## TL:DR

This batched proposal is to Accept/Open an HRMP channel with Parallel and to register the PARA token

## Summary

We propose to open a bi-directional channel between Moonbeam and Parallel. Initially, the main use case will be to transfer GLMR and PARA between the two chains, but it can be further expanded to other use cases. The proposal also includes the PARA asset registration as xcPARA, with the following details:

 - Multilocation: *{ "parents": 1, "interior": {"X2": { "Parachain": 2012}, {"GeneralKey": [80,65,82,65]}}*
 - Decimals: *12*
 - Name: *Parallel*
 - Symbol: *xcPARA*

xcPARA will have the following asset ID and XC-20 address:

 - Asset ID: 32615670524745285411807346420584982855
 - XC-20 address: 0xffffffff18898cb5fe1e88e668152b4f4052a947

## Proposal

Referendum #41 with the following hash: *0xab53cd3144ea0448ab6285c2155ee9c6b378be715236546a3c046a9d2a7e63e4*

## Technical details:

The procedure for opening the channels is as follows:

 - Parallel: already proposed to open an HRMP channel to Moonbeam
 - Moonbeam: democracy batched proposal
    - Open Moonbeam to Parallel HRMP channel
    - Accept Parallel to Moonbeam HRMP channel
    - Register PARA asset as an XC-20 
 - Parallel: democracy proposal to accept Moonbeam to Parallel HRMP channel

Once the HRMP channels are ready, XCM based cross-chain transfer will be possible. The extrinsics that need to be executed on the relay chain, are:

 - To open the HRMP channel from Moonbeam: *hrmp.hrmpInitOpenChannel(recipient: 2012, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400)*, which its hex-encoded call data is *0x3c00dc070000e803000000900100*
 - To accept this HRMP channel: *hrmp.hrmpAcceptOpenChannel(sender: 2012)*, which hex-encoded call data is *0x3c01dc070000*

The *proposedMaxCapacity* and *proposedMaxMessageSize* are set to the values of Polkadot’s *configuration.activeConfig.hrmpChannelMaxCapacity* and *configuration.activeConfig.hrmpChannelMaxMessageSize* values, respectively.

These extrinsics need to be called from the parachain’s sovereign account as origin, via a democracy proposal. The proposal will use *polkadotXcm* pallet to send XCM message to the Relay Chain with the following items:

 - Withdraw asset: take funds out of the Sovereign Account of the origin parachain (in the relay chain) to a holding state
 - Buy execution: buys execution time from the relay chain, to execute the XCM message
 - Transact: provides the call data to be executed
 - Deposit asset (optional): refunds the leftover funds after the execution. If this is not provided, no refunds will be carried out

The asset will be registered with the metadata described in the summary. The *setAssetUnitsPerSecond* was calculated using an estimated value for PARA on May 24th 2022, targeting a XCM transaction cost of 0.02$.

If you are interested, the hex-encoded call data for this proposal in [Moonbeam](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fwss.api.moonbeam.network#/extrinsics/decode) is:

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

As a prerequisite, the parachain’s sovereign account must contain at least 20 DOT to be locked as collateral (10 for each channel direction), plus some DOT to pay for XCM execution fees.

 

Send a batch of dispatch calls and atomically execute them.
The whole transaction will rollback and fail if any of the calls failed.

May be called from any origin.

- `calls`: The calls to be dispatched from the same origin. The number of call must not
  exceed the constant: `batched_calls_limit` (available in constant metadata).

If origin is root then call are dispatch without checking origin filter. (This includes
bypassing `frame_system::Config::BaseCallFilter`).

# <weight>
- Complexity: O(C) where C is the number of calls to be batched.
# </weight>

- The proposal is to open a channel between Moonbeam and Parallel to transfer GLMR and PARA tokens.
- The PARA token will be registered as xcPARA with specific details.
- The proposal has a referendum number and technical details for opening the channels.
- XCM based cross-chain transfers will be possible once the channels are open.
- The proposal requires certain extrinsics to be executed and the asset will be registered with specific metadata.

#41 Open/Accept HRMP channel to/from Parallel and Register PARA