Author: agruber
Date: Thu Sep 22 14:54:04 2011
New Revision: 1174179
URL: http://svn.apache.org/viewvc?rev=1174179&view=rev
Log:
typos and links for keywordlinkingengine
Added:
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordlinkingengine.mdtxt
- copied, changed from r1174130,
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordextractionengine.mdtext
Removed:
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordextractionengine.mdtext
Modified:
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/engines.mdtext
Modified: incubator/stanbol/site/trunk/content/stanbol/docs/trunk/engines.mdtext
URL:
http://svn.apache.org/viewvc/incubator/stanbol/site/trunk/content/stanbol/docs/trunk/engines.mdtext?rev=1174179&r1=1174178&r2=1174179&view=diff
==============================================================================
--- incubator/stanbol/site/trunk/content/stanbol/docs/trunk/engines.mdtext
(original)
+++ incubator/stanbol/site/trunk/content/stanbol/docs/trunk/engines.mdtext Thu
Sep 22 14:54:04 2011
@@ -16,7 +16,13 @@ Title: Enhancement Engines and their mai
- NLP processing using OpenNLP NER
- detect occurrences of persons, places and organizations only
-- __Taxonomy Linking Engine__
+
+- __[KeywordLinkingEngine](engines/keywordlinkingengine.html)__
+ - NLP processing using OpenNLP
+ - supports multiple languages
+ - dedect occurences of untyped entities as concepts, takes local
taxonomies as linking target
+
+- _Taxonomy Linking Engine_ (deprecated, see KeywordLinkingEngine)
- NLP processing using OpenNLP POS
- detect occurrences of untyped entities as concepts, takes local
taxonomies as linking target
Copied:
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordlinkingengine.mdtxt
(from r1174130,
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordextractionengine.mdtext)
URL:
http://svn.apache.org/viewvc/incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordlinkingengine.mdtxt?p2=incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordlinkingengine.mdtxt&p1=incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordextractionengine.mdtext&r1=1174130&r2=1174179&rev=1174179&view=diff
==============================================================================
---
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordextractionengine.mdtext
(original)
+++
incubator/stanbol/site/trunk/content/stanbol/docs/trunk/enhancer/engines/keywordlinkingengine.mdtxt
Thu Sep 22 14:54:04 2011
@@ -1,38 +1,39 @@
-# KeywordExtractionEngine #
+Title: The Keyword Linking Engine: custom vocabularies and multiple languages
+
+The
[KeywordLinkingEngine](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/)
is a re-implementation of the
[TaxonomyLinkingEngine](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/taxonomylinking/)
that is more modular and therefore better suited for future improvements and
extensions as requested by
[STANBOL-303](https://issues.apache.org/jira/browse/STANBOL-303). Its main
improvements are its ability to support multiple languages and provide
enhancement results specific to custom vocabulary.
-The
[KeywordExtractionEngine](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/)
is a re-implementation of the
[TaxonomyLinkingEngine](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/taxonomylinking/)
that is more modular and therefore better suited for future improvements and
extensions as requested by
[STANBOL-303](https://issues.apache.org/jira/browse/STANBOL-303).
## Multiple Language Support ##
-The KeywordExtractionEngine can supports multiple languages. However the
performance and to some extend also the quality of the enhancements are
depended on the following parameters
+The KeywordLinkingEngine supports multiple languages. However, the performance
and to some extend also the quality of the enhancements for a specific language
is depended on the following:
-* **Language detection:** The KexwordExtractionEngine depends on the correct
detection of the language by the LangIdEnhancementEngine. If no language was
detected or this information is missing than "English" is assumed as default.
-* **Multi-Lingual labels of the Controlled Vocabulary:** Occurrences are
searched within labels of the current Language and labels without any defined
language. e.g. English labels will not be matched against German language texts.
