Why unbound function is called without namespace

[mainakaich]

As per OData basic tutorial in Basic Tutorial · OData - the Best Way to REST, an unbound function example was given as
GET serviceRoot/GetNearestAirport(lat = 33, lon = -118)

Here the function name was given without namespace. On the other hand, when calling a bound function, the namespace was provided like below.
GET serviceRoot/People('russellwhyte')/Microsoft.OData.SampleService.Models.TripPin.GetFavoriteAirline()

I wanted to understand what the rule is here. I was thinking that namespace is mandatory for function all the time. But this is not the case here. Kindly provide the suggestion.

[xuzhg]

@mainakaich Here's AI response :)

Here's why this convention exists
Static Operations on the Service:
Unbound functions are essentially static operations on the OData service, similar to a static method in a programming language. They don't operate on a particular instance of an entity, but rather on the service as a whole or to perform operations not easily defined as CRUD operations on entities.
Function Imports:
In OData, unbound functions are exposed as "function imports". The canonical URL for a function import is the service root followed by the name of the function import, without a namespace prefix. This makes the URL shorter and easier to read.
Simplicity and Consistency:
Omitting the namespace makes the URL for invoking unbound functions more concise and consistent with how they are conceptualized as top-level operations within the service.
In contrast
Bound functions are associated with an entity type or collection and are called with a namespace because they operate within the context of that specific type or collection. The namespace helps to distinguish between functions with the same name that are bound to different types.
Essentially, the lack of a namespace for unbound functions reflects their independent nature and their direct availability at the service root, simplifying their invocation.

[mainakaich]

@xuzhg
Thanks so much for your(AI ;)) valuable comments. I was searching the OData V4 protocol documentation but couldn't find the answer. Would you be able to provide reference from the protocol documentation for the same.
Thanks,
Mainak