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From "Adam Lally (JIRA)" <...@uima.apache.org>
Subject [jira] [Commented] (UIMA-2391) Uima type merging for string subtypes not working
Date Wed, 25 Apr 2012 18:24:20 GMT

    [ https://issues.apache.org/jira/browse/UIMA-2391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13261891#comment-13261891
] 

Adam Lally commented on UIMA-2391:
----------------------------------

Currently, code using the core type system can rely on the fact that instances of the Type
can only ever be a, b, or c.  They can be used like enums in this way.  If we implement merging
this way we would break that.  Are we sure we want to do that?  Code built off the core type
system would not be expecting a value "d" and might not know what to do with it.

An analogous case might be - what happens if I merge two type systems that the same type with
the same named feature (call it Foo.bar) but different range types.  In type system 1, Foo.bar
has range type A and in type system 2 it has range type B.  Would you want to say that in
the merged type system, Foo.bar could be A or B?  Probably not.

Or course, I might just be biased against extending the scope of type merging since I was
never happy it existed in the first place. :)
                
> Uima type merging for string subtypes not working
> -------------------------------------------------
>
>                 Key: UIMA-2391
>                 URL: https://issues.apache.org/jira/browse/UIMA-2391
>             Project: UIMA
>          Issue Type: Bug
>          Components: Core Java Framework
>    Affects Versions: 2.3.1AS
>         Environment: Linux on Power
>            Reporter: Charles de Saint-Aignan
>            Priority: Critical
>
> The basic situation is that we are providing a UIMA-based core that other teams can extend
to suit their needs.  As such we are making use of UIMA type merging to allow them to add
new features to existing types.  This approach works fine since JCasGen merges the two definitions
of the given type and produces a superset of the features.  This is well documented here:
> http://uima.apache.org/d/uimaj-2.3.1/references.html#ugr.ref.jcas.merging_types.jcasgen_support

> However, in addition to this, we have the case where we have a string subtype with given
allowedValues - lets say values a, b and c.  The other team wants to extend this type and
have additional allowedValues, say value d.  Ideally, what I would like to do is the following
(which follows the pattern used for adding features):
> Type Definition #1 (provided by core):
>     <typeDescription>
>       <name>com.ibm.Type</name>
>       <description></description>
>       <supertypeName>uima.cas.String</supertypeName>
>       <allowedValues>
>         <value>
>           <string>a</string>
>           <description></description>
>         </value>
>         <value>
>           <string>b</string>
>           <description></description>
>         </value>
>         <value>
>           <string>c</string>
>           <description></description>
>         </value>
>       </allowedValues>
>     </typeDescription>	    
> Type Definition #2 (extension to core):
>     <typeDescription>
>       <name>com.ibm.Type</name>
>       <description></description>
>       <supertypeName>uima.cas.String</supertypeName>
>       <allowedValues>
>         <value>
>           <string>d</string>
>           <description></description>
>         </value>
>       </allowedValues>
>     </typeDescription>
> In this case I wanted UIMA to recognize the two definitions at runtime and allow the
superset of allowedValues.  However, this does not do the trick - at runtime UIMA throws an
exception saying that value d is not an allowed value for com.ibm.Type.

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