Quality Characteristic

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A Quality Characteristic is an Evaluation Characteristic concerning the degree to which a subject exhibits a quality property.

A Quality Characteristic can apply to:

• A Candidate Solution
• A Distributed System
• A Node
• A Node Set
• A Test Item
• A software product
• A hardware product
• A service
• A technology
• A process
• A result
• Another evaluation subject

Quality Characteristics can include:

• Functional Correctness
• Performance Efficiency
• Reliability
• Operational Stability
• Security
• Interoperability
• Scalability
• Maintainability
• Recoverability

A Quality Characteristic can be decomposed into more specific Quality Characteristics or quality subcharacteristics.

A Quality Characteristic can identify:

• Its identity
• Its name
• Its description
• Its parent Quality Characteristic
• Its child Quality Characteristics
• Its evaluation subject
• Its applicable context
• Its applicable measures
• Its applicable measurement methods
• Its applicable measurement units
• Its applicable reference values
• Its applicable DIDO Baselines
• Its applicable Validation Criteria
• Its applicable Acceptance Criteria
• Its applicable Governance Policies
• Its Evidence
• Its Provenance
• Its Traceability

Evaluation Characteristic concerning the degree to which a subject exhibits a quality property

Adapted from:

• ISO/IEC 25010:2023, Systems and software Quality Requirements and Evaluation (SQuaRE) — Product quality model
• ISO/IEC 25002:2024, Systems and software Quality Requirements and Evaluation (SQuaRE) — Quality model overview and usage
• Evaluation Characteristic
• DIDO Reference Implementation Conceptual Model
• DIDO-TE draft Requirements Register

ISO/IEC 25002 describes quality models composed of quality characteristics and subcharacteristics.

ISO/IEC 25010 defines a product-quality model containing characteristics and subcharacteristics applicable to ICT and software products.

This definition places Quality Characteristic within the broader DIDO Evaluation Characteristic model so DIDO-TE can evaluate both quality properties and non-quality characteristics such as cost and resource consumption.

Every Quality Characteristic is an Evaluation Characteristic. An Evaluation Characteristic is not necessarily a Quality Characteristic.

A Quality Characteristic differs from a measure:

• A Quality Characteristic identifies the quality property subject to evaluation
• A measure identifies how a value is assigned to the Quality Characteristic

A Quality Characteristic differs from a quality requirement:

• A Quality Characteristic identifies a quality property
• A quality requirement establishes a normative obligation concerning that quality property

A Quality Characteristic differs from a Test Result:

• A Quality Characteristic identifies what is evaluated
• A Test Result records an outcome produced by Test Execution

One Test Result can provide information about multiple Quality Characteristics.

Multiple Test Results can contribute to the evaluation of one Quality Characteristic.

A Quality Characteristic does not by itself establish:

• A required value
• A minimum value
• A maximum value
• A preferred direction
• A measurement method
• A permitted tolerance
• An acceptance threshold

The applicable Acceptance Criteria or Validation Criteria establish those constraints.

A higher numerical value does not necessarily indicate better quality. The interpretation depends on the Quality Characteristic and its applicable measure.

For example:

• Higher throughput can indicate greater Performance Efficiency
• Higher response time can indicate lower Performance Efficiency
• Higher failure frequency can indicate lower Reliability
• Higher recovery success can indicate greater Recoverability

A DIDO-TE comparative evaluation selects Reliability as a Quality Characteristic.

The applicable Acceptance Criteria establish:

• The Candidate Solutions subject to evaluation
• The workload
• The Test Environment
• The duration of the evaluation
• The failure conditions
• The Reliability measures
• The required measurement precision
• The comparison method

DIDO-TE produces Test Results used to evaluate Reliability for each Candidate Solution.

Reliability identifies the quality property being evaluated. The Test Results contain the observations and measurements used to evaluate it.