James Ytow wrote:

Here we see a tipical trouble with identifier and identity. Do you mean identity of an object (a unique thing, so we don't need identifier because it is the thing) or equivalence of data (there can be multiple data objects having the same value)? Where we need GUID we can't rely on identity, in my understanding.

The DOI Handbook (http://dx.doi.org/10.1000/186) addresses this issue. The DOI approach centres on the use of Application Profiles. Each DOI can be associated with a profile which defines the metadata elements with which it is to be associated (and therefore by implication which pieces of information must remain stable for two records to be considered copies of the same object).

On page 17, the Handbook states:

A common question is: if I identify entity A with a DOI, and then I adapt it in some way to create entity B, should I assign a new DOI to entity B?

The answer is: there can be no general rule which applies to all cases and each must be treated in context. If a registrant finds it useful to do so, they may. The rules of Application profiles, and business rules of Registration Agencies, will help in deciding for DOIs registered in Application Profiles. The key point is that one should precisely specify what A is and what B is; two digital entities are never the same in any absolute sense and can be considered copies of each other only in the context of some defined purpose.

For a more detailed explanation of this fundamental topic, see the article "On Making and Identifying a Copy" http://dx.doi.org/10.1045/january2003-paskin

This is a very important point, and one that we will need to bear in mind as we consider the application of GUIDs to digital representations of real world objects such as specimen records. Two completely differently formatted records may be considered as copies of the same object if they serve the same purpose for some user. This is one area which the DOI infrastructure particularly tries to address.

Donald

--------------------------------------------------------------- Donald Hobern (dhobern@gbif.org) Programme Officer for Data Access and Database Interoperability Global Biodiversity Information Facility Secretariat Universitetsparken 15, DK-2100 Copenhagen, Denmark Tel: +45-35321483 Mobile: +45-28751483 Fax: +45-35321480 ---------------------------------------------------------------

-----Original Message----- From: Taxonomic Databases Working Group GUID Project [mailto:TDWG-GUID@LISTSERV.NHM.KU.EDU] On Behalf Of Nozomi Ytow Sent: 12 October 2005 18:40 To: TDWG-GUID@LISTSERV.NHM.KU.EDU Subject: Re: What do we mean by GUID?

Matt Jones wrote:

The term GUID is one we started using in SEEK when looking for a solution to the identity and resolution problems that we saw looming for the Taxonomic COncept Standard. Dave Thau's presentation on this (linked on the GUID wiki) defines this pretty well and explores the

issues.

Here we see a tipical trouble with identifier and identity. Do you mean identity of an object (a unique thing, so we don't need identifier because it is the thing) or equivalence of data (there can be multiple data objects having the same value)? Where we need GUID we can't rely on identity, in my understanding.

"globally unique" means simply that an identifier that is issued can only have one valid interpretation across all possible systems.

What do you mean by valid? Suppose a data object in data provider's database. A GBIF portal has its copy when last a user accessed to the data object. The data provider changes its contents for some reason afther the last access through the GBIF portal. What is the valid interpretation of these data objects? Tha provider's one?

Regardless of the mechanism used to resolve the identifier, the object that the id 'identifies' will be bit-for-bit identical.

So you mean equivalence, not identity. If it is bit-for-bit equivalence, why do you need GUID? The contents IS the GUID you defined.

There are some tricky issues dealing with granularity of the identifier for digital data (does the identifier point at a tuple in an entity, or at a whole entity, or at multiple entities).

Do you mean your bit-for-bit GUID requires scope disamibugater also? Isn't it assigned to a data object, i.e. unit to be handled as a chunk?

It may be better to use other words such as globally disambiguateor or distinguisher, because we do not mean identity by identifier.

Cheers, James