process methods in

1. process methods in ZERO-DEFECT software engineering

2. process methods in ZERO-DEFECT INTRODUCTION software engineering What are zero-defect methods? “Zero-defect methods are practices that aim for zero defects in the software before software is built.”

3. process methods in ZERO-DEFECT INTRODUCTION software engineering Why zero-defect methods? • Software testing can only remove about 73%of defects on average • Software testing can be impossible to carryout in specific end systems (asynchronousentities, embedded systems) “The expensive and inefficient phase of software testing can be avoided with the use of zero-defect methods.”

4. process methods in ZERO-DEFECT INTRODUCTION software engineering About Sitoni Oy • Sitoni Oy is a software engineering, consultingand training company established in 1991 • Its software aims for elastic management andhandling of data • The software seeks to abandon predefineddefinitions of processed data

5. process methods in ZERO-DEFECT INTRODUCTION software engineering About Sitoni Oy • The software attempts to manage largeheterogeneous flows of data and solve thedemanding data processing problems relatingto them Continue?

6. process methods in ZERO-DEFECT INTRODUCTION software engineering The work consists of two parts • Research part • Researching Sitoni zero-defect concepts • Development part • Developing the media for the researchedconcepts

7. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering Phases of the work: Preliminary Study Analysis / Requirements Definition Design Implementation QA / Testing / Deployment

8. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering Preliminary study • Project plan • Schedule with phases and milestones • Development web site (for the supervisor)

9. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering Requirements Definition • Division of requirements (content part,web site part) • Definition of individual requirements and theirpriorities • Combining the content requirements into largerentities

10. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering Design • Designing of the linguistic issues of the contentpart • Designing of the web site (“User Interface”,appearance, markup language, highest leveluse cases, script intended functions, etc.)

11. process methods in ZERO-DEFECT UML USE CASE EXAMPLE software engineering

12. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering Implementation • Writing of the content part • Implementing the web site by the design • Standard markup language XHTML 1.0 • Modular design • User-agent dependencies avoided

13. process methods in ZERO-DEFECT CONTENT EXAMPLE software engineering Content Example: The WndProc function (WinAPI)

15. process methods in ZERO-DEFECT CONTENT EXAMPLE software engineering Adding basic zero-defect concepts to the default form of the WndProc function • Removing of extra return statements so that thefunction complies with an axiom of one input –one output • Adding basic parameter checking • Is the hwnd handle valid? (IsWindow) • Safety limits for msg parameter • Making code layout systematic and to supportzero-defect concepts

16. process methods in ZERO-DEFECT WEB SITE EXAMPLE software engineering Web site Example: PHP-function write_hit_log ($file_name,$file_size) “Gathers date, time, IP-address, user-agent information and writes them to a text file (log). The current entry is not appended to the end of thetext file but previous entries are read from the file first and then thecurrent entry is written to the beginning of the file followed by theprevious entries. The relative path of the log file is given as a parameter‘$file_name’. The maximum limit of the size of the text file size is givenas parameter ‘$filesize_limit’. When this limit is exceeded it willoverwrite the file and start from 0 bytes. This function does not returnanything.”

17. process methods in ZERO-DEFECT WEB SITE EXAMPLE software engineering function write_hit_log ($file_name,$file_size_limit) { $truncate_ok_flag = FALSE ; $rewind_ok_flag = FALSE ; $write_ok_flag = FALSE ; $file_size = NULL ; $in_buffer = NULL ; $out_buffer = NULL ; $date = &get_server_date (0) ; $time = &get_server_time (0) ; $ip_address = &get_remote_address (); $user_agent = &get_user_agent () ; $file_handle = NULL ; settype ($truncate_ok_flag,"boolean") ; settype ($rewind_ok_flag,"boolean") ; settype ($write_ok_flag,"boolean") ; settype ($file_size,"integer") ; settype ($file_size_limit,"integer") ; settype ($file_name,"string") ; settype ($in_buffer,"string") ; settype ($out_buffer,"string") ; settype ($date,"string") ; settype ($time,"string") ; settype ($ip_address,"string") ; settype ($user_agent,"string") ;

18. process methods in ZERO-DEFECT WEB SITE EXAMPLE software engineering if ($file_name != NULL) { if ($file_size_limit > 0) { $file_handle = fopen ($file_name,"r+") ; if ($file_handle != FALSE) { $file_size = filesize ($file_name) ; if ($file_size < $file_size_limit) { $in_buffer = fread ($file_handle,$file_size) ; $out_buffer = $date . "," . $time . "," . $ip_address . "," . $user_agent . "\n" . $in_buffer ; $rewind_ok_flag = rewind ($file_handle) ; if ($rewind_ok_flag != FALSE) { $write_ok_flag = fwrite ($file_handle,$out_buffer) ; if ($write_ok_flag != FALSE) { ; } else { echo "\nAn expected event has happened in the PHP script: Unable to write to the file\n" ; } } else { echo "\nAn expected event has happened in the PHP script: Unable to rewind the file pointer\n" ; } } else { $truncate_ok_flag = ftruncate ($file_handle,0) ; if ($truncate_ok_flag != FALSE) { $rewind_ok_flag = rewind ($file_handle) ; if ($rewind_ok_flag != FALSE) { $out_buffer = $date . "," . $time . "," . $ip_address . "," . $user_agent . "\n" ; $write_ok_flag = fwrite ($file_handle,$out_buffer) ;

19. process methods in ZERO-DEFECT WEB SITE EXAMPLE software engineering if ($write_ok_flag != FALSE) { ; } else { echo "\nAn expected event has happened in the PHP script: Unable to write to the file\n" ; } } else { echo "\nAn expected event has happened in the PHP script: Unable to rewind the file pointer\n" ; } } else { echo "\nAn expected event has happened in the PHP script: Unable to truncate the file\n" ; } } fclose ($file_handle) ; } else { echo "\nAn expected event has happened in the PHP script: Unable to open a file\n" ; } } else { echo "\nAn expected event has happened in the PHP script: Invalid filesize parameter\n" ; } } else { echo "\nAn expected event has happened in the PHP script: Invalid filename parameter\n" ; } } ?>

20. process methods in ZERO-DEFECT PHASES OF THE WORK software engineering QA / Testing / Deployment • Website quality controlled with validationservices provided by W3C • Content quality controlled by linguisticchecking • Testing carried out by viewing the web sitewith several different browsers • Deployment consists of setting-up the web siteon the client’s web server

21. process methods in ZERO-DEFECT FUTURE DEVELOPMENT software engineering Future Development • Studying of zero-defect methods profoundlyand on a wider scale • Results combined into a full scientific specificationof the process • The study could be published as an appendingspecification or a full-length book • Adding the interactivity level of the web site

22. process methods in ZERO-DEFECT CONCLUSIONS software engineering Conclusions • The project succeeded in terms of the requiredspecification and defined schedule • The pragmatic orientation diminishes the scientificvalue of the content part • Sitoni zero-defect concepts are independent andextremely contrary to “normal” SE methods • A hope that this thesis work enlightens theworld of zero-defect programming

23. process methods in ZERO-DEFECT software engineering