= uProtocol Core Service APIs
:toc:

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Core uProtocol services interfaces to define:

.Protobuf Files
|===
|File |Description

|link:udiscovery/v3/udiscovery.proto[*udiscovery.proto*]
|Contract for dynamically discovery uThings (other uEs, uDevices, uDomains, uResources, uMethods, etc...), for example what topics a service in another device shall publish, properties of a service, etc...

|link:usubscription/v3/usubscription.proto[*usubscription.proto*]
|Contract for publishers and subscribers to subscribe/publish to topics

|link:utwin/v2/utwin.proto[*utwin.proto*]
a|* Device-to-device Twin:
** To enable remote Apps to access last published state (and received by the device)
** To remain accessible even if connectivity is lost
* In-vehicle Twin:
** To avoid re-sending (re-publishing) data when apps are launched/subscribed

|===