An Explanation of Substrate For Humans

Polkadot, Kusama, Moonbeam, Edgeware etc. are Substrate-based chains. What does it mean to be a Substrate-based chain? What is Substrate? Let's find out.

Video version:

Parity, the company building the software powering the Polkadot Network, has been a blockchain development shop for a while. In their past work, they had to build blockchains from scratch multiple times, and always reinvented certain elements more or less common to all blockchains.

For the curious: elements like the database, the transaction queue, the consensus layer...

Based on this experience, they decided to build a framework - a bundle of code from which all future blockchains can grow: Substrate.

Substrate is a framework, a template on which you can build your blockchain's custom functionality, and use pre-built plug-and-play modules called pallets to add additional functionality on top.

For example, say Starbucks wanted to replace their payment and loyalty systems with a custom made blockchain which perfectly executes these functions. They can take Substrate and:

• plug in the Balances pallet to keep track of how many $tar Bucks each customer has, and to enable customers to send Bucks to each other.
• plug in the Identity pallet to let users set their identities in the system, for coffee delivery and reliable identification when ordering
• tweak the block time to something like 1-2 seconds from the default 6 seconds, because the network can take it if it's only relaying information within a private blockchain between Starbucks shops
• build a custom pallet (module) which tracks loyalty points for each customer and displays them as special non-transferable tokens

An experienced team of developers could finish all these tasks within a month, as opposed to several months or years when developing a custom Starbucks blockchain from scratch, saving millions in man-hours and support costs.

For the curious: To get started developing on Substrate, please see Substrate.io

When we say that a chain is a Substrate-based chain, it has been built on Substrate, much like the Starbucks chain above. It started from the template and has been customized to match the needs of the team.

• Polkadot is a Substrate-based chain
• Kusama is a Substrate-based chain
• Edgeware is a Substrate-based chain

It also means that the chain comes with certain features built-in - features not found in other blockchains:

• a Substrate-based chain will expose metadata about itself. This means it will describe what it can do to an external client reading it (like a wallet or a user interface). For example, the web application Polkadot Apps will change the layout and functionality based on the chain it is connected to due to this metadata.
• a Substrate-based chain can perform a forkless upgrade. Forkless upgrades are explained in detail in this video, and touched on in the What is Polkadot Explainer.

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