This cluster provides deferred classes that abstract out component behaviour:

- `CODE` is the interfave of the `tools/code` component. It represents a code element (either an expression or an instruction). Note that each code is either an instruction or an expression (see below). The classes in the `tools/code` component are intended to be inserted rather than inherited (they add specific behaviour to some instructions and expressions).
- `EXPRESSION` is the interface of the `tools/expression` component. It represents an Eiffel expression, i.e. a syntactic construction having a result type.
- `INSTRUCTION` is the interface of the `tools/instruction` component. It represents an Eiffel instruction.
- `PARSER` is the interface of the `tools/parser` component. It parses a file (an Eiffel file, an ACE file or a configuration file) and extracts syntactic information.
- `RUN_FEATURE` is the interface of the `tools/run_feature` component. It represents a live feature, i.e. a callable feature tailored for some particular `LIVE_TYPE`.
- `TYPE_MARK` is the interface of the `tools/type_mark` component. It represents an Eiffel type.

Moreover, the class `SMART_EIFFEL` drives the compilation process. It stays in this cluster because it is so important.