# Alloy Authors - Practical Alloy - Module system (Highlights) ![rw-book-cover|256](https://readwise-assets.s3.amazonaws.com/static/images/article4.6bc1851654a0.png) ## Highlights - To include a module in another model, we must to use an `open` instruction with the path to the corresponding file (without the `.als` extension). ([View Highlight](https://read.readwise.io/read/01jsy0zffnxx5dg61fy40hevda)) ^882995666 - Alloy modules can be declared with signature parameters, that are specified by the including modules. These are declared after its name in the `module` declaration between square brackets. ([View Highlight](https://read.readwise.io/read/01jsy10wgnf8290h15dwsgaj35)) ^882995717 - To avoid using the projected ternary relation, we can derive a binary relation from the auxiliary `aux_time` by declaring an auxiliary function that projects away `TimeAux` ([View Highlight](https://read.readwise.io/read/01jsy19f132srf97h86s5gzh4d)) ^882996335 Functions can be used in dot operator like fields.