-* **Natural Language Processing support:** The KexwordExtractionEngine is able
to use [Sentence
Detectors](http://opennlp.sourceforge.net/api/opennlp/tools/sentdetect/SentenceDetector.html),
[POS (Part of Speech)
taggers](http://opennlp.sourceforge.net/api/opennlp/tools/postag/POSTagger.html)
and
[Chunkers](http://opennlp.sourceforge.net/api/opennlp/tools/chunker/Chunker.html).
If such components are available for a language the they are used to optimize
the enhancement process.
+* **Language detection:** The KeywordLinkingEngine depends on the correct
detection of the language by the LanguageIdentificationEngine. If no language
is detected or this information is missing then "English" is assumed as default.
+* **Multi-lingual labels of the controlled vocabulary:** Occurrences are
searched within labels of the current language and labels without any defined
language. e.g. English labels will not be matched against German language texts.
+* **Natural Language Processing support:** The KeywordLinkingEngine is able to
use [Sentence
Detectors](http://opennlp.sourceforge.net/api/opennlp/tools/sentdetect/SentenceDetector.html),
[POS (Part of Speech)
taggers](http://opennlp.sourceforge.net/api/opennlp/tools/postag/POSTagger.html)
and
[Chunkers](http://opennlp.sourceforge.net/api/opennlp/tools/chunker/Chunker.html).
If such components are available for a language then they are used to optimize
the enhancement process.
- **Sentence detector:** If a sentence detector is present the memory
footprint of the engines improves, because Tokens, POS tags and Chunks are only
kept for the currently active sentence. If no sentence detector is available
the whole content is treated as a single Sentence.
+ **Sentence detector:** If a sentence detector is present the memory
footprint of the engines improves, because Tokens, POS tags and Chunks are only
kept for the currently active sentence. If no sentence detector is available
the entire content is treated as a single sentence.
- **Tokenizer:** A (word)
[tokenizer](http://opennlp.sourceforge.net/api/opennlp/tools/tokenize/Tokenizer.html)
is required. If no tokenizer is available for a given language, than the
[OpenNLP
SimpleTokenizer](http://opennlp.sourceforge.net/api/opennlp/tools/tokenize/SimpleTokenizer.html)
is used as default.
+ **Tokenizer:** A (word)
[tokenizer](http://opennlp.sourceforge.net/api/opennlp/tools/tokenize/Tokenizer.html)
is required. If no tokenizer is available for a given language, then the
[OpenNLP
SimpleTokenizer](http://opennlp.sourceforge.net/api/opennlp/tools/tokenize/SimpleTokenizer.html)
is used as default.
- **POS tagger:** POS taggers annotate tokens with there type. Because of the
KeywordExtractionEngine is only interested in Nouns, Foreign Words and Numbers
the presence of such an tagger allows to skip a lot of the tokens and to
improve performance. However POS taggers use different sets of tags for
different languages. Because of that it is not enough that a POS tagger is
available for a language there MUST BE also a configuration of the POS tags for
that language that need to be processed.
+ **POS tagger:** POS taggers annotate tokens with their type. Because of the
KeywordLinkingEngine is only interested in Nouns, Foreign Words and Numbers,
the presence of such a tagger allows to skip a lot of the tokens and to improve
performance. However POS taggers use different sets of tags for different
languages. Because of that it is not enough that a POS tagger is available for
a language there MUST BE also a configuration of the POS tags for that language
that need to be processed.
- **Chunker:** There are two types of Chunkers. First the
[Chunkers](http://opennlp.sourceforge.net/api/opennlp/tools/chunker/Chunker.html)
as provided by OpenNLP (based on statistical models) and second a [POS tag
based
Chunker](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/commons/opennlp/src/main/java/org/apache/stanbol/commons/opennlp/PosTypeChunker.java)
provided by the openNLP bundle of Stanbol. Currently the Availability of a
Chunker does not have an big influence on the performance nor the quality of
the Enhancements.
+ **Chunker:** There are two types of Chunkers. First the
[Chunkers](http://opennlp.sourceforge.net/api/opennlp/tools/chunker/Chunker.html)
as provided by OpenNLP (based on statistical models) and second a [POS tag
based
Chunker](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/commons/opennlp/src/main/java/org/apache/stanbol/commons/opennlp/PosTypeChunker.java)
provided by the openNLP bundle of Stanbol. Currently the availability of a
Chunker does not have a big influence on the performance nor the quality of the
Enhancements.
