This document proposes defining standardized semantic metadata annotations for network anomaly detection. This would help network operators, vendors, and academia collaborate by enabling data exchange and facilitating supervised/semi-supervised machine learning development. Key benefits include testing and comparing outlier detection methods, making anomalies understandable for humans, and automating the learning process from network incidents. The document discusses categorizing network symptoms and defining their associated actions, reasons, and causes using YANG data models to annotate operational and analytical data.