[Dbappbuilder-relannounce] ANNOUNCE: Rel version 1.0.4 Beta released

[Rel a. list. <dba...@li...>]

This version of Rel -- an implementation of Date & Darwen's "Tutorial D"
database language -- provides two enhancements and several bug fixes.

Enhancements:

1. Inference of most specific common supertype (excluding Alpha) has
been implemented, such that evaluating...

  RELATION {
    TUPLE {x Triangle(Point(0,0), Point(2,3), Point(7,4))}
    TUPLE {x Square(Point(1,1), Point(4,3))}
  }

...returns...

  RELATION {x Shape} {
    TUPLE {x Triangle(Point(0,0), Point(2,3), Point(7,4))}
    TUPLE {x Square(Point(1,1), Point(4,3))}
  }

...assuming the existence of types 'Triangle' and 'Square' which are
subtypes of 'Shape'.

2. Selectors are now generated for immediate subtypes of built-in types,
as per Date & Darwen's "Database Explorations" (ISBN 978-1-4269-3723-1),
Chapter 21, page 348 "Selectors for System Defined Types".  E.g., the
following...

  TYPE PosInt IS {INTEGER CONSTRAINT INTEGER >= 0};

...will automatically create a selector called PosInt which accepts an
INTEGER as its sole argument and returns a PosInt value.

Bug Fixes:

1. A derived POSSREP definition list should be allowed to be empty when
defining a type whose immediate supertype is a built-in type.  However,
Rel previously required at least one POSSREP.  E.g., the following
legitimate definition was not allowed:

  TYPE PosInt IS {INTEGER CONSTRAINT INTEGER >= 0};

This has been fixed.

2. A bug has been corrected that could, in rare circumstances, cause a
database to fail to open due to an internal "LOG INTEGRITY" error.

3. A bug has been corrected that could, in rare circumstances, cause
corruption of user-defined type values when inserted into a relvar
immediately after any Rel error (e.g., a syntax error) has been
generated. 

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