The Essential Tools Module Error Model

The following table describes errors in the Essential Tools Module error model.

Table 19 – Error Types in the Essential Tools Module
Error Types:	Internal Non-recoverable	Internal Recoverable	External
Cause:	Faulty logic or coding in the program	Faulty logic or coding in the program	Events beyond the scope of the program
Examples:	Bounds error; inserting a null pointer into 0a collection	Bounds error in a linked list; attempt to use an invalid date	Attempts to write a bad date, or to invert a singular matrix; stream write error; out of memory
Predictable?	Yes	Yes	No
Cost to detect:	High	Low	Low
Level of abstraction:	Low	Low	High
Where detected:	Debug version of library	Debug and production version of library	Debug and production version of library
Response:	No recovery mechanism	Throws an exception inheriting from RWInternalErr	Throws an exception inheriting from RWExternalErr, or provide test for object validity