# CloudKit Catalog: An Introduction to CloudKit
CloudKit Catalog consists of a native iOS application and a web application which demonstrate use of
The two apps share an *Items* record type which has fields
* name : String
* location : Location
* asset : Asset
# Records, Notifications and Sync
Both apps allow an authenticated user to write *Items* records to a zone in their private database. Additionally they
allow you to subscribe to changes to Items. So if you create or delete Items in the web app you will get notifications
of these changes in the native app and vice versa. Upon receipt of a notification, you can use the sync APIs in either app to
update a local cache of records with subscribed changes.
A user of the native app can opt to be discoverable to other users of the app through the sign-in
flow (the Authentication tab). In the native app a user is typically already signed in to iCloud on their device and
they can opt in to discoverability with the *requestApplicationPermission* method in the Discoverability section.
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