Item and piece in OPC

[MURATA Makoto]

Hi Chris,


2014-06-07 7:36 GMT+09:00 Chris Rae <Chris.Rae at microsoft.com>:

>  Hi all – for reference, here are the definitions of “logical item name”
> (which really seems to me to actually define “logical item”), “piece” and
> “zip item” from the T&Ds:
>
>
>
> *logical item name *— An abstraction that allows package implementers to
> manipulate physical data items
>
> consistently regardless of whether those data items can be mapped to parts
> or not or whether the package is
>
> laid out with simple ordering or interleaved ordering.
>
>
>
> *piece *— A portion of a part. Pieces of different parts can be
> interleaved together. The individual pieces are
>
> named using a unique mapping from the part name. Piece name grammar is not
> equivalent to the part name
>
> grammar. Pieces are not addressable in the package model.
>
>
>
> *ZIP item *— A ZIP item is an atomic set of data in a ZIP archive that
> becomes a file when the archive is
>
> uncompressed. When a user unzips a ZIP-based package, the user sees an
> organized set of files and folders.
>
>
>
> I’m not sure what you mean about the relationship being 1:1 – a piece, for
> example, definitely does not always correspond to a whole part. But I might
> be misunderstanding your wording.
>
[snip]

I agree that a piece does not always corresponds to a whole part.  That's
why I did not mention parts in my mail.  But doesn't a piece always
correspond to a logical, physical, and zip item?

Regards,
Makoto
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