Documented feature requirements.

doc/output-format.md

@@ -2,18 +2,24 @@
 
 `plasp` 3 translates SAS and PDDL files into the same ASP fact format.
 
-## Sections
+## Syntax and Semantics
 
-The `plasp` output contains the following sections:
+`plasp` structures the translated ASP facts into the multiple sections, which are explained in the following.
 
-section | description
---------|------------
-feature requirements | advanced features (such as conditional effects or axiom rules) required by the input planning problem
-types (PDDL only) | object types used by the planning problem (only if typing is enabled)
-variables | fluents used by the planning problem (variables in SAS and predicates in PDDL) and their possible values
-actions | actions (operators in SAS and actions in PDDL), their preconditions, and effects
-mutex groups (SAS only) | sets of mutually exclusive variable assignments
-axiom rules (SAS only) | special actions that are immediately executed when the preconditions are satisfied
-objects (PDDL only) | constant objects defined by PDDL domains or problems
-initial state | initial variable assignment
-goal | target variable assignment
+### Feature Requirements
+
+Declares advanced features required by the input planning problem, such as conditional effects and axiom rules.
+
+Feature requirements may be used in meta encodings to warn about features that are unsupported by the encoding.
+
+syntax | description
+-------|------------
+`requiresFeature(<feature>).` | declares the feature `<feature>` to be required by the input problem
+
+Currently, feature requirements are only recognized with SAS problems.
+
+SAS feature | description
+------------|------------
+`actionCosts` | actions have associated costs
+`axiomRules` | immediate actions used, which are executed as soon as the preconditions are satisfied
+`conditionalEffects` | some effects of an action may have additional conditions