Semantics of o.fd.DBus.Properties

Thiago Macieira thiago at
Thu Feb 7 14:17:27 PST 2008

Simon McVittie wrote:
>* Every implementation of (the same version of) an interface has the
>  same properties with the same access rights

The interface is the contract. If you claim to support it, you must 
support each and every item (method, signal and slot) with the proper 
arguments, types and access rights.

The only case where this may not hold is if an interface has 
been "upgraded". The XML interface introspection matches the new format, 
but the old is still in use by existing programs. But if that's the case, 
there must be a way for caller and callee to determine which version of 
the interface they implement.

>* In particular, every implementation of an interface has *all* the
> properties specified for that interface, and all of them (that are
> readable) have some sort of value

By "some sort of value", I understand that "Get will not return with 
error". In that sense, yes.

That doesn't mean that "the sort of value" is a meaningful value. But then 
this is something that the interface must define: if there's a specific 
value that means "not a valid value" (like a size of -1). This is not 
defined by the D-Bus protocol and the bindings should not enforce 

  Thiago Macieira  -  thiago (AT) - thiago (AT)
    PGP/GPG: 0x6EF45358; fingerprint:
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