Identity of what exactly?
As the name would suggest, it's an ID that's been assigned by the Point of Sale to an item, variant or order. It's the way each uniquely identify a dataset independently to Doshii IDs.
Commonly as a Partner, you would see the property posId against items and variants. Sending up your order with an invalid posId may result in your order being rejected! If you request the menu from the location first, that will help in only sending valid items and variants.
Note: POS "ID" should not be confused with POS "Ref", which describes how an order has been linked and referred to by a POS' order.
What are the benefits of using posId menu items?
There are so many. We recommend sending valid posIds with your items, variants etc. whenever possible.
When sent with a valid posId, you get ALL the following benefits for you and your customers - Docket printing - Reporting - Analysis - Reconciliation - Automatic accept or reject and value validation
It's powerful because it emulates the POS. Basically, it's seen by the POS as if a staff member has keyed the item, variant etc. in another terminal.
We wanted to keep flexibility by allowing you to send without posIds, for custom orders and the like. These are called "open items/variants" when sent without a posId.