One of the items we will be looking to do with Alpha is exporting a core set of lineage to all our clients and keeping this in synch. To do this we will need consistent assetUids and RelationUids between environments. Right now I can post an Asset from one environment to another with the same assetUid BUT cannot do the same for a relationship, unless I'm mistaken adding a relationship does not allow me to keep the same relationUid from the source. This makes keeping track of assets and lineage is undoable or very very complicated at best.
What needs to be done
Via the Post relationship API allow for the ability to provide/import the Uid for the relationship in much the same way as the platform allows for the ability to provide/import Uids when posting assets. With this clients will be able to export lineage between environments as the assets and their relationships will have the same consistent Uids.