ODM v2.0 can be serialized as either XML or JSON.

XML File Conformity

An XML file conforms to the ODM v2.0 standard only if it satisfies all the criteria detailed in this standard. These criteria include both syntactic constraints and semantic ones.

The syntactic constraints for ODM v2.0 XML files are:

1. The ODM file must be a well-formed XML file. See the XML standard for details.
2. The ODM file must conform to the XML Namespace standard. See the XML Namespace standard for details.
3. The ODM file must contain only elements and attributes defined in the ODM standard schema or in a valid vendor extension schema, and must satisfy the rules about element nesting and the formats of attribute values and element bodies.
4. The ODM file must contain a single (top-level) ODM element
5. The ODM file must use the ODM v2.0 namespace, which is "http://www.cdisc.org/ns/odm/v2.0"
6. The ODMVersion attribute on the top-level ODM element must be set to "2.0"
7. The ODM file should begin with a prolog, or XML declaration, as this is considered a best practice 

The XML schema for Version 2.0 of the ODM can be found at https://github.com/cdisc-org/DataExchange-ODM. The final version of this specification will be posted at https://www.cdisc.org/standards/data-exchange/odm.

<?xml version="1.0" encoding="UTF-8"?>
<ODM xmlns="http://www.cdisc.org/ns/odm/v2.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    ODMVersion="2.0"
    FileOID="000-00-0000"
    FileType="Transactional"
    Description="Sample ItemData Extension"
    AsOfDateTime="2022-06-04T07:57:00"
    CreationDateTime="2022-06-06T10:30:00">

The semantic constraints are expressed throughout the rest of this document.

The ODM Version 2.0 XML Schema file can be used with a validating XML parser to test that an ODM file is syntactically valid. To ensure semantic correctness, the use of an ODM-specific validation application is recommended.

JSON File Conformity

The syntactic constraints for ODM v2.0 JSON files are:

1. The ODM file must be a well-formed JSON file. See the ECMA-404 standard for details.
2. The ODM file must satisfy the rules about element nesting and the formats of values defined in the ODM standard.
3. The root object corresponds to the ODM element.
4. The ODMVersion attribute of the root object must be set to "2.0".

{
    "ODM": {
        "ODMVersion": "2.0",
        "FileOID": "000-00-0000",
        "FileType": "Transactional",
        "Description": "Sample ItemData Extension",
        "AsOfDateTime": "2022-06-04T07:57:00",
        "CreationDateTime": "2022-06-06T10:30:00",
        "Study": {
            "OID": "xxx",
            "StudyName": "NIH Chronic Low Back Pain example",
            "MetaDataVersion": {
                "OID": "yyy",
         ...
            }
        }
    }
}