Quality Attributes In Software Architecture & Design Patterns

extent to which a product satisfies stated and implied it’s needs when
used under those specified conditions.
FUNCTIONALITY: It is the ability of the system to do the work for which it was
intended.
(OR)
The capability of the software product to provide functions or work to do which meet
those requirements needed when this software product is used under specified
conditions.
For example, A task requires that many or most of the system’s elements work in a
coordinated manner to complete the job, just as framers, electricians, plumbers,
drywall hangers, painters, and finish carpenters all come together to cooperatively
build a house.
To design a good Software Architecture it constraints it’s allocation to structure some
Quality Attributes in particular to adopt those needs required by that product or any
architecture are important.
Hence the need of good software architecture design is to best go-forth with the
quality attributes importance under to know both what are functional & non-
functional requirements?

states that those system services provide,
how the system should reset to particular inputs and how the system should
behave in those particular situations. It also states that what the system
should not to do.
NON-FUNCTIONAL REQUIREMENTS: It states that what those system
services like timing constraints, constraints on development process,
standards are offered at a given time. It also offers these systems applicable
as a whole rather than individual features or services it provides.
Finally, the Quality Attributes that are required at a particular time which
are meant in the design of good Software Architecture design are:
Availability, Installability,
Integrity, Interoperability,
Performance, Reliability,
Recoverability, Robustness,
Safety, Usability,
Efficiency, Flexibility,
Maintainability, Portability,
Reusability, Scalability,
Supportability, and, Testability.

quality attribute scenario is a quality-attribute-specific requirement that are requried to
design a good Software Architecture. It consists of “6” parts like,
Source of Stimulus: This is some entity (a human, a computer system, or any other
actuator) that generated the stimulus.
Stimulus: The stimulus is a condition that needs to be considered when it arrives at a
system.
Environment: The stimulus occurs within certain conditions. The system may be in an
overload condition or may be running when the stimulus occurs, or some other
condition may be true.
Artifact: Some artifact is stimulated. This may be the whole system or some pieces of
it.
Response: The response is the activity undertaken after the arrival of the stimulus.
Response Measure: When the response occurs, it should be measurable in some
fashion so that the requirement can be tested.

The following are the main system quality attributes
required in the design of good Software Architecture are:
1. Availability Scenario,
2. Modifiability Scenario,
3. Performance Scenario,
4. Security Scenario,
5. Testability Scenario,
6. Usability Scenario,
7. Scalability Scenario, and,
8. Portability Scenario.
1. AVAILABILITY SCENARIO:
 “What’s the probability that the system works when I need it?”
 Concerns:
 Mean time to failure,
 Fault Detection,
 Repair Time,
 Fault Making, and, …..,.
 Hence Availability Scenario can be given as,

Performance is about timing.
 Events (interrupts, messages, requests from users, or the passage of time) occur,
and the system must respond to them.
 There are a variety of characterizations of event arrival and the response but
basically performance is concerned with how long it takes the system to respond
when an event occurs.

CONCEPTS USING GENERAL SCENARIOS:
 One of the uses of general scenarios is to enable stakeholders to communicate.
 The below table gives the stimuli possible for each of the attributes used in the design
of a good Software Architecture that shows a number of different concepts.
 Some stimuli occur during runtime and others occur before i.e., after runtime.
 So, the problem for the Software Architect or any person is to must understand that
which of these stimuli represent the same occurrence, which are aggregates of other
stimuli, and which are independent.

the design of a Software Architecture the Business Qualities Attributes are mainly
described in the following ways:
 Time to Market,
 Cost & Benefit,
 Projected Lifetime of the System,
 Targeted Market,
 Rollout Schedule, and,
 Integration with Legacy Systems.

the design of a Software Architecture the Architecture Qualities Attributes are
mainly described in the following ways:
 Conceptual Integrity,
Correctness & Completeness, and,
Build-ability.