Multi-Station and Fault Tolerance  A single computer controlling all features of the Home is problematic. –In multi-floor homes access to Home features should be available on all floors When you call from the 2 nd floor you still need the address book no matter where it’s stored When you talk on the phone and get a meeting date and time from someone you want to enter it into the calendar and not on a piece of paper for future use

Requirement  Access to PIM from different locations in the home  Update of PIM database from different locations in the home  A common interface to computers in the house (The, by now infamous, Common GUI for which we wait now for more than 2 months.) –Each computer may have a customized facet of the common GUI Calendar on one, To-Do-List on another

Faults –A failure of the home computer, if only one exists, causes a traumatic experience to the resident.  We suggest a solution to handle faults in the controlling computer. –Unless the home is a collection of gadgets, facilities and services are connected to a computer to provide: Archival repository Sophisticated services cannot be provided by bare bones gadgets

Faults - continued –A pressure tile may response with the weight of two kids stepping on it concurrently. –They may weigh exactly as much as an adult –This conflict has to resolved –Can be resolved easily by a computer consulting previous weight measures

Fault Tolerance - continued  Additional computers IPAQs, Web Tablets, and similar devices connected wirelessly will get periodic updates of essential data required for home functioning.  In the case of a backup computer, it will have the identical software.  In the case of more limited devices such as Web Tablets, such devices will have a smaller of Personalization and data.

Requirements  A common denominator Personalization and PIM –This may not be a major problem PIM is essentially a set of operations on a small database The local database has to be synchronized with the other databases –The database should fit easily any of the computers connected –Can use 2PC –Small enough to: Fit all computers Sufficient for regular activities –An alternative is to provide remote services Looking up a phone number may travel to the main computer, an answer be located and sent back to requesting computer Many remote services exist; easy to mimic

Requirements - continued  RM has to be duplicated or loaded only at computers connected to external devices –JAVAphone  We must find a way to have devices connected to more than a single box –Otherwise, a failure in the main box is fatal

Requirements - continued  Database version –Sufficient for regular activities or –Needed data will be acquired, if exist, from another node through a simple protocol A simple solution is to use on the more powerful computers a Web server to which access is simple HTTP and data itself can be XML. Implies  Personalization at the controlling computer must run with a Web server

Fault Tolerance - continued  Upon failure, a new control computer will be elected and it will take over home support.  Since the infrastructure already exists, access to home services will be available through any of the computing devices at all times.

Requirements  Create middleware consisting of: –Data send/receive APIs –Facility for remote services –Basic hand shake protocol –Database synchronization and 2PC –Election algorithm –Home Computer Status

Requirements - continued  Data send/receive APIs –A basic service –Can use a simple socket interface  Facility for remote services –Several versions are possible: RPC-like except that marshalling is not needed; use XML Rewrite Personalization to work off messages –Then a local message or a remote message have the same effect except for Windows.  Basic hand shake protocol to find out who is up and who is down –Such protocols are simple and can be copied

Requirements - continued  Database synchronization and 2PC –2PC code can be found on the Web –It should be invoked when the local database changes  Election algorithm –Typically use the Bully Algorithm Takes care of both failure and recovery This algorithm is simple and can be copied  Home Computer Network Status –Maintained by each node –Displayed upon request No need to bother residents with this information unless they ask for it