RE: oBix Version 1.1, wd 09

["Gemmill, Craig" <craig.gemmill@tridium.com>]

Hi Ludo-

Thanks for the feedback!  I am including the obix list on my responses, so that others may contribute to the discussion too, in case they have other ideas about my comments.  I've included your comments here as well, to provide context for people.


1.1	  Are all sections 4.1 to 4.18 intended to appear in Figure 1 on line 460?  If so, it looks like "facets" and "null" are missing in Figure 1, and description is missing for "val" in written sections 4.1 to 4.18.

A: It is intended that all the "concrete" types should appear (to borrow from Java's terminology).  'Val' is an an 'abstract' type in this picture, so it's not really necessary.  The list of value-type objects is in 4.1.  'Null' as an attribute is listed in the <obj> box.  'Facets' is itself not an attribute, but the category of attributes that provide additional information about the <obj>, such as what name should be presented on a UI display (displayName), a URI to the icon file for this object (icon), the minimum (min) and maximum (max) allowable values for this object, etc.

1.2	  Should the list of attributes for "obj" in Figure 1 on line 460 be the same as the description in Section 4.1, lines 466 to 473?  Are all attributes mandatory, or are some optional?  Have all default conditions been defined, or do all other attributes have no default conditions?  Similar questions for the other objects.

A: The list of attributes in Figure 1 under each box describes the allowed attributes for that object type.  Note that an object type's allowed attributes include those of its 'super-type'.  The contract definition for each object type defines what the attributes' default values must be.  If no default is specified, the default is that the attribute does not exist on the object.



2.	[Section 8.1, line 1120]
 
It looks like there is a missing "/" and should be:

<obj href="b/c"/>

A: Yes, I will add this to WD10.



3.	 [Section 4.18, "Facets", lines 615 to 617]

The following is stated:
"The set of available facets is: displayName, display, icon, min, max, precision, range, and unit. Vendors which wish to annotate objects with additional facets SHOULD consider using XML namespace qualified attributes."

Are facets different than other attributes - that is, they are allowed to be extended but other attribute names are not?  If so, this should be clearly stated first.  For example, a statement could be made something like: "Although oBIX predefines a number of attributes called facets, additional facets can be added."  If so, this should appear before the statement starting with "Vendors which . . . ".

When does one add additional names, and when not?  Is there encourage to first use the predefined ones?

A: I'm not sure what you're asking here.  The set of available facets defines the list of predefined attributes that can be placed on <obj>s.  It's not a question of being allowed to 'extend' these facets but not other attributes - what exactly would 'extending' one of these facets look like anyway?  I think a statement like you suggest might be helpful, in that it would make clear that implementers are allowed to add additional attributes to <obj>s, with the follow-on comment that they should qualify these attributes with an appropriate namespace.

Of course, this then brings up the concept of namespace, which is an XML-centric concept.

My proposed solution would be to add the following sentence before the sentence beginning "Vendors which" (also change 'which' to 'that', I think that is more grammatically appropriate):

"Although oBIX predefines a number of facets attributes, vendors MAY add additional facets.  Vendors that wish..."

Thanks again for the feedback.  I plan to have WD10 available soon.

Craig


-----Original Message-----
From: Ludo Bertsch [mailto:ludob@horizontec.com] 
Sent: Thursday, May 02, 2013 10:53 AM
To: Gemmill, Craig
Subject: oBix Version 1.1, wd 09

Craig,

I could not attend the last oBix call, and couldn't get you my questions before your issue of wd 09.

You dealt with some of my questions in wd 09, but as I go through the documents, I still have some other questions - find attached.

Cheers,
Ludo

--
Ludo Bertsch, P.Eng.
Horizon Technologies
www.horizontec.com
ludob@horizontec.com
(250) 592-1488

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