LISTSERV mailing list manager LISTSERV 16.0

Help for METS Archives


METS Archives

METS Archives


[email protected]


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

METS Home

METS Home

METS  July 2005

METS July 2005

Subject:

version 1.5 discussion

From:

Brian Tingle <[log in to unmask]>

Reply-To:

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

Date:

Fri, 29 Jul 2005 14:02:17 -0700

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (151 lines)

Forwarded for Jerome McDonough

Greetings,

The editorial board is considering several potential revisions to the
primary METS schema. However, some of these revisions would not be
backwards-compatible with existing METS documents, and we would like
some input from the community before we decide to implement
these. Roughly summarized, the areas where we are considering changes
to the schema include 1. Adding support for nested files; 2. Bringing
the <structLink> 'to' and 'from' attributes into conformance with the
Xlink standard; and 3. Loosening the processContents specification for
xsd:any elements within METS.

----------------

One issue that has come up repeatedly is a need to record within METS
information about files that may be embedded inside of other
files. Typical examples of this would be *.zip or *.tar.gz files. Some
archives are using these and other formats to package together sets of
files, and they would like a mechanism to indicate that a file contains
subsidiary files, and to allow the association of descriptive and
administrative metadata with those subsidiary files. This also implies
a need for recording some type of information regarding how to 'unpack'
a packaging file. An issue related to the embedded file problem has
arisen with respect to multimedia file formats that support the
multiplexing of audio and video streams together in a single file; some
libraries/archives would like the ability to record the existence of
separate streams within a file, as well as linking to separate
technical metadata records for different streams.

A relatively straightforward way to achieve these goals might be to do
the following:

1.      Make the <file> element recursive, so that a <file> element
could
contain other <file> elements;
2.      Add a subsidiary <stream> element beneath <file>, to record the
existence of separate data streams within a particular file;
3.      Add a new <transformFile> element beneath <file>, to provide an
indication of the 'unpacking' steps that need to be taken to gain
access to subsidiary <file> elements. This would need to be repeatable
to allow for specifying a series of steps to unpack a file, and might
provide a link to a <behavior> in the <behaviorSec> for performing the
transformation.

So, for example, if you had a *tar.gz file with two embedded files, one
of which had two embedded streams, you'd have a METS fileSec including
something like this:

<file>
    <Flocat />            <!-- location of *tar.gz file -->
    <transformFile /> <!-- Instructions on reversing gzip -->
    <transformFile /> <! Instructions on reversing tar -->
    <file />                 <!-- first embedded file -->
    <file >                  <!-- second embedded file -->
         <stream />      <!-- first embedded stream -->
         <stream />      <!-- second embedded stream -->
    </file>
 </file>

These changes could be made to the METS schema without breaking
backwards compatibility; METS documents created under the current
schema would also validate against this schema. However, if we allow a
<transformFile> element to link to a behavior in the <behaviorSec>, we
would be breaking with past practice, which specified that you should
be able to remove the <behaviorSec> of any METS document and still have
a valid METS document. This could be avoided by placing the
<transformFile> element in the behavioral metadata section and having
it link to the appropriate <file> element. While this would remove the
information regarding necessary transformations from proximity with the
<file> they are paired with, it might also have the advantage of
allowing a single description of a set of transformations (like the
ungzip/untar combo) above to point to a variety of files, eliminating
duplication of information in those cases where a METS document refers
to multiple *.tar.gz files.

Our questions for the METS community on these changes would be:

1.      Does making <file> recursive and adding a <stream> element
provide
the needed functionality for addressing compound/embedded files? Would
people prefer another approach?
2.      Would people rather have a <transformFile> element be located
within
the <file> element (which would be easier to read) or have it located
within the <behaviorSec> somewhere (which might eliminate duplication
of information regarding transformations)?

----------------------

In the current METS schema, the 'to' and 'from' attributes on the
smLink element in the structLink section are currently in the METS
namespace, and are defined as type IDREF. This makes it very easy for
the attributes to point to <div> elements in the structMap and to
validate that the attributes are linking to real elements. However,
this is somewhat problematic inasmuch as the 'to' and 'from' attributes
are really drawn from the XLink standard, and compatability with other
schema and tools which use XLink would be enhanced if these attributes
were placed within the XLink namespace. Additionally, having 'to' and
'from' defined as being of type IDREF limits them to serving as a link
between <div> elements in a single METS document. Users wishing to
decompose extremely complicated objects into a series of METS documents
cannot link between <div> elements in separate METS documents using the
current schema. To rectify these problems, it has been proposed that
'to' and 'from' be placed within the XLink namespace, and that they
draw their definitions from the current XLink schema available at the
METS website; this will have the practical upshot of renaming them
xlink:to and xlink:from and defining both of them as type
"string". Presumably most users would use either an Xpath or a URI to
specify links in these attributes, but this would not be enforced by
the schema.

This change would not be backwards compatible. Existing METS documents
which use the smlink 'to' and 'from' attributes would not validate
against an updated schema. It might be possible to avoid this, but only
by leaving in the existing 'to' and 'from' attributes and also adding
new xlink:to and xlink:from attributes. Having the two sets of
attributes seems guaranteed to cause confusion.

The question for the METS community at this point is: would you rather
1. Leave the 'to' and 'from' attributes as they are, even though this
means that METS uses a variant of xlink not conformant with the
standard; 2. Change the 'to' and 'from' attributes to xlink:to and
xlink:from and redefine them as strings, so that METS' use of Xlink
conforms to the standard (although this breaks backwards compatibility;
or 3. Keep the existing 'to' and 'from' attributes, add xlink:to and
xlink:from attributes to smLink, and indicate that the use of 'to' and
'from' is now deprecated and may eventually be discontinued?

----------------------

A final change to the METS schema that has been suggested seems
relatively unproblematic to the editorial board: changing the
definition of all METS elements which are of type xsd:any (mdWrap and
FContent) so that they have a processContents attribute value of
'lax'. This will allow METS documents that contain XML metadata records
in a format not defined by a schema placed within an mdWrap element to
validate; currently they produce an error. XML metadata that does
conform to a schema will still validate if a schema is available.

Any and all comments on these topics are welcomed, and should be
addressed to the METS mailing list. Thank you!

==============




Jerome McDonough

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

May 2023
April 2023
March 2023
January 2023
November 2022
December 2021
November 2021
November 2020
October 2020
September 2020
July 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
May 2019
April 2019
March 2019
November 2018
October 2018
September 2018
July 2018
June 2018
April 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
July 2017
June 2017
May 2017
April 2017
January 2017
October 2016
August 2016
July 2016
June 2016
May 2016
April 2016
January 2016
September 2015
August 2015
June 2015
May 2015
April 2015
March 2015
February 2015
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
January 2014
December 2013
October 2013
September 2013
August 2013
June 2013
May 2013
April 2013
February 2013
November 2012
October 2012
September 2012
August 2012
June 2012
May 2012
March 2012
February 2012
January 2012
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003
December 2002
November 2002
October 2002
September 2002
August 2002
July 2002
June 2002
May 2002
April 2002
March 2002
February 2002
January 2002
December 2001
November 2001
October 2001
September 2001
August 2001
July 2001
June 2001
May 2001
April 2001

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager