create <rname> ( <adefs> ) <size>       - create a new relation
insert <rname>                          - insert tuples into a relation
delete <rse> ;                          - delete tuples from relations
update <anames> from <rse> ;            - update tuples within a relation
print [<u>] <anames> from <rse> [<i>] ; - print tuples
sort <rname> by <snames> ;              - sort a relation file
import <fname> into <rname>             - import tuples from a file
export <rname> [<i>] ;                  - export tuples to a file
extract <rname> [<i>] ;                 - extract definition to a file
compress <rname>                        - compress a relation file
define <mname>                          - define a macro
exit                                    - exit SDB

<u>             ::=     using <fname>
<i>             ::=     into <fname>
<adefs>         ::=     <a list of attribute definitions>
<rse>           ::=     <rnames> [where <boolean-expression>]
<rname>         ::=     <a relation name>
<rnames>        ::=     <a comma separated list of <rname>s>
<aname>         ::=     [<rname> .] <an attribute name>
<anames>        ::=     * | <a comma separated list of <aname>s>
<sname>         ::=     <aname> { ascending | descending }
<snames>        ::=     <a comma separated list of <sname>s>