-* **Configuration:** The set of languages to be annotated can be configured
for the KexwordExtractionEngine. An empty configuration indicates that texts in
any language should be processed. By using this configuration it is possible to
configure different KexwordExtractionEngine instances for different languages
(e.g. with different configurations)
+* **Configuration:** The set of languages to be annotated can be configured
for the KeywordLinkingEngine. An empty configuration indicates that texts in
any language should be processed. By using this configuration it is possible to
configure different KeywordLinkingEngine instances for different languages
(e.g. with different configurations)
-## Keyword extraction workflow ##
+## Keyword extraction and linking workflow ##
-Basically the Text is parsed from the beginning to the end and words are
looked up in the configured Controlled Vocabulary.
+Basically the text is parsed from the beginning to the end and words are
looked up in the configured controlled vocabulary.
### Text Processing ###
-The
[AnalysedContent](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/AnalysedContent.java)
Interface is used to access natural language text that was already processed
by an NLP framework. Currently there is only a single implementation based on
the commons.opennlp
[TextAnalyzer](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/commons/opennlp/src/main/java/org/apache/stanbol/commons/opennlp/TextAnalyzer.java)
utility. In general this part is still very focused on OpenNLP. Making it also
usable together with other NLP frameworks would probably need a lot of
refactoring.
+The
[AnalysedContent](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/AnalysedContent.java)
Interface is used to access natural language text that was already processed
by an NLP framework. Currently there is only a single implementation based on
the commons.opennlp
[TextAnalyzer](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/commons/opennlp/src/main/java/org/apache/stanbol/commons/opennlp/TextAnalyzer.java)
utility. In general this part is still very focused on OpenNLP. Making it also
usable together with other NLP frameworks would probably need some re-factoring.
-The current state of the processing is represented by the
[ProcessingState](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/impl/ProcessingState.java).
Based on the capabilities of the NLP framework for the current language it
provides a different set of information:
+The current state of the processing is represented by the
[ProcessingState](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/impl/ProcessingState.java).
Based on the capabilities of the NLP framework for the current language it
provides a the following set of information:
-* **AnalysedSentence:** If a sentence detector is present, than this represent
the current sentence of the text. If not, than the whole text is represented as
a single sentence. The AnalysedSentence also provides access to POS tags,
Chunks (if available)
-* **Chunk:** If a chunkier is present, than this represents the current chunk.
Otherwise this will be null
-* **Token:** The currently processed word part of the chunk and the sentence
+* **AnalysedSentence:** If a sentence detector is present, than this represent
the current sentence of the text. If not, then the whole text is represented as
a single sentence. The AnalysedSentence also provides access to POS tags and
Chunks (if available)
+* **Chunk:** If a chunker is present, then this represents the current chunk.
Otherwise this will be null.
+* **Token:** The currently processed word part of the chunk and the sentence.
* **TokenIndex:** The index of the currently active token relative to the
AnalysedSentence.
The ProcessingState provides means to navigate to the next token. If chunks
are present tokens that are outside of chunks are ignored.
@@ -40,14 +41,14 @@ The ProcessingState provides means to na
### Entity Lookup ###
A "OR" query with [1..MAX_SEARCH_TOKENS] tokens is used to lookup entities via
the
[EntitySearcher](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntitySearcher.java)
interface. If the actual implementation cut off results, than it must be
ensured that Entities that match both tokens are ranked first.
-Currently there are two implementations of this interface (1) for the
Entityhub
([EntityhubSearcher](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/impl/EntityhubSearcher.java))
and (2) for ReferencedSitess
([ReferencedSiteSearcher](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/impl/ReferencedSiteSearcher.java)).
There is also an
[Implementation](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/test/java/org/apache/stanbol/enhancer/engines/keywordextraction/impl/TestSearcherImpl.java)
that holds entities in-memory, however currently this is only used for unit
tests.
