RE: [odata] [OASIS Issue Tracker] (ODATA-1292) CSDL 7.2.1 Nullable: impr

We had a long discussion on whether null is a value back in 2016, see https://www.oasis-open.org/committees/download.php/58261/NullInOData.html.

In the meantime we seem to have moved more into the programming language camp, treating null as a value.

This is also consistent with the role of null in JSON, our predominant data format. There it definitely is a value.

âThe Amount property can have the value nullâ clearly expresses that

{

"Amount":null

}

is a valid JSON request/response.

âShould support not having a valueâ is not that clear. Does it mean ânullâ, or does it mean âomittedâ or âundefinedâ?

We should not underestimate the fact that most readers of our specifications are programmers and use the programming language interpretation of null. The suggested changes below will most likely lead to more confusion.

From: odata@lists.oasis-open.org <odata@lists.oasis-open.org> On Behalf Of Ericson, George
Sent: Dienstag, 19. MÃrz 2019 21:39
To: OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>; odata@lists.oasis-open.org
Subject: RE: [odata] [OASIS Issue Tracker] (ODATA-1292) CSDL 7.2.1 Nullable: improve wording

I wish I was able to attend last week.

I don't agree with asserting that null is a value. Rather null is an indication,

when specified in schema, that a property or parameter supports not having value
when specified in a reply, that the property or parameter does not have a value
when specified in a request, that the property or parameter is to be set to have no value.

I suggest the following changes:

7.2.1 Nullable

A Boolean value specifies, in addition to values consistent with its type, a property or parameter should support not having a value. ~~specifying whether the property can have the value null.~~

Attribute Nullable

The value of Nullable is one of the Boolean literals true or false.

For single-valued properties the value true means that the property or parameter supports not having a value. ~~allows the null value.~~

For collection-valued properties the property or parameter ~~value~~ will always be a collection that MAY be empty of values consistent with its type. In this case the Nullable attribute applies to items of the collection and specifies whether individual items of the collection MAY not have a value, as indicated by null. ~~contain null values.~~

If no value is specified for a single-valued property or parameter, the Nullable attribute defaults to true.

In OData 4.01 responses a collection-valued property or parameter MUST either specify a value for the Nullable item~~attribute~~ or MUST specify null to indicate that the item has no value .

If no value is specified for a collection-valued property or parameter, the client cannot assume any default value. Clients SHOULD be prepared for this situation even in OData 4.01 responses.

George

-----Original Message-----
From: odata@lists.oasis-open.org <odata@lists.oasis-open.org> On Behalf Of OASIS Issues Tracker
Sent: 13 March, 2019 5:53 AM
To: odata@lists.oasis-open.org
Subject: [odata] [OASIS Issue Tracker] (ODATA-1292) CSDL 7.2.1 Nullable: improve wording

[EXTERNAL EMAIL]

Ralf Handl created ODATA-1292:

---------------------------------

Summary: CSDL 7.2.1 Nullable: improve wording

Key: ODATA-1292

URL: https://issues.oasis-open.org/browse/ODATA-1292

Project: OASIS Open Data Protocol (OData) TC

Issue Type: Improvement

Components: CSDL JSON , CSDL XML

Affects Versions: V4.01_CS01

Reporter: Ralf Handl

Fix For: V4.01_CS02

The current text in section 7.2.1 Nullable is {quote}

7.2.1 Nullable

A Boolean value specifying whether a value is required for the property.

{quote}

This is misleading and suggests that the property can be omitted. Actually it only means that the property can be null.

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