network barter transactions?

hi all, :)

after reading the Interest Group charter (
http://lists.w3.org/Archives/Public/public-webpayments/2014Jul/0034.html),
i realized in the (hopefully non-exhaustive) list of "possible legal
payments methods", there is no mention of barter, namely exchanging assets
directly for assets instead of currencies (or points, etc).

in the relevants docs: the Web Commerce spec (
https://web-payments.org/specs/source/web-commerce/), Web Commerce
vocabulary (https://web-payments.org/specs/source/vocabs/commerce.html),
and the general Web Payments use cases (
https://web-payments.org/specs/source/use-cases/), there is no mention of
barter transactions, instead the only mentioned way of paying for an asset
is through a currency.

i'm wondering if it is within scope of Web Payments to support barter
transactions. in particular, i'm thinking about network barter transactions
like http://edgeryders.eu/makerfox, where a single transaction may involve
any number of participants each with any number of offers or wants, all
denominated in assets. it's currently possible to model each individual
offer and want, but what about modeling the transaction?

the only solution i can imagine currently is that a new currency type is
generated for every network transaction, and one unit of this currency is
transferred in every sub-transaction, such that the sum of the currency for
each participan cancels out. however, is there even support for such a
multi-party transaction, basically can a single transaction contain many
sub-transactions?

cheers,
Michael