GS1 Digital Link Compliant Primary Keys

/ GS1 Application Identifiers

Compiled based on: GS1 Official Application Identifier (AI) Standard, GS1-Conformant Resolver Standard, GS1 Digital Link URI Syntax Standard
Applicable Scenarios: GS1 Resolver v3.0 Configuration, GS1 Digital Link URI Construction, Encoding Legitimacy Validation, Supply Chain Identification System Setup

Preface

This document provides a detailed description of all compliant primary keys in the GS1 Digital Link system, covering the Chinese definition, format length, validation rules, and core use cases within the GS1 Digital Link framework for each primary key.

General Terminology Explanation

  • Primary Key AI: A GS1 Application Identifier, which is the core identifier of a GS1 Digital Link URI. It uniquely identifies an entity object and serves as the core anchor point of the digital link system.
  • Check Digit: A check code generated by the GS1 standard algorithm, used to verify the legitimacy of the encoding and ensure data transmission accuracy.
  • Validation Rules: Human-readable validation logic converted from official regular expressions, used for pre-encoding validation.
  • Core Use Cases: Based on the GS1 Digital Link standard, this clarifies the primary application scenarios and business value of each primary key within the digital link system.

I. Detailed Description of GS1 Digital Link Compliant Primary Keys

1. Primary Key AI: 00

  • Description: Serial Shipping Container Code (SSCC)
  • Format Length: The AI code is a fixed 2-digit numeric string. The core data segment is a fixed 18-digit numeric string.
  • Validation Rules:
    • The core data segment must be an 18-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 18-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. When SSCC is used as a logistics primary key, other AI attributes (such as 10 Batch/Lot, 21 Serial, 11 Production Date, 15 Best Before Date, 17 Expiration Date, etc.) can be freely combined as needed, with no mandatory pairing requirements.
    • Excludes: No explicit invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Secondary AIs that can be used in parallel with this primary key can be appended according to business scenarios.
  • Core Use Case: The core identifier for the logistics segment within the GS1 Digital Link system. It uniquely identifies a logistics unit and can link to resources such as logistics tracking, warehouse information, shipping and receiving documents, cold chain temperature/humidity data, and customs declaration materials, enabling full-chain traceability of logistics. Widely used in supply chain logistics, warehouse management, cross-border transportation, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/00/376104250021234569

2. Primary Key AI: 01

  • Description: Global Trade Item Number (GTIN)
  • Format Length: The AI code is a fixed 2-digit numeric string. The core data segment is a fixed 14-digit numeric string.
  • Validation Rules:
    • The core data segment must be a 14-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 14-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. GTIN, as a general-purpose primary key, can be used independently or freely combined with other AIs.
    • Excludes:
      • AI02 (CONTENT, Contained GTIN): Two different GTIN primary keys cannot appear simultaneously in the same digital link.
      • AI03 (MTO GTIN, Made-to-Order GTIN): Cannot be used simultaneously with 01 to avoid confusion between standard and customized product identification.
      • AI255 (GCN, Global Coupon Number): A coupon scenario primary key; it cannot coexist with a trade item GTIN within the same scanning unit.
      • AI37 (COUNT, Count of Trade Items): A quantity attribute cannot be simultaneously recognized as a sub-primary key of a GTIN.
    • gs1DigitalLinkQualifiers: Only the following two officially defined sets of qualifiers can be used with 01:
      • Group 1: 22 + 10 + 21, appearing together: Consumer Product Variant (CPV) + BATCH/LOT + SERIAL. Used to uniquely identify a product at the fine-grained level of variant, batch, and individual item.
      • Group 2: 235, Third Party Controlled, Serialised GTIN Extension (TPX). Used for scenarios where a third-party system manages unique identification at a different level.
  • Core Use Case: The most core and versatile primary key in the GS1 Digital Link system. It uniquely identifies global trade items (goods, products, services, etc.) and can link to various resources like product information pages, traceability data, user manuals, marketing campaigns, compliance certifications, after-sales support, nutritional facts, etc. It is the foundation for the “one code, multiple scenarios” capability and is widely used across consumer goods, retail, manufacturing, pharmaceuticals, and other industries.
  • Compliant Example Link: https://id.gtin.xin/01/12345678901231
  • Example with Qualifiers: https://id.gtin.xin/01/12345678901231/22/Red/10/ABC123/21/SN-001 (CPV + Batch + Serial qualifier combination)

