Create a new rule called “Trades”:

An Individual can post a Trade Ad, which is a blog post with the following:
- Its title contains the string “[Trade]”
- Its text body is “Trading X for Y”, where X (known as the Offered Artefact) and Y (known as the Desired Artefact) are Artefacts.

A Trade Ad can be Open or Closed, and begins Open. A Trade Ad can be Closed by its creator if they post a comment to it with the string “[CLOSED]”.

An Individual can perform the action of Fulfill an Trade Ad only if all of the following are true:
- It is Open.
- They are carrying the Trade Ad’s Desired Artefact.
- The Individual who posted the Trade had is holding the Offered Artefact.
- They are at the Location of the Individual that posted that Trade Ad.

An Individual can Fulfill an Open Trade Ad by posting a comment to it with the string “[FULFILLED]”. Doing so sets the Desired Artefact’s Location from yourself to the Individual that posted the Trade Ad and sets the Offered Artefact’s Location from the Individual that posted the Trade Ad to yourself.

A Fulfilled Trade Ad is Closed. Once a Trade Ad is Closed, it can never become Open again.