How to deal with analog devices?

Hi, everyone!
        I want to ask one simple and naive
question. WHen we do signal integrity analysis
for PCB, we can assign IBIS model to the
digital devices, but how to deal with the
analog devices coexisting in the same board?
And also, how about the discrete diodes and
transistors?
Thanks in advance.

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Chen XiaoYuan
R&D Basic, CAD
HuaWei Technology Co.Ltd
Scientific Industrial Park
ShenZhen City, GuanDong 
P.R China	518057
Tel: 86-755-6633828-3310
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