3. Primary Key AI: 253

  • Description: Global Document Type Identifier (GDTI)
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 13-digit numeric string, with an optional extension of up to 17 GS1 standard printable characters.
  • Validation Rules:
    • Must include a 13-digit continuous numeric core data segment, with the last digit being the check digit.
    • Can optionally append 0-17 characters, allowing upper and lower case English letters, numbers, and GS1 standard 82-character set symbols (ISO/IEC 646) such as ! % - ? _ ".
  • Association Rules:
    • Requires: No mandatory dependencies. GDTI, as a document primary key, can be used independently or combined with other supplementary attribute AIs.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Other AIs that can be used in parallel with this primary key can be appended according to document business requirements.
  • Core Use Case: The core identifier for document management within the GS1 Digital Link system. It uniquely identifies electronic/paper documents, certificates, invoices, compliance documents, etc. It can link to digital documents such as electronic contracts, product certificates, inspection reports, compliance declarations, electronic manuals, patent files, enabling global unique identification and online access for documents. Widely used in compliance management, legal affairs, quality management, medical devices, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/253/1234567890128 (example including optional characters)

4. Primary Key AI: 255

  • Description: Global Coupon Number (GCN)
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 13-digit numeric string, with an optional extension of up to 12 numeric digits.
  • Validation Rules:
    • Must include a 13-digit continuous numeric core data segment, with the last digit being the check digit.
    • Can optionally append 0-12 numeric digits for identifying sub-scenarios of the coupon.
  • Association Rules:
    • Requires: No mandatory dependencies. GCN can be used as an independent coupon primary key or combined with other promotional attributes (such as 8111 Points, 8112 North American Coupon Code).
    • Excludes:
      • AI01 (GTIN): A coupon cannot be simultaneously recognized as a primary key for the same entity as a trade item GTIN.
      • AI02 (CONTENT, Contained GTIN): Prevents different trade item primary keys from appearing alongside a coupon primary key in the same scanning unit.
      • AI415 (PAY TO, GLN of Invoicee): Finance and coupon belong to different scenarios; their primary keys cannot coexist.
      • AI8006 (ITIP, Individual Trade Item Piece Identification): ITIP represents a piece of a trade item and cannot be a qualifier primary key for GCN.
      • AI8020 (REF No., Payment Slip Reference Number): Payment slips and coupons belong to different scenarios and cannot coexist.
      • AI8026 (ITIP CONTENT, ITIP contained in a Logistics Unit): Also a trade item piece primary key, cannot be used in parallel with GCN.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Common additional attributes include 8111 (POINTS) and North American region coupon codes 8110/8112, used to supplement marketing scenario information under the coupon primary key.
  • Core Use Case: The core identifier for marketing scenarios within the GS1 Digital Link system. It uniquely identifies globally applicable coupons, promotional vouchers, discount coupons, redemption vouchers, etc. It can link to coupon details, usage rules, applicable stores, validity periods, redemption records, campaign mechanics, enabling full-chain digital management of marketing activities. Widely used in retail, FMCG, catering, and other industries.
  • Compliant Example Link: https://id.gtin.xin/255/1234567890128789012 (example including optional additional digits)

5. Primary Key AI: 401

  • Description: Global Identification Number for Consignment (GINC)
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is up to 30 characters and at least 1 character long, consisting of GS1 standard printable characters.
  • Validation Rules: The core data segment is 1-30 characters long, allowing upper and lower case English letters, numbers, and GS1 standard printable symbols such as ! % - ? _ ". No check digit is required.
  • Association Rules:
    • Requires: No mandatory dependencies. GINC, as a consignment batch primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Other AIs that can be used in parallel with this primary key can be appended according to freight business needs.
  • Core Use Case: The core identifier for freight scenarios within the GS1 Digital Link system. It uniquely identifies a consigned goods unit and can link to resources such as waybills, customs declaration documents, transportation tracking, cargo details, insurance documents, customs clearance progress, enabling full-process traceability and digital management of international/domestic freight. Widely used in logistics, freight forwarding, cross-border trade, bulk commodity transportation, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/401/2026-001-abc (example using 1-30 printable ASCII characters)

