Rel Files

This version of Rel -- an implementation of Date & Darwen's 
"Tutorial D" database language -- is a maintenance release 
featuring one enhancement and two bug fixes:

1. Enhancement: Rel: Error reporting has been improved when Java-based
   built-in operators fail.  E.g., SUBSTRING("blah", 1, 20) used to
   fail in an un-helpful manner. Now, the error message goes some way
   toward explaining and locating the problem.

2. Fix: Rel: The following failed with a low-level error; now fixed:
    var items private relation { id  integer, name  character } init ( 
     relation { 
      tuple {id 1, name "hi"}, 
      tuple {id 2, name "lo"}, 
      tuple {id 3, name "do"}}) key {id};
    var result private relation {r relation same_heading_as(items)} key {r};
    var inner private relation same_heading_as(items) key {id};
    insert inner relation {tuple from items where id = 1};
    insert result relation {tuple {r inner}};

3. Fix: Rel: Updating a relation-valued attribute, as in the following...
    var x private relation {a integer, b relation {c integer}} 
         init (relation {tuple {a 1, b relation {tuple {c 2}}}}) 
         key {a};
    update x where a = 1 (b := update (b) (c := 33));
   ... used to cause an error like the following:
   "ERROR: '%tuple23' has not been defined."  This has been corrected.

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