To understand properly the EAC GraphQL API, make sure you are familiar with the EAC market design. Refer to the EAC webpage to find the latest document.

We have gathered in this section a brief definition of the main concepts of the EAC market design. In case of inconsistency between this documentation and the procurement rules, refer to the procurement rules.

• A Service represents an Ancillary Service procured by the Buyer. For example, Dynamic Containment High (DCH) and Dynamic Containment Low (DCL).
• A Service Type is a categorization of the services. For example, Response, Balancing Reserve, Quick Reserve, and Slow Reserve.
• A Service Window is a pre-defined delivery period of a service.

• An Auction Session is a single occurrence of an auction at a specific date and time consisting in the matching of sell and buy orders to return a selection of executed orders and market clearing prices. Auctions are co-optimised and cover multiple services.
• An Auction Session Log Item is an event related to an auction session.

• A Unit is a collection of one or several assets entitled to offer capacity.

• A Basket is a grouping of orders, it contains exactly one parent order and can in addition contains up to 10 child orders and 10 non-substitutable child orders (so up to 20 children in total).
• A Parent Order is a non-curtailable order whose acceptance is a pre-condition to the acceptance of one or more other (child) orders in the same Basket. A parent order may not have any linked child orders. A parent order has a single price and can offer a volume for each eligible service.
• A Child Order is an order that can only be accepted if another order to which it is linked, the “parent order” is also accepted (i.e., the parent order can be accepted alone or the parent and child orders can be accepted together, but the child order cannot be accepted alone). A child order has a single price and can offer a volume for each eligible service.
• A Substitutable Child Order is a normal child order with an additional rule. Substitutable child orders of the same basket are exclusive, the sum of their percentage of acceptance is limited to 100%. So, if one is fully accepted, the other must be fully rejected. But four substitutable child orders may also be accepted at 25% each.
• A Basket Family is a grouping of non-concomitant baskets. Baskets belonging to the same family are looped together meaning that they will all be accepted or rejected together. Baskets with the same family name belong to the same family. A basket can belong to a single family.

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