hierarchy.xsd

XML Schema definition Reference

An .xsd file contains an XML Schema definition. The schema describes the permitted structure and the data types of an XML document. Validation tools compare a document against the schema and report each difference. Code generators can also create data classes from a schema. XSD is a standard of the W3C.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.