# Week 4 Updates

In this week I mostly spent time analyzing Erigon execution client code and FOCIL specs.
I added notes in the execution client for the changes that were required in Erigon.

Below ill be attaching some snippets from my analysis and notes necessary for implementing FOCIL in Erigon's execution layer.

## Execution clients changes/additions
These are very high level changes and might require more changes internally and additional helper functions will be required.

**[Engine api changes/additions](https://github.com/erigontech/erigon/blob/main/execution/engineapi/engine_api_methods.go):**
Introduce ```NewPayloadV5``` which will introduce ```inclusionList``` as a parameter.

Add ```GetInclusionListV1``` method in the engine api. This internally will call the local view of the mempool and create the IL based on that.

Add ```UpdatePayloadWithInclusionListV1```. This method essentially adds the current inclusion lists in the payload for the provided payload id.

Add function to validate the inclusion list.

**[constants](https://github.com/erigontech/erigon/blob/main/execution/engineapi/engine_helpers/constants.go):**

**[jsonrpc](https://github.com/erigontech/erigon/blob/main/execution/engineapi/engine_types/jsonrpc.go):**
Add type ```InclusionList [][]byte```.
Introduce marshall and unmarshall json functions for ```InclusionList```.

## Next week:
I'll be mostly focusing on completing my project proposal and refining it. And also getting feedback on it from the mentors.