[SAGA-RG] Fwd (andre at merzky.net): Re: More confusion

[Ceriel Jacobs]

Thilo Kielmann wrote:
> All,
> 
> I did a global search for "wildcard" in the SAGA core spec.
> The result is that we are having three places using wildcards:
> 
> 1. attributes
> 2. logical directory (using both attribute and path wildcards)
> 3. namespace.directory, using path wildcards.
> 
> 
> Attribute wildcards don't pose a problem (at least to me, or until
> Ceriel will find one ;-)

So far, I have really let you down :-) No problems with the attribute
wildcards.

> The path wildcards from namespace.directory, however, do bring a problem,
> in combination with URLs.
> 
> 
> If I remember correctly, we switched from strings to URLs for a good reason.
> 
> URLs, however, do not allow for wildcards, according to RFC1738.
> And the here mentioned query parts of URLs are for http only, and not for
> files as we would need them here.
> If we define some "URL with wildcards" that would no longer be URLs, so this
> is no way to go.
> 
> 
> Why do we want/need wildcards for?
> The core spec writes about "shell wildcards", so we want to apply a single
> operation to several namespace entries at a time.
> (e.g.: move, copy, find,...)
> 
> This reminds me of bulk operations with SAGA tasks. But this also feels like
> "overkill" for the use case of file wildcards.
> 
> 
> My suggestion is thus to follow Ceriel (version 2):
> 
> On Thu, Nov 22, 2007 at 11:12:58AM +0100, Ceriel Jacobs wrote:
>> Another approach would be to have an explicit method to do wildcard expansion.
>> For instance, in namespace.ns_directory:
>>
>>        expand        (in string pattern,
>>                       out array<saga::url> urls);
>>
>> Here, the pattern only specifies the "path" part, but with wildcards (the directory
>> implicitly specifies the rest of the url). I am not sure whether the resulting urls
>> should be resolved with respect to the directory or not. I think not.
> 
> I think we need to spend some good thoughts on getting the parameters to this
> call right (do we need a pattern to compose the URLs from the expanded 
> patterns???)

Good question. I don't have an immediate answer.

> Besides this "expand" method, we would have to change the relevant
> namespace.directory methods to accept arrays of URLs instead of individual
> URLs.

... or in addition to. Adds more bulk, but makes methods easier to call
for the user.

> The other radical approach could be: remove file name wildcards alltogether...

But the SAGA specs are quite specific that wildcards MUST be 
implemented, so I assume that they are required by several
use-cases?

Ceriel