Data standards

Data standards are the rules for structuring information collected by the ID system which facilitate semantic interoperability. A set of agreed-upon data standards ensures that the data entered into a system can be reliably read, sorted, indexed, retrieved, and communicated between systems. Data standards are therefore crucial for ensuring interoperability and the accuracy and portability of identity data, helping protect its long-term value. Data standards can specify, for example:

  • Length of a field (e.g., how many characters a name can be)

  • Format (e.g., numeric or strings of letters)

  • Permissible values (e.g., male, female, other)

  • Order of entry (e.g., year, then month, then date)

  • Code directories (i.e., standard codes used to abbreviate fields, such as states or provinces)

Table 37. Comparative data standards for India, EU and ICAO

Field India (Aadhaar) EU (eIDAS) ICAO


99-character string

Family name, first name (character string)

Primary identifier, secondary identifier

(varies from 39 to 30 characters depending on the form factor of the card/document)

Date of birth



DD MM YY or DD MM YYY or DDmonYY, etc. For machine readable zone (MRZ) the format YYMMDD


8 strings (lines) + Pincode

8 strings (lines) + post code

Place of birth—town, city, country, citizenship country code (3) or full name




M/F/< (unspecified)

ID number

12-digit random number

<issuer country code>/<service provider country code>/< alphanumeric identifier>

(e.g., ES/AT/02635542Y, Spanish ID number for an Austrian service provider)

9 character alphanumeric

Table 37 provides some illustrative examples of different standards used by three organizations for attributes such as name and date of birth. Although the particular data standards used will vary by context, it is crucial that identity providers define and enforce an agreed-upon set of data standards by registration agents and any other users able to edit data fields. Such standards will help:

  • Prevent data loss. The length of data fields (e.g., how many characters you can enter for a person’s name) should be standard across database applications. If fields differ by length, it will be necessary to truncate the data in some cases, which results in loss of data and added computational complexity to define and implement rules for truncation. [Note that ICAO Doc 9303 has detailed standards for truncating names.]

  • Avoid wrong interpretation of data. Certain attributes (such as first, middle, and family names, or years, months, and days) have a defined order in which they must be captured in order to avoid error and misinterpretation.

  • Promote efficiency and accuracy of data collection and exchange. Code directories—such as standardized abbreviations or numerical codes for geographic units—help improve the efficiency of data entry and minimize data errors due to misspellings, while improving interoperability with other systems that use the same standards.

  • Facilitate data sharing across systems and borders. Data standards provide a framework for the interpretation of data shared across the information systems that help avoid loss of data and facilitate translations across systems.

The ID4D-led Data Standards Working Group is in the process of developing more detailed guidance on data standards.