From the [yellow paper][1]; for a block to be accepted as valid, an 8 byte number, n_rand, must be found that satisfies equation 253:

> [![`PoW`(H_<strike>n</strike>,n_rand,**d**)\[1\] _< 2^256/H_d][2]][2]   

[![H_<strike>n</strike>][3]][3] = block header without n_rand and MixHash  
[![H_d][4]][4] = difficulty          
[![n_rand][5]][5] = nonce


My interpretation is that **d** is the dataset - a value cryptographically derived from the number of previous blocks. From this, the Mixhash is calculated in the `PoW` function

**Why are the dataset and MixHash values required?**

If the network were to agree to accept the `PoW` function with **d** set to 0, wouldn't the system still be cryptographically dependent on valid state transistions, as there must be consensus on H_<strike>n</strike>? Would the system not, therefore, still work?


  [1]: https://github.com/ethereum/yellowpaper
  [2]: https://i.sstatic.net/eEmRc.png
  [3]: https://i.sstatic.net/xYcY6.png
  [4]: https://i.sstatic.net/ebfu5.png
  [5]: https://i.sstatic.net/MN2V3.png