Toying with ZCatalogs, I am starting to wonder if many of the uses I envisioned are not better served with a backend database. For example, for a publication database where nearly all of the instance data needs to be indexed (author, title, journal, year), this results in near total duplication of the instance data within the catalog. It seems that ZCatalogs are meant to be used if (i) only a fraction of the instance data needs to be indexed, or (ii) the dataset is small enough that one can live with the duplication. As another example, consider a catalog of URLs (descriptor, link, creation_date) gleaned from a URLClass ZClass. Here we might have hundreds of URLClass instances peppered throughout user folders and all of the data needs to be indexed. Is the overhead of object creation and duplication within the catalog better served with a simple backend database? Darran.