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METS  December 2001

METS December 2001

Subject:

Resp to msgs: this time re: fileGrp, files-in-general

From:

Carl Fleischhauer <[log in to unmask]>

Reply-To:

Metadata Encoding and Transmission Standard <[log in to unmask]>

Date:

Sun, 9 Dec 2001 20:38:20 -0500

Content-Type:

TEXT/PLAIN

Parts/Attachments:

Parts/Attachments

TEXT/PLAIN (135 lines)

Thanks to Jerry, the MSU crew, and Dave Ackerman for some very helpful
exchanges.  I am doing my level best to digest various hunks of the
information they provided and will hazard some [rebut-able]
interpretations, starting with two today, of which this is the
first.  This message is more or less about fileGrp and some
"orphaned" data units that tend to be about files-in-general rather than
specific categories of files (images, audio, video, text).  For my LC AV
colleagues, I have inserted some references to our data-capture database,
which we are frantically trying to move to its next state this week.  Many
readers will therefore wish to skim the <LCdb></LCdb> notes.


PART I.  Data units that everyone seems to agree are suitable for fileGrp,
all of which seem to be there already. The item numbers are from the METS
gamma schema.  The long and the short of it is that I endorse what Jerry
did some time ago.

1. ID: an XML ID for the element

2.  MIMETYPE: the MIME type for the file
<LCdb reference note>43. ALLFILES/internet_media_type: The Multipurpose
Internet Mail Extensions (MIME) type for the object of the file_locat,
e.g., audio/wav, image/jpeg, video/mpeg, etc.  Goes to fileGrp in METS
primary schema.</LCdb>

3.  SEQ: an integer indicating the sequence of this file relative to the
others in its file group

4.  SIZE: the size of the file in bytes
<LCdb reference note> 44 ALLFILES/filesize: The size of the file in bytes,
e.g., 1024.  Goes to fileGrp in METS primary schema.</LCdb>

5 CREATED: the date of creation for the file [NOTE: presumably, this is
being extended to cover modify and access]
<LCdb reference note> 46 ALLFILES/datetime_ create: Date and time of
creation for the file, e.g., 1997-04-22 (date only),
1997-04-22T19:20+01:00 (full expression), etc.    Goes to fileGrp in METS
primary schema.
47 ALLFILES/datetime_ modify:Date and time of file last modified, e.g.,
1997-04-22 (date only), 1997-04- 22T19:20+01:00 (full expression),
etc.  Goes to fileGrp in METS primary schema.
48 ALLFILES/datetime_ access: Date and time of file last accessed, e.g.,
1997-04-22 (date only), 1997-04- 22T19:20+01:00 (full expression),
etc.  Goes to fileGrp in METS primary schema.</LCdb>

6 OWNERID: a primary identifier assigned to the file by its owner

7 ADMID: IDREFS to administrative metadata sections in the METS document
that correspond with this file

8 GROUPID: an identifier that establishes a correspondence between this
file and files in other file groups


PART II.  Data units that look like they will go into the various specific
techMD schemas.  The LC AV project database design specialists will decide
whether to continue to capture these data units in an ALLFILES table or
instead in the domain-specific tables.  In the following rundown, however,
the LCdb references are to the current ALLFILES table.

Byte_order. The order of bit significance in a byte from left to
right.  (Field 49 in LCdb)
NOTE: Jerry says put this in techMD.  Dave says this is in AES audioMD,
called "audio_data_orientation" (big_endian | little_endian), which is an
attribute of "data_format."  But byte order appears _not_ to be in the
NISO image set, which strikes this lay analyst as odd.
<LCdb>Shall we leave this in our ALLFILES table but consider repeating it
in the AUDIOMD table to facilitate producing AES audio-schema
instances?</LCdb>

Checksum trio: (1) checksum_type (type of checksum algorithm employed,
e.g., MD-5, RSA-MD4, HC), (2) checksum_value (checksum value of the file,
e.g.,  57edf4a22be3c955ac49da2e2107b67a), and
(3) checksum_datetime. (creation date and time of the checksum, e.g.,
1997-04-22 (date only), 1997-04- 22T19:20+01:00 [full expression],
etc.).  (Fields 50, 51, and 52 in LCdb.)
NOTE: Jerry says the standing rule-of-thumb would put checksum_type in
techMD since it does not vary from file to file, with checksum_value and
checksum_datatime in fileGrp.  But Jerry agrees that there is an argument
for putting this trio in the same place, which seems more logical to
Carl.  Regarding the standing rule-of-thumb, Carl notes that LOTS of data
units in the techMD specific schemas change from file to file, e.g., pixel
counts and audio duration.
<LCdb>For now, shall we leave these 3 in our ALLFILES table?</LCdb>

Security (we used to call this encryption but wanted a more generic
name).  Type of encryption used in the file, e.g.,  symmetric, assymetric,
RSA encryption, Rabin encryption etc. (Field 53 in LCdb.)
NOTE: Jerry says techMD.
<LCdb>For now, shall we leave this in our ALLFILES table?</LCdb>

Watermark.  Type of watermark used in the file, e.g.,  Digimarc, Giovanni,
Alpha-Tec, StirMark, etc. (Field 54 in LCdb.)
NOTE: Jerry says techMD.
<LCdb>For now, shall we leave this in our ALLFILES table?</LCdb>

Encapsulation. Type of encapsulation used in the file, e.g., zip, tar,
etc.  (Field 55 in LCdb.)
NOTE: Jerry says techMD.
<LCdb>For now, shall we leave this in our ALLFILES table?</LCdb>

Owner (this may be a special LC administrative need not be shared by other
projects). The name of the owner or administrator of the file, e.g.,
LC/NDLP, etc. (Field 45 in LCdb.)
NOTE: Jerry says techMD.
<LCdb>For now, shall we leave this in our ALLFILES table?</LCdb>

Use (this may be a special LC administrative need not be shared by other
projects). Use of the file, e.g., Master, Service High, Service Low,
Preview. (Field 56 in LCdb.)
NOTE: Jerry says techMD.
<LCdb>For now, shall we leave this in our ALLFILES table?</LCdb>


PART III.  Other stuff.

Compression types, codec, and related matters.  Responses from Dave and
MSU suggest pretty strongly that compression-related information requires
domain-specific expression and thus truly belongs in techMD.  Note that
the current list of NISO values for compression is borrowed from TIFF
version 6 and will probably need to add some other enumerated values,
e.g., for JPEG2000 and MrSID.  BTW: I didn't see in the NISO document any
place to do something like, say, track the JPEG quantization table; did I
miss it?
<LCdb>Leave what we have in AUDIOMD and VIDEOMD; change tiff_compression
to compression and define to be in synch with NISO.</LCdb>

Some of the MSU and Dave Ackerman comments suggest that we might want to
think about:

format_name [which could be used to identify the class, and thus be used
in data-administration system to "get" format-level documentation]

filename_extension (as distinct from MIMEtype)

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