EMIX Terms and EMIX Products are defined in WD20 but the schemas define EMIXBaseType.

line 317 EMIX describes the Terms (EMIX Terms) of tenders and transactions for products whose market value varies with time of delivery. An energy product typically is delivered over time at a specific location. Five kW at 2:00 AM does not provide the same energy services as five kW at 2:00 PM. EMIX describes the terms of tenders and transactions for which time and location are essential characteristics. For example, the price and quantity (rate of delivery) of energy in each time Interval of a Sequence of Intervals may vary for energy transactions made in a Sequence of Intervals.
EMIX Terms are created by applying Product Descriptions to WS-Calendar Sequences. WS-Calendar Sequences embody the same calendaring standards used by most business and personal calendaring systems. This enables greater interoperation between grid systems and business and personal systems. An EMIX Product Description describes the elements of an energy product at a location for one time Interval or a Sequence of time Intervals. An EMIX Product Description for a constant rate of delivery power product over a single Interval of time comprises a (1) start time, (2) duration, (3) rate of delivery, (4) price and (5) location. If the rate of delivery (kW) and price ($/kWh) have been messaged in advance, the message to deliver the product is simply "start (reference [URI] to product) at 3:00 AM for 0.75 hours."

EMIX Terms are referenced in other places in WD20.

Line 357 and other places define

EMIX Product EMIX Products are created by applying a Product Description to a Schedule using the Base Product abstract class.

The EMIX and EI schemas define EmixBaseType which I think is the same as EMIX Terms and EMIX Products

The EMIX and EI schemas refer to an EMIXBaseType