Operating System Module Inheritance

{gliffy:name=OS Modularization Transition|space=VCL|page=Operating System Module Inheritance|align=center|size=L} {gliffy:name=OS Module Inheritance|space=VCL|page=Operating System Module Inheritance|align=center|size=L}

• Each row in the image table is configured with an OSid (image.OSid), this points to the id column in the OS table (OS.id)

• Each row in the OS table is configured with a moduleid (OS.moduleid), this points to the id column in the module table (module.id)

• The module table contains a column named perlpackage (module.perlpackage), this tells the backend VCL code which Perl module to load and use

• The module.perlpackage value, the package statement in the Perl module file, and the directory structure of the Perl modules must all align ** module.perlpackage = VCL::Module::OS::Windows_mod::Version_5::XP_mod ** lib/VCL/Module/OS/Windows_mod/Version_5/XP_mod.pm:

  package VCL::Module::OS::Windows_mod::Version_5::XP_mod;

• Inheritance reduces redundant code

• Subroutines should reside as high up in the hierarchy as possible ** This allows all objects which are instantiated as a child class to use the subroutine

• Child classes can implement subroutines with the same name as one implemented by a parent class ** The child subroutine in the child class overrides the subroutine in the parent class {gliffy:name=Inheritance Example|space=VCL|page=Operating System Module Inheritance|align=center|size=L}