Binder and architecture terms
Follow one request through the system: a person supplies a time and place, a provider calculates positions, and the application turns them into chart data. The words below name the responsibilities along that journey.
A provider supplies astronomical calculations. A frame states the origin, reference plane and direction conventions in which its coordinates are expressed. With those ideas in place, we can follow how a number becomes a shared result.
Adapter
Providers do not all speak the same interface. An adapter fits a provider’s native calls and response format to the application’s shared contract. For example, it can parse a Horizons response into position fields expressed in decimal degrees. It translates the interface rather than introducing a new astronomical model.
Contract
A contract is the agreement between packages about requests, results and errors. It covers meaning as well as field names: a longitude needs units and coordinate context before a consumer can use it correctly.
A body identifier in a shared contract establishes a name. The provider’s capabilities establish whether it can actually calculate that body for the request.
Canonical
Once several providers share an interface, their answers need a common form. Canonical means that agreed representation: for example, decimal degrees accompanied by explicit observer and frame declarations.
The standard makes comparison and consumption easier. It does not, by itself, make a position more accurate or decide which astronomical model is preferred.
Capability
A capability declares supported bodies, dates, observers or calculation modes. The router can compare a request with these declarations before selecting a provider. Think of a catalogue of supported work rather than a record of completed work: a supported request can still fail during execution.
Normalization
Normalization puts values into consistent representations and validates them. For a longitude, −1° and 359° describe the same direction; wrapping the first to the second gives consumers one consistent form.
Normalization does not supply missing observations or silently invent a tropical-to-sidereal conversion. A transformation needs an explicit rule and owner.
Semantics
With geometry available, semantics gives it the meaning expected by the chart. A longitude of 35° becomes 5° Taurus in the chosen zodiac. Longitude speed can identify direct or retrograde motion; an angular comparison can identify an aspect.
These are meanings derived from declared numerical inputs. Predictive interpretation is a further layer and should not be confused with every use of the word “semantics.”
Provenance
Suppose two charts disagree. The coordinates show the disagreement; provenance helps explain it. It records the provider, engine version, files, time model and processing choices behind the result.
Keeping that evidence makes reproduction possible. Returning it with a response does not necessarily mean it has also been saved in a database.
Drift
Drift is a difference between calculations made under comparable assumptions. For longitudes of 359.9° and 0.1°, the circular difference is 0.2°. Ordinary subtraction would misleadingly suggest a gap of 359.8°.
Before interpreting a difference, compare the observer, frame, time scale and corrections. A changed reference can explain a changed number without either calculation being wrong. This is why provenance belongs alongside comparison.
Host
The host is the application that constructs and runs these packages. It owns lifecycle, transport, scheduling and storage. It might run on a server or elsewhere; the term identifies responsibility rather than an internet hostname.
Coverage fallback
If the preferred provider cannot cover a requested body or date, a coverage fallback is an explicitly permitted alternative. It is a routing choice made under declared rules. It does not imply that every error should be retried with another provider, whose support and behaviour may differ.
Circuit breaker
A circuit breaker temporarily refuses calls after failures, by analogy with an electrical breaker interrupting a faulty circuit. It helps avoid repeatedly calling an unhealthy dependency while it recovers.
The host can maintain state inspected by router hooks; an adapter can separately protect its own remote calls. The boundary matters when tracing why a request was not attempted.
For the implemented and planned boundaries, continue with the designs for routing, normalization, semantics and comparison.