> For the complete documentation index, see [llms.txt](https://city-protocol.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://city-protocol.gitbook.io/docs/issuance-and-operation-layer/structured-product-architecture.md). # Structured Product Architecture

The Issuance & Operation Layer is the product layer inside the capital stack. It composes TaaS and VaaS outputs into products that downstream applications can understand and integrate. TaaS supplies tokenized assets and product metadata. VaaS supplies vault operations, accounting, NAV, and redemption infrastructure. The Issuance & Operation Layer defines how multiple components become one product with one methodology, one product-level NAV, and one subscription/redemption experience. *** ### Core Modules

Module	Function
Product Registry	Canonical registry of live products, product IDs, component lists, methodology versions, fees, capacity, eligibility policy, and lifecycle status.
Issuance Engine	Creates the product token, share, receipt, or position record and links it to the product registry, eligibility logic, NAV source, and redemption path.
Composition Engine	Defines components, target weights, allocation bands, sleeves, wrappers, and approved component sources across TaaS, VaaS, and external whitelists.
Methodology and Rules Engine	Stores product methodology, rebalance cadence, trigger rules, concentration limits, drawdown controls, liquidity requirements, and allowed actions.
Unified NAV Module	Aggregates component NAV, pricing feeds, idle assets, liabilities, accrued fees, and settlement records into product-level NAV.
Rebalancing Controller	Executes rebalance instructions only inside approved allocation bands, component whitelists, venue rules, and governance limits.
Primary Market Module	Handles subscription, creation, redemption, epoch closure, price locks, liquidity checks, and claim execution.
Eligibility and Transfer Policy	Applies KYC/AML, jurisdictional rules, allowlists, investor limits, transfer restrictions, and product-specific access rules where required.
Disclosure and Reporting Layer	Publishes methodology, component exposure, NAV history, fee schedule, risk disclosures, verification records, product events, and wind-down notices.
Lifecycle Manager	Supports launch, component changes, methodology updates, fee changes, pauses, migrations, product maturity, and final wind-down.