Protocol versioning model
Trust State Protocol employs explicit versioning to distinguish between revisions of the specification that may introduce new features, constraints, or clarifications. Each version of the protocol defines a complete and self consistent set of rules governing trust representation, event handling, state transition, decay, and verification assumptions.
Version identifiers are intended to be unambiguous and immutable. A trust state produced under a given protocol version must be interpretable only with reference to that version. This requirement prevents semantic drift, where identical trust values are interpreted differently across revisions.
Implementations may support multiple protocol versions concurrently. However, trust states generated under different versions must not be combined or compared unless an explicit and well defined migration mechanism exists outside the core protocol.
Backward compatibility principles
Backward compatibility in TSP is defined in terms of semantic preservation rather than mechanical similarity. A protocol revision is considered backward compatible if trust states generated under the previous version retain their meaning and behavior when interpreted according to the rules in force at the time they were created.
Backward compatible changes may include clarifications, additional constraints that do not alter existing behavior, or optional extensions that do not affect default operation. Changes that alter trust state evolution, decay behavior, or event interpretation are considered semantically breaking and require a new protocol version.
The protocol does not mandate automatic migration of trust states across versions. Migration, if desired, must be explicit and must not occur implicitly through version upgrades.
Extensibility through contextual parameters
Extensibility in Trust State Protocol is achieved primarily through contextual parameters rather than through modification of core mechanics. Contexts may define their own event classifications, verification assumptions, weighting functions, decay parameters, and baseline uncertainty levels, provided that these definitions conform to the constraints imposed by the protocol.
This approach allows new interaction domains to be supported without altering the underlying trust state model. Extending the protocol therefore typically involves defining new contexts rather than introducing new trust primitives.
Separation of core and extension space
TSP distinguishes between core protocol elements and extension space. Core elements include trust state representation, event driven updates, decay requirements, boundedness, and determinism. These elements are fixed within a given protocol version.
Extension space includes context definitions, parameter choices, and optional metadata that do not affect the core semantics of trust evolution. Extensions must not redefine or bypass core constraints. Any extension that modifies core behavior constitutes a protocol revision rather than an extension.
This separation ensures that innovation occurs without fragmenting the protocol or introducing incompatible interpretations of trust.
Forward compatibility considerations
Forward compatibility is addressed by requiring that unknown extensions or parameters be safely ignorable by implementations that do not recognize them. An implementation that encounters a context or parameter it does not understand must either decline to process it or treat it as opaque, rather than attempting to infer behavior.
This principle prevents misinterpretation of trust states generated under future extensions and ensures that unsupported features do not degrade trust correctness.
Explicit deprecation
When protocol elements are deprecated, deprecation must be explicit and version scoped. Deprecated features remain valid within the versions in which they were defined but are not recommended for use in new contexts or implementations.
Deprecation does not retroactively alter the interpretation of existing trust states. This preserves historical consistency and auditability.
Governance neutrality
Trust State Protocol does not define a governance model for version evolution. Decisions regarding when and how to publish new versions, accept extensions, or deprecate features are external to the protocol specification.
This neutrality allows the protocol to be adopted and evolved by different communities without embedding authority structures into the protocol itself.
