The purpose of the FDSN StationXML schema is to define an XML representation of the most important and commonly used metadata structures to describe digital seismological data, in particular for the purposes of data use. The predecessor format of StationXML is SEED 2.4, from which many structures and field were inherited.
This base schema may be extended with additional fields to represent similar data types.
version attribute of the schema definition identifies the version of the schema. This version is not enforced when validating documents.
schemaVersion attribute of the root element identifies the version of the schema that the document is compatible with. Validation only requires that a value is present but not that it matches the schema used for validation.
The targetNamespace of the document identifies the major version of the schema and document, version 1.x of the schema uses a target namespace of
http://www.fdsn.org/xml/station/1. All minor versions of a will be backwards compatible with previous minor releases. For example, all 1.x schemas are backwards compatible with and will validate documents for 1.0. Major changes to the schema that would break backwards compatibility will increment the major version number, e.g. 2.0, and the namespace, e.g.
This combination of attributes and targetNamespaces allows the schema and documents to be versioned and allows the schema to be updated with backward compatible changes (e.g. 1.2) and still validate documents created for previous major versions of the schema (e.g. 1.0).
StationXML schema development is done in a Github repository owned by the FDSN institutional account. All proposals and changes to the schema should follow the procedure documented on the development site.