Thilo Goetz wrote: > Adam Lally wrote: > >> On Mon, Aug 10, 2009 at 5:32 PM, Marshall Schor<m...@schor.com> wrote: >> >>> Adam Lally wrote: >>> >>>> On Mon, Aug 10, 2009 at 4:07 PM, Jörn Kottmann<kottm...@gmail.com> wrote: >>>> >>>> >>>>> Marshall Schor wrote: >>>>> >>>>> >>>>>> The generification of FSIndex currently specifies one type, <T extends >>>>>> FeatureStructure> that is the type of item being returned. >>>>>> >>>>>> >>>>>> The contains and find methods have arguments of type FeatureStructure. >>>>>> These could be changed to take type "T". >>>>>> >>>>>> >>>>>> >>>>> No I do not think that they could be changed to take type T. >>>>> Lets take the case of the contains method. >>>>> The javadoc says: >>>>> "Check if the index contains an element equal to the given feature >>>>> structure >>>>> according to the >>>>> ordering of the index. Note that this is in general not the same as >>>>> feature >>>>> structure identity." >>>>> and it for the param fs it says "The FS we're looking for.". There is no >>>>> place where >>>>> it says that contains can only be called for FSes which have the type of >>>>> the >>>>> index. >>>>> >>>>> The change of the parameter from FeatureStructure to T would also change >>>>> the contract of the method a little, because then it would not be possible >>>>> anymore >>>>> to pass a FeatureStructure which has not type T. >>>>> >>>>> >>>>> >>>> I agree. It's sometimes useful to call FSIterator.moveTo method and >>>> pass an FS of a Type other than the one that the index was defined >>>> over, as part of implementing something like a subiterator. >>>> >>>> >>> I agree with the case where it's the "bag" index being used, because >>> that uses a test which works on all feature structures. >>> >>> However, for Set and Sorted, the implication of passing a FS which is >>> not in the type hierarchy is, according to the JavaDocs, "undefined". >>> This is because the code assumes the layout of the features and their >>> values is appropriate for the type. In other words, if the type of some >>> key was a string, it might take a value from the main int heap and use >>> it as an index into the string array - and if the int heap object was >>> not the right type, it could pull an arbitrary value from that slot, and >>> end up throwing an array index out of bounds exception. When I looked, >>> it didn't appear to me that the code checked for any kind of type >>> subsumption before proceeding... (but I may have missed it...) >>> >>> It could turn out that the data (whatever is being pulled) would just >>> happen to "match", even though the types are different. >>> >>> Because this is an undefined operation that could throw various kinds of >>> runtime errors, or return an equal match where none really exists, I >>> think it should not be allowed, for set and sorted indexes. >>> >>> >> In the case of the AnnotationIndex, the object that you pass to >> FSIterator.moveTo must be a subtype of Annotation (else you would get >> all the weird effects that you describe). But it is still valid for a >> user to do: >> FSIndex<AnnotType1> index = cas.getAnnotationIndex(annotType1); >> index.moveTo(annotType2); >> >> where annotType1 and annotType2 are both subtypes of uima.tcas.Annotation. >> >> In general, the object that you pass to moveTo() must be a subtype of >> the type that was in the index definition (in the user's descriptor, >> or for the case of the built-in AnnotationIndex, >> uima.tcas.Annotation). >> >> -Adam >> > > One concrete example of Adam's point: suppose you have a sentenceFS > and a tokenIterator. Then tokenIterator.moveTo(sentenceFS) will > position the token iterator at the first word in the sentence (modulo > some subtleties that are beside the point here). Very useful. >
Yes. This works because the "index" being iterated over is the general annotation index (the one that's built-it) - and the presumeption is that "token" and "sentenceFS" are both subtypes of AnnotationFS. Is there any reason *not* to add a check to the various methods in indexing that take one or more Feature Structures, to see if they are being passed a subtype of the type being indexed (except for bag indexes)? -Marshall > --Thilo > > > >
