Model Management

Core ML Models need to be updated frequently. However, pushing app updates to distribute an updated version of the ML Model is not necessary. SAPML provides SAPMLModelManager APIs to remotely download, update, and keep track of models used by the app.

Core ML Model files are uploaded as client resources on the SAP Mobile Services. The versioning support of client resources is essential to versioning of the Core ML Model files. SAPMLModelManager downloads the latest version of the model file hosted on the SAP Mobile Services.

Initialization and Configuration

Create anSAPMLModel object that provides information about the Core ML model. SAPMLModel encapsulates model properties such as the name and URL of the model. SAPMLModelManager APIs take SAPMLModel instances to download and delete downloaded models. SAPMLModelManager also provides a list of downloaded SAPMLModel instances.

let helloCPMS = SAPMLModel(named:"HelloCPMSModel" , localURL: nil)

localURL is an optional parameter to use a local Core ML model as the initial version. Refer to Use a local Core ML Model File as the Initial Version for additional information.

You can use SAPMLModelManager to download, update, delete, and list downloaded ML models. Before using SAPMLModelManager all of its properties needs to be set. SAPMLModelManager follows a singleton design pattern. To invoke SAPMLModelManager APIs, use an SAPMLModelManager.shared instance.

SAPMLModelManager.shared.sapUrlSession = //set the fully configured SAPURLSession
SAPMLModelManager.shared.cpmsSettingsParameters = //set the cpmsSettingsParameters
SAPMLModelManager.shared.delegate = MyMLModelManagerDelegate() //set the delegate that will receive callbacks on events

Example Usage

//Configure `SAPMLModelManager` by setting the `sapUrlSession` and `cpmsSettingsParameters` properties, which will be used for downloading the Core ML Models from SAP Mobile Services
   SAPMLModelManager.shared.sapUrlSession = //set the fully configured SAPURLSession
   SAPMLModelManager.shared.cpmsSettingsParameters = //set the cpmsSettingsParameters
   SAPMLModelManager.shared.delegate = MyMLModelManagerDelegate() //set the delegate that will receive a callback on download completion

//Specify the name of the Core ML model that needs to be downloaded from Mobile Services using SAPMLModel
   let helloCPMS = SAPMLModel(named:"HelloCPMSModel" , localURL: nil)

//Trigger download of the model
   SAPMLModelManager.shared.download(model: helloCPMS)

//Handle completion callback received on SAPMLModelManagerDelegate
func sapMLModelManager(_ manager: SAPMLModelManager, model: SAPMLModel?, didCompleteWithError error: SAPMLModelManagerError?) {
    if let err = error {
        switch err {
        case .compilationError(let compilationError):
            // Handle model compilation error
        case .downloadUnderway:
            // Handle model compilation error
        case .other(let otherError):
            // Handle otehr errors
        case .server(let serverError):
            // Handle server error
        case .cpmsSettingsMissing:
            // Handle CPMS Settings missing error
        case .modelNotFound:
            // Handle model not found error

        }
    }
    else {
        // Model downloaded/updated successfully
    }
}
//Access the downloaded and compiled ML model
    do {
       try SAPMLModelManager.shared.mlModel(for: helloCPMS)
    }
    catch _ {
       //Error Handling
    }

NOTE: SAPMLModelManager download and update complies with network synchronization policies specified by the SAP Mobile Services administrator.

Modifications Required in AppDelegate

Because ML models can be quite large in size, the ML model files are downloaded in the background. It is recommended to invoke download of the SAPMLModel in the AppDelegate applicationWillEnterForeground lifecycle method, so that the app gets to use the latest version.

func applicationWillEnterForeground(_: UIApplication) {
    let helloCPMS = SAPMLModel(named:"HelloCPMSModel" , localURL: nil)
    SAPMLModelManager.shared.download(model: helloCPMS)
}
//Because the `SAPMLModelManager` performs the download of Core ML models in the background, the `handleEventsForBackgroundURLSession` event must be forwarded to the SDK to handle
completion of tasks when the application is launched or resumed in the background
func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: @escaping () -> Void) {
    AppDelegateDispatcher.application(application, handleEventsForBackgroundURLSession: identifier, completionHandler: completionHandler)
}

Use a local Core ML Model File as the Initial Version

There is an option to use a local Core ML Model file that is bundled with the app. This is treated as the initial version of the Core ML Model and will be served by the SAPMLModelManager, until a client resource file with the same name is uploaded to SAP Mobile Services. So, the application starts with a local Core ML model within the app, which is updated subsequently with the remotely distributed model from SAP Mobile Services.

//The Core ML model located at `localURL` will be available using the `mlModel(..)` function.
   let helloCPMS = SAPMLModel(named:"HelloCPMSModel" , localURL: Bundle.main.url(forResource: "myModel", withExtension: "mlmodelc"))
   SAPMLModelManager.shared.download(model: helloCPMS)
   try? SAPMLModelManager.shared.mlModel(for: helloCPMS) //returns local model

 //If a new version of the Core ML model is uploaded on Mobile Services Client Resources, it will be downloaded and compiled.
   let helloCPMS = SAPMLModel(named:"HelloCPMSModel" , localURL: Bundle.main.url(forResource: "myModel", withExtension: "mlmodelc"))
   SAPMLModelManager.shared.download(model: helloCPMS)
   try? SAPMLModelManager.shared.mlModel(for: helloCPMS) //returns remote model