Chapter 3: Observations Data Model
Observations are fundamental to hydrology and water resources, and the way these data are organized and manipulated either enables or inhibits the analyses that can be performed. The Observations Data Model (ODM) presented here serves as the foundation for the systematic organization, storage and retrieval of point observations within the CUAHSI HIS. At a conceptual level, the ODM is a schema for the representation of point observations using tables linked by associations or relationships between key fields. The ODM schema has been implemented in a relational database designed to facilitate integrated analysis of large datasets collected by multiple investigators. Within the ODM, observations are stored with sufficient ancillary information (metadata) about the observations to allow them to be unambiguously interpreted and to provide traceable heritage from raw measurements to useable information. The design is based upon a relational database model that exposes each single observation as a record, taking advantage of the capability in relational database systems for querying based upon data values and enabling cross dimension data retrieval and analysis. The conceptual organization of point observations provided by the ODM serves as a foundation for the representation of hydrologic observations throughout much of the HIS, including WaterML, the WaterOneFlow web services, and the various metadata catalogs that support HIS functionality.