[OAI-implementers] Some OAI-PMH protocol issues
Frederic.Merceur at ifremer.fr
Fri Dec 7 09:46:07 EST 2007
Thank you for your answer. It is clear that it is not really OAI-PMH
issues but rather application issues.
However about vocabularies for types, an extra field information with
one or several selections in the DCMI Type Vocabulary
<http://dublincore.org/documents/dcmi-type-vocabulary/> , for example,
will be so much useful. Even it is true that no recommendation will be
perfect and there will be always exception that will not match it in a
For managing duplicates, I was really thinking about national
aggregators. The French archive HAL is a good example. You can get all
the records for the HAL OAI server, or you can get a part of them
through institutional repositories server such as HAL-IN2P3 OAI server,
HAL-INSERM OAI server. So if the manager of an harvester does not know
about the architecture of those national or thematic projects, he may
record the two different servers and generate duplicates in his
harvester’s result lists. This is the same for BePress server. You can
load all institutional repositories managed by BePress separately or all
in one time through the general BePress OAI server. I know there is a
ARROW project in Australia that harvest institutional repositories and
re-expose records in its own server. Once again the description of the
repository information about the involvement of the said repository in a
national or thematic aggregation system that would re-expose the records
in OAI-PMH from a different server could be useful in some cases.
And I agree there is no solution for dates…
What do you think about Records without free access to the digital
object issues? Could the addition of a normalised and mandatory
information about the degree of accessibility of the digital object be a
OAI-PMH issues for a possible future versions?
Anyway, thanks again for your attention and for your answer.
Leslie Carr a écrit :
> I don't think that these are OAI-PMH data transport issues, but
> application issues that arise from the interpretation and usage of
> metadata from heterogenous data providers.
> Managing duplicates: while it makes life inconvenient for your service
> users, it is not something that can in general be controlled by
> independent data providers. I'm afraid that your service must have the
> ability to reconcile duplicate (or near duplicate) items.
> Controlled vocabularies for types: you will need to make a
> recommendation and try to gain support among the OAI data providers. I
> am not sure that the selection that you propose will work in practice.
> Is a PDF a text if it has embedded images? Is an image a text if it is
> an OCR scan?
> Enforced publication dates: what do you enforce if the item has never
> been officially published?
> Les Carr
> On 5 Dec 2007, at 09:40, Frederic MERCEUR wrote:
>> Further to the previous email I sent about the document
>> <http://www.ifremer.fr/docelec/doc/2007/acte-3238.pdf> we redacted to
>> assess the main difficulties met during the first year of management
>> of our Avano <http://www.ifremer.fr/avano/> harvester, I would like
>> to focus, in this email, on just 3 problems linked to the OAI-PMH
>> protocol, Dublin Core or to repositories implementation. I would like
>> to focus particularly on these 3 problems because I guess they should
>> not be so difficult to fix.
>> *Managing duplicates *
>> Too many duplicates in a result list in Harvesters list can affect
>> the user’s comfort. This is not the main problem harvesters are
>> facing today, but this should increase in the coming years. Today, at
>> least two phenomenons can generate duplicates in the harvesters’
>> * Several research organisations or universities can record the
>> same electronic resource in their own institutional repository.
>> If Avano harvests those repositories, it will get descriptive
>> index files of the same topic stored in several places. This
>> can happen if, for example, a publication is written in
>> collaboration with several institutions. If so, this
>> publication may be archived on the server of each institution.
>> Considering the current low auto-archiving rate, especially in
>> life sciences, this phenomenon is not the main cause of the
>> production of duplicates.
>> * Projects for national or thematic aggregators can pose problem.
>> In some countries, projects of merged institutional
>> repositories can agregate records from a selection of
>> repositories in a centralised database before displaying them
>> again in OAI-PMH on their own server. As a consequence, records
>> referenced on those servers are displayed twice in OAI-PMH: via
>> the institutional repository and via the centralised database.
>> If the manager of an harvester does not know about the
>> architecture of those national or thematic projects, he may
>> record the two different servers and generate duplicates in his
>> harvester’s result lists.
>> /To help harvesters administrator to avoid recording repositories
>> generating duplicates, could we imagine adding to the description of
>> the repository information about the involvement of the said
>> repository in a national or thematic agregation system that would
>> reexpose the records in OAI-PMH from a different server?
