Re: Decoding an octet stream

[ka@socrates.hr.lucent.com.no_spam (Kenneth Almquist)]

Geoff Bull <geoff@research.canon.com.au> wrote:
> Kenneth Almquist wrote:
>> 
>> The allegedly novel idea is to write the data in a
>> cannonical format, making it unnecessary to run conversion programs
>> when moving files or file systems.
>
> Not quite, as that would involve magic!

No magic.  Conversion code is still required, but it is executed
every time you read or write the data from/to secondary storage.
It is not executed when you move the secondary storage media from
one system to another.

> I read it that the patent claims as novel the idea of
> transmitting data in a canonical format, so that the
> sender doesn't need to know the binary representation
> required by the receiver.

On rereading the patent, I have to agree with your reading.  The
description talks about files and file systems, which makes it appear
that the authors were primarily thinking of data stored on hard disks,
but in certain places the language is general enough ("auxiliary
storage or communications", "data source", "data destination") that
network communications would be covered.

> This patent would cover any program that, for example,
> exchanges data in standard "network" order.
>
> As I said, I think XDR predates it, can anybody verify that?

I don't know what the relevant date is, because the patent is dated
1990, but is a "continuation" (whatever that is) of a 1986 patent
application, which is in turn a "continuation" of an abandoned 1982
patent application.  In any case, using "network order" when transmitting
data of a network has been around almost as long as networks have.

The patent comes closer to being original when applying to data files,
but I think that the Common Object File Format (COFF) is prior art.
COFF was in use prior to 1986, but I'm not sure if it was around in
1982.  COFF is a format for UNIX files containing machine code, and
machine code is of course hardware dependent.  However, all the other
binary data in these files is stored in a machine-independent manner.
In addition, the library routines developed for processing COFF files
were placed in a library (libld.a), and as I recall the documentation
specificly pointed out that these would be useful for other applications
that wanted to write other types of machine-independent binary files.
Thus we have (1) data in a cannonical format, (2) stored on secondary
storage devices, and (3) used on UNIX, which is a UNIX-like operating
system.
				Kenneth Almquist