An optional group of data elements which together describe a contractual term or constraint (or the absence of such a constraint) that forms part of the commercial offer for a product. Repeatable in order to describe multiple constraints on usage.

The Price constraint composite has the same structure as <EpubUsageConstraint>. Use <EpubUsageConstraint> for constraints that limit the user experience of the product, whether or not they are enforced by technical protection measures (DRM). Use <PriceConstraint> where a single product is available under multiple terms and conditions (ie multiple commercial offers for the same product which differ in their Price constraints, and whether or not they are enforced by DRM).