For point 3 (Is it possible to convert XML(XMI) schema to SQLite schema automatically?), are you asking about a tool that takes an XML schema and gives you back an SQL schema?
I haven't heard of anything, but I would imagine it exists. I have, on the other hand, done a fair amount of XML to SQL conversion and have found that generating a good schema involves understanding the data so you know what to denormalize. You don't really want to have thousands of tables, each representing an XML tag. That would make your database very hard to use.
Trial and error, and a good knowledge of what kind of questions you are going to be asking your database to answer...
I haven't heard of anything, but I would imagine it exists. I have, on the other hand, done a fair amount of XML to SQL conversion and have found that generating a good schema involves understanding the data so you know what to denormalize. You don't really want to have thousands of tables, each representing an XML tag. That would make your database very hard to use.
Trial and error, and a good knowledge of what kind of questions you are going to be asking your database to answer...