See the NodeBrain Library manual for a description of C API functions.

`math.sqrt(a)

Modules may also be used to implement one or more node skills. For each skill, the module must implement one or more skill methods (functions) within a defined set. Once declared, a skill may be associated with any number of nodes. A node is an object that has the defined skill, but also (often) the ability to accumulate a set of knowledge independent of other nodes with the same skill.

You will not find enough information here to learn how to write a node module. Here we only provide enough information, hopefully, to demystify NodeBrain modules for those installing or using an existing module. The NodeBrain Library manual describes the API.

See http://nodebrain.org for more information.

/usr/include/nb/nb.h	NodeBrain API header file.
/usr/lib64/nb-series/nb_module.suffix	NodeBrain modules may be located anywhere, provided you direct nb to them using the NB_MODULE_PATH environment variable or a path in a module declaration command. If no path is specified and a module is not found using the native search path, NodeBrain checks in libdir/nb/x.x as show above, where libdir and suffix are determined by the platform.
nb_module.so	[Solaris and Linux]
nb_module.sl	[HP-UX]
nb_module.dylib	[Mac OS x]
nb_module.dll	[Windows]

# declare module - unnecessary if the module is in the standard directory

declare tree module {"."}tree;

# declare skill - unnecessary if no special parameters are specified

declare tree skill tree:trace;

# table of critical devices

define criticalDevice node tree;

# table of problem devices

define problemDevice node tree;

# rules that respond when a device has a new problem

define event node;

event. define r1 if(type="problem" and ?problemDevice(device)) problemDevice(device):actionA

event. define r2 if(type="problem" and ?problemDevice(device) and criticalDevice(device)):actionB

event. define r3 if(type="restored") ?problemDevice(device);

# sample initialization of the critical device table

assert criticalDevice("abc");

assert criticalDevice("def");

# sample events from a monitoring application

event. alert type="problem",device="abc";

event. alert type="restored",device="abc";

NB_MODULE_PATH

The NB_MODULE_PATH environment variable provides a platform independent way of specifying a path for locating node modules. This path overrides the native system search paths by qualifying module names so that a search is avoided. The following example illustrates a setting that directs NodeBrain to search the current directory first and then the parent directory when loading modules (plug-ins). NB_MODULE_PATH="./:../" nb myscript.nb

yyyy/mm/dd hh:mm:ss NB000E Unable to load file

When a module is successfully loaded but the symbol referenced in a skill declaration is not found, a message is displayed.

yyyy/mm/dd hh:mm:ss NB000E Symbol symbol not found

NodeBrain does not attempt to load a module when it is declared. Instead, it waits until a module is referenced by a DEFINE command for a node to avoid loading modules unnecessarily. For this reason, either of the messages above will follow a node definition when there is an error.