Actor vs Party

Actor is not a synonym of Party, although they may be identical in some architectures / Implementations. There may be Actors that are not Parties.

Strengthened Party discussion in reference to Actors as in Table 2-1

Party A Party is an Actor that buys or sells Instruments in a CTS Marketplace. A Party may be described by a specific role in a specific interaction, such as Party or Counter Party. For semantic and privacy issues, see Section 2.2.3 below.

And in Section 1.1, where definition is drawn directly from [EI]

CTS does not presume a market with a single seller (e.g., a utility). CTS recognizes two parties to a transaction, and the role of any Party can switch from buyer to seller from one transaction to the next. Each Resource Offer (Tender) has a Side attribute (Buy or Sell). when each transaction is committed (once the product has been purchased) it is owned by the purchaser, and it can be re-sold as desired or needed.

In Privacy section of the Introduction (which is expanded) we refer to Parties not to Actors

The essence of any transaction is the agreement of a party to sell, and a party to buy. The identity of the buyer and the identity of the seller are each part of the transaction. Some transaction notifications may hide the identity of the buyer from the seller. Some transaction notifications may hide the identity of the seller from the buyer. Some transactions, such as double auction, may be between the market as a whole, and not with any particular counterparty. Where this is required, the market itself may be designated as the counterparty in a notification.

Actor is not a synonym of Party, although they may be identical in some architectures / Implementations. There may be Actors that are not Parties, that is, do not participate in market activities.

Strengthened Party discussion in reference to Actors as in Table 2-1