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>

ess a relation file
define <mname>				- define a macro
exit					- exit SDB

<u>		::=	using <fname>
<i>		::=	