+Currently there are two implementations of this interface: (1) for the
Entityhub
([EntityhubSearcher](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/impl/EntityhubSearcher.java))
and (2) for ReferencedSites
([ReferencedSiteSearcher](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/impl/ReferencedSiteSearcher.java)).
There is also an
[Implementation](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/test/java/org/apache/stanbol/enhancer/engines/keywordextraction/impl/TestSearcherImpl.java)
that holds entities in-memory, however currently this is only used for unit
tests.
Queries do use the configured
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).getNameField()
and the language of labels is restricted to the current language or labels
that do not define any language.
-Only "processable" Tokens are used to lookup entities. If a Token is
processable is determined as follows:
+Only "processable" tokens are used to lookup entities. If a token is
processable is determined as follows:
* If POS tags are available the "Boolean processPOS(String posTag)" method of
the
[AnalysedContent](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/AnalysedContent.java)
is used to check if a Token needs to be processed.
-* If this method returns NULL or no POS tags are available, than all Tokens
with equals or more Chars than
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).getMinSearchTokenLength()
(default=3) are considered as processable.
+* If this method returns NULL or no POS tags are available, then all Tokens
longer than
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).getMinSearchTokenLength()
(default=3) are considered as processable.
Typically the next MAX_SEARCH_TOKENS processable tokens are used for a lookup.
However the current Chunk/Sentence is never left in the search for processable
tokens.
@@ -64,8 +65,8 @@ For each label that fulfills the above c
Entities are
[Suggested](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/Suggestion.java)
if:
-* a label does matches exactly with the text following the current position it
the entity is suggested. (e.g.
[Passerine](http://en.wikipedia.org/wiki/Passerine))
-* a label matches at least
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).getMinFoundTokens()
(default=2) are matching with the text. This ensures that "[Rupert
Murdoch](http://en.wikipedia.org/wiki/Rupert_Murdoch)" is not suggested for
"[Rupert](http://en.wikipedia.org/wiki/Rupert)" but ensures that "Barack
Hussein Obama" is suggested for "Barack Obama". Setting "minFoundToken" to
values less than two will usually cause a lot of false positives, but would
also come up with a suggestion for "Barack Obama" if the content contains the
word "Obama".
+* a label does match exactly with the text following the current position it
the entity is suggested. (e.g.
[Passerine](http://en.wikipedia.org/wiki/Passerine))
+* a label matches at least
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).getMinFoundTokens()
(default=2) are matching with the text. This ensures that "[Rupert
Murdoch](http://en.wikipedia.org/wiki/Rupert_Murdoch)" is not suggested for
"[Rupert](http://en.wikipedia.org/wiki/Rupert)" but on the other hand "Barack
Hussein Obama" is suggested for "Barack Obama". Setting "minFoundToken" to
values less than two will usually cause a lot of false positives, but would
also come up with a suggestion for "Barack Obama" if the content contains the
word "Obama".
The described matching process is currently directly part of the
[EntityLinker](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinker.java).
To support different matching strategies this would need to be externalized
into an own "EntityLabelMatcher" interface.
@@ -73,14 +74,14 @@ The described matching process is curren
In case there are one or more
[Suggestion](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/Suggestion.java)s
of Entities for the current position within the text a
[LinkedEntity](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/LinkedEntity.java)
instance is created.
-LinkedEntity is an object model representing the Stanbol Enhancement
Structure. After the processing of the parsed content is completed the
LinkedEntities are "serialized" as RDF triples to the metadata of the
ContentItem.
+LinkedEntity is an object model representing the Stanbol Enhancement
Structure. After the processing of the parsed content is completed, the
LinkedEntities are "serialized" as RDF triples to the metadata of the
ContentItem.
