NESC1021 TREDRA.

1. NAME OR DESIGNATION OF PROGRAM:  TREDRA.

3. DESCRIPTION OF PROBLEM OR FUNCTION

TREDRA is a computer program for drafting report-quality fault trees. The input to TREDRA is similar to input for standard computer programs that find minimal cut sets from fault trees. Output includes fault tree plots containing all standard fault tree logic and event symbols, gate and event labels, and an output description for each event in the fault  tree. TREDRA contains the following features: a variety of program options that allow flexibility in the program output; capability for automatic pagination of the output fault tree, when necessary; input groups which allow labeling of gates, events, and their output descriptions; a symbol library which includes standard fault tree symbols plus several less frequently used symbols; user control of character size and overall plot size; and extensive input error checking and diagnostic oriented output.

4. METHOD OF SOLUTION

Fault trees are generated by user-supplied control parameters and a coded description of the fault tree structure consisting of the name of each gate, the gate type, the number of inputs to the gate, and the names of these inputs.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

TREDRA can produce fault trees with a minimum of 3 and a maximum of 56 levels. The width of each level may range from 3 to 37. A total of 50 transfers  is allowed during pagination.

6. TYPICAL RUNNING TIME

NESC executed each sample problem in less than 2 CPU seconds on an IBM 3033.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

TREDRA extends the earlier MOTH and HERCULES programs, which used together produce computer drawn fault trees from processing MOCUS or PREP input data, by combining their features into one program. MOCUS (NESC Abstract 653) and PREP,KITT (NESC Abstract 528) are computer programs for determining  minimum cut sets and minimal path sets from existing fault trees.
Six of the seven program options in TREDRA require a MOCUS/PREP description of the fault tree structure.

10. REFERENCES

- J.B. Fussell, E.B. Henry, N.H. Marshall:
  MOCUS: A Computer Program to Obtain Minimal Sets from Fault Trees
  ANCR-1156, August 1974
- W.E. Vesely, R.E. Narum:
  PREP and KITT: Computer Codes for the Automatic Evaluation of a
  Fault Tree
  IN-1349, August 1970
- N.H. Marshall:
  MOTH -- MOCUS to HERCULES
  Aerojet Nuclear Company document, August 1974.
- J.B. Fussell:
  Special Techniques in Fault Tree Analysis
  Aerojet Nuclear Company document, March 1974.
- J.B. Fussell:
  Particularities of Fault Tree Analysis
  Aerojet Nuclear Company document, September 1974.

- L.S. Baker, D.P. Wagner, C.L. Cate and J.B. Fussel:
  TREDRA - A Computer Program to Draft Fault Trees.
  NESC No. 1021  (October 1978)

11. MACHINE REQUIREMENTS:  270K bytes of memory are required for execution.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
OS/MVT (IBM 360/370), MVS (IBM 3033).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Function NCHARS, which determines the length of a string, is written in Basic Assembly Language. Graphical output is accomplished through calls to the proprietary CalComp graphics system.

15. NAME AND ESTABLISHMENT OF AUTHOR

         J.B. Fussell
         JBF Associates, Inc.
         1000 Technology Park Center
         Knoxville, Tennessee 37932, U. S. A.

File name	File description	Records
NESC1021_01.003	TREDRA INFORMATION FILE	50
NESC1021_01.004	TREDRA SOURCE (FORTRAN-4)	3551
NESC1021_01.005	NCHARS SOURCE (ASSEMBLER)	25
NESC1021_01.006	TEST CASE INPUT USING 'CONVERT' OPTION	21
NESC1021_01.007	TEST CASE INPUT USING 'PRINTPLOT' OPTION	50
NESC1021_01.008	TEST CASE INPUT USING 'BYPASS' OPTION	119
NESC1021_01.009	JCL	106