Such consultants can be invited to join at the start of a new phase, but the buy-in should meet or exceed the accumulated investment of the original partners. Regarding authorship and editorial control of publications, there are several cases which must be weighted to achieve fairness. Finally, there will be a various contribution classes, such as hired observers, drected undergraduates, external contributors who want to collaborate, and external contributors who just want recognition. The astronomy model would have an author list determined by the first author in consultation with a nominal set of secondary authors consisting of people who worked on a paper. The author order would reflect the relative contribution to that specific paper.
Authorship related to contribution of data is determined in advance of the analysis.
Ultimate responsibility for the paper rests with the first author. A hybrid model, adopted by SDSS, has a set of authors, in contribution order, who actually worked on the analysis or writing of the paper. Those on the builders list can decide whether they wish to be listed on any given paper, and if they think they meet the criteria for being in the first list of authors they can present their case. Ultimate responsibility for the paper rests with the first author. Here is a suggested scoring scheme covering, Stage 2, the discovery through reduction stage of the SN factory.