A FORMAL APPROACH TO DISTRIBUTED INFORMATION SYSTEMS
Gjpm Geert-Jan Houben, Jan Paredaens · TU/e Research Portal · 1987
We describe a mathematical model for distributed information systems.which have a distributed scheduler and in which each site acts as an automaton-like process.We consider information systems.which contain functional distributed database systems.In a distributed database system the information is stored in several sites.Each site is managed by a machine.A machine is able to execute actions at its site.An action represents some manipulation of the information stored in the site.As such.each machine is responsible for the information in its local database component. An information system executes transactions. Transactions have to be translated intoWhen h goes, in order to execute.L, from A to FV, the scheduler s gives a time stamp, say j, which is one higher than the previous one, so 11.= h (j) and.L = t (j), and s calculates from t (j ) F j , Vj ,Vj : F j := ( machines to which h U) will send functional actions in order to execute t U) } Vj := ( machines to which h U) will send view actions in order to execute t U) } Vj := ( machines to which h U) will send update actions in order to execute t U) } -Before h U) sends, in order to execute t (j), a view action to a machine m, h U) waits until m does not belong to .u. Vi .• O. for all i;c j and all m of U j AU i (m) := AU,cm) -1 if AU i em) > O. for all i ;C j and all m of U j U(m) := U(m) -1 for all m of U j