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Jonathan Borden ha scritto:
> On Nov 22, 2003, at 6:54 PM, Alaric B Snell wrote:
> > Jonathan Borden wrote:
> >> On the contrary, I'd say that only those folks who are
> concerned with
> >> binary goo are concerned with encodings. Folks that deal
> with text,
> >> i.e. XML, don't generally have to be concerned (to a significant
> >> extent) with encodings, which is the *big win* of XML.
> > Hmm? XML is just an encoding.
> That's the crux of this thread. Is the message that is transmitted
> *what is transmitted* or rather *something else* that is
> encoded in the
> message. If you are primarily looking from the vantage point of an
> application which communicates with another application *as if via
> RPC*, then the interface is primary and the bits on the wire are
> secondary. On the other hand if you are sending a document from one
> place to the other, then the document is primary. XML was not
> to be the "perfect" RPC protocol. XML remains a great way to "encode"
> documents -- saying this seems like a tautology -- because to a large
> extent the XML *is* the document.
I don't actually disagree with these statements.
In ASN.1, we have some abstract syntax and its instances ("abstract values")
can be encoded **as XML documents**. Or they can be encoded as BER/PER byte
strings. We say, there are, obviously, many XML documents that just "exist"
and aren't the encoding of anything at all. The abstract syntax is central
in ASN.1, and the abstract types have abstract values.
So, in ASN.1, there is no interface that is primary (as you say is true of
RPC). The abstract syntax is primary. Then, the (standard) encoding rules
determine how the instances of the abstract syntax are represented on the
wire. Interoperability is achieved by having a standard abstract syntax
notation and standard encoding rules.