Demystifying JAM - Presentation

#polkadot #jam

Demystifying

blog.kianenigma.com/posts/tech/demystifying-jam/presentation/

Note:
blog.kianenigma.com/posts/tech/demystifying-jam/

Polkadot 1

Social
- OpenGov
- DOT Token → Security
- Fellowship
Technological
- Heterogeneous Execution Sharding, with Shared Security

Note:
Sharding and heterogeneity enabled by the use of WASM.

Heterogeneous Execution Sharding, with Shared Security

Let's break it down:

Execution Sharding
With Shared Security
Heterogeneous

Sequential Blockchain

Opposite of execution sharding.
How blockchains usually work

Poorly Execution Sharded

Sharding the validator set: less security

Execution Sharded with Shared Security

Original vision of ETH 2 was to be this, with 64 shards.
ELVES

Heterogeneous

WASM bytecode

Evolution of Polkadot

... is all about flexible usage of cores

You need more to get more out of your core? Async Backing!
You need more cores? Elastic scaling!
You don't want to commit to 6m? Agile-coretime!
You need less than one core? On-demand coretime!
You want to do something other than a parachain in your core? JAM!

Path of a Parachain Block

Path of a Parachain ::: block

Notes:

Execution by core validators + made available for further auditing
State root updated by all Polkadot validators

On-chain vs. In-core

In-core
- Executed by a subset of validators + made available for further auditing
On-chain
- Executed by all validators: state root update.

In-core, on-chain dualism in execution sharding.

Data Availability

Polkadot validators already attest to keeping some data available for a long (few weeks) period of time

JAM

Now you know everything to understand JAM.

JAM (0)

Gutting of Polkadot such that the following are directly exposed to developers.

What happens In-core
What happens On-chain
What is placed in Data Availability

Note:

A parachain can only control what happens in-core. It cannot really control what happens on-chain. It also cannot readily add any data to the Data availability layer (well, it can, using remarks, which is a hack)

JAM (1)

..and removes a lot of blockchain/parachain-centric opinions.

JAM (2)

..and is therefore an evolution for the Polkadot Relay Chain (Cloud).
Parachains, Governance, Staking, AH and everything else remains intact.

Removing Opinions

JAM is programmable via a Service.
- PVM Bytecode.
Invocation of a service are called a Work Item^[1].
- A group of work Items are called Work Package.

Note:

In-core and On-chain

A Service is:
- fn refine(): What happens in-core
- fn accumulate(): What happens on-chain
- fn on_transfer(): Send messages to other services post accumulate
  --

Refine

Massive amounts of gas available.
Access to data availability (~28 day persistence)
No direct access to the JAM state (stateless)

Accumulate

Direct access to the JAM state (stateful)
Less gas available
Fully synchronous: Access the refine results of all other services, from possibly all other cores at once.

JAM (Recap)

Allowing Services to program exactly how they want to use:

In-core execution
On-chain execution
Data availability

Path of a JAM Work Package

JAM

PVM

Metered
Very fast (50% native)
PVM instance can invoke another instance
Pause and resume

CoreChains Service

Polkadot Parachains as a JAM Service.

Insights

(personal opinion)

What is best implemented as a service?
- Low level
- Crucial to get this right
Polkadot has JAM within it, but it is "fixed"
Services <> Interoperability
Semi-coherence
No transactions? Great!

Note:

Services will likely not be equivalent to smart contract or even parachains; Think more along the lines of "Kernel functions".
- Crucial to get this right
Service interoperability? Wrong question.
Semi-Coherence. Good!
Polkadot has all the JAM components, but they are fixed.
Less is more: No transactions? Good!
come to think of it, a smart contract can have arbitrary, user-defined entry-points. A service is not.

Questions

resources/JAM.png

Appendix

Kernel Update Analogy

Note:

Hardware is what provides compute and bandwidth, and the kernel is part of the OS that moderates the hardware access.
Current Polkadot. A lot of stuff is part of the "Kernel/OS".

Work Item

graph LR 
	subgraph WorkPackage 
		WI1[Work Item 1]
		WI2[Work Item 2]
		WI3[Work Item 3]
	end
	subgraph WorkReport
		WR1[Work Result 1]
		WR2[Work Result 2]
		WR3[Work Result 3]
	end
	
	WI1 --> WR1
	WI2 --> WR2
	WI3 --> WR3

And depending on the context, Work Package, Work Result and Work Report. ↩︎

Made with 💎 Obsidian-Digital-Garden