I was asked last meeting to document
an example with COBOL ODO to see if our expectations that discriminators
did not impact defaulting was correct.
Through the following example I've convinced
myself that although discriminators may not be involved with defaults that
occursCount should be. The difference is a very fine point on how
the rules are expressed. Let me step through the example...
The little odo copybook looks like so:
XML 01 ODO.
XML 10 DEPOSITS.
20 DEPOSIT-COUNT
PIC 9(5).
20 DEPOSITA OCCURS 0 TO 9999 TIMES DEPENDING
ON DEPOSIT-COUNT
PIC X(10).
example data could look like:
00003111111111122222222223333333333
| |
| | |
CORE-FUND-COUNT
| |
|
| |
|
CORE-FUND[1]
| |
|
|
CORE-FUND[2] |
|
CORE-FUND[3]
-w .\dpa\fls\cob\dpaflscob2.tdf
-t
*************************************************************
*Test Case: dpaflscob_01
*************************************************************
<Infoset xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ODO>
<DEPOSITS>
<DEPOSIT-COUNT
xsi:type="xs:integer">3</DEPOSIT-COUNT>
<DEPOSITA>1111111111</DEPOSITA>
<DEPOSITA>2222222222</DEPOSITA>
<DEPOSITA>3333333333</DEPOSITA>
</DEPOSITS>
</ODO>
</Infoset>
The question that we are trying to answer
is 'is a discriminator used in establishing existence'. In other
words, does it make us
create something that we would otherwise
not create in the infoset or in the output datastream? Or - will
defaulting take place?
If we look at this as being modelled
in DFDL we could model this in several ways...one is the way of WTX with
discriminators and another way is using occursCount:
a la WTX:
<xs:element name="ODO"
dfdl:lengthKind="implicit">
<xs:complexType>
<xs:sequence
dfdl:sequenceKind="ordered">
<xs:element name="DEPOSITS" dfdl:lengthKind="implicit">
<xs:complexType>
<xs:sequence dfdl:sequenceKind="ordered">
<xs:element name="DEPOSIT-COUNT"
type="Cobol_9" dfdl:length="5"></xs:element>
<xs:element name="DEPOSITA"
minOccurs="1" maxOccurs="unbounded" type="Cobol_X"
dfdl:length="10" default="XXXXXXXXXX">
<xs:annotation>
<xs:documentation>Beginning
of Hierarchical Transaction</xs:documentation>
<xs:appinfo source="http://www.ogf.org/dfdl/">
<dfdl:discriminator test="{ dfdl:count(/ODO/DEPOSITS/DEPOSITA)
le /ODO/DEPOSITS/DEPOSIT-COUNT}"/>
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
The other way would be to use an OccursCount
<xs:element
name="DEPOSITA" minOccurs="1"
maxOccurs="unbounded" type="Cobol_X"
dfdl:length="10" default="XXXXXXXXXX"
dfdl:occursCountKind="expression"
dfdl:occurCount= "{/ODO/DEPOSITS/DEPOSIT-COUNT}"
/>
The difference in these approaches is
that the model with occursCount is expressed as a fixed point wheras the
model with the discriminator
is a moving point using 'less than or
equals'. I'm expecting that the occursCount logic when implemented
incorporates
this concept when parsing/unparsing.
When I must have three of something then the second occur of it is VALID
for it
is less than the maximum. I don't
think that we could expect that concept to be in the discriminator implementation.
This wording seems trivial but it impacts my expectations for default
(not sure if rightly so!)
____________________________________
So parsing with the discriminator version.
If my datastream was missing the third occur of DEPOSITA, would we
expect
a DEFAULT to be applied? Would
discriminator versus occursCount make a difference?
Input datastream: 0000311111111112222222222
<Infoset xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ODO>
<DEPOSITS>
<DEPOSIT-COUNT
xsi:type="xs:integer">3</DEPOSIT-COUNT>
<DEPOSITA>1111111111</DEPOSITA>
<DEPOSITA>2222222222</DEPOSITA>
</DEPOSITS>
</ODO>
</Infoset>
OR
<Infoset xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ODO>
<DEPOSITS>
<DEPOSIT-COUNT
xsi:type="xs:integer">3</DEPOSIT-COUNT>
<DEPOSITA>1111111111</DEPOSITA>
<DEPOSITA>2222222222</DEPOSITA>
<DEPOSITA>XXXXXXXXXX</DEPOSITA>
</DEPOSITS>
</ODO>
</Infoset>
In this case I would expect the
discriminator to create the first infoset (sans the default) but the occursCount
to create
the second infoSet with the default.
