[sc34wg3] Feedback on TMDM

Lars Heuer sc34wg3@isotopicmaps.org
Wed, 27 Apr 2005 16:48:39 +0200

Hi Robert,

> On Fri, Apr 22, 2005 at 01:43:43PM +0200, Lars Heuer wrote:

>> > - 5.1: Source Locators
> So do I, but they do not have anything to do 'from where' (source) the
> topic actually originates. As Jan (Algermissen) said before, this can
> be just an ephemeral data stream over the wire.

The note paragraph makes IMO pretty clear, that they are just
identifiers. If the term "origin" is misleading, the last sentence of
the first paragraph of the note can be shorten to

  "[...] these may be automatically assigned to information items to
  provide them with an identifier."

But I'm not sure about that because I find the definition of the term
"source locator" pretty clear and it seems to be logic to call them
"source" locators, because they are created during the deserialization
process from some topic map syntax.
If you build a topic map in memory from scratch the standard does not
force you to use source locators at all. They are just an empty set.

>> [...]
>> > - 5.1: Constraint
>> >   They cannot be the same unless items are topics. In that case, these
>> >   have to be merged. So there is only one topic afterall. So the source locators
>> >   are different afterall for _EVERYHTING_! Or not?
>> I don't understand the last but one sentence. :(
> If the [source locators] are the same, then the two have to be merged
> in the first place, so there is only one. And no conflict. So the
> restriction "unless they are topic items" sounds superfluous to me.

Thanks for the explanation. I don't think that restriction is
superfluous because the main intention is to explain that

  "It is an error for two different information items to have string
  that are equal in their [source locators] [...]"

And to explain that it is not an _error_ if topic items have the same
source locator, because they are fulfilling one of the "equality
rules" in "5.3. Topic Items" and must be merged.

The paragraph makes just an distinction between an error situation and
an equality rule.

>> > - 5.2: Base Locator
>> [...]
>> >   The only reason can be that the base locator is modified in a TM
>> >   instance changing all relative URIs in there. I cannot see any use
>> >   case for this.
>> Not directly related to TMDM, but how do you identify topic maps
>> during a TMQL query? I assume that queries across different topic maps
>> are possible. How do you distinguish them?

> [I am not sure what this has to do with the base locator.]

I thought that the URIs for addressing the maps are base locators. But
according to your example someone may address them differently. Thanks
for clarification.

Best regards,