The IClassifier interface provides a classification of text content, image content, etc. by returning a list o key value pairs. This list defines implicit metadat which is analyzed from the file content.
A list of sample data which defines a learning sample for machine learning software may be provided as an option. This URL represents a file which can be downloaded. This file may either contain sample data or connection information to connect to a Web Service and retrieve sample data.
It is up to the classifier to implement persistence so that sample data only needs to be downloaded from time time. In between, the learning model should remain unchanged and persistent in RAM or on the filesystem.