6. Primary Key AI: 402

  • Description: Global Shipment Identification Number (GSIN)
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 17-digit numeric string.
  • Validation Rules:
    • The core data segment must be a 17-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 17-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. GSIN can be used as an independent primary key for a whole shipment.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Other AIs consistent with the freight topic that can be used in parallel with this primary key can be appended.
  • Core Use Case: The core identifier for line-haul transportation scenarios within the GS1 Digital Link system. It uniquely identifies a whole shipment unit and can link to resources such as freight documents, transport plans, proof of delivery, cargo summaries, supply chain finance documents, in-transit monitoring, enabling global unique identification and full-chain management for full-truckload/whole-shipment freight. Widely used in line-haul transportation, full-truckload logistics, bulk cargo transport, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/402/12345678901234560

7. Primary Key AI: 414

  • Description: Global Location Number (GLN) – Physical Location
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 13-digit numeric string.
  • Validation Rules:
    • The core data segment must be a 13-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 13-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. GLN, as a physical location primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: Only the following two officially defined sets of qualifiers can be used with 414:
      • Group 1: 254 (GLN EXTENSION COMPONENT), used to subdivide internal sub-locations under a location GLN, such as specific storage positions within a warehouse.
      • Group 2: 7040 (UIC+EXT, GS1 UIC + Extension 1 + Importer Index), applicable for location sub-scenarios in restricted industries like rail.
  • Core Use Case: The core identifier for location management within the GS1 Digital Link system. It uniquely identifies physical locations, retail stores, warehouses, offices, production workshops, etc. It can link to store information, warehouse inventory, address and navigation, business hours, store events, warehouse operation processes, on-site safety regulations, enabling management of physical locations. Widely used in retail, warehousing, supply chain network node management, industrial production, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/414/0614141000005

8. Primary Key AI: 415

  • Description: Global Location Number (GLN) – Invoicee
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 13-digit numeric string.
  • Validation Rules:
    • The core data segment must be a 13-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 13-digit number is the check digit.
  • Association Rules:
    • Requires: 8020 (REF No., Payment Slip Reference Number). Must appear together to fully represent a payment voucher. When 415 appears alone, it represents the invoice issuer’s primary key subject; when 8020 is appended, it forms a complete payment voucher entry.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 8020 (REF No.) can be used with 415 to form a digital link entry for a payment voucher.
  • Core Use Case: The core identifier for financial settlement scenarios within the GS1 Digital Link system. It uniquely identifies the entity issuing the invoice and can link to resources such as company qualifications, invoicing information, tax data, reconciliation portals, electronic invoice downloads, payment instructions, compliance qualifications. Widely used in supply chain financial settlement, tax compliance, B2B transaction reconciliation, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/415/0614141000005/8020/INV202600123 (including the required 8020 Payment Slip Reference Number qualifier)

9. Primary Key AI: 417

  • Description: Global Location Number (GLN) – Party
  • Format Length: The AI code is a fixed 3-digit numeric string. The core data segment is a fixed 13-digit numeric string.
  • Validation Rules:
    • The core data segment must be a 13-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 13-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. PARTY, as a trading partner primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 7040 (UIC+EXT) can be used with 417 for trading partner sub-scenarios in restricted industries.
  • Core Use Case: The core identifier for B2B transaction scenarios within the GS1 Digital Link system. It uniquely identifies supply chain trading partners (buyers, suppliers, collaborators, etc.) and can link to company information, cooperation qualifications, business integration portals, supply chain collaboration platforms, credit information, cooperation agreements. Enables global unique identification of supply chain trading partners, widely used in manufacturing procurement, distributor management, supply chain collaboration, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/417/0614141000005

10. Primary Key AI: 8003

  • Description: Global Returnable Asset Identifier (GRAI)
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is a fixed 14-digit numeric string, with an optional extension of up to 16 GS1 standard printable characters.
  • Validation Rules:
    • Must start with a fixed leading zero (0), followed by 13 continuous numeric digits. The last digit of the 14-digit number is the check digit.
    • Can optionally append 0-16 characters, allowing upper and lower case English letters, numbers, and GS1 standard 82-character set symbols (ISO/IEC 646) such as ! % - ? _ ".
  • Association Rules:
    • Requires: No mandatory dependencies. GRAI, as a returnable asset primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Often used with status-related AIs (such as 11 Production Date, 15 Best Before Date, 17 Expiration Date) and 8030 (DIGSIG, Digital Signature) to represent asset lifecycle and anti-counterfeiting.
  • Core Use Case: The core identifier for circular asset management within the GS1 Digital Link system. It uniquely identifies reusable assets (such as returnable containers, pallets, logistics bins, rental equipment, reusable packaging). It can link to asset information, rental records, movement history, maintenance, inventory data, service life, enabling full lifecycle management of returnable assets. Widely used in logistics rental, circular packaging, automotive manufacturing, FMCG supply chains, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8003/01234567890128ASSET-A001 (example including optional extension characters)

11. Primary Key AI: 8004

  • Description: Global Individual Asset Identifier (GIAI)
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is up to 30 characters and at least 1 character long, consisting of GS1 standard printable characters.
  • Validation Rules: The core data segment is 1-30 characters long, allowing upper and lower case English letters, numbers, and GS1 standard printable symbols such as ! % - ? _ ". No check digit is required.
  • Association Rules:
    • Requires: No mandatory dependencies. GIAI, as an individual asset primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 7040 (UIC+EXT) can be used with 8004 for individual asset sub-scenarios in restricted industries.
  • Core Use Case: The core identifier for fixed asset management within the GS1 Digital Link system. It uniquely identifies individual fixed assets, high-value equipment, precision instruments, medical devices, IT assets, etc. It can link to asset records, equipment parameters, maintenance logs, calibration certificates, user manuals, ownership information, depreciation data, enabling full lifecycle digital management of individual assets. Widely used in equipment management, medical devices, high-end manufacturing, IT operations, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8004/2026-7890-ASSET-DEV

12. Primary Key AI: 8006

  • Description: Individual Trade Item Piece Identification (ITIP)
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is 14 numeric digits + 2 numeric digits + 2 numeric digits, total fixed length 18 numeric digits.
  • Validation Rules:
    • The first 14 digits are the trade item GTIN code, with the last digit being the check digit.
    • The last 4 digits are the piece identifier: the first 2 digits are the current piece number, and the last 2 digits are the total number of pieces. Both are numeric.
  • Association Rules:
    • Requires: No mandatory dependencies. ITIP already includes the 14-digit GTIN as an internal primary key component; the primary key itself can independently identify a piece.
    • Excludes:
      • AI01 (GTIN): ITIP already includes the trade item-level GTIN; an independent GTIN primary key cannot be listed again simultaneously to avoid two product primary keys in the same scan.
      • AI37 (COUNT, Count of Trade Items): The quantity is an attribute-type AI and cannot be simultaneously recognized as a sub-item of a piece primary key.
    • gs1DigitalLinkQualifiers: Only the officially defined set of qualifiers 22 + 10 + 21, appearing together, can be used with 8006. This corresponds to CPV + BATCH/LOT + SERIAL, used to further subdivide the piece represented by ITIP.
  • Core Use Case: The core identifier for piece management within the GS1 Digital Link system. It uniquely identifies individual pieces within a case or set of trade items (e.g., a single component of a furniture set, an individual box of pharmaceuticals from a case, a part of a home appliance, a standalone unit of a complete equipment set). It can link to component information, assembly instructions, spare parts lists, repair guides, batch traceability, warranty information, enabling item-level identification and management of kit products. Widely used in home appliances, furniture, pharmaceuticals, complete equipment manufacturing, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8006/123456789012310126 (first 14 digits include GTIN check digit, last 4 digits are piece numbers 01/26)

13. Primary Key AI: 8010

  • Description: Component/Part Identifier (CPID)
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is up to 30 specified characters and at least 5 characters long.
  • Validation Rules: The core data segment is 5-30 characters long, allowing only upper case English letters, numbers, and the symbols / # -. No check digit is required.
  • Association Rules:
    • Requires: No mandatory dependencies. CPID, as a component primary key, can be used independently; however, for unique serial number identification, it is recommended to use it with 8011 (CPID SERIAL).
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 8011 (CPID SERIAL) can be used with 8010 to uniquely identify individual instances of the same component.
  • Core Use Case: The core identifier for component management within the GS1 Digital Link system. It uniquely identifies product components, parts, spare parts, etc. It can link to part parameters, design drawings, BOM lists, alternative models, procurement channels, repair and replacement guides, inventory information, enabling global unique identification and supply chain management at the component level. Widely used in automotive, electronics, mechanical manufacturing, repair services, aerospace, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8010/12345-XYZ-PN-ABC

