# Stacks: Main Models in Molecule

It's helpful to understand the data models and use cases for the main position-creating models (stacks) in Molecule. Broadly:

* [Trades](https://help.molecule.io/reference/resources/calculation-and-model-references/trades-stack) are for actual transactions. Users can't manipulate heavily downstream.
* [Assets](https://help.molecule.io/reference/resources/calculation-and-model-references/assets-stack) are for arbitrary bits of shape or other time series (that aren't market data).
* [Tickets](https://help.molecule.io/reference/resources/calculation-and-model-references/inventory-and-tickets-stack) are for injections & withdrawals from inventory.

The linked articles above describe each stack in more detail.

#### Cross-Model Interactions

Each of the above models (Trades, Assets, and Tickets) are associated with their own Valuations model. They generally live independently, but for the following cases:

* **As-Generated Trades**: updating Asset Valuations also updates linked Trade Sublegs and Valuations
* **Tickets representing Deliveries**: linking a Ticket to a Trade Subleg, actualizes & settles the Trade.
* **Asset field on Tickets**: simply allows for a finer grouping of Tickets
* **Asset field on Sublegs**: currently a label — does not have downstream impact