Rel Files

This version of Rel -- an implementation of Date & Darwen's "Tutorial
D" database language -- is a maintenance release featuring various
enhancements and bug fixes.

Prior to installing this version of Rel, you must make a backup of
your database(s). Then, install this update and load and attempt to
execute your backup script(s). If your script successfully loads,
you're done. If Rel complains of syntax errors, you'll need to edit
the backup script — based on the "Rel Version 1.0.11+ Syntax" article
at http://dbappbuilder.sourceforge.net — until the script successfully
loads.

Changes in this update:

* Enhancement: DBrowser: Now displays human-friendly messages when
attempting to open an already-open database, or when a connection
attempt to a remote Rel server fails.

* Enhancement: DBrowser: Now provides options to hide headings and
declared types in headings in displayed output of relations.

* Enhancement: DBrowser: Now provides a "Get File Path" button to
simplify putting file paths in source code.  This facilitates use of
external data sources, described below.

* Enhancement: Rel: Some minor syntax improvements have been made, in
accordance with changes to Tutorial D.  Formerly-required parentheses
around WRAP, UNWRAP, GROUP, UNGROUP clauses have been removed. UNGROUP
(a) and UNWRAP (a) are now UNGROUP a and UNWRAP a, respectively.
 
* Enhancement: Rel: All error messages are now uniquely identified to
disambiguate references to them.

* Enhancement: Rel: Updated to version 6.0.11 of the Berkeley Java DB,
which is used as a storage engine.

* Enhancement: Rel: A student project has produced simple support for
external CSV/XLS/XLSX/JDBC sources as relvars:

 e.g., VAR myvar EXTERNAL CSV "/home/dave/test.csv";
 e.g., VAR myvar EXTERNAL XLS "/home/dave/test.xls" DUP_REMOVE;
 e.g., VAR myvar EXTERNAL XLS "/home/dave/test.xlsx" DUP_COUNT;
 e.g., VAR myvar EXTERNAL XLS "/home/dave/test.xlsx" AUTOKEY;
 e.g., VAR myvar EXTERNAL JDBC "<host>,<user>,<password>,<database>.<table>,<driverpath>,<drivername>";

This feature also makes it possible to define new relvar types as Rel
plug-ins.  Documentation for this feature will be provided in the
future.

* Enhancement: Rel: 'x RENAME {}' is now valid syntax.

* Enhancement: Rel: Errors occurring in a database constraint are now
treated as if the constraint evaluates to false, and the failing
constraint is named in the error message.

* Fix: DBrowser: Fixed minor errors parsing certain error messages.

* Fix: Rel: Given...

   VAR S BASE RELATION { 
        SNO CHAR, SNAME CHAR, STATUS INTEGER, CITY CHAR 
   } KEY {SNO};
   VAR SP BASE RELATION { SNO CHAR, PNO CHAR, QTY INTEGER } KEY {SNO, PNO};
   VAR SPQ BASE INIT(
      EXTEND S: {PQ := RELATION {TUPLE {SNO SNO}} COMPOSE SP}
   ) KEY{SNO};

...these failed: 

  UPDATE SPQ WHERE SNO = "S2": 
      {INSERT PQ RELATION {TUPLE {PNO "P5", QTY 500}}};	
  UPDATE SPQ WHERE SNO = "S2": {UPDATE PQ WHERE PNO="P5": {QTY := 250}};	
  UPDATE SPQ WHERE SNO = "S2": {DELETE PQ WHERE PNO="P5"};
  
This has been corrected.

* Fix: Rel: The following should have returned true but returned
  false:

	 RELATION  {
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P5"}
	        }},
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P2"}
	        }},
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P4"}
	        }}
	 } 
	 = 
	 RELATION  {
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P5"}
	        }},
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P2"}
	        }},
	        TUPLE { SUPPLIES RELATION {
	          TUPLE {PID "P4"}
	        }}
	 }

This has been corrected.  Internal changes to address this and similar
errors in comparing relations with relation-valued attributes may have
performance impact -- some queries may run faster, others slower.

* Fix: Rel: JOIN {}, TIMES {}, and COMPOSE {} now return DEE.

* Fix: Rel: XUNION {}, D_UNION {}, UNION {} now return TUPLE {}.

* Fix: Rel: XUNION {} {}, D_UNION {} {}, UNION {} {} return DUM.

* Fix: Rel: INTERSECT {} and INTERSECT {} {} throw an error.

* Fix: Rel: Type checking was too weak on comparison operators,
allowing incorrect expressions like 'tuple{x 1} = tuple{y 2, x 1}' to
return a result instead of throwing an error.  Fixed.

* Fix: Rel: RELATION {TUPLE {x 10, y DEE}} WHERE x = 100 UNGROUP y
threw a fatal error.  It should have thrown a type error due to an
attempt to ungroup integer 100. This has been fixed.

* Fix: Rel: Built-in operator name OP_GREATHERTHANOREQUALS corrected
to OP_GREATERTHANOREQUALS.

* Fix: Rel: Assignment to a real relvar altered its CreationSequence.
Fixed.

* Fix: Rel: CAST_AS_INTEGER("blah") and CAST_AS_RATIONAL("blah")
should have thrown semantic errors, not fatal errors.  Fixed.

Note: This release includes experimental support for a work-in-progress visual query language called Rev. Using an icons-on-strings data-flow style, it permits constructing queries visually and iteratively, and allows testing sub-expressions whilst constructing a query. To experiment with it, install the Rev package and it will appear as an additional tab in a DBrowser session. To remove it, delete the rev.jar file. Further documentation and video demonstrations will be provided in the future. 

For more information, or to download Rel, see
http://dbappbuilder.sourceforge.net/Rel.html