Interface to aggregated type

[ms <m.siedlarek@nctz.net>]

My question is half-ada/half-architectural, I'll explain it on simple HTTP server example.

Imagine HTTP library providing two packages - `Headers` which provides container for HTTP headers (`Header_Container` type) and `Requests` which is a abstraction over HTTP request message (`Request` type).

Clearly `Request` aggregates `Header_Container`, as HTTP requests generally contain some set of headers.

My dilemma is - `Headers` package already provides some sort of `Header_Container` manipulation interface - procedures for inserting and deleting headers and functions to return them, but I want allow these operations also on container aggregated inside `Request` type (which is probably a private record).

Now I have several options such as duplicating header manipulation interfaces entirely (eg. function Header_Value (R : Request, Name : String) in `Requests` package) or making aggregated `Header_Container` field public (can I make only some of the record's fields public and leave others private?). Both have pros and cons, and possibly even more solutions exist.

What would you do?