Hi Hardy: I can share my perspective - although it is almost entirely 'cons'. The need to order bitstreams for display is of course quite legitimate, and the fact that DSpace currently doesn't offer any convenient 'out-of-the-box' solution is regrettable and frustrating. But the sequence_id was intended to serve a different purpose, and that purpose would be compromised if it bore the additional role of display order index.
At all levels, DSpace encourages the idea that the 'item' is the intellectual work - it is that which is given a persistent ID (Handle), and users are encouraged to cite that identifier. However, it is an undeniable fact that in practice, the bitstream is what is often cited or referenced (e.g. in Google Scholar, etc). This is something of a problem for DSpace, since: unlike items, bitstreams have no handle or other unique, persistent ID (the filename is not required to be unique within an Item). Originally, DSpace URLs to bitstreams contained the database ID (primary key) - which was *kind of* unique - but obviously not robustly persistent (if one ever reloaded the database, which can happen at upgrades, etc, that ID could change). In response to this problem, DSpace added the sequence_id to be a persistent, item-relative unique name for a bitstream. (As a historical note, various other identifiers were considered, e.g. millisecond timestamp, MD5 checksum, etc. These were perfectly fine as IDs, but were deemed 'unfriendly' as part of a URL: http://dspace.umich.edu/bitstream/handle/1734.43/3405340958340958340980034958340985/myfile.pdf) The needs of display ordering are quite different: one could effortlessly imagine many cases where they conflict: e.g I have a display sequence 1-2-3 where I have to put a revised edition of the second bitstream in. The original can't keep ID 2, since it has been evicted from the display, but if I change it, I have broken the persistent name it was assigned, and so have falsified all the citations to it (they now refer to something else). So yes, we could 'recruit' sequence_id to be used for display order, but then we would need a *new* identifier for persistent reference, and that seems rather self-defeating... To close on a brighter note, there is an effort underway to generalize the metadata model in DSpace - to allow greater expressivity for objects other than Items (Collections, Bitstreams, etc). When this is in place, there should be much better ways to manage these issues. And Peter Dietz's patch using a new column might figure as a stop-gap measure. Thanks, Richard R On Apr 15, 2011, at 6:49 PM, Pottinger, Hardy J. wrote: > Hi, I'm writing because some of our folks are interested in taking > advantage of the bitstream ordering capability that was made possible with > DS-192. The discussion attached to DS-192 sounds a bit worrisome, and > we're concerned about the implications of using sequence_id to control > bitstream order. Can someone go over the pros/cons of using sequence_id > for this purpose? > > Here's a link to DS-192 in case you need it: > https://jira.duraspace.org/browse/DS-192 > > Thanks in advance for whatever guidance you can provide, it is much > appreciated. > > --Hardy > > > > ------------------------------------------------------------------------------ > Benefiting from Server Virtualization: Beyond Initial Workload > Consolidation -- Increasing the use of server virtualization is a top > priority.Virtualization can reduce costs, simplify management, and improve > application availability and disaster protection. Learn more about boosting > the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev > _______________________________________________ > Dspace-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/dspace-devel ------------------------------------------------------------------------------ Benefiting from Server Virtualization: Beyond Initial Workload Consolidation -- Increasing the use of server virtualization is a top priority.Virtualization can reduce costs, simplify management, and improve application availability and disaster protection. Learn more about boosting the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev _______________________________________________ Dspace-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/dspace-devel
