For high value assets, it's important to have a contract. It defines a related set of transactions and conditions under which they occur. A contract normally centers around a particular asset type and involves a well-defined set of participant types. If you look at a real-world contract, it includes a combination of statements about instances and statements about definitions. At the top of the contract, all the assets and participants will be laid out with particular values—namely Daisy (the buyer), Winchester bicycles (the seller), 300 GBP (the price), 10 May 2018 ( the date of purchase) and so on. It's only after all these type-to-instance mappings have been laid out, that the contract is then defined in terms of these types, transactions, and conditions under which they occur, without reference to the particular instance values. This is what makes contracts a little strange to read at first—but once you can see the structure in terms of participants, assets, and transactions, and their respective values, they are actually quite easy to understand, and all the more powerful for this structure.