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https://issues.apache.org/jira/browse/CSV-293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17872149#comment-17872149
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Gary D. Gregory commented on CSV-293:
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Hello [~paulmillar] and all
I looked at the PR and briefly at the [CSVW
document|https://www.w3.org/ns/csvw] (from 2017).
My main concern is that we are introducing the concept of a multi-valued
setting where none currently exists.
I don't count "header comments" and "headers" since those occur once per file
instead of possibly once per line or value, as a null definition would.
If we start with one setting, we are opening the door to nearly all settings
being multi-valued, and that sounds like a mess to me.
At some point, it would be simpler to use multiple CSV instances or define a
specialized subclass for a specific use case.
My second concern is whether or not this would be enough to support all of
CSVW. If not, then this feels half-baked. While I can appreciate a pragmatic
approach to solving a specific use case. I'd like to know if this is a IRL use
case of just something that's just for fun. Also, what would it mean to fully
support CSVW? Would it be clearer to have a separate class, a subclass, or
refactor into an abstract class with CSV and CSVW subclasses. I don't know. I'm
looking for someone who already knows CSVW to let us know... ;)
> Add support for multiple null String values
> -------------------------------------------
>
> Key: CSV-293
> URL: https://issues.apache.org/jira/browse/CSV-293
> Project: Commons CSV
> Issue Type: Improvement
> Components: Parser
> Reporter: Paul Millar
> Priority: Minor
>
> The [CSVW namespace|https://www.w3.org/ns/csvw] provides metadata describing
> a CSV file. One element of this is the ability to associate certain certain
> values with the {{null}} value, as recorded by the [csvw:null
> property|https://www.w3.org/ns/csvw#property-definitions].
> This definition corresponds (broadly) to the "null String" concept (see
> [org.apache.commons.csv.CSVFormat#setNullString|http://commons.apache.org/proper/commons-csv/apidocs/org/apache/commons/csv/CSVFormat.Builder.html#setNullString-java.lang.String-]),
> with one noticeable difference: {{CSVFormat}} supports only a single "null
> String" value while CSVW, through {{csvw:null}}, supports multiple Strings.
> In order to fully support CSVW, it would be helpful if {{CSVFormat}} were to
> be updated to allow multiple null String values.
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