there any trade-offs?
• design level, the role model SQL99,
• Adding role model has what impact to other part of DBMS design?

I had searched the DBLP(ACM) and goole.com, but got a lot of unrelated reference. :-((

Would you give me some references or links or people I can refer to?

Thanks,
Rena

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