Revocation in Idemix and U-prove

Question

I read some materials about MS u-prove and IBM Idemix.

But according to these materials, the opinion about revocation is different.

Some materials say that u-prove and idemix do not provide revocation, but others say that they provide.

I tried to read technical papers about both but it was too hard to read.

Am I correct in understanding that only a user (not issuer or IdP) of both schemes can revoke it voluntarily?

Can anyone explain about specific details of revocation in u-prove and idemix?

Thanks

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U-prove: https://www.microsoft.com/en-us/research/project/u-prove/

Idemix: http://www.research.ibm.com/labs/zurich/idemix/