## 3. Conventions

The following conventions are used in the synopsis of a command: brackets (`[` and `]`) indicate optional parts. (In the synopsis of a Tcl command, question marks (`?`) are used instead, as is usual in Tcl.) Braces (`{` and `}`) and vertical lines (`|`) indicate that you must choose one alternative. Dots (`...`) mean that the preceding element can be repeated.

Where it enhances the clarity, SQL commands are preceded by the prompt `=>`, and shell commands are preceded by the prompt `$`. Normally, prompts are not shown, though.

An administrator is generally a person who is in charge of installing and running the server. A user could be anyone who is using, or wants to use, any part of the PostgreSQL system. These terms should not be interpreted too narrowly; this book does not have fixed presumptions about system administration procedures.