Re: Quick TMQL question re namespaces

On 6 Mar 2011, at 5:50 PM, Lars Heuer wrote:

> Hi Andrew,
> 
>> After thinking about TMQL and path navigation in general quite a
>> bit this week, how would you resolve conflicts with pre-defined axis
>> names vs. user-defined role names?  In TMQL as it stands, since it's
>> really based on a particular TMRM->TMDM mapping, can this happen?
> 
> I wouldn't be afraid of namespace clashes since it's always possible
> to use your own namespace:
> 
>   proxy/mytmrm:instance-of
> 
> Well, a default TMQL engine would interpret it as (Python pseudo-code):
> 
>   for x in (proxy/occurrence::mytmrm:instance-of,
>                proxy/name::mytmrm:instance-of,
>                proxy/role::mytmrm:instance-of):
>       yield x
> 
> In plain words: Iterate over all occs, names, and roles played with
> the type "mytmrm:instance-of".
> 
>> I know I currently have only two places where this is an issue in
>> my TMRM-based system, but, if I were to implement TMQL on top of it,
>> I would ideally like to be able to do so without the TMDM baggage
>> and operate more directly on the proxy roles themselves.
> 
> Where do you see the issues?
> 
> BTW, probably the proposal at [1] wouldn't suffer that much from
> (default) namespace/path/axis issues since it uses another syntax for
> axes than for topic identifiers. If I understood it correctly, all
> axes use the following notation:
> 
>    axis ::= <axis-name> '::' <topic-identifier> | '*'
> 
> so there is a clear distinction between axes and topic identifiers.
> The current draft seems to make no distinction. Having a distinction
> would make extensions to TMQL easily possible and may solve your TMRM
> vs. TMDM problem, since
> 
>    proxy/mytmrm:instance-of::*
> 
> can never be interpreted as a topic identifier. It would always be
> interpreted as axis name (and probably rejected by a default TMQL
> engine since it does not know the axis name "mytmrm:instance-of").
> 
> So, the "::" notation from the older draft seems to have it's value
> even if it means that the author to be type a bit more.
> 
> [...]
>> I had an admittedly brief skim through the latest slides, the CTM
>> spec and the previous TMQL drafts, but I couldn't really see any
>> support for doing something like this.
> 
> In CTM/TMCL the 'default' 'namespace' is the document address. If you
> write
> 
>   this isa topic.
> 
> and the topic map is stored at http://www.example.org/tms/ the
> identifiers are resolved as follows:
> 
>   ^<http://www.example.org/tms/#this>
>       isa ^<http://www.example.org/tms/#topic>
>   .
> 
> (the "^" is an indicator for item identifiers). The same works for the
> topics specified by subject identifiers and subject locators:
> 
>   =<#this> isa <#topic>.
> 
> Result:
> 
>   =<http://www.example.org/tms/#this>
>       isa <http://www.example.org/tms/#topic>
>   .
> 
> 
> [1] <http://www.itscj.ipsj.or.jp/sc34/open/1536.pdf>
> 
> Best regards,
> Lars
> -- 
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--
Andrew S. Townley <[email protected]>
http://atownley.org