## 13.5 Debugging and updating deployed systems

SWI-Prolog provides several facilities to debug and update running (server) applications. The core to these facilities are:

- Hot-swap recompilation (section 4.3.2 and the library `library(hotswap)`) allow, with some limitation, making modifications to running services. This includes adding debugging and logging statements.

- To make this useful some form of interaction is required. This can be implemented using signal handlers (Unix), specific HTTP services, generic HTTP services (e.g., SWISH) or networked interaction using the library `library(prolog_server)` that allow interaction using netcat (nc) or telnet.