The deal model

Every trade on Switchboard composes a handful of orthogonal dimensions, so a buy is a combination, not one item off a fixed list. Three questions shape it: what you pay for, when you buy it, and how you place the order.

Dimension	Values
Package	Selling-title daypart, program, genre, rotator, run of network, sponsorship, or custom. Seller-defined, versioned, and optionally market-scoped. See Packages.
Distribution	network, syndication, or spot: the layer the inventory sits in, composing with the package's optional market rather than duplicating it. See Packages.
Buy type	preemptible, non_preemptible, fixed_position, or audience_guaranteed. See Buy types and guarantees.
Rate	Rate card keyed by advertiser class, creative length, buy type, clearance tier, and market class, within a card scoped open or to an agreement. Price locks at order time. See Rates.
Workflow	Catalog, document, or proposal. Wire values: the workflow enum.

What you pay for

The buy type states the pay basis, what the seller stands behind, and who picks the spots. There are four wire values and three spot-cost buying patterns. There is no non-guaranteed CPM cell: a CPM is priced against a delivery guarantee, while a buyer taking delivery risk buys a spot cost.

Buying pattern	Wire value	Pay basis	Seller stands behind
Preemptible	preemptible	Spot cost	No contractual airing guarantee; clearance_tier states priority.
Non-Preemptible	non_preemptible	Spot cost	The spot airs; placement within the package remains the seller's.
Fixed Position	fixed_position	Spot cost	The spot airs in the position bought.
Audience Guaranteed	audience_guaranteed	CPM	Delivered audience; shortfalls follow the make-good policy.

The wire values live at the buy_type enum. The full guarantee semantics live on Buy types and guarantees.

When you buy

The same inventory prices differently by how far ahead you commit. The market class on the rate card names the point on that spectrum:

Market class	When	What it is
upfront	Ahead of the season	Commit a budget early and lock rates, then draw it down order by order. See Upfront commitments.
scatter	In-quarter	Buy at the going rate as the quarter unfolds, with no commitment.
remnant	Near air	Discounted inventory still unsold as air approaches.
opportunistic	Near air	Inventory that opens late, marked down with a signal agents can act on.

The commercial choice is guaranteed premium access versus flexible opportunistic access. Upfront and scatter are where that choice is expressed; remnant and opportunistic are its far end. Near-air discounted inventory remains preemptible.

How you place it

Send the seller a brief and let them build it, or take what is already published. Both are first-class:

• Proposal. Send an audience plan, campaign specs, or an open brief. On the wire, the request uses workflow: "proposal" on POST /orders and carries a request instead of line items. The returned plan carries buy_type per line. Accepting it books one order whatever mix of buy types it contains. See Proposals.
• Catalog order. Pick published packages, prices, and availability. Every order still passes the seller's gate: a person, or rules that person set. See Approve orders.

Sellers declare which buy types and market classes each package supports; buyers filter by them. Political buys are an advertiser_class that overlays any compatible buy type rather than a type of their own.