[DFDL-WG] examples of decimal validation using pattern facet

[Steve Hanson]

I'd still like to know whether Roger had examples of logical xs:decimal 
values that he was unable to validate using the min/max 
inclusive/exclusive and total/fractional digits facets. That would be a 
justification for allowing pattern facets but only for validation (ie, 
same as how pattern facets are used for xs:string).

Regards

Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848



From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     dfdl-wg at ogf.org, 
Date:   24/05/2013 13:22
Subject:        Re: [DFDL-WG] examples of decimal validation using pattern 
facet
Sent by:        dfdl-wg-bounces at ogf.org




Forgot to distribute this to the WG.

I now recall one of the discussions of patterns on numbers was this. 

XML has this characteristic that everything is both a string, and whatever 
type it's logical XML Schema type says it is. 

So a pattern that requires leading zeros makes sense on an integer because 
in XML, everything is a string; hence, we can talk about a pattern facet 
for the string-behavior of what XML-schema tells us is an integer.

Not so in DFDL.

In DFDL, the integer is converted to a pure conceptual number. Facet 
constraints can have to do only with the value of this logical type. The 
facets aren't about the representation. They are about the value only.

Hence, talking about leading zeros on an integer simply doesn’t make 
sense. Leading zero is a representation concept. 

Here's the simplest way to think about it. If I had binary integers, would 
this same pattern facet requiring leading zeros make sense?  --- no it 
would not; and therefore it isn't allowed in DFDL for any integers, binary 
nor textual representations. Facets must be about the logical value, not 
the representation. Hence, patterns aren't allowed on numbers, because 
patterns are fundamentally about strings. 


On Sat, May 18, 2013 at 2:42 PM, Mike Beckerle <mbeckerle.dfdl at gmail.com> 
wrote:

Roger costello of Mitre provides this example of using pattern facet.

Basically, it expresses several different possible formats, all of which 
are some combination of digits and a optional decimal point.  In terms of 
cobol-style patterns it is one of these formats:

99
99.9
99.99
99.999
99.9999

I am not sure a textNumberPattern can handle the optionality of the 
decimal point. I know we can deal with the varying number of fraction 
digits, and the fixed number of integer digits, but conditional decimal 
point I am unsure about.







---------- Forwarded message ----------
From: Costello, Roger L. <costello at mitre.org>
Date: Fri, May 17, 2013 at 4:00 PM
Subject: RE: examples of decimal validation using pattern facet
To: Mike Beckerle <mbeckerle.dfdl at gmail.com>
Cc: "Cranford, Jonathan W." <jcranford at mitre.org>


Hello Mike,
 
Ø  Can you send an example of the lat/lon validation 
Ø  you mentioned on yesterday's Daffodil call?
 
Here ya go:

            <xsd:simpleType name="foo"> 
                        <xsd:restriction base="xsd:decimal">
                                    <xsd:minInclusive value="00"/>
                                    <xsd:maxInclusive value="59.9999"/>
                                    <xsd:pattern value=
"[0-9]{2}|[0-9]{2}\.[0-9]{1}|[0-9]{2}\.[0-9]{2}|[0-9]{2}\.[0-9]{3}|[0-9]{2}\.[0-9]{4}"
/>
                        </xsd:restriction>
            </xsd:simpleType>
 
/Roger
 
From: Mike Beckerle [mailto:mbeckerle.dfdl at gmail.com] 
Sent: Thursday, May 16, 2013 8:15 AM
To: Costello, Roger L.
Subject: examples of decimal validation using pattern facet
 
Roger,

Can you send an example of the lat/lon validation you mentioned on 
yesterday's Daffodil call?

The other members of the workgroup are wondering what can't be done via 
totalDigits/fractionDigits, etc.

The rationale for why pattern facet is not supported on numbers in DFDL is 
that we already have a much more powerful mechanism for parsing and 
unparsing numbers called textNumberPattern. The pattern facet only allows 
pass/fail using a regex, and is considered redundant (and problematic) for 
numbers as a result.

...mike

-- 
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com



-- 
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com




-- 
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com
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