The membership of stars to open clusters is certainly the most difficult problem to solve as a preliminary to any study. However there are very few methods to used when proper motions probabilities are not available. Existing codes developed at several observatories are not yet publicly available.
An expert system, adapted from Jonathan (Frot 1988), has been implemented in the database with a number of rules that should help the user to determine if a given star is a cluster member or not. Rules have to be improved to resolve the ambiguities resulting from the curvature of the sequences in some photometric diagrams and to extend the number of data taken into consideration. Presently, the expert system looks in the database for the UBV data, spectral types, proper motion membership probability and radial velocity, and distance from the cluster center and makes inference on the membership. It does the work of extracting the data itself and proposes a decision according to the data it has found and the rules it knows to analyse the situation. This behaviour reproduces the way the same question is solved by a human user. It could of course use more information than it does now, speak English instead of French, the language in which it has been developed, and above all, have better rules. It would however be extremely useful to be able to sort out the member stars more or less automatically, on the basis of objective criteria.