TextAnnotations as defined in the [Stanbol Enhancement
Structure](http://wiki.iks-project.eu/index.php/EnhancementStructure) do use
the [dc:type](http://www.dublincore.org/documents/dcmi-terms/#terms-type)
property to provide the general type of the extracted Entity. However suggested
Entities might have very specific types. Therefore the
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java)
provides the possibility to map the specific types of the Entity to types used
for the dc:type property of TextAnnotations. The
[EntityLinkerConfig](http://svn.apache.org/repos/asf/incubator/stanbol/trunk/enhancer/engines/keywordextraction/src/main/java/org/apache/stanbol/enhancer/engines/keywordextraction/linking/EntityLinkerConfig.java).DEFAULT_ENTITY_TYPE_MAPPINGS
contains some predefined mappings.
-Note that field used to retrieve the types of an suggested Entity can be
configured by the EntityLinkerConfig. The default value for the type field is
"rdf:type".
+*Note that the field used to retrieve the types of an suggested Entity can be
configured by the EntityLinkerConfig. The default value for the type field is
"rdf:type".*
-In some cases suggested entities might redirect to others. In the case of
Wikipedia/DBpedia this is often used to link from acronyms like
[IMF](http://en.wikipedia.org/w/index.php?title=IMF&redirect=no) to the real
entity [International Monetary
Fund](http://en.wikipedia.org/wiki/International_Monetary_Fund). But also some
Thesaurus define labels as own Entities with an URI and users might want to use
the URI of the Concept rather than one of the label.
-To support such use cases the KeywordExtractionEngine has support for
redirects. Users can first configure the redirect mode (ignore, copy values,
follow) and secondly the field used to search for redirects
(default=rdfs:seeAlso).
-If the redirect mode != ignore for each suggestion the Entities referenced by
the configured redirect field are retrieved. In case of the copy values mode
the values of the name, and type field are copied. In case of the follow mode
the suggested entity is repressed with the first redirected entity.
+In some cases suggested entities might redirect to others. In the case of
Wikipedia/DBpedia this is often used to link from acronyms like
[IMF](http://en.wikipedia.org/w/index.php?title=IMF&redirect=no) to the real
entity [International Monetary
Fund](http://en.wikipedia.org/wiki/International_Monetary_Fund). But also some
Thesauri define labels as own Entities with an URI and users might want to use
the URI of the Concept rather than one of the label.
+To support such use cases the KeywordLinkingEngine has support for redirects.
Users can first configure the redirect mode (ignore, copy values, follow) and
secondly the field used to search for redirects (default=rdfs:seeAlso).
+If the redirect mode != ignore for each suggestion the Entities referenced by
the configured redirect field are retrieved. In case of the "copy values" mode
the values of the name, and type field are copied. In case of the "follow" mode
the suggested entity is replaced with the first redirected entity.
### Confidence for Suggestions ###
@@ -105,14 +106,14 @@ The calculation of the confidence is cur
## Future Plans for the TaxonomyLinkingEngine ##
-The TaxonomyLinkingEngine is still available and fully functional. However it
is marked as deprecated and not included in any of the launchers. Current users
are encouraged to switch over to the KeywordExtractionEngine.
+The TaxonomyLinkingEngine is still available and fully functional. However it
is marked as deprecated and not included in any of the launchers. Current users
are encouraged to switch over to the KeywordLinkingEngine.
-In Future it is planed to repurpose the TaxonomyLinkingEngine as a special
version of the KeywordExtractionEngine with a specialized configuration and
feature set targeted for (hierarchical) Taxonomies.
+In the future it is planed to repurpose the TaxonomyLinkingEngine as a special
version of the KeywordLinkingEngine with a specialized configuration and
feature set targeted for (hierarchical) Taxonomies.
This will include:
* default configuration specific for SKOS
* support for term hierarchies - adding suggestions for parent concepts
-* support for restricting enhancements to a specific Taxonomy
(skos:ConceptScheme) - this would allow to index several Taxonomies in the same
ReferencedSite but still use only a specific one for the enhancements.
+* support for restricting enhancements to a specific Taxonomy
(skos:ConceptScheme) - this would allow to index several taxonomies in the same
ReferencedSite but still use only a specific one for the enhancements.
