Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.
Recently I came across a great article on BizTalk permissions. You know the production questions you get asked "Do I need to make them DB Owner?" to do the install??
Finally here's a matrix that Thomas Canter created,(yes a picture) that outlines permissions vs task/role.Check it out Here
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I've been working on understanding the BizTalk Security model for quite a while and I keep working my Visio diagram over and over.
For BizTalk Server 2004 simply do not use the Level 0 Security Membership column.
Please feel free to send me any feed back if this is not clear.