# Cross-Consensus Query Language (XCQ) **URL:** \ **Category:** Tech Talk\ **Created:** [April 26, 2024, 4:39am UTC](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583 "2024-04-26T04:39:17Z")\ **Posts on this page:** 4\ **Page:** 2
**Author:** ![indirection42](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.polkadot.network/indirection42/32/4894_2.png) [@indirection42](https://forum.polkadot.network/u/indirection42)\ **Post date:** [October 25, 2024, 2:42am UTC](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583/21 "2024-10-25T02:42:26Z")
We just opened a PR about XCQ RFC. Feedback is welcome! > > > Looking for feedback. > > \## Summary > This proposal introduces XCQ (Cross Consens…us Query), which aims to serve as an intermediary layer between different chain runtime implementations and tools/UIs, to provide a unified interface for cross-chain queries. > > \## Related RFC > A related XCM-format RFC is drafting. > > \## Related Discussions > https://forum.polkadot.network/t/wasm-view-functions/1045 > > \## PoC implementations > https://github.com/open-web3-stack/XCQ ---
**Author:** ![indirection42](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.polkadot.network/indirection42/32/4894_2.png) [@indirection42](https://forum.polkadot.network/u/indirection42)\ **Post date:** [March 31, 2025, 5:39am UTC](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583/22 "2025-03-31T05:39:45Z")
# PVQ Status Report ## Summary - Rename project from `XCQ` to `PVQ` - Refactor PVQ extension system - Refactor PVQ program macros - XCM Intergration PoC ## Example Usage - PVQ Extensions Definitions: [Example](https://github.com/open-web3-stack/PVQ/blob/09da858d7731617a78bbedc1737095e3f5f9e955/pvq-extension-fungibles/src/lib.rs) - Use `pvq-program` macros to write a guest program. [Example](https://github.com/open-web3-stack/PVQ/blob/09da858d7731617a78bbedc1737095e3f5f9e955/guest-examples/sum-balance-percent/src/main.rs) - PVQ Extensions Implementation: [Example](https://github.com/open-web3-stack/PVQ/blob/09da858d7731617a78bbedc1737095e3f5f9e955/pvq-test-runner/src/lib.rs) ## Run Examples Available PoC PVQ examples: - `guest-sum-balance`: sum the balances of multiple accounts - `guest-total-supply`: get the total supply of an asset - `guest-sum-balance-percent`: sum the balances of multiple accounts and calculate the percentage of the total supply 1. Build guest program: `make guests` 2. Run test runner: `cargo run -p pvq-test-runner -- --program output/` `guest-examples` contains several guest programs to test the PVQ. ## XCM Integration PoC The test case of XCM integration is located in [vendor/polkadot-sdk/polkadot/xcm/xcm-simulator/example/src/tests.rs](https://github.com/indirection42/polkadot-sdk/blob/ececb4cbd68d94d1f73b6ab8e5ad8afed1cc9456/polkadot/xcm/xcm-simulator/example/src/tests.rs) ```rust #[test] fn test_report_query() { ... } ``` ---
**Author:** ![indirection42](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.polkadot.network/indirection42/32/4894_2.png) [@indirection42](https://forum.polkadot.network/u/indirection42)\ **Post date:** [July 7, 2025, 1:43pm UTC](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583/23 "2025-07-07T13:43:14Z")
We are happy to share the recent progress of PVQ: ### PVQ Frontend SDK We have created a [TypeScript SDK](https://github.com/open-web3-stack/pvq-sdk) for interacting with PolkaVM Query(PVQ) enabled chains. In summary, the SDK supports the following use cases: - Create a PVQ program instance by providing the guest program and corresponding metadata files. - List queryable entrypoints by accessing the metadata. - Check if the guest program is compatible with the chain’s supported extensions. For more details, please refer to the [github repo](https://github.com/open-web3-stack/pvq-sdk). ### PVQ Frontend Demo And we also created a [demo](https://open-web3-stack.github.io/pvq-sdk/) to demonstrate the usage of PVQ-SDK. In this demo, you can interact with a PoC runtime that implements the `core` and `fungibles` extensions. 1. Clone the [PVQ](https://github.com/open-web3-stack/pvq) repository. 2. Install [bun](https://bun.sh/docs/installation). 3. Run `make tools` to install the required tools. 4. Run `make run` to start the local PoC runtime. 5. Run `make guests` to build the PVQ programs and generate their metadata. 6. Open the [demo](https://open-web3-stack.github.io/pvq-sdk/) in your browser. ![Demo Index](https://europe1.discourse-cdn.com/flex005/uploads/polkadot2/original/2X/0/08dab67b06995a48573cd49705c83ea97afdb2ce.png) 7. Enter the custom endpoint shown in Step 4 and connect to the chain. 