File:  [LON-CAPA] / nsdl / README
Revision 1.4: download - view: text, annotated - select for diffs
Sat Jul 20 17:24:50 2002 UTC (20 years ago) by harris41
Branches: MAIN
CVS tags: HEAD
clarifying different parts of the documentation

This is a pilot release of the NSDL-LONCAPA Gateway.

The goal
Implement a metadata exchange of resources from
and vice versa.

More information is in the doc/ directory.

What's new
For a history of this software, you should work through
the CVS repository.

cvs login
cvs co nsdl

How to build and install

cd nsdl/build
make build
make install

Important files
To get a good overview on the metadata conversion, I recommend
you look at the nsdl/prototypes/ script
(perldoc -f  Among other things, this
provides a list regarding the crosswalk possibilities of
LON-CAPA to&from IEEE-LOM and LON-CAPA to&from Dublin Core.

Currenty, the four stylesheets for carrying out the metadata conversion are:
* nsdl/lib/stylesheets/dcnsdl_to_loncapa.xsl
* nsdl/lib/stylesheets/lomnsdl_to_loncapa.xsl
* nsdl/lib/stylesheets/loncapa_to_dcnsdl.xsl
* nsdl/lib/stylesheets/loncapa_to_lomnsdl.xsl

The Apache web handler modules are defined in the directory:
nsdl/lib/perl/Apache/  .

The Apache configuration file (see below also) is
nsdl/conf/nsdl.conf  .

The source-to-target information is defined by nsdl/build/gatewayfiles.lpml
(an XML file defines how the software is "rendered" onto the system).
gatewayfiles.lpml is used in many locations inside nsdl/build/Makefile.

And, there are other files.

System requirements
* Apache and mod_perl
* Graham Barr's TimeDate module (
* XML::Xalan perl module (

To configure your machine, you will need to add the following
line to your /etc/httpd/conf/httpd.conf file.

  Include conf/nsdl.conf

(You will then need to restart your web server;
 /etc/rc.d/init.d/httpd restart)

This is a pilot effort.  The goal was to enact a reasonable
solution and directly uncover difficult issues.

Here are some of the remaining issues
* ISSUE: User authentication
  PROBLEM: users are crossing domains, so browser-cookie validation can't work
  SUGGESTED SOLUTIONS: should require a GPG public key and/or
                       servers should communicate to coordinate passing of user
                       and/or some kind of proxy or central verification system
* ISSUE: Imperfect metadata cross-walking
  PROBLEM: There are a range of imperfect mappings between Dublin Core and
           LON-CAPA metadata fields as well as between IEEE LOM and LON-CAPA
           metadata fields.
  SUGGESTED SOLUTIONS: Improve the LON-CAPA metadata that is collected and
                       place more importance on the exhaustive IEEE LOM
                       standard rather than the weaker Dublin Core standard.
                       In the future, to get to Dublin Core, it might make
                       sense to first convert LON-CAPA to IEEE LOM and *then*
                       go to the Dublin Core metadata standard.
* ISSUE: Set hierarchies
  PROBLEM: Asking for ListIdentifiers from LON-CAPA will return a really long
           list that represents a "jumbled" repository.  Currently,
           ListIdentifiers, ListRecords, etc return error messages--
           we do not yet support set hierarchy results.
  SUGGESTED SOLUTIONS: authors should be able to nominate their records
                       for being part of a meaningful collection of academic
                       resources; thus multiple OAI-distributed metadata sets
                       would actually be contained within LON-CAPA
* ISSUE: Code thoroughness
  PROBLEM: Limited time.  I had limited time (100 hours) to enact a gateway.
  SUGGESTED SOLUTIONS: Invest more time.  The API and documentation
                       could be a better match for what is implemented
                       and vice versa.
* ISSUE: Making SMETE available to LON-CAPA
  PROBLEM: Ummm... I thought SMETE supported OAI.  The only interface I find
           is enriched HTML forms.
  SUGGESTED SOLUTIONS: SMETE should support OAI or some exporting of XML files
                       in Dublin Core or IEEE LOM or whatever they are using.

Scott Harrison, 2002

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