14. Primary Key AI: 8013

  • Description: Global Model Number (GMN)
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is up to 25 characters and at least 1 character long, consisting of GS1 standard printable characters.
  • Validation Rules:
    • The core data segment is 1-25 characters long, allowing upper and lower case English letters, numbers, and GS1 standard printable symbols such as ! % - ? _ ".
    • The last 2 characters of the code are check characters.
  • Association Rules:
    • Requires: No mandatory dependencies. GMN, as a product model primary key, can be used independently.
    • Excludes: No officially defined invalid combinations defined yet.
    • gs1DigitalLinkQualifiers: No officially defined Digital Link qualifiers. Can be used with status-related AIs (such as 8012 SOFTWARE VERSION, 8030 DIGSIG) to represent model version and anti-counterfeiting information.
  • Core Use Case: The core identifier for product model management within the GS1 Digital Link system. It uniquely identifies product models and product series and can link to model specifications, technical parameters, user manuals, firmware updates, certifications, compatible parts, after-sales policies. Enables unified digital management of identical product models, widely used in consumer electronics, home appliances, industrial equipment, automotive, medical devices, and other industries.
  • Compliant Example Link: (Not provided in the original text)

15. Primary Key AI: 8017

  • Description: Global Service Relation Number (GSRN) – Provider
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is a fixed 18-digit numeric string.
  • Validation Rules:
    • The core data segment must be an 18-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 18-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. Provider GSRN can independently identify the service provider’s identity.
    • Excludes:
      • AI8018 (GSRN – RECIPIENT): The service provider and service recipient are two different subject roles within the same service relationship and cannot appear as parallel primary keys in the same digital link.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 8019 (SRIN, Service Relation Instance Number) can be used with 8017 to distinguish between multiple independent service session instances under the same provider.
  • Core Use Case: The core identifier for service provider management within the GS1 Digital Link system. It uniquely identifies the service relationship between a service provider and the service subject and can link to service personnel qualifications, service scope, service records, scheduling information, rating systems, service contracts, skill certifications. Enables identity recognition and full-chain service management for service providers, widely used in after-sales repair, home services, medical services, professional technical services, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8017/061414100000000007

16. Primary Key AI: 8018

  • Description: Global Service Relation Number (GSRN) – Recipient
  • Format Length: The AI code is a fixed 4-digit numeric string. The core data segment is a fixed 18-digit numeric string.
  • Validation Rules:
    • The core data segment must be an 18-digit continuous numeric string, letters, symbols, or other characters are not allowed.
    • The last digit of the 18-digit number is the check digit.
  • Association Rules:
    • Requires: No mandatory dependencies. Recipient GSRN can independently identify a customer/member/patient identity.
    • Excludes:
      • AI8017 (GSRN – PROVIDER): The service provider and service recipient are two different subject roles within the same service relationship and cannot appear as parallel primary keys in the same digital link.
    • gs1DigitalLinkQualifiers: Only the officially defined qualifier 8019 (SRIN) can be used with 8018 to distinguish between multiple independent service session instances (e.g., different medical visits, different orders) under the same customer/member identity.
  • Core Use Case: The core identifier for service recipient management within the GS1 Digital Link system. It uniquely identifies the service relationship between a service organization and the service recipient (customer, member, patient, user, etc.) and can link to membership information, service history, consumption records, entitlement information, service appointments, health records, personalized tags. Enables precise identification and personalized service management for recipients, widely used in membership systems, healthcare, lifestyle services, financial services, and other scenarios.
  • Compliant Example Link: https://id.gtin.xin/8018/061414100000000014

References

  • GS1 Official Application Identifier (AI) Standard Library: https://ref.gs1.org/
  • GS1-Conformant Resolver Standard Release 1.2.0
  • GS1 Digital Link Standard: URI Syntax Release 1.1.1
  • GS1 Resolver CE v3.0 Official Development Documentation