Solid vs cloud in terms of where and how data is stored

could anyone help me understand the data storing mechanism of solid and also possibly how data is stored on a cloud (as almost all IIoT platforms use cloud for data analysis), what i mean with the data storing mechanism is where is user data stored on a cloud vs on solid and how is it stored, also how secure or accessible is it to a 3rd party. Also references to papers or other sources would be very helpful
thank you

The physical storage mechanism (file system, database, triplestore) is not specified by Solid. The physical location (local, IoT, cloud) is not specified by Solid. What is specified by Solid is semantic mechanisms (RDF. linked data) and access mechanisms (user data-access controls). So your thermostat might have a mini-Solid server in it that stores your temperature changes and you might choose to make some or all of that data available to your heating company. Or the thermostat could be sending data to a remote cloud-based Solid server under your control rather than storing data locally. So local/cloud does not really matter.

The data-access mechanisms mean that 3rd parties need your permission to access your data. A 3rd party app could store your data - there is no way to physically stop them. This needs to be addressed with laws protecting data and by a web of trust - since there will be many pod and app providers, those who chose to store user data will be outed and scorned.

There are many pointers to papers and introductory materials at https://solidproject.org/.