Each ASN.1 type is mapped to a corresponding XSD type. Some ASN.1 types have a natural mapping to an XSD type (for example, an ASN.1 BOOLEAN type maps to an xsd:boolean type). In other cases, custom types were needed because a natural mapping did not exist within XSD (for example, there was no direct mapping for an ASN.1 BIT-STRING type). These custom types can be found in the low-level ASN.1 XML schema definitions library at the following URL:

http://www.obj-sys.com/v1.0/XMLSchema/asn1.xsd

The following sections describe the mappings for each of the ASN.1 built-in types.