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DATA Factual information used as a basis for reasoning, discussion, or calculation; often refers to quantitative information.
Data analysis (IEEE) (1) Evaluation of the description and intended use of each data item in the software design to ensure the structure and intended use will not result in a hazard. Data structures are assessed for data dependencies that circumvent isolation, partitioning, data aliasing, and fault containment issues affecting safety, and the control or mitigation of hazards. (2) Evaluation of the data structure and usage in the code to ensure each is defined and used properly by the program. Usually performed in conjunction with logic analysis.
Data Collection Gathering facts on how a process works and/or how a process is working from a customer's point of view. All data collection is driven by a knowledge of the process and guided by statistical principles.
Data corruption (ISO) A violation of data integrity. Syn: data contamination.
Data dictionary (IEEE) (1) A collection of the names of all data items used in a software system, together with relevant properties of those items; e.g., length of data item, representation, etc. (2) A set of definitions of data flows, data elements, files, data bases, and processes referred to in a leveled data flow diagram set.
Data flow analysis (IEEE) A software V&V task to ensure that the input and output data and their formats are properly defined, and that the data flows are correct.
Data flow diagram (IEEE) A diagram that depicts data sources, data sinks, data storage, and processes performed on data as nodes, and logical flow of data as links between the nodes. Syn: data flowchart, data flow graph.
Data integrity (IEEE) The degree to which a collection of data is complete, consistent, and accurate. Syn: data quality.
Data validation(1) (ISO) A process used to determine if data are inaccurate, incomplete, or unreasonable. The process may include format checks, completeness checks, check key tests, reasonableness checks and limit checks. (2) The checking of data for correctness or compliance with applicable standards, rules, and conventions.
DCP Dynamic Control Plan/Dimensional Control Plan.
Dead code Program code statements which can never execute during program operation. Such code can result from poor coding style, or can be an artifact of previous versions or debugging efforts. Dead code can be confusing, and is a potential source of erroneous software changes.
Debugging (Myers) Determining the exact nature and location of a program error, and fixing the error.
Decision coverage (Myers) A test coverage criteria requiring enough test cases such that each decision has a true and false result at least once, and that each statement is executed at least once. Syn: branch coverage. Contrast with condition coverage, multiple condition coverage, path coverage, statement coverage.
Decision matrix A tool used to evaluate problems, solutions, or ideas. The possibilities are listed down the left-hand side of the matrix and relevant criteria are listed across the top. Each possibility is then rated on a numeric scale of importance or effectiveness (e.g. on a scale of 1 to 10) for each criterion, and each rating is recorded in the appropriate box. When all ratings are complete, the scores for each possibility are added to determine which has the highest overall rating and thus deserves the greatest attention.
Decision table (IEEE) A table used to show sets of conditions and the actions resulting from them.
Defect An error in construction of a product or service that renders it unusable; an error that causes a product or service to not meet requirements.
DEFECT FREE A personal performance standard that says specifications should be met every time. An attitude that displays personal commitment to doing the job right the first time, every time.
Defect Nonconformance to requirements. See: anomaly, bug, error, exception, fault. defect analysis. See: failure analysis.
DEGREES OF FREEDOM The number of independent measurements available for estimating a population parameter
Deming cycle Alternate name for the Plan-Do-Check-Act cycle, a four-stage approach to problem-solving. It is also sometimes called the Shewhart cycle.
Deming Cycle Plan Do Study Act also Shewhart cycle
Deming, W. Edwards Known as the father of quality control. Deming began his work in quality control in the United States during World War II to aid the war effort. After the war, he went to Japan to help in the rebuilding of their country. His methods of quality control became an integral part of Japanese industry. Deming is a celebrated author and is well-known for his "14 Points" for effective management.
DENSITY FUNCTION The function which yields the probability that a particular random variable takes on any one of its possible values.
DEPENDENT VARIABLE A Response Variable; e.g., y is the dependent or "Response" variable where Y=f (Xl. . . XN) variable.
Design for Manufacturability and Assembly A simultaneous engineering process designed to optimize the relationship between design function, manufacturability, and ease of assembly.
Design Information Checklist A mistake proofing checklist designed to assure that all important items were considered in establishing design requirements.
Design phase (IEEE) The period of time in the software life cycle during which the designs for architecture, software components, interfaces, and data are created, documented, and verified to satisfy requirements.
Design Reviews A proactive process to prevent problems and misunderstandings.
Design specification (NIST) A specification that documents how a system is to be built. It typically includes system or component structure, algorithms, control logic, data structures, data set [file] use information, input/output formats, interface descriptions, etc Contrast with design standards, requirement. See: software design description.
Design Validation Testing to ensure that product conforms to defined user needs and/or requirements. Design validation follows successful design verification and is normally performed on the final product under defined, operating conditions. Multiple validations may be performed if there are different intended uses.
Design Verification Testing to ensure that all design outputs meet design input requirements. Design verification may include activities such as: Design Review, Performing Alternate Calculations, Understanding Tests & Demonstrations and Review of Design Stage Documents Before Release.
Development methodology (ANSI) A systematic approach to software creation that defines development phases and specifies the activities, products, verification procedures, and completion criteria for each phase. See: incremental development, rapid prototyping, spiral model, waterfall model.
DFA Design For Assembly
DFM Design For Manufacturing
DFMEA Design Failure Mode Effects Analysis: An analytical technique used to assure that potential design failure modes and associated causes have been considered and addressed. [See FMEA, PFMEA]
Diagnostic journey/Remedial journey A problem-solving approach in which a problem is investigated by looking first at symptoms, and gradually working back towards root causes. Once root causes have been established, experimentation and tracking are used in the remedial journey - the finding of a cure for the roots of the problem.
Diagnostic (IEEE) Pertaining to the detection and isolation of faults or failures. For example, a diagnostic message, a diagnostic manual.
Discounted Cash Flow A method of performing an economic analysis that takes the time value of money into account. Used to remove interest rates and inflation factors from a calculation so that the results of analysis are comparable.
DISCRETE RANDOM VARIABLE A random variable which can assume values only from a definite number of discrete values.
DISTRIBUTIONS Tendency of large numbers of observations to group themselves around some central value with a certain amount of variation or "scatter" on either side
Documentation Material defining the process to be followed (e.g, quality manual, operator instructions, graphics, pictorials).
DOE (Design of experiments) DOE is the science of designing sets of experiments which will generate enough useful data to make sound decisions without costing too much or taking too long.

DPU defects per unit
DPMO defects per million opportunities
Durability The probability that an item will continue to function at customer expectation levels, at the useful life without requiring overhaul or rebuild due to wear out.
Dynamic analysis (NBS) Analysis that is performed by executing the program code. Contrast with static analysis. See: testing.