ISO 9126 distinguishes between internal characteristics which pertain to the internal static properties of the software and external characteristics which are the characteristics which can be observed when the system is in operation. There is some connection here with the notions of glass box and black box evaluation.
Characteristics of measurements in general
A measurement is the use of a metric to assign a measure (a value, which may be a number or category) from a scale to a quality/attribute of an entity (ISO/IEC 9126-1:2001(E)). Whatever the measure applied, all measures share certain characteristics. An adequate description of a measure should include the following properties:
1. Definitional characteristics
1.a Textual definition and description of the metric
1.b Input to measurement process (e.g., sentence, text, source+target text, system, etc.)
1.c Measure, i.e., output of measurement process (e.g., number on a scale, symbolic value, Y/N decision, etc.)
2. Dependencies
2.a Domain/genre dependence (lists of subject domains and/or genres to which the measure applies or doesn't)
2.b Task dependence (suitability; tasks for which the measure is or is not appropriate)
2.c Language dependence (source or target languages for which the measure holds or does not)
3. Metric Sensitivity (for numeric measurements only)
3.a Accuracy (accuracy of measurement: confidence interval, error bars, correlation with human judgments, etc.)
3.b Variance (variance of measurement across tests; inter-evaluator agreement)
4. Coverage
4.a Completeness of the metric (scope; proportion/degree/percentage of the quality that the measurement is designed to measure)
4.b Completeness of the measurement (scope; proportion/degree/percentage of the quality that the measurement has measured)
5. Costs
5.a Cost to prepare test materials (taking into account its reusability later)
5.b Cost to perform measurement (if necessary, expressed per repeatable unit)
6. Resources/knowledge required
6.a What people/equipment/data/information is required to perform the measurement?
6.b What knowledge/skill is required of the evaluators?
6.c How much time is required to perform the measurement?