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https://issues.apache.org/jira/browse/UIMA-4049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14171181#comment-14171181
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Richard Eckart de Castilho commented on UIMA-4049:
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I do not think that annotations should be immutable. If the features were not
part of an index, there would not be any problem. The problem is that
* annotations cannot be added/removed to/from an index while iterating over it
(removing might be possible using a FSIterator.remove method... not sure)
* indexes cannot be updated while iterating over them (or can they?)
* indexes are not updated when indexed features change (as would be the case
e.g. in an SQL database)
* there is no prominent feedback to a programmer that the actions above are
problematic - other than behaving strangely or throwing odd exceptions
> The curious case of the zombie annotation
> -----------------------------------------
>
> Key: UIMA-4049
> URL: https://issues.apache.org/jira/browse/UIMA-4049
> Project: UIMA
> Issue Type: Bug
> Components: Core Java Framework
> Reporter: Richard Eckart de Castilho
> Assignee: Marshall Schor
> Attachments: CuriousTestCase.java
>
>
> When annotations are removed from indexes, sometimes they come back... the
> following test case shows how an annotation is removed but still present when
> iterating over the index later.
> {code}
> @Test
> public void testForZombies() throws Exception
> {
> // No zombie here
> int[] offsets1 = { 0, 4, 5, 11, 12, 21, 22, 25, 26, 29, 30, 35, 36,
> 40, 41, 50, 51, 60, 61,
> 64, 64, 65 };
> testForZombies("Dies flößte Friedrich II. für seine neue Eroberung
> Besorgnis ein.", offsets1);
>
> // Zombie hiding in here
> int[] offsets2 = { 0, 3, 4, 7, 8, 13, 14, 18, 19, 22, 23, 33, 34, 35
> };
> testForZombies("Ich bin Franz III. von Hammerfels !", offsets2);
> }
> public void testForZombies(String aText, int[] aOffsets) throws Exception
> {
> // Init some dictionaries we ues
> Set<String> names = new HashSet<String>();
> names.add("Friedrich");
> names.add("Franz");
> Set<String> suffix = new HashSet<String>();
> suffix.add("II.");
> suffix.add("III.");
> // Set up type system
> TypeSystemDescription tsd = new TypeSystemDescription_impl();
> tsd.addType("Token", "", CAS.TYPE_NAME_ANNOTATION);
>
> // Create CAS
> CAS jcas = CasCreationUtils.createCas(tsd, null, null);
> jcas.setDocumentText(aText);
>
> Type tokenType = jcas.getTypeSystem().getType("Token");
> Feature beginFeature = tokenType.getFeatureByBaseName("begin");
>
> // Create tokens in CAS
> for (int i = 0; i < aOffsets.length; i += 2) {
> jcas.addFsToIndexes(jcas.createAnnotation(tokenType, aOffsets[i],
> aOffsets[i+1]));
> }
>
> // List the tokens in the CAS
> for (AnnotationFS token : jcas.getAnnotationIndex(tokenType)) {
> System.out.printf("Starting with %s%n", token.getCoveredText());
> }
> // Merge some tokens, in particular "Franz" "III." -> "Franz III."
> and "Friedrich" "II."
> // into "Friedrich II."
> AnnotationFS previous = null;
> List<AnnotationFS> toDelete = new ArrayList<>();
> for (AnnotationFS token : jcas.getAnnotationIndex(tokenType)) {
> if (previous != null && names.contains(previous.getCoveredText())
> && suffix.contains(token.getCoveredText())) {
> token.setIntValue(beginFeature, previous.getBegin());
> toDelete.add(previous);
> }
> previous = token;
> }
> // Remove the no longer necessary tokens ("Friedrich" and "Franz"),
> since we expanded the
> // following tokens "III." and "II." to include their text
> Set<String> removedWords = new HashSet<String>();
> for (AnnotationFS token : toDelete) {
> System.out.printf("Removing %s%n", token.getCoveredText());
> removedWords.add(token.getCoveredText());
> jcas.removeFsFromIndexes(token);
> }
> // Check if the tokens that we wanted to remove are really gone
> for (AnnotationFS token : jcas.getAnnotationIndex(tokenType)) {
> System.out.printf("Remaining %s%n", token.getCoveredText());
> if (removedWords.contains(token.getCoveredText())) {
> org.junit.Assert.fail("I saw a zombie!!!");
> }
> }
> }
> {code}
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