C-Spec
A Product/Fabrication specification in the MIL-STD-490 framework, collecting (whether directly or by reference) the acceptance requirements for a single design, which may (or may not) be the only design for a single CI. It is both possible and reasonable for a single B-spec to have more than one C-spec, if multiple designs are being competed... read more
Capability Requirements Document (CRD)
A current-practice collection of operational requirements addressing the needs of exactly one developmental spiral or increment. Contrast with its predecessor, the ORD.
Capture Contact Dynamics
The movement of a chase vehicle (the “trajectory”) during a berthing event is dominated by several factors. These include the mass properties of the two elements, forces acting on the in-coming element by the item surrendering control authority, forces exerted by the CBM on the in-coming elements, and constraints deriving from the alignment structures of the... read more
Causal Factor
A causal factor is an event or circumstance which, if removed from an antecedent chain of events or conditions, will alter the details of a result (e.g., magnitude or probability of occurrence) but not preclude its essential nature. The term is most often used in the context of Root Cause Analysis, where the “result” is... read more
Certification
The legally binding act of promising large sums of shareholder money and/or loss of personal freedom if what you said was true turned out not to be. Also, the act of accepting such a promise, often on behalf of the tax-paying citizen.
Change
A formal acknowledgement of intent to alter a baseline while maintaining control over a configuration. Note that the act of establishing a baseline in the first place (as for a new project) is considered the “base change” or “change zero”, which permits all baseline actions to fit into a single database structure.
Change Board
A group of people assigned to assess proposed changes to determine whether they are legitimate and, if so, adequately define the vertical and horizontal integration of associated tasks across a project. A good Change Board can make a project run very smoothly, even if management is idiots. A bad one can make an unrecoverable mess... read more
Characteristic
A feature which, when possessed by the dingus, at least partially qualifies said dingus as being of some particular class (often, but not always, a design). That is, such a feature is considered essential to the “character” of the dingus. In the common usage, a characteristic can be represented in an unstructured manner as text... read more
Chief Engineer
The individual, usually a member of management, charged with ensuring the technical integrity of a project. It used to be that there was exactly ONE Chief Engineer for any given project. More recently, we have more Chief Engineers than Carter has pills. I haven’t figured out why that happened: being a real Chief Engineer is... read more
Circumstance
A circumstance expresses the exogenous dependencies of a measure parameter’s output value. Here, the plural “dependencies” is used to indicate that the relationship between the circumstance and the measure can be thought of as a tensor field of arbitrary order on a non-Euclidean manifold and, therefore, can be very complicated.
Class I Change
During the production phase, a change in design that requires prior approval from the Acquisition Customer because it threatens the applicability of the Qualification data on file. A Class I Change is an external change. Contrast with Class II Change. In this context, “threatens” more-or-less means any combination of the following: The revised design might... read more
Class II Change
During the production phase, any change in design that is NOT a Class I Change. A Class II Change is an external change. Contrast with Class I Change. The primary difference in the execution of a Class I Change vs. the execution of a Class II change is one of permission vs. forgiveness (respectively). If... read more
Closed Form
Broadly, an expression solving a mathematical problem that is composed entirely of analytic functions, or other “well-behaved”, continuous mathematical functions. The solution is “exact” on one or more continuous ranges, involving no approximations (other than those applicable to measurement of the independent variables). Its applicability is complete within each interval of the underlying function(s). This... read more
Cognition
Simplistically1, the mental processes by which knowledge and understanding are gained. For our purposes, cognition can involve either reasoning 2, intuition3, or a bit of both. The concept of cognition roughly corresponds to military concepts of “Situational Awareness” and “Situational Understanding”. Along with affection4 and conation5, cognition is one of the three ways humans are... read more
Cognitive Bias
A departure from impartiality in cognition. This notion is distinct from concepts of error in morality or ethics. Being a bias, we’d expect to get approximately the same wrong answer every time a specific (cognitive) process is executed on the same set of inputs. Several types of cognitive bias have been identified, all of which... read more
Coloring as Fast as I Can
A story told by Phil Glynn when we first brought the CBM Assembly Level Qualification Test setup on line:
Command Media
A term for the organization-specific collection of process standards we are supposed to know and follow.
