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https://issues.apache.org/jira/browse/DAFFODIL-2535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17546758#comment-17546758
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Mike Beckerle commented on DAFFODIL-2535:
-----------------------------------------
Probably can't deprecate this.
DFDL Schemas get used as XML schemas, and so can be used to validate XML
documents in separate validators unrelated to Daffodil.
These may be tools/libs cannot use Daffodil's resolver. (C-based for example.)
They may not interpret schemaLocations the same way, so may require use of an
XML Catalog in order to resolve the locations of schemas.
> Deprecate XML Catalog Feature
> -----------------------------
>
> Key: DAFFODIL-2535
> URL: https://issues.apache.org/jira/browse/DAFFODIL-2535
> Project: Daffodil
> Issue Type: Improvement
> Components: Front End
> Affects Versions: 3.1.0
> Reporter: Mike Beckerle
> Priority: Major
>
> Quiet consensus discussion on dev list is that we should deprecate support
> for XML Catalogs for the reasons below (taken from email thread)
>
> XML Catalogs seem very fragile, with important aspects that don't work (I was
> unable to get relative-catalogs to work at all) and I am wondering if we
> really need to support XML Catalogs or not. Our classpath based resolution of
> schema locations works quite well and can be used to make quite modular DFDL
> schemas.
>
> Currently, XML schemas built into Daffodil (e.g., tdml.xsd, the schema for
> DFDL schemas, etc.) are resolved from a built-in XML catalog, but really the
> fact that this is using a catalog is not particularly important. You can
> think of it as they're just built into our resolver.
>
> XML Schemas referenced using the schemaLocation attribute on an
> xs:import/xs:include or the xsi:schemaLocation on XML instance documents are
> resolved by either:
>
> 1) relative to the file containing the reference, i.e., the file containing
> the include/import statement
>
> 2) relative to the root of any directory or jar on the classpath, searching
> them in classpath order. First one found wins.
>
> This enables one to create multi-part DFDL schemas, such as for an envelope
> format, and a payload format carried inside the envelope format. Each can be
> testable separately, and a combining schema can be created that puts the
> payload on the classpath first, followed by the envelope format, and combines
> the two.
>
> Given that this works, and works well, XML Catalogs can be deprecated.
>
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