The ISO 9126 Software Quality Standards

Function	Sub Category	DEFINITION
Functionality	Suitability	Attributes of software that bear on the presence and appropriateness of a set of functions for specified tasks
	Accurateness	Attributes of software that bear on the provision of right or agreed upon results or effects
	Interoperability	Attributes of software that bear on its ability to interact with other systems
	Compliance	Attributes of software that make the software adhere to application-related standards or conventions or regulations in laws and similar prescriptions
	Security	Attributes of software that bear on its ability to prevent unauthorized access, whether accidental or deliberate, to programs or data
Reliability	Maturity	Attributes of software that bear on the frequency of failure by faults in the software
	Fault tolerance	Attributes of software that bear on its ability to maintain a specified level of performance in case of software faults or of infringement of its specified interface
	Recoverability	Attributes of software that bear on the capability to re-establish its level of performance and recover the data directly affected in case of a failure and on the time and effort needed for it
Usability	Understandability	Attributes of software that bear on the users’ effort for recognizing the logical concept and its applicability
	Learnability	Attributes of software that bear on the users’ effort for learning its application
	Operability	Attributes of software that bear on the users’ effort for operation and operation control
Efficiency	Time behavior	Attributes of software that bear on response and processing times and on throughput rates in performing its function
	Resource behavior	Attributes of software that bear on the amount of resources used and the duration of such use in performing its function
Maintainability	Analyzability	Attributes of software that bear on the effort needed for diagnosis of deficiencies or causes of failures or for identification of parts to be modified
	Changeability	Attributes of software that bear on the effort needed for modification, fault removal, or environmental change
	Stability	Attributes of software that bear on the risk of unexpected effect of modifications
	Testability	Attributes of software that bear on the effort needed for validating the modified software
Portability	Adaptability	Attributes of software that bear on the opportunity for its adaptation to different specified environments without applying other actions or means than those provided for this purpose for the software considered
	Installability	Attributes of software that bear on the effort needed to install the software in a specified environment
	Conformance	Attributes of software that make the software adhere to standards or conventions relating to portability
	Replaceability	Attributes of software that bear on opportunity and effort using it in the place of specified other software in the environment of that software