Commercial Development
Development financed on speculation1 by the developer, so that any errors or flaws are entirely at the developer’s risk. The antithesis of Contracted Development. Footnotes “on spec”, not to be confused with “within spec” or “to spec”, both of which refer to some form of Specification or Envelope Drawing.[↩]
Compile
The conversion of software from human-readable form to machine readable form (usually referred to as “object code”). Depending on the software production strategy and structure of the code being compiled, compilation might, or might not, result in a body of code immediately capable of execution. Contrast with linking, which is sometimes bundled with the compiler,... read more
Complex Number
A number comprised of two parts: a real part, and an imaginary part. An unpreferred number that is hard for non-SME’s to understand, usually the result of a complex calculation.
Complexity
That property of a system having to do with: the number of widgets in the system the number of DoF in the relationships between the widgets one or more of those widgets and the outside world the precision and/or accuracy required the rate of change during development and/or during operation the criticality or importance the... read more
Conceptual Design
An abstract design, more concrete than Notional, but less concrete than Preliminary. The term is most frequently used to represent the cartoons that made things look like the Development Team had a firm design at SDR. It can, however, be explicitly represented when Technical Characteristics are tensor-valued.
Configuration
1) A relative arrangement of parts or elements. The term can be applied in either the sense of a design or in the sense of an operational situation1. 2) An internally-consistent set of data collectively describing specific known (or desired) aspects of a project, usually a CI or group of related CI’s. The project is usually... read more
Configuration Control
The systematic direction and guidance of development and production to achieve two goals: 1) Correct data are used for each purpose and 2) Particularly during development, the purpose for each controlled data item is known The data include (but are not limited to) designs, specifications, performance analysis, qualification results, and acceptance data.
Configuration Identification
The existential practice of deciding what Configuration Items there will be on a project. This process executes in two distinct modes, depending on the phase of development:
Configuration Item (CI)
An item designated for management by agreement between customer and supplier.
Configuration Item Classification
In the MIL-STD-490 context, CI’s could be differentiated within a single specification (see section 4.1.2) as follows: Types: differences as to design, model, shape, etc. Designated with capital Roman numerals. These were typically used to distinguish differences in performance (function) or other really important features that were critical to different intended end uses. Class: subdivisions... read more
Configuration Management
The practice of applying assets to establish and maintain control over a configuration(2). In this context, "assets" include, but are not limited to, skills, budget, schedule, tools, facilities, and legal instruments with regard to subcontractors and suppliers. read more.
Confirmation Bias
The (possibly unwitting) cognitive search for, filtering and interpretation of information that will support prior conclusions or belief. The reason that “independent verification” exists as a concept.
Conformity
An FAA-specific term establishing a high level of independent verification that an article or test setup is compliant with its previously established requirements. Roughly equivalent to mandatory government witnessing in DoD development and production, except that certain supplier personnel might be permitted to conduct the inspection on behalf of the FAA. The term is applicable... read more
Confuscation
The combination, not always willful, of confusion and obfuscation. See also rat hole and bake your noodle. The proper defense against confuscation is to keep coloring as fast as you can.
Constraint
In the legacy System Engineering context, any technical requirement that is not a Performance Requirement. Sometimes referred to as “Design Constraint”, but this is a misnomer. In the context of optimization, a limit on what values may be obtained by some measure contributing to, or a necessary correlative design feature of, an Objective Function.
Contact Mechanics Under High-Vacuum
The most basic characteristic of a mechanism is the relative motion of faying surfaces under load. Points, lines, and surfaces of contact are assessed by calculating deformations and the resulting contact stresses1. The objectives of the analysis are to 1) estimate the forces due to friction and 2) predict whether damage occurs2. Footnotes That is,... read more
Contract
A legally binding agreement between two or more parties forming the context for most non-commercial development. The contract’s T&C are what tie everything together including (but not limited to) SoW, End Items, and deliverable data. Note that it is possible for no party in the contract to be an Acquisition Customer of any other party... read more
Contract End Item (CEI)
An item (a product, as opposed to a “service”) which, when accepted by the Acquisition Customer, results in the Supplier getting paid.
