Dataset-JSON

Dataset-JSON was adapted from the Dataset-XML Version 1.0 specification, but uses JSON format. Like Dataset-XML, each Dataset-JSON file is connected with a Define-XML file containing detailed information about the metadata. One aim of Dataset-JSON is to address as many of the relevant requirements in the PHUSE 2017 Transport for the Next Generation paper as possible, including the efficient use of storage space.

Dataset-JSON is using lowerCamelCase notation for attribute names, comparing to Dataset-XML PascalCase (e.g., clinicalData vs ClinicalData).

JSON format does not allow to specify or control order of attributes. Despite of that, as most JSON engines allow to control the order of attributes it is strongly recommended to follow the attribute order specified in details. The reason for that is that due to a possible large size of Dataset-JSON files, following the specified order will enable a software using steaming approaches to read the file to work in an efficient and fast way.

Dataset-JSON must contain only one dataset per file. 

Top Level Attributes

At the top level of Dataset-JSON object, there are technical attributes and two main optional attributes: clinicalData and referenceData, corresponding to Dataset-XML elements. At least 1 of the main attributes must be provided. Subject data is stored in clinicalData and non-subject data is stored in referenceData.

{
    "creationDateTime": "2023-03-22T11:53:27",      
    "datasetJSONVersion": "1.0.0",
    "fileOID": "www.sponsor.xyz.org.project123.final",
    "asOfDateTime": "2023-02-15T10:23:15",
    "originator": "Sponsor XYZ",
    "sourceSystem": "Software ABC",
    "sourceSystemVersion": "1.0.0",
    "clinicalData": { ... },
    "referenceData": { ... }
}

ClinicalData and ReferenceData Attributes

Both clinicalData and referenceData have the same structure. Each of these attributes contains study and metadata OIDs, optional reference to the metadata file and an object describing an item group (dataset). The following attributes are defined on this level.

Values of the studyOID and metaDataVersionOID must match corresponding values in the Define-XML file.

{
    "clinicalData": {
        "studyOID": "xxx",
        "metaDataVersionOID": "xxx",
        "metaDataRef": "https://metadata.location.org/api.link",
        "itemGroupData": { ... }
}

ItemGroupData attribute

itemGroupData is an object with a single attribute corresponding to an individual dataset. There must be only one dataset per Dataset-JSON file. The attribute name is OID of a described dataset, which must be the same as the OID of the corresponding itemGroupDef in the Define-XML file.

"itemGroupData": { 
    "IG.DM": { ... }
}

The dataset description contains basic information about the dataset itself and its items.

"IG.DM": {
    "records": 100,
    "name": "DM",
    "label": "Demographics",
    "items": [ ... ],
    "itemData": [ ... ]
}

items is an array of basic information about dataset variables. The order of the elements in the array must be the same as the order of variables in the described dataset. The first element always describes the Record Identifier (ITEMGROUPDATASEQ).

"items": [    
    {
        "OID": "ITEMGROUPDATASEQ",
        "name": "ITEMGROUPDATASEQ",
        "label": "Record identifier",
        "type": "integer",
    },
    {
        "OID": "IT.DM.STUDYID",
        "name": "STUDYID",
        "label": "Study Identifier",
        "type": "string",
        "length": 12,
        "keySequence": 1,
    },
    ...
]

itemData is an array of records with variables values. Each record itself is also represented as an array of variables values. The first value is a unique sequence number for each record in the dataset.

"itemData": [
   [1, "MyStudy", "001", "DM", 56],
   [2, "MyStudy", "002", "DM", 26],
   ...
]

Missing values are represented by null in the case of numeric variables, and an empty string in case of character variables: [1, "MyStudy", "", "DM", null]

The following is a full example of a Dataset-JSON file:

{
    "creationDateTime": "2023-03-22T11:53:27",      
    "datasetJSONVersion": "1.0.0",    
    "fileOID": "www.sponsor.org.project123.final",
    "asOfDateTime": "2023-02-15T10:23:15",
    "originator": "Sponsor XYZ",
    "sourceSystem": "Software ABC",
    "sourceSystemVersion": "1.2.3",
    "clinicalData": {
        "studyOID": "xxx",
        "metaDataVersionOID": "xxx",
        "metaDataRef": "https://metadata.location.org/api.link",
        "itemGroupData": {
            "IG.DM": {
                "records": 600,
                "name": "DM",
                "label": "Demographics",
                "items": [                      
                    {"OID": "ITEMGROUPDATASEQ", "name": "ITEMGROUPDATASEQ", "label": "Record identifier", "type": "integer"},
                    {"OID": "IT.STUDYID", "name": "STUDYID", "label": "Study identifier", "type": "string", "length": 7, "keySequence": 1}, 
                    {"OID": "IT.USUBJID", "name": "USUBJID", "label": "Unique Subject Identifier", "type": "string", "length": 3, "keySequence": 2}, 
                    {"OID": "IT.DOMAIN", "name": "DOMAIN", "label": "Domain Identifier", "type": "string", "length": 2},
                    {"OID": "IT.AGE", "name": "AGE", "label": "Subject Age", "type": "integer", "length": 2}
                ],
                "itemData": [
                    [1, "MyStudy", "001", "DM", 56],
                    [2, "MyStudy", "002", "DM", 26],
                    ...
                ]
            }
        }
    }
}

The TypeScript model representation and the JSON schema for Dataset-JSON version 1.0 can be found at https://github.com/cdisc-org/DataExchange-DatasetJson.