System and method for on-line replacement of software

A method of implementing on-the-fly replacement of an implementation library so as to allow updating the implementation library while maintaining correct operation of an application that uses a software routine within the implementation library, the replacement method comprising the steps of:

• providing a first version of the implementation library;
• establishing an interface library corresponding to the implementation library, the interface library including a proxy routine for the software routine within the implementation library;
• linking the interface library to the application that uses the software routine within the implementation library;
• executing a call in the application to the software routine within the implementation library;
• responsive to the call to the software routine, transferring control to the corresponding proxy interface in the interface library;
• determining whether the implementation library is marked for updating, and if it is, replacing the first version of the implementation library with a second version of the implementation library;
• transferring control to the corresponding software routine in the implementation library;
• executing the corresponding software routine in the implementation library;
• returning control to the application at a return point immediately following executed call;
• and
• continuing executing of the application beginning at the said return point.

An on-the-fly replaceable implementation library for use in a replaceable software system embodied in a computer, the implementation library comprising:

• one or more software routines for implementing a selected service;
• an interface for use by an external software component using the selected service, the interface allowing for a call from the external software component but not allowing for a binding to the external software component;
• one or more state variables, each state variable having a respective value, the values of the state variables together defining a library state;
• and
• a means for restoring the library state to match a library state of a previous version of the implementation library.

A proxy interface library for use in a replaceable software system embodied in a computer, the proxy interface library being associated with a corresponding implementation library and comprising:

• a proxy interface corresponding to a routine within the corresponding implementation library;
• the proxy interface being linkable to an application as a proxy for the corresponding routine in the implementation library;
• means for locating the corresponding routine in the implementation library;
• and
• means for transferring execution control to the corresponding routine in the implementation library in response to execution of a call in an application to the corresponding routine in the implementation library, whereby the proxy interface library is transparent to the application.