Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Boolean algebra (structure)
(section)
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
== Axiomatics == {| align="right" class="wikitable collapsible collapsed" style="text-align:left" ! colspan="2" | '''Proven properties''' |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''UId<sub>1</sub>''' !! !! colspan="2" | If ''x'' ∨ ''o'' = ''x'' for all ''x'', then ''o'' = 0 |- | Proof: || || colspan="2" | If ''x'' ∨ ''o'' = ''x'', then |- | || || 0 |- | || = || 0 ∨ ''o'' || by assumption |- | || = || ''o'' ∨ 0 || by '''Cmm<sub>1</sub>''' |- | || = || ''o'' || by '''Idn<sub>1</sub>''' |} | '''UId<sub>2</sub>''' [dual] If ''x'' ∧ ''i'' = ''x'' for all ''x'', then ''i'' = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''Idm<sub>1</sub>''' !! !! ''x'' ∨ ''x'' = ''x'' |- | Proof: || || ''x'' ∨ ''x'' |- | || = || (''x'' ∨ ''x'') ∧ 1 || by '''Idn<sub>2</sub>''' |- | || = || (''x'' ∨ ''x'') ∧ (''x'' ∨ ¬''x'') || by '''Cpl<sub>1</sub>''' |- | || = || ''x'' ∨ (''x'' ∧ ¬''x'') || by '''Dst<sub>1</sub>''' |- | || = || ''x'' ∨ 0 || by '''Cpl<sub>2</sub>''' |- | || = || ''x'' || by '''Idn<sub>1</sub>''' |} | '''Idm<sub>2</sub>''' [dual] ''x'' ∧ ''x'' = ''x'' |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''Bnd<sub>1</sub>''' !! !! ''x'' ∨ 1 = 1 |- | Proof: || || ''x'' ∨ 1 |- | || = || (''x'' ∨ 1) ∧ 1 || by '''Idn<sub>2</sub>''' |- | || = || 1 ∧ (''x'' ∨ 1) || by '''Cmm<sub>2</sub>''' |- | || = || (''x'' ∨ ¬''x'') ∧ (''x'' ∨ 1) || by '''Cpl<sub>1</sub>''' |- | || = || ''x'' ∨ (¬''x'' ∧ 1) || by '''Dst<sub>1</sub>''' |- | || = || ''x'' ∨ ¬''x'' || by '''Idn<sub>2</sub>''' |- | || = || 1 || by '''Cpl<sub>1</sub>''' |} | '''Bnd<sub>2</sub>''' [dual] ''x'' ∧ 0 = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''Abs<sub>1</sub>''' !! !! ''x'' ∨ (''x'' ∧ ''y'') = ''x'' |- | Proof: || || ''x'' ∨ (''x'' ∧ ''y'') |- | || = || (''x'' ∧ 1) ∨ (''x'' ∧ ''y'') || by '''Idn<sub>2</sub>''' |- | || = || ''x'' ∧ (1 ∨ ''y'') || by '''Dst<sub>2</sub>''' |- | || = || ''x'' ∧ (''y'' ∨ 1) || by '''Cmm<sub>1</sub>''' |- | || = || ''x'' ∧ 1 || by '''Bnd<sub>1</sub>''' |- | || = || ''x'' || by '''Idn<sub>2</sub>''' |} | '''Abs<sub>2</sub>''' [dual] ''x'' ∧ (''x'' ∨ ''y'') = ''x'' |- valign="top" | colspan="2" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''UNg''' !! !! colspan="2" | If ''x'' ∨ ''x''<sub>n</sub> = 1 and ''x'' ∧ ''x''<sub>n</sub> = 0, then ''x''<sub>n</sub> = ¬''x'' |- | Proof: || || colspan="2" | If ''x'' ∨ ''x''<sub>n</sub> = 1 and ''x'' ∧ ''x''<sub>n</sub> = 0, then |- | || ||''x''<sub>n</sub> |- | || = || ''x''<sub>n</sub> ∧ 1 || by '''Idn<sub>2</sub>''' |- | || = || ''x''<sub>n</sub> ∧ (''x'' ∨ ¬''x'') || by '''Cpl<sub>1</sub>''' |- | || = || (''x''<sub>n</sub> ∧ ''x'') ∨ (''x''<sub>n</sub> ∧ ¬''x'') || by '''Dst<sub>2</sub>''' |- | || = || (''x'' ∧ ''x''<sub>n</sub>) ∨ (¬''x'' ∧ ''x''<sub>n</sub>) || by '''Cmm<sub>2</sub>''' |- | || = || 0 ∨ (¬''x'' ∧ ''x''<sub>n</sub>) || by assumption |- | || = || (''x'' ∧ ¬''x'') ∨ (¬''x'' ∧ ''x''<sub>n</sub>) || by '''Cpl<sub>2</sub>''' |- | || = || (¬''x'' ∧ ''x'') ∨ (¬''x'' ∧ ''x''<sub>n</sub>) || by '''Cmm<sub>2</sub>''' |- | || = || ¬''x'' ∧ (''x'' ∨ ''x''<sub>n</sub>) || by '''Dst<sub>2</sub>''' |- | || = || ¬''x'' ∧ 1 || by assumption |- | || = || ¬''x'' || by '''Idn<sub>2</sub>''' |} |- valign="top" | colspan="2" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''DNg''' !! !! ¬¬''x'' = ''x'' |- | Proof: || || ¬''x'' ∨ ''x'' = ''x'' ∨ ¬''x'' = 1 || by '''Cmm<sub>1</sub>''', '''Cpl<sub>1</sub>''' |- | || and || ¬''x'' ∧ ''x'' = ''x'' ∧ ¬''x'' = 0 || by '''Cmm<sub>2</sub>''', '''Cpl<sub>2</sub>''' |- | || hence || ''x'' = ¬¬''x'' || by '''UNg''' |} |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''A<sub>1</sub>''' !! !! ''x'' ∨ (¬''x'' ∨ ''y'') = 1 |- | Proof: || || ''x'' ∨ (¬''x'' ∨ ''y'') |- | || = || (''x'' ∨ (¬''x'' ∨ ''y'')) ∧ 1 || by '''Idn<sub>2</sub>''' |- | || = || 1 ∧ (''x'' ∨ (¬''x'' ∨ ''y'')) || by '''Cmm<sub>2</sub>''' |- | || = || (''x'' ∨ ¬''x'') ∧ (''x'' ∨ (¬''x'' ∨ ''y'')) || by '''Cpl<sub>1</sub>''' |- | || = || ''x'' ∨ (¬''x'' ∧ (¬''x'' ∨ ''y'')) || by '''Dst<sub>1</sub>''' |- | || = || ''x'' ∨ ¬''x'' || by '''Abs<sub>2</sub>''' |- | || = || 1 || by '''Cpl<sub>1</sub>''' |} | '''A<sub>2</sub>''' [dual] ''x'' ∧ (¬''x'' ∧ ''y'') = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''B<sub>1</sub>''' !! !! (''x'' ∨ ''y'') ∨ (¬''x'' ∧ ¬''y'') = 1 |- | Proof: || || (''x'' ∨ ''y'') ∨ (¬''x'' ∧ ¬''y'') |- | || = || ((''x'' ∨ ''y'') ∨ ¬''x'') ∧ ((''x'' ∨ ''y'') ∨ ¬''y'') || by '''Dst<sub>1</sub>''' |- | || = || (¬''x'' ∨ (''x'' ∨ ''y'')) ∧ (¬''y'' ∨ (''y'' ∨ ''x'')) || by '''Cmm<sub>1</sub>''' |- | || = || (¬''x'' ∨ (¬¬''x'' ∨ ''y'')) ∧ (¬''y'' ∨ (¬¬''y'' ∨ ''x'')) || by '''DNg''' |- | || = || 1 ∧ 1 || by '''A<sub>1</sub>''' |- | || = || 1 || by '''Idn<sub>2</sub>''' |} | '''B<sub>2</sub>''' [dual] (''x'' ∧ ''y'') ∧ (¬''x'' ∨ ¬''y'') = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''C<sub>1</sub>''' !! !! (''x'' ∨ ''y'') ∧ (¬''x'' ∧ ¬''y'') = 0 |- | Proof: || || (''x'' ∨ ''y'') ∧ (¬''x'' ∧ ¬''y'') |- | || = || (¬''x'' ∧ ¬''y'') ∧ (''x'' ∨ ''y'') || by '''Cmm<sub>2</sub>''' |- | || = || ((¬''x'' ∧ ¬''y'') ∧ ''x'') ∨ ((¬''x'' ∧ ¬''y'') ∧ ''y'') || by '''Dst<sub>2</sub>''' |- | || = || (''x'' ∧ (¬''x'' ∧ ¬''y'')) ∨ (''y'' ∧ (¬''y'' ∧ ¬''x'')) || by '''Cmm<sub>2</sub>''' |- | || = || 0 ∨ 0 || by '''A<sub>2</sub>''' |- | || = || 0 || by '''Idn<sub>1</sub>''' |} | '''C<sub>2</sub>''' [dual] (''x'' ∧ ''y'') ∨ (¬''x'' ∨ ¬''y'') = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''DMg<sub>1</sub>''' !! !! ¬(''x'' ∨ ''y'') = ¬''x'' ∧ ¬''y'' |- | Proof: || || by '''B<sub>1</sub>''', '''C<sub>1</sub>''', and '''UNg''' |} | '''DMg<sub>2</sub>''' [dual] ¬(''x'' ∧ ''y'') = ¬''x'' ∨ ¬''y'' |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''D<sub>1</sub>''' !! !! (''x''∨(''y''∨''z'')) ∨ ¬''x'' = 1 |- | Proof: || || (''x'' ∨ (''y'' ∨ ''z'')) ∨ ¬''x'' |- | || = || ¬''x'' ∨ (''x'' ∨ (''y'' ∨ ''z'')) || by '''Cmm<sub>1</sub>''' |- | || = || ¬''x'' ∨ (¬¬''x'' ∨ (''y'' ∨ ''z'')) || by '''DNg''' |- | || = || 1 || by '''A<sub>1</sub>''' |} | '''D<sub>2</sub>''' [dual] (''x''∧(''y''∧''z'')) ∧ ¬''x'' = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''E<sub>1</sub>''' !! !! ''y'' ∧ (''x''∨(''y''∨''z'')) = ''y'' |- | Proof: || || ''y'' ∧ (''x'' ∨ (''y'' ∨ ''z'')) |- | || = || (''y'' ∧ ''x'') ∨ (''y'' ∧ (''y'' ∨ ''z'')) || by '''Dst<sub>2</sub>''' |- | || = || (''y'' ∧ ''x'') ∨ ''y'' || by '''Abs<sub>2</sub>''' |- | || = || ''y'' ∨ (''y'' ∧ ''x'') || by '''Cmm<sub>1</sub>''' |- | || = || ''y'' || by '''Abs<sub>1</sub>''' |} | '''E<sub>2</sub>''' [dual] ''y'' ∨ (''x''∧(''y''∧''z'')) = ''y'' |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''F<sub>1</sub>''' !! !! (''x''∨(''y''∨''z'')) ∨ ¬''y'' = 1 |- | Proof: || || (''x'' ∨ (''y'' ∨ ''z'')) ∨ ¬''y'' |- | || = || ¬''y'' ∨ (''x'' ∨ (''y'' ∨ ''z'')) || by '''Cmm<sub>1</sub>''' |- | || = || (¬''y'' ∨ (''x'' ∨ (''y'' ∨ ''z''))) ∧ 1 || by '''Idn<sub>2</sub>''' |- | || = || 1 ∧ (¬''y'' ∨ (''x'' ∨ (''y'' ∨ ''z''))) || by '''Cmm<sub>2</sub>''' |- | || = || (''y'' ∨ ¬''y'') ∧ (¬''y'' ∨ (''x'' ∨ (''y'' ∨ ''z''))) || by '''Cpl<sub>1</sub>''' |- | || = || (¬''y'' ∨ ''y'') ∧ (¬''y'' ∨ (''x'' ∨ (''y'' ∨ ''z''))) || by '''Cmm<sub>1</sub>''' |- | || = || ¬''y'' ∨ (''y'' ∧ (''x'' ∨ (''y'' ∨ ''z''))) || by '''Dst<sub>1</sub>''' |- | || = || ¬''y'' ∨ ''y'' || by '''E<sub>1</sub>''' |- | || = || ''y'' ∨ ¬''y'' || by '''Cmm<sub>1</sub>''' |- | || = || 1 || by '''Cpl<sub>1</sub>''' |} | '''F<sub>2</sub>''' [dual] (''x''∧(''y''∧''z'')) ∧ ¬''y'' = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''G<sub>1</sub>''' !! !! (''x''∨(''y''∨''z'')) ∨ ¬''z'' = 1 |- | Proof: || || (''x'' ∨ (''y'' ∨ ''z'')) ∨ ¬''z'' |- | || = || (''x'' ∨ (''z'' ∨ ''y'')) ∨ ¬''z'' || by '''Cmm<sub>1</sub>''' |- | || = || 1 || by '''F<sub>1</sub>''' |} | '''G<sub>2</sub>''' [dual] (''x''∧(''y''∧''z'')) ∧ ¬''z'' = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''H<sub>1</sub>''' !! !! ¬((''x''∨''y'')∨''z'') ∧ ''x'' = 0 |- | Proof: || || ¬((''x'' ∨ ''y'') ∨ ''z'') ∧ ''x'' |- | || = || (¬(''x'' ∨ ''y'') ∧ ¬''z'') ∧ ''x'' || by '''DMg<sub>1</sub>''' |- | || = || ((¬''x'' ∧ ¬''y'') ∧ ¬''z'') ∧ ''x'' || by '''DMg<sub>1</sub>''' |- | || = || ''x'' ∧ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'') || by '''Cmm<sub>2</sub>''' |- | || = || (''x'' ∧ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'')) ∨ 0 || by '''Idn<sub>1</sub>''' |- | || = || 0 ∨ (''x'' ∧ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'')) || by '''Cmm<sub>1</sub>''' |- | || = || (''x'' ∧ ¬''x'') ∨ (''x'' ∧ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'')) || by '''Cpl<sub>2</sub>''' |- | || = || ''x'' ∧ (¬''x'' ∨ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'')) || by '''Dst<sub>2</sub>''' |- | || = || ''x'' ∧ (¬''x'' ∨ (¬''z'' ∧ (¬''x'' ∧ ¬''y''))) || by '''Cmm<sub>2</sub>''' |- | || = || ''x'' ∧ ¬''x'' || by '''E<sub>2</sub>''' |- | || = || 0 || by '''Cpl<sub>2</sub>''' |} | '''H<sub>2</sub>''' [dual] ¬((''x''∧''y'')∧''z'') ∨ ''x'' = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''I<sub>1</sub>''' !! !! ¬((''x''∨''y'')∨''z'') ∧ ''y'' = 0 |- | Proof: || || ¬((''x'' ∨ ''y'') ∨ ''z'') ∧ ''y'' |- | || = || ¬((''y'' ∨ ''x'') ∨ ''z'') ∧ ''y'' || by '''Cmm<sub>1</sub>''' |- | || = || 0 || by '''H<sub>1</sub>''' |} | '''I<sub>2</sub>''' [dual] ¬((''x''∧''y'')∧''z'') ∨ ''y'' = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''J<sub>1</sub>''' !! !! ¬((''x''∨''y'')∨''z'') ∧ ''z'' = 0 |- | Proof: || || ¬((''x'' ∨ ''y'') ∨ ''z'') ∧ ''z'' |- | || = || (¬(''x'' ∨ ''y'') ∧ ¬''z'') ∧ ''z'' || by '''DMg<sub>1</sub>''' |- | || = || ''z'' ∧ (¬(''x'' ∨ ''y'') ∧ ¬''z'') || by '''Cmm<sub>2</sub>''' |- | || = || ''z'' ∧ ( ¬''z'' ∧ ¬(''x'' ∨ ''y'')) || by '''Cmm<sub>2</sub>''' |- | || = || 0 || by '''A<sub>2</sub>''' |} | '''J<sub>2</sub>''' [dual] ¬((''x''∧''y'')∧''z'') ∨ ''z'' = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''K<sub>1</sub>''' !! !! (''x'' ∨ (''y'' ∨ ''z'')) ∨ ¬((''x'' ∨ ''y'') ∨ ''z'') = 1 |- | Proof: || || (''x''∨(''y''∨''z'')) ∨ ¬((''x'' ∨ ''y'') ∨ ''z'') |- | || = || (''x''∨(''y''∨''z'')) ∨ (¬(''x'' ∨ ''y'') ∧ ¬''z'') || by '''DMg<sub>1</sub>''' |- | || = || (''x''∨(''y''∨''z'')) ∨ ((¬''x'' ∧ ¬''y'') ∧ ¬''z'') || by '''DMg<sub>1</sub>''' |- | || = || ((''x''∨(''y''∨''z'')) ∨ (¬''x'' ∧ ¬''y'')) ∧ ((''x''∨(''y''∨''z'')) ∨ ¬''z'')|| by '''Dst<sub>1</sub>''' |- | || = || (((''x''∨(''y''∨''z'')) ∨ ¬''x'') ∧ ((''x''∨(''y''∨''z'')) ∨ ¬''y'')) ∧ ((''x''∨(''y''∨''z'')) ∨ ¬''z'')|| by '''Dst<sub>1</sub>''' |- | || = || (1 ∧ 1) ∧ 1 || by '''D<sub>1</sub>''','''F<sub>1</sub>''','''G<sub>1</sub>''' |- | || = || 1 || by '''Idn<sub>2</sub>''' |} | '''K<sub>2</sub>''' [dual] (''x'' ∧ (''y'' ∧ ''z'')) ∧ ¬((''x'' ∧ ''y'') ∧ ''z'') = 0 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''L<sub>1</sub>''' !! !! (''x'' ∨ (''y'' ∨ ''z'')) ∧ ¬((''x'' ∨ ''y'') ∨ ''z'') = 0 |- | Proof: || || (''x'' ∨ (''y'' ∨ ''z'')) ∧ ¬((''x'' ∨ ''y'') ∨ ''z'') |- | || = || ¬((''x''∨''y'')∨''z'') ∧ (''x'' ∨ (''y'' ∨ ''z'')) || by '''Cmm<sub>2</sub>''' |- | || = || (¬((''x''∨''y'')∨''z'') ∧ ''x'') ∨ (¬((''x''∨''y'')∨''z'') ∧ (''y'' ∨ ''z'')) || by '''Dst<sub>2</sub>''' |- | || = || (¬((''x''∨''y'')∨''z'') ∧ ''x'') ∨ ((¬((''x''∨''y'')∨''z'') ∧ ''y'') ∨ (¬((''x''∨''y'')∨''z'') ∧ ''z'')) || by '''Dst<sub>2</sub>''' |- | || = || 0 ∨ (0 ∨ 0) || by '''H<sub>1</sub>''','''I<sub>1</sub>''','''J<sub>1</sub>''' |- | || = || 0 || by '''Idn<sub>1</sub>''' |} | '''L<sub>2</sub>''' [dual] (''x'' ∧ (''y'' ∧ ''z'')) ∨ ¬((''x'' ∧ ''y'') ∧ ''z'') = 1 |- valign="top" | {| align="left" class="collapsible collapsed" style="text-align:left" ! '''Ass<sub>1</sub>''' !! !! ''x'' ∨ (''y'' ∨ ''z'') = (''x'' ∨ ''y'') ∨ ''z'' |- | Proof: || || by '''K<sub>1</sub>''', '''L<sub>1</sub>''', '''UNg''', '''DNg''' |} | '''Ass<sub>2</sub>''' [dual] ''x'' ∧ (''y'' ∧ ''z'') = (''x'' ∧ ''y'') ∧ ''z'' |- | colspan="2" | {| align="left" class="collapsible" style="text-align:left" |- ! colspan="2" | Abbreviations |- | '''UId''' || Unique Identity |- | '''Idm''' || [[Idempotence]] |- | '''Bnd''' || [[Bounded lattice|Boundaries]] |- | '''Abs''' || [[Absorption law]] |- | '''UNg''' || Unique Negation |- | '''DNg''' || [[Double negation]] |- | '''DMg''' || [[De Morgan's Law]] |- | '''Ass''' || [[Associativity]] |} |} {| align="right" class="wikitable collapsible collapsed" style="text-align:left" ! colspan="4"| '''Huntington 1904 Boolean algebra axioms''' |- valign="top" | '''Idn<sub>1</sub>''' || ''x'' ∨ 0 = ''x'' | '''Idn<sub>2</sub>''' || ''x'' ∧ 1 = ''x'' |- valign="top" | '''Cmm<sub>1</sub>''' || ''x'' ∨ ''y'' = ''y'' ∨ ''x'' | '''Cmm<sub>2</sub>''' || ''x'' ∧ ''y'' = ''y'' ∧ ''x'' |- valign="top" | '''Dst<sub>1</sub>''' || ''x'' ∨ (''y''∧''z'') = (''x''∨''y'') ∧ (''x''∨''z'') | '''Dst<sub>2</sub>''' || ''x'' ∧ (''y''∨''z'') = (''x''∧''y'') ∨ (''x''∧''z'') |- valign="top" | '''Cpl<sub>1</sub>''' || ''x'' ∨ ¬''x'' = 1 | '''Cpl<sub>2</sub>''' || ''x'' ∧ ¬''x'' = 0 |- | colspan="4" | {| align="left" class="collapsible" style="text-align:left" |- ! colspan="2" | Abbreviations |- | '''Idn''' || [[Identity element|Identity]] |- | '''Cmm''' || [[Commutativity]] |- | '''Dst''' || [[Distributivity]] |- | '''Cpl''' || [[Complemented lattice|Complements]] |} |} The first axiomatization of Boolean lattices/algebras in general was given by the English philosopher and mathematician [[Alfred North Whitehead]] in 1898.