>I don't know what you mean by the "domain of valid blocks". Blocks are considered valid by a consensus set if they have certain attributes. Consider each att

>I don't know what you mean by the "domain of valid blocks". Blocks are considered valid by a consensus set if they have certain attributes. Consider each attribute an axis in a multi-dimensional space. One axis for the block size [1], one for the type of PoW function it has[2], one for the sign of the R S values used in an ECDSA function[3], another for the required difficulty[4] For example, Bitcoin went through a soft fork when the domain of valid blocks was reduced in BIP66 to decrease the number of domains DER signatures could exist in [3]. Bcash /increased/ the domains in which blocks would be considered valid in their chain by changing the difficulty-retargeting algorithm used in Bitcoin[4], 8X'ing the blocksize [1]. As a result, if you turn on a bitcoin node running ~0.6-.7 it won't sync to the bcash chain but will sync to the bitcoin chain (with implementations such as Bitcoin Knots, bcoin, Bitcoin Core) because bcash is a hard fork of bitcoin.