The SPDX v3 logical model depicts the Elements used to build an SPDX knowledge graph.
- Each element value is uniquely identified by an IRI
- Each element value is immutable - once an IRI has been assigned to a value, the IRI cannot be reused and the value cannot be changed
- Each element is independent - no element depends on the value of any other element
The independence property ensures that each logical element instance can be serialized separately into a data instance, and that data instance is hashable. A collection of element instances can also be serialized together into a data file referred to as a transfer unit, in order to reduce size and enable an integrity check value to cover the entire collection.