Criterion 2: State Updates Without Execution

The second core property of declarative blockchains is that they achieve state updates without execution.

This is an emergent property of using constraints:

“Constraints differ from the common primitives of imperative programming languages in that they do not specify a step or sequence of steps to execute, but rather the properties of a solution to be found.”

In declarative blockchains, state updates are specified directly within a block. These updates must then pass relevant predefined constraint checks to be considered valid. This contrasts with imperative blockchains, where transactions are included in a block and then executed to compute a new state.

Executionless State Updates

Achieving state updates without execution is a significant breakthrough in blockchain protocol design. Previously, we discussed how in-protocol execution (i.e., processing step-by-step instructions) is a limiting factor for imperative blockchains.

The “executionless” property of declarative blockchains removes the need for the most costly aspects of general-purpose blockchains—execution and the consensus needed for it—without sacrificing functionality or verifiability. This approach even makes verification of state transitions trivial, thanks to the nature of constraint-based problems: they are hard to compute but easy to verify.