[jsdl-wg] Question on jsdl:HostName element

[Andreas Savva]

Michel

I can understand your reservations but an id is just a name. (And, in an 
earlier version of the document, there used to be a filesystemname 
element which I had intended to use for this case but it got deleted in 
favour of the id. Anyway, never mind.)

To quickly comment then on the other options in the initial email.
a) is possible as the spec stands
b-1) ditto (and is one simple usage pattern)
b-2) doesn't quite look right to me since filesystemtype describes the 
persistency semantics of the filesystem and presumably "home" is a 
'normal' filesystem. But is one option I guess.
c) It feels like overkill. We got along so far without it and I don't 
see why we should introduce it just to solve what looks to me like a 
fairly minor issue.

Let's talk about it on the call later today.
Andreas

Michel Drescher wrote:

> Andreas,
>
> thanks for the answer.
>
> I appreciate that the solution sketched below has its pros. But, 
> unfortunately, this overloads the semantics of the id attribute and, 
> frankly, I am not happy with this.
>
> This attribute is in JSDL (and other specs) consistently used as an 
> identifier to a particular element for _referencing_ purposes, and not 
> for declarative purposes such as describing a uniform path to the home 
> directory of a user, a particular spool directory etc. The fact that 
> the identifier _can_ carry a very similar value to that is another 
> story (and an often used technique).
>
> Cheers,
> Michel
>
>
> On 1 Mar 2005, at 1:37, Andreas Savva wrote:
>
>> Michel
>>
>> I've done most of the writeup for the filesystem section so I'll have 
>> a first go at this.
>>
>> My intention in writing the  filesystem section was to address the 
>> case you raise with option (a) (with some extra support to pass the 
>> value of the mountpoint  to the job via an environment variable 
>> present during execution, see daft 0.9.2).  If the consensus is to 
>> try and formalize this more then I would suggest defining the meaning 
>> of a small set of values for the filesystem  "id"; the meaning of ids 
>> such as "HOME", "TMP" etc. The filesystem id is already tied into 
>> other JSDL constructs (e.g., DataStaging) so this approach would be a 
>> natural one.
>>
>> Andreas
>>
>> Michel Drescher wrote:
>>
>>>     From:       Michel.Drescher at uk.fujitsu.com
>>>     Subject:     Various questions sourcing from external
>>>     Date:     28 February 2005 14:06:02 GMT
>>>     To:       jsdl
>>>
>>> Dear JSDL wranglers,
>>>
>>> I got assigned to relay the following question to the JSDL working 
>>> group:
>>>
>>> 1) jsdl:FileSystem
>>> A very popular use case for this element is to mount the user's home 
>>> directory to the execution environment.
>>> How do I do that using JSDL?
>>>
>>> Solution a) - "Magic interpreter"
>>> The JSDL snippet would be
>>>    <jsdl:FileSystem id="Home">
>>>       <jsdl:Description>foo</jsdl:Description>
>>>    <jsdl:FileSystem>
>>> and the genie interpreter would recognise the id attribute to mount 
>>> the execution user's home dir.
>>> JDSL goes "Genie in the bottle", if I may say so. ;-)
>>>
>>> Solution b) - Platform specific incarnation
>>> The JSDL snippet would be
>>>    <jsdl:FileSystem id="Home">
>>>       <jsdl:Description>foo</jsdl:Description>
>>>       <jsdl:MountPoint>/home/mdrescher</jsdl:MountPoint>
>>>    <jsdl:FileSystem>
>>> This solution lacks abstraction since I cannot resubmit that very 
>>> job to another site where my home directory is mounted to another 
>>> path (i.e. /users/drescher).
>>> Brokering this job is also hardly possible even if I try to mess 
>>> around with an incredibly large set of jsdl:Profile elements (to 
>>> match all possible mount points for home directories).
>>>
>>> Solution b) - adding "abstractable" directories to jsdl:FileSystemType
>>> The JSDL snippet would be
>>>    <jsdl:FileSystem id="Home">
>>>       <jsdl:Description>foo</jsdl:Description>
>>>       <jsdl:FileSystemType>home</jsdl:FileSystemType>
>>>    <jsdl:FileSystem>
>>> This way, JSDL would introduce the "home directory" syntactically. 
>>> The downside is that $HOME is not a filesystem. But, then, is "tmp" 
>>> always a different filesystem?
>>>
>>> Solution c) - Allowing globbing in jsdl:MountPoint
>>> The JSDL snippet could be
>>>    <jsdl:FileSystem id="Home">
>>>       <jsdl:Description>foo</jsdl:Description>
>>>       <jsdl:MountPoint>{$HOME}</jsdl:FileSystemType>
>>>    <jsdl:FileSystem>
>>>    or something similar
>>> This mechanism would introduce the well-known globbing mechanisms 
>>> from PERL or the shells like tcsh, bash etc.
>>>
>>> Solution d) - A revised jsdl:FileSystem element
>>> I don't have any idea yet to propose, but personally, I think JSDL 
>>> would benefit from an abstraction of file systems (like UNICORE or 
>>> Globus provide).
>>>
>>> Any thoughts?
>>>
>>>
>>>
>>> Cheers,
>>> Michel
>>>
>