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1. block is received by a node
2. sumeragi clones the wsv (we'll call it wsv')
3. every transaction is validated on the wsv' (during validation every instruction is also executed on wsv')
4. if validation is successful:
4.1. original wsv is destroyed
4.2. every transaction is executed on the original wsvoriginal wsv is replaced by wsv' clone
4.3. block is applied
5. otherwise:
5.1. cloned wsv is destroyed
5.2. block is not applied
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