CEP 24 - Default Preferences

Title:Default Preferences
Author:Matthew Gidden
Type:Standards Track


This CEP describes agreed-upon default preference values within the DRE.


The current default preference is zero. Preferences of zero are problematic because they are invariant under multiplication and do not behave well under monotonic transformations (e.g., the inversion operator).


The default preference will change from zero to unity. Default preferences will then be stable under both additive and multiplicative operations. Currently, negative preferences denote potential trades to be removed from resource exchanges before the solution phase. This will change from negative to non-positive preferences (see Backwards Compatibility).

Specification & Implementation

See [1] and [2] for the implementation of unity default preferences.

Backwards Compatibility

API backwards compatability is not broken with this CEP. However, trade logic backwards compatability will be broken if any previous model was dependent on a default preference value of 0. Developers will have to update models given the new default preference value of 1.

For a simulator, however, this is still backwards incompatability – simulation behavior for valid input files can (and will) change if explicit use of 0-valued preferences is engaged. Accordingly, to make this deprecation loud and explicit, an error will be thrown for the remainder of this minor release cycle (currently release 1.3.1 to 1.3.2). At the end of this cycle, arcs with 0-valued preferences will be “quietly” removed (i.e., as quietly as negative-preference arcs are currently). An issue will be made to perform this update.

For updating archetype code, look primarily to the AddRequest and Adjust*Pref APIs.

Document History

This document is released under the CC-BY 3.0 license.