>> *Managing Type and Date field*
>> As far as I understand, in order to comply with the OAI-PMH protocol,
>> repositories have to expose their data in the non-qualified Dublin
>> Core DTD. In this DTD all fields are optional. Those fields are also
>> non-qualified, meaning, for example, that they do not have to
>> correspond to an enclosed value list. This optional and
>> non-formalised information trait raises several issues, especially
>> for the Type field.
>> Indeed, even if the Dublin Core DTD recommends storing the Type
>> information by using standardised text strings, few repositories take
>> this into consideration and still present the information as free
>> text (ex: publication, artjournal, text, article are used to describe
>> an article). Some harvesters, including Avano, offer their users to
>> limit their search to one or several types of resources. To set up
>> this filter, harvesters try to standardise the Type field using a
>> system based on key-word recognition in this character string. This
>> standardising is therefore imperfect and the filter system may
>> exclude resources from the result list when a user narrows his search
>> to one or several types of specific data. Some informations contained
>> in this Type field cannot be standardised.
>> Even more problematic is the fact that some repositories do not fill
>> in this field. As an example, in September 2007, out of the 107.000
>> records available in Avano, more than 26.000 did not have a Type
>> field. All of those records are automatically barred from the search
>> space if a user limits is search to one or several selected types.
>> /Could it be possible to imagine getting a new normalised and
>> mandatory information about the type of the digital object (text,
>> image, video….) so harvesters could offer an reliable option to
>> filter one or several types ob objects from the end-user search.
>> The publication date is also problematic for harvester. For example,
>> In September 2007, out of the 107.000 records available in Avano,
>> about 15.000 did not have a publication date. When a record does not
>> have a publication date or when it cannot be standardised, it is
>> automatically located at the end of the list if the user wants the
>> results to be sorted by date. In the same way, when a user limits his
>> search to a specific period of time (see fig. 9), those files are
>> barred from the search even if they correspond to the specified search.
>> But I guess this problem with the publication date will be more
>> difficult to fix because it is difficult to define it as mandatory.
>> *Records without free access to the digital object*
>> As far as I understand, the OAI-PMH protocol defines only the sharing
>> process of bibliographical records contained in a group of
>> repositories. As a consequence, some repositories mix records without
>> links to the digital object together with records providing free
>> access to the resource. Others provide records with paying access (ex
>> : BePress) or records with restricted access, for example, for
>> university staff.
>> In my opinion, this is the major problem harvesters have to face
>> today. There is no indication in the Dublin Core DTD showing the
>> harvesters the degree of accessibility of the objects described in
>> the records. As a consequence, harvesters cannot pass on this
>> information to their users or provide them with the ability to filter
>> empty records or records offering paying access to the resource.
>> It is my opinion that hiding records with free full text among
>> records with inaccessible full text is not helpful. For lack of time
>> and/or interest, scientists are reluctant to join the Open Access
>> movement and the archiving rate of free access publications stays
>> very low, especially in life sciences. Free and immediate access to
>> documentation is, without doubt, the best way to convince the
>> scientists of the interest of the Open Access movement. And drowning
>> a minority of records providing free access publications in an ocean
>> of records without link to the full text and/or records offering
>> paying access to the documents may not be the best way to promote the
>> Open Access movement.
>> Again, those records without free access to the full text would not
>> be a problem for the harvesters if the Dublin Core DTD enabled to
>> signify the harvesters the degree of accessibility of the objects
>> described in the records. Harvesters could then provide their users
>> with the possibility of filtering the records without free access to
>> the digital object. But it is still not the case.
>> /Could we then imagine that, in a possible future version of the
>> OAI-PMH, each record will have to provide a normalised and mandatory
>> information about the degree of accessibility of the digital object
>> (free, paying, impossible, restricted,...)? This will help harvesters
>> so much to provide a better service to theirs end-users.
>> What do you think?
>> Kind regards,
>> Fred Merceur
>> Ifremer / Bibliothèque La Pérouse
>> frederic.merceur at ifremer.fr
>> Tél : 02-98-49-88-69
>> Fax : 02-98-49-88-84
>> Bibliothèque La Pérouse <http://www.ifremer.fr/blp/>
>> Archimer, Ifremer's Institutional Repository
>> Avano, a marine and aquatic OAI harvester <http://www.ifremer.fr/avano/>
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Ifremer / Bibliothèque La Pérouse
frederic.merceur at ifremer.fr
Tél : 02-98-49-88-69
Fax : 02-98-49-88-84
Bibliothèque La Pérouse <http://www.ifremer.fr/blp/>
Archimer, Ifremer's Institutional Repository
Avano, a marine and aquatic OAI harvester <http://www.ifremer.fr/avano/>
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