> For clean Markdown of any page, append .md to the page URL. > For a complete documentation index, see https://tieback.io/docs/academy/foundations/module-4/llms.txt. > For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://tieback.io/docs/_mcp/server. # Module 4: How a Passport Works in Practice > The fourth module of the free tieback Academy DPP Foundations path: the scan path from carrier to record, identifiers versus resolvers, why a passport must persist after the sale, and why a published record should not change silently. ## Overview Modules 1 to 3 established what a passport is and who has to produce one. This module answers a different question: what actually happens, mechanically, once a passport exists. Most programmes that stall after launch do so because nobody working on them can describe the scan path in enough detail to diagnose a fault, or because the team quietly treats publication as the end of the job rather than the start of a multi-year obligation. This module prevents both failures by walking the path from carrier to record, separating the two components that get confused most often, and setting out why a passport keeps working long after the point of sale. **Estimated completion time: 40 minutes.** Four lessons of 8 minutes each, plus a ten question assessment of about 8 minutes. ## Learning Objectives #### Module learning objectives Every objective is tested. Each assessment question is tagged to one of the four. ## Lesson Sequence Then take the [module assessment](/docs/academy/foundations/module-4/assessment). ## Canonical Reading This module teaches from three canonical articles. Each is the authoritative text and remains free and open to everyone: * [How Does a Digital Product Passport Work?](/docs/knowledge-base/digital-product-passports/how-does-a-digital-product-passport-work) * [What is a Data Carrier?](/docs/knowledge-base/standards-and-technology/what-is-a-data-carrier) * [What is a Product Identifier?](/docs/knowledge-base/standards-and-technology/what-is-a-product-identifier) The lessons add sequence, framing, examples and practice. They do not restate the regulatory content, and they never introduce a date, article number or citation that is not in the source article. ## Frameworks Used **TBF-004, The Digital Product Passport Data Flow.** Describes the stages a passport passes through end to end, from product creation through to end of life, and places the scan path inside the market access stage. **TBF-009, The Product Compliance Transformation Model.** Describes the shift from document based, point in time compliance to continuous, data based product accountability, which is why a passport behaves less like a certificate and more like a record kept true over time. Full descriptions of both are in the [framework registry](/docs/knowledge-base/frameworks/overview). ## The Running Case Product Every Foundations module uses one product so the examples accumulate rather than reset. **The Aurelia S2 cordless hedge trimmer.** A mid-price consumer power tool with a removable lithium-ion battery pack, a moulded polymer housing, and a woven textile shoulder strap. This module follows it through a failed scan, a tangle of internal identifiers, a battery replacement three years after sale, and a correction to a mistaken published figure. ## Completion The module is complete when all four lessons are marked complete and the assessment is passed at the Foundations pass mark of 80 percent. Retakes are unlimited and your best score is kept. Progress is saved on this device. ## Next Step After the assessment, [Module 5](/docs/academy/foundations/module-5) moves from mechanics to timing: when the obligation actually becomes mandatory, and why so much of the practical detail is still missing. ## Related Docs * [Lesson 1: The Scan Path End to End](/docs/academy/foundations/module-4/lesson-1) * [Module 4 assessment](/docs/academy/foundations/module-4/assessment) * [Module 5](/docs/academy/foundations/module-5) * [DPP Foundations](/docs/academy/foundations) * [How Does a Digital Product Passport Work?](/docs/knowledge-base/digital-product-passports/how-does-a-digital-product-passport-work) > The fourth module of the free tieback Academy DPP Foundations path: the scan path from carrier to record, identifiers versus resolvers, why a passport must persist after the sale, and why a published record should not change silently. ## Docs - [Lesson 1: The Scan Path End to End](https://tieback.io/docs/academy/foundations/module-4/lesson-1.md): Academy Foundations Module 4 Lesson 1: what actually happens between a scan and a displayed record, and why each hop in that path has an owner. - [Lesson 2: Identifiers and Resolvers](https://tieback.io/docs/academy/foundations/module-4/lesson-2.md): Academy Foundations Module 4 Lesson 2: why the identifier and the resolver are separate things with separate jobs, and what happens when organisations conflate them. - [Lesson 3: Life After the Sale](https://tieback.io/docs/academy/foundations/module-4/lesson-3.md): Academy Foundations Module 4 Lesson 3: why a passport has to keep working for years after the sale, who adds to it, and what that means for how it is designed. - [Lesson 4: Why a Published Record Should Not Change](https://tieback.io/docs/academy/foundations/module-4/lesson-4.md): Academy Foundations Module 4 Lesson 4: what snapshot immutability means in plain terms, and why corrections belong in a new version rather than a silent edit. - [Module 4 Assessment](https://tieback.io/docs/academy/foundations/module-4/assessment.md): Academy Foundations Module 4 summative assessment: ten scenario-weighted items covering the scan path, identifiers and resolvers, post-sale persistence and snapshot immutability.