title: Glossary
Data Preparator
- Part of Engine. It reads data from source and transforms it to the desired format.
Data Source
- Part of Engine. It preprocesses the data and forward it to the algorithm for model training.
Engine
- An Engine represents a type of prediction, e.g. product recommendation. It is comprised of four components: [D] Data Source and Data Preparator, [A] Algorithm, [S] Serving, [E] Evaluation Metrics.
EngineClient
- Part of PredictionSDK. It sends queries to a deployed engine instance through the Engine API and retrieves prediction results.
Event API
Event Server
- Event Server is designed to collect data into PredictionIO in an event-based style. Once the Event Server is launched, your application can send data to it through its Event API with HTTP requests or with the EventClient of PredictionIO's SDKs.
EventClient
Live Evaluation
- Evaluation of prediction results in a production environment. Prediction results are shown to real users. Users do not rate the results explicitly but the system observes user behaviors such as click through rate.
Offline Evaluation
- The prediction results are compared with pre-compiled offline datasets. Typically, offline evaluations are meant to identify the most promising approaches.
Test Data
- Also commonly referred as Test Set. A set of data used to assess the strength and utility of a predictive relationship.
Training Data
- Also commonly referred as Training Set. A set of data used to discover potentially predictive relationships. In PredictionIO Engine, training data is processed through the Data layer and passed onto algorithm.