Added “known issues” file.

KNOWN-ISSUES.md

@@ -0,0 +1,20 @@
+# Known Issues
+
+## Parser
+
+- multiple PDDL features are not yet supported (see list of PDDL features supported by `plasp`)
+- several error messages obtained with syntax errors are misleading
+
+## Translator
+
+- in compatibility mode, the outdated `vars` sections within action definitions are handled just like `parameters`, which is semantically incorrect
+- equality expressions currently partly supported by parser but not the translator
+
+## ASP Output Format
+
+- SAS axiom rules and `plasp`’s derived predicates (obtained through normalization) are semantically similar, but differently represented
+
+## Encodings
+
+- the [simple example encoding](encodings/sequential-horizon.lp) does not support layers of SAS axiom rules
+- [multiple encodings](encodings/outdated) are outdated and need to be adapted to the output format introduced with `plasp` 3.1.0