The final version of DIGGS Schema version 2.0.b was released May, 2016.

Complete Schema:  http://diggsml.org/schemas/2.0.b/Complete.xsd
Geotechnical Schema:  http://diggsml.org/schemas/2.0.b/Geotechnical.xsd
Kernel Schema:  http://diggsml.org/schemas/2.0.b/Kernel.xsd

DIGGS also relies on the following XML schemas

Geography Markup Language (GML) Schemas (reference link)
GML 3.2 Subset Schema:  http://diggsml.org/schemas/2.0.b/gml3.2Profile_diggs.xsd
Draft GML 3.3 Subset Schema:  http://diggsml.org/schemas/2.0.b/gml3.3Profile_diggs.xsd

Wellsite Information Transfer Standard Markup Language (WITSML) Schemas (reference link)
Data Types:  http://diggsml.org/schemas/2.0.b/witsml/1.3.1.1/typ_dataTypes.xsd
Catalog:  http://diggsml.org/schemas/2.0.b/witsml/1.3.1.1/typ_catalog.xsd
Measure Type:  http://diggsml.org/schemas/2.0.b/witsml/1.3.1.1/typ_measureType.xsd
Quantity Class:  http://diggsml.org/schemas/2.0.b/witsml/1.3.1.1/typ_quantityClass.xsd
Base Type:  http://diggsml.org/schemas/2.0.b/witsml/1.3.1.1/typ_baseType.xsd

DIGGS Online Dictionary Page

This is a page that allows you to review on the web the entire DIGGS dictionary
http://diggsml.org/schemas/2.0.b/documentation//DiggsDocumentation.html