The above NIP relies on POS service suppliers and defines three new events that compose Trade support.
## Building blocks
The following 4 building blocks enable trading products over Nostr.
### POS Service Supplier
A web service that allows setting up a single product sell page. Preferably with lightning, as it integrates well with Nostr.
A POS supplier url can be part of a Product event allowing redirecting users to a buy page of the product supplied by the POS service.
### Product Event
A new special event of kind xx that describes a purchasable product.
### Product Purchase Event
A new special event of kind xx+1 describes how to purchase a product. This event links a POS service supplier to the product.
Keeping the method of purchasing separated from the product allows changing POS suppliers with no effect on product data, rating, and reputation.
### Rating Event
A new special event of kind xx+2 that describes ratings assigned by a Nostr user to a product.