RE: [plcs-dex] Implementer guidance

[Tim Turner <tjt@lsc.co.uk>]

Title: RE: [plcs-dex] Implementer guidance

I have several thoughts about this.

Dave has a point, although (at the risk of being contentious) if we are to enforce this, should there not be Rules in each DEX's EXPRESS schema to state that the relevant (entities') attribute value shall be "/IGNORE"?

With respect to the earlier question, I have pasted the usage guidance from PDM schema below.
Quote:
"* Empty string '' indicates user data managed by the sending system but not provided for data exchange.
* String '/NULL' indicates user data in a mandatory attribute that is not managed by the sending system or currently not known.

* $ is used in the physical file, if an optional attribute is not instantiated."
End Quote.

Adapting this I think that:-

"/IGNORE" should be used where an optional attribute is instantiated as reference data and reference data has been provided;

 "" the empty string, could be used where an optional attribute would be instantiated as reference data, but none is provided (i.e. I have it but will not provide it at present);

"/NULL" could be used where an optional attribute would normally be instantiated without reference data, but the value is either not managed by the sending system or not currently known.

Else, "$" could be used in a P21 file where an optional attribute is not instantiated reference data and is not available in the reference data;

Regards,
Tim
NB - all these situation revolve around the attributes of the ARM entity. What about the case where there is NO attribute present in the EXPRESS arm, but reference data is needed?

-----Original Message-----
From: Mike Ward [mailto:mike.ward@eurostep.com]
Sent: 16 January 2006 07:51
To: 'David Price'; plcs-dex@lists.oasis-open.org
Subject: RE: [plcs-dex] Implementer guidance

I tend to agree with Dave here. 

Another (albeit minor) consideration is that P28 data files can simply miss out the elements corresponding to OPT attributes and the distinction between /IGNORE and $ provides a handy way of reconciling p21 and p28 files.

Mike

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All,

Specifying /IGNORE is not useful to a post-processor at all as the attribute value will never be read. Any DEX-based post-processor reading the file will know to use Reference Data, not the explicit attribute. So, you should simply leave it as $ as that takes less space and does not require the pre-processor to set a value for every attribute replaced by the use of Reference Data which can add noticable costs for very large datasets.

Cheers,
David

--------- Original Message --------
From: nigel.shaw@eurostep.com
To: plcs-dex@lists.oasis-open.org <plcs-dex@lists.oasis-open.org>
Subject: RE: [plcs-dex] Implementer guidance
Date: 16/01/06 09:07

>
> There are multiple possible interpretation of &quot;$&quot; whilst
> /IGNORE
has a
> defined meaning. Therefore send &quot;/IGNORE&quot; would be my
preference.
>
> As examples, &quot;$&quot; can be interpreted as &quot;there is no
value&quot;, &quot;I do not know
> the value&quot;, &quot;I know the value but do not want to tell
> you&quot;,
&quot;you are not
> allowed to know the value&quot;,...
>
>       Nigel
>
>
>
> -----Original Message-----
> From: Barker, Sean (UK) [mailto:sean.barker@baesystems.com]
> Sent: 16 January 2006 08:47
> To: plcs-dex@lists.oasis-open.org
> Subject: [plcs-dex] Implementer guidance
>
>
>
> I am resolving an issue on the implementer guidance for /IGNORE.
>
>  Attribute values are set to '/IGNORE' when the information that could
> be held by the attribute will be instead assigned to the instance of
> the entity. Note: required attributes will always have an equivalent
> assigned, whereas optional attributes need not be assigned.
>
> While this describes how to populate instance diagrams, the question
arises,
> what happens in the physical file. That is, should an unpopulated
> optional attribute contain the value &quot;$&quot; or
> &quot;/IGNORE&quot;?
>
>
> Sean Barker
> 0117 302 8184
>
>
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