DHL types

Type	Holds	Notes
`Int`	A signed integer	Money as an integer of minor units (`amount_minor`)
`Decimal`, `Decimal(scale=2)`	A fixed-point decimal	JSON carries it as a string
`Ratio`	A ratio
`Bool`	`true` or `false`
`Text`, `Text(len=200)`	Text, at most `len` bytes	Always give a length
`Email`	An email address
`Currency`	A three-letter currency code (`"EUR"`)	Contracts holding money cannot be `buffered`
`Timestamp`	A point in time
`Duration`	A length of time
`Identity`	A 32-byte identity (a person, organisation, space, agent or record id)	Lowercase hex in JSON
`GeoPoint`	A latitude and longitude
`Enum(a,b,c)`	One of the listed names
`Ref<Aggregate>`	A reference to a record
`SubjectRef<Aggregate>`	A reference to a record at a revision (`{id, seq}`)	Used for delegation evidence and child records
`Struct<Name>`	A struct value
`List<T>`, `List<T>(capacity=16)`	A list	Declare a capacity for lists carried by commands
`Map<K, V>`, `Map<K, V>(capacity=N)`	A map
`T?`	Optional	`Int?`, `Timestamp?`

In JSON

Integers, timestamps, durations and decimals travel as decimal strings so nothing loses precision in JavaScript. Identities are lowercase hex. A SubjectRef is {"id": "…", "seq": "…"}. Keep these representations in clients.