The reason being that the discriminator is expressly written as 'less than
or equal'
but the occursCount (even though
it acts as le while processing) is expressed as a finite number, But
this is a very slight
distinction.
I've come to the reverse on unparsing...I
contend that we consider what the following infoset yields:
<Infoset xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ODO>
<DEPOSITS>
<DEPOSIT-COUNT
xsi:type="xs:integer">3</DEPOSIT-COUNT>
<DEPOSITA>1111111111</DEPOSITA>
<DEPOSITA>2222222222</DEPOSITA>
</DEPOSITS>
</ODO>
</Infoset>
datastream: 0000311111111112222222222XXXXXXXXXX
or
datastream: 0000311111111112222222222
My gut reaction is the first (with defaults)
for occursCount and the second sans default for the discriminator
I'm hoping there are lots of comments!
If there is a simpler way to look at this I've missed it thus far -
so please correct me.
Stephanie Fetzer
WebSphere Common Transformation
Industry Packs - Software Engineer
| From:
| Alan Powell <alan_powell@uk.ibm.com>
|
| To:
| dfdl-wg@ogf.org
|
| Date:
| 06/02/2010 06:22 AM
|
| Subject:
| [DFDL-WG] Fw: Fw: Action 086 Nils
and Default processing
|
| Sent by:
| dfdl-wg-bounces@ogf.org |
I have updated based on last weeks call
|
|
| Regards
|
|
|
| Alan Powell
|
|
|
| Development - MQSeries, Message Broker,
ESB
|
| IBM Software Group, Application and
Integration Middleware Software
|
| -------------------------------------------------------------------------------------------------------------------------------------------
|
| IBM
|
| MP211, Hursley Park
|
| Hursley, SO21 2JN
|
| United Kingdom
|
| Phone: +44-1962-815073
|
| e-mail: alan_powell@uk.ibm.com |
----- Forwarded by Alan Powell/UK/IBM on 02/06/2010 11:20 -----
| From:
| Alan Powell/UK/IBM@IBMGB
|
| To:
| dfdl-wg@ogf.org
|
| Date:
| 25/05/2010 17:27
|
| Subject:
| [DFDL-WG] Fw: Action 086 Nils and Default
processing |
All
I have added unparsing and corrected some of the existing information in
this latest version.
I did attempt to write out the dfdl:nilValueDelimiterPolicy and dfdl:emptyValueDelimiterPolicy
options in full but it became unreadable hence the 'as controlled by' short
cut.
Links still don't work
|
| Regards
|
|
|
| Alan Powell
|
|
|
| Development - MQSeries, Message Broker,
ESB
|
| IBM Software Group, Application and
Integration Middleware Software
|
| -------------------------------------------------------------------------------------------------------------------------------------------
|
| IBM
|
| MP211, Hursley Park
|
| Hursley, SO21 2JN
|
| United Kingdom
|
| Phone: +44-1962-815073
|
| e-mail: alan_powell@uk.ibm.com |
----- Forwarded by Alan Powell/UK/IBM on 25/05/2010 17:22 -----
| From:
| Alan Powell/UK/IBM
|
| To:
| dfdl-wg@ogf.org
|
| Date:
| 13/05/2010 17:28
|
| Subject:
| Action 086 Nils and Default processing |
All
Attached is an updated version of the nils and defaults sections of the
specification. I have only completed the parsing section so far which you
should be able to review while I am on vacation. If someone would like
to add the unparsing section that would be great.
| Note that the cross references
are not correct.
|
| Regards
|
|
|
| Alan Powell
|
|
|
| Development - MQSeries, Message Broker,
ESB
|
| IBM Software Group, Application and
Integration Middleware Software
|
| -------------------------------------------------------------------------------------------------------------------------------------------
|
| IBM
|
| MP211, Hursley Park
|
| Hursley, SO21 2JN
|
| United Kingdom
|
| Phone: +44-1962-815073
|
| e-mail: alan_powell@uk.ibm.com |
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
#### dfdl-nils-defaults v2.doc moved to MyAttachments Repository V3.8 (Link)
on 23 May 2010 by Alan Powell.
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
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#### dfdl-nils-defaults v3.doc moved to MyAttachments Repository V3.8 (Link)
on 01 June 2010 by Alan Powell.
Unless stated otherwise above:
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741598.
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3AU
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