Tag Data Specification

Tag Data Specification

The GS1 Tag Data Specification (TDS) defines how GS1 identification keys -- such as GTIN, SSCC, GIAI, and GLN -- are encoded into binary format for storage on RFID tag memory. TDS is the bridge between the human-readable world of GS1 barcodes and the binary world of EPC memory on RFID tags.

Encoding Structure

Each GS1 key type has a corresponding EPC scheme with a defined binary layout. For example, the SGTIN-96 scheme encodes a GTIN plus a serial number into exactly 96 bits of EPC memory. The encoding includes a header (identifying the scheme), a filter value (distinguishing packaging levels), a partition (defining field boundaries), the company prefix, item reference, and serial number.

TDS defines encoding rules for over 15 EPC schemes, each optimized for a specific application domain:

• SGTIN: Serialized trade items (retail products)
• SSCC-96: Shipping containers and logistics units
• GIAI-96: Individual assets
• SGLN-96: Physical locations
• GRAI-96: Returnable assets (pallets, totes)
• GDTI-96: Documents

Translation and Interoperability

A critical function of TDS is defining bidirectional translation between binary EPC, tag URI, and pure-identity URI formats. The Tag Data Translation (TDT) library implements these conversions, allowing systems to move between the compact binary format stored on the tag and the human-readable URI format used in EPCIS events and databases.

For example, a 96-bit binary string on a tag might translate to urn:epc:id:sgtin:0614141.812345.6789, which in turn maps to GTIN 00614141812345 with serial 6789.

Implementation Considerations

When commissioning RFID tags, the printer-encoder software must correctly implement TDS encoding rules, including proper partition selection based on company prefix length and valid serial number ranges. Incorrect encoding is a common source of ship-and-deduct chargebacks. GS1 provides free TDS validation tools that should be part of every source tagging quality assurance workflow.