What is Service Layer (Tooling Layer)?

The service layer, sometimes known as middleware or the tooling layer, is the portion of the software stack that computing systems utilize to support the functionality of the application layer. In blockchain specifically, the service layer is generally made up of smart contracts, application programming interfaces (APIs), software development kits (SDKs), decentralized oracles, databases, digital identities, and more. Without the service layer, the application layer and the network layer would be unable to interact with each other, rendering the system useless.