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README.md

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+UTF-8 Automaton Learner
+=======================
+
+See [my blog post](https://joshuamoerman.nl/2025/6/The-UTF-8-Automaton.html).
+
+Using LearnLib to learn a model of *UTF-8* validators (or decoders). It only
+learns the acceptance behaviour, not the transduction to unicode code points.
+
+UTF-8 implementations tested:
+* JDK decoder in `java.nio.charset.CharsetDecoder` (depends on java platform)
+* Guava validator `com.google.common.base.Utf8`
+* Apache decoder `org.apache.commons.codec.binary.StringUtils`
+* ICU4J has a charset detector; this gives a very different result
+
+For the equivalence oracle, I have a chain of several testers:
+1. First a small but precise test suite is tried
+2. Then some random testing based on the Wp method
+3. Then exhaustive testing based on the W method
+
+All implementations tested result in the same DFA (except for the ICU4J,
+because it is not a validator, but a detector and accepts much more).
+
+How to build and run (should run in a couple of seconds):
+```bash
+./run.sh
+```
+
+
+## Decomposition
+
+See the subdirectory `dfa-decompose`.
+
+
+## Dependencies
+
+I currently use the development version of `LearnLib` (and `automatalib`).
+And I build them as follows:
+```bash
+mvn clean package -Pbundles -DskipTests
+```
+
+Other dependencies can be installed with maven. Note that I have very limited
+experience in java development, and that my maven set-up may be less than
+ideal.
+
+
+## Copyright notice
+
+(c) 2025 Joshua Moerman, Open Universiteit, licensed under the EUPL (European
+Union Public License). If you want to use this code and find the license not
+suitable for you, then please do get in touch.
+
+```
+SPDX-License-Identifier: EUPL-1.2
+```