8. Upload a PVQ program, such as `guest-sum-balance`, along with the corresponding metadata JSON file, `guest-sum-balance-metadata.json`. ![Upload page](https://europe1.discourse-cdn.com/flex005/uploads/polkadot2/original/2X/0/0bb9f655190b01154be065b6fc65845387af2460.png) 9. Select the program; the program bytecode and metadata should be displayed in the UI. ![Program details](https://europe1.discourse-cdn.com/flex005/uploads/polkadot2/original/2X/9/9c02bb63cada1ae24f4cb38fe4124bbb7d76010f.png) 10. Switch to the `Query` tab, input the query argument, and execute the query to get the result. In the following example, we query the sum of the balances of asset `21` for two accounts: `Alice` and `Bob`. ![Execute query](https://europe1.discourse-cdn.com/flex005/uploads/polkadot2/original/2X/8/8c172a3038f74caf39ad1d68b2f894885c9aa324.png) ### Ongoing Works We are targeting to the first release of the PVQ as well as demonstrating a more decent Demo to show how PVQ works with different chains. ---
**Author:** ![indirection42](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.polkadot.network/indirection42/32/4894_2.png) [@indirection42](https://forum.polkadot.network/u/indirection42)\ **Post date:** [August 4, 2025, 12:23pm UTC](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583/24 "2025-08-04T12:23:37Z")
We’ve built a simple [swap demo](https://open-web3-stack.github.io/pvq-sdk/swap/) showcases how PVQ can facilitate the development of multi-chain Dapps. It has the following core functions: - List Liquidity Pools: Displays the available token pair pools on the selected chain. - Get Pool Reserves: Shows the current liquidity reserves for a selected pool. - Get Swap Price: Show price quote for swapping a specific amount of one token for another. ![截屏2025-08-04 20.23.16](https://europe1.discourse-cdn.com/flex005/uploads/polkadot2/original/2X/0/0158b5e11a577caf23bdcb3214af933fb9fb949f.png) **The main takeaway is that the demo works seamlessly with both Acala and AssetHub, using the exact same front-end logic despite the DEX implementations on these chains being entirely different:** - Acala: Uses its own custom `module-dex` pallet. - AssetHub: Uses the `AssetConversion` pallet. ### How It Works #### Front-end side From the client’s perspective, the process is simple: - Check for Extension: The UI first checks if the connected chain (Acala or AssetHub) implements the `swap` extension. - Construct PVQ program query arguments: If the extension is available, the UI constructs its query with the required arguments (e.g., token pair, amount to swap). - Call PVQ program Entrypoints: The UI sends the query to the entrypoints of the PVQ program. The front-end code is completely agnostic of whether it’s talking to Acala’s DEX pallet or AssetHub’s AssetConversion pallet. #### Runtime side The heavy lifting is done at the runtime side, which is tailored for each chain. We implement [swap extension](https://github.com/open-web3-stack/PVQ/blob/61950049b9c668f0db4b9fd059f5abb11d3b65e5/pvq-extension-swap) on both Acala and AssetHub, which exposes five extension functions: `quote_price_tokens_for_exact_tokens`, `quote_price_exact_tokens_for_tokens`, `get_liquidity_pool`, `list_pools`, `asset_info`, `assets_info`. #### PVQ Program For the corresponding PVQ program, it only has four entrypoints. This is by design and demonstrates one of PVQ’s most powerful features: the ability to perform custom computations in PVQ program. For example, the `list_pools` entrypoint is actually a composition of extension functions `list_pools` and `assets_info`: ```rust #[program::entrypoint] fn entrypoint_list_pools() -> Vec<(AssetInfo, AssetInfo)> { let pools = list_pools(); let mut result = Vec::new(); let assets_info = assets_info(); for pool in pools { let asset1_info = assets_info.get(&pool.0).cloned(); let asset2_info = assets_info.get(&pool.1).cloned(); if let (Some(a1), Some(a2)) = (asset1_info, asset2_info) { result.push((a1, a2)); } } result } ``` #### Key Advancement This demo is a concrete validation of the PVQ vision. We have successfully created a unified, high-level interface for a non-trivial operation (DEX interactions) across two parachains with fundamentally different runtime implementations. For dApp developers: - Reduced Complexity: No need to learn the low-level details of every parachain’s pallets. - Faster Development: Write code once and deploy it across multiple chains. - Easy Extensibility: As more chains adopt the PVQ swap extension, they will instantly work with existing UIs without requiring any front-end updates. This advancement is a crucial step toward a more cohesive and developer-friendly Polkadot ecosystem. #### Next Steps We are targeting the first release of the PVQ and integrating it into the `polkadot-sdk`. We welcome feedback, questions, and collaboration from the community. Please feel free to check out the demo and share your thoughts below. Thank you! [Previous page](https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583.md?page=1)