HYDROXC: A COMMON SCHEMA FOR HYDROLOGIC DATA TRANSFER AND OBJECT DESCRIPTIONS

The National Weather Service (NWS) Office of Hydrologic Development (OHD) has been sponsoring the development of the HydroXC initiative, which is now in Phase III. The overall goal of this initiative, which is also supported by a consortium comprised of members of the hydrologic community originating in government (National Weather Service, US Geological Survey, Natural Resources Conservation Service, US Army Corps of Engineers), academia (Duke University, Drexel University, University of Pittsburg, University of Virginia), and also private companies (APEX Digital Systems, Environmental Science Research Institute, Vieux and Assoc., Wier and Assoc.), is to develop a general XML schema that can be used for data transfer between entities interested in hydrologic data. While some efforts are already under way to “schematize” hydrologic information (for example the HydroML effort lead by USGS), most efforts are very specific to a certain task prompting the need for an exchange vehicle that is generic enough such that any type of hydrologic information can be described and packaged in a language that is machine readable, i.e. XML.

The third phase of this project will address pragmatic requirements for using the XML schema, and for making it more specific to daily needs of hydrologic software users. Current research efforts are focused on further evolving the HydroXC XML schema that has been derived from the Standard Hydrologic Exchange Format (SHEF) developed at the NOAA National Weather Service. To do so, the current thrust is to focus on the derivation of several specific hydrologic object representations including a few examples that highlight the new areas of the schema, i.e. a Reservoir object, a flow rating curve object, a stream reach object, and cross section object. The focus is on compiling descriptions that are useful for data exchange by identifying key attributes that are also used by other standards (for example GML, or HydroML). Additional work is underway to use the HydroXC schema to develop data adapters that are capable of reading and writing messages between some proprietary format and HydroXC-compliant XML.

This work will demonstrate the general composition of the schema, which is aligned along elements used for defining components and example instantiations the derived object descriptions. We will also outline the inclusion of internal standards (like ISO 19115 & 8601, GML, and EPSG codes) into this schema and the importance they have in representing geospatial and temporal referencing as well as some of the challenges that arrive from attempting to incorporate legacy systems.