The issue is where a url of an email address should be stored - Email is an Url object, which uses url_string property. But some implementations need to quickly find a person by his email address, which causes a need to add tables to catalog email (url_string). Maybe we can treat a url string of a Url as its reference? This seems in line with the ERP5 philosophy, would eliminate one property, and make url searchable through portal_catalog.
Seb : If a new table is created, I guess the name should be url, because several portal types might use Url, not only Email.
Jerome: Maybe we can put this in catalog table. If someone's afraid it will be too big, we can discuss removing corporate_registration_code and ean13_code columns which are too specific, Type and Type2 indexes which are probably never used.
JPS: corporate_registration_code is really required. ean13_code may be less required.
Bartek: And how about simply stating that url is a reference of an Url object?
JPS: I see two possibilities. One is to use reference as the reference of URLs. This supposes that there is no need for any other reference of URLs, which I do not think is true (especially in the DMS context). The solution I would prefer is to use short_title (a new column which will soon be created in catalog) as a placeholder for all kinds of short values (phone, email, etc.).