{{sfn|Padmanabhan|Rudeanu|2008|p=[https://books.google.com/books?id=JlXSlpmlSv4C&pg=PA73 73]}}{{sfn|Whitehead|1898|p=37}} It included the [[#Definition|above axioms]] and additionally {{math|1=''x'' ∨ 1 = 1}} and {{math|1=''x'' ∧ 0 = 0}}. In 1904, the American mathematician [[Edward V. Huntington]] (1874–1952) gave probably the most parsimonious axiomatization based on {{math|1=∧}}, {{math|1=∨}}, {{math|1=¬}}, even proving the associativity laws (see box).{{sfn|Huntington|1904|pp=292-293}} He also proved that these axioms are [[Independence (mathematical logic)|independent]] of each other.{{sfn|Huntington|1904|p=296}} In 1933, Huntington set out the following elegant axiomatization for Boolean algebra.{{sfn|Huntington|1933a}} It requires just one binary operation {{math|1=+}} and a [[unary functional symbol]] {{math|1=''n''}}, to be read as 'complement', which satisfy the following laws: {{olist |1= ''Commutativity'': {{math|1=''x'' + ''y'' = ''y'' + ''x''}}. |2= ''Associativity'': {{math|1=(''x'' + ''y'') + ''z'' = ''x'' + (''y'' + ''z'')}}. |3= ''Huntington equation'': {{math|1=''n''(''n''(''x'') + ''y'') + ''n''(''n''(''x'') + ''n''(''y'')) = ''x''}}. }} [[Herbert Robbins]] immediately asked: If the Huntington equation is replaced with its dual, to wit: {{olist|start=4 |1= ''Robbins Equation'': {{math|1=''n''(''n''(''x'' + ''y'') + ''n''(''x'' + ''n''(''y''))) = ''x''}}, }} do (1), (2), and (4) form a basis for Boolean algebra? Calling (1), (2), and (4) a ''Robbins algebra'', the question then becomes: Is every Robbins algebra a Boolean algebra? This question (which came to be known as the [[Robbins conjecture]]) remained open for decades, and became a favorite question of [[Alfred Tarski]] and his students. In 1996, [[William McCune]] at [[Argonne National Laboratory]], building on earlier work by Larry Wos, Steve Winker, and Bob Veroff, answered Robbins's question in the affirmative: Every Robbins algebra is a Boolean algebra. Crucial to McCune's proof was the computer program [[Equational prover|EQP]] he designed. For a simplification of McCune's proof, see Dahn (1998). Further work has been done for reducing the number of axioms; see [[Minimal axioms for Boolean algebra]]. {{clear}}
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)