I'm developing an iPhone application which uses standard iPhone address book (database) of contacts. I need to add some extra property to contacts but as I see iOS API does not permit addition of extra/custom properties to contacts.
Questions: 1. Is there an ability to deal with extra properties in iOS adressbook API? 2. I need expert's advice about standard approaches of how to store extra data for users/contacts: using SQLite, XML or maybe there is some data store dedicated for every application?