Contract Line Number (CLIN)
Contract Line Number: a unique number assigned by a contract to identify exactly one chargeable1item on the contract. In this context, “item”2 may be either goods or services, either of which may originate with the contract supplier3.”. Footnotes Meaning that, when it has been delivered and accepted by the customer, the supplier gets paid (eventually).[↩]... read more
Contracted Research and Development (CRAD)
A type of contract in which one party (the Acquisition Customer) pays the other party (the Developer) to conduct R&D in response to some form of Development Specification or Envelope Drawing. Because the customer paid for the effort, the customer owns any intellectual property discovered under the CRAD. Contrast with IRAD and commercial development.
Contractor And Government Agency (CAGE)
The Defense Logistics Agency assigns a unique identifier (the “CAGE Code”) to provide for “…a standardized method of identifying a given facility at a specific location. The code may be used for a Facility Clearance, a Pre-Award survey Engineering Rights, automated Bidders Lists, pay processes, source of supply, etc. In some cases, prime contractors require... read more
Cost
A financial outlay or expenditure to achieve some objective1, or the loss or penalty incurred by the failure to do so. Footnotes In the context of System Engineering, a product or a service.[↩]
Cost Avoidance
The process of holding down the cost estimate for activities not yet attempted. From a System Engineering perspective, it dodges costs for things we haven’t tried to do yet, without compromising the expected (eventual, anticipated) satisfaction of development requirements. The concept of avoidance is generally found in the context of development (or planning for it).... read more
Cost Reduction
The act of decreasing an on-going cost (usually a baseline cost). In the Engineering context, this is sometimes referred to as “value engineering”. Cost reduction is usually encountered during a production phase, with the objective of reducing the unit cost of a production item. It is typically associated with re-development: the design can change in... read more
Critical Design Review (CDR)
A type of Technical Review held in order to determine a Configuration Item’s readiness to for manufacturing of Qualification Articles. Legacy DoD practices for CDR were according to MIL-STD-1521.
Critical Item
A type of CI that is less significant (in some senses, from some perspectives) than a Prime Item, but more important than a Non-complex Item. In the MIL-STD-490 framework, this class of CI had its own Specification (Spec) format (the “B2” specification) along with explicit rules for when it should be used. The specification was... read more
Customer
The agent holding recognized1 moral authority (e.g., the sugar daddy footing the bill) over a supplier’s activities with regard to products and services (including, if specified in the Contract, Intellectual Property). See also Acquisition Customer, End User and Regulatory Customer. Footnotes Including, but not limited to, legal recognition.[↩]
Database Design
The process, or the result therefrom, of determining how to store and retrieve information and the relationships between types of data. read more.
Dataset
The electronically stored analog of a drawing. All usages and constraints and variations thereof that apply to drawings also apply to datasets.
DD1149
A DD1149 is a US Government form that formally records a temporary transfer of possession of an item and accountability for its safe-keeping during that possession. Contrast with DD250.
DD250
A DD250 is a US Government form that formally acknowledges a transfer of legal responsibility and authority for an item from a supplier to the US Government (sometimes referred to as “transfer of title”). Completion of this form is what gets the developer paid. Contrast with DD1149.
Decomposition
A “decomp” is any process of dividing a thing into pieces. To be a valid decomposition, it must be shown that the pieces encompass the entire scope of the “parent”. It is important to assess any proposed decomposition process with respect to this criterion. The details of any given decomposition process depend on the domain... read more
Deductive Reasoning
Deductive reasoning (sometimes referred to as “deduction”) occurs when two or more previously proven assertions are used to draw a demonstrably related conclusion1. In most cases, deduction is what we think of when we talk about Engineering processes that arrive at valid conclusions (e.g., sizing, derivation, and verification). In classical logic2 each assertion is usually... read more
Degree of Freedom (DoF)
In Systems Engineering, a $10 expression referring to the number of system characteristics that can take values without regard to interactions with those taken by any other system characteristics, i.e., “independent” variables. This concept is important in System Engineering, because it is the key to limiting the number of Performance Requirements we write. Without it,... read more
Deliverable Data
Publications and other information owed to a customer. Generally listed as part of a DIL.
Deliverable Items List (DIL)
A listing of things (products) contractually owed to a customer by a supplier (e.g., CEI’s or documentation), or to a supplier by a customer (e.g., GFE, facility upgrades, or documentation). The DIL can be sub-divided into various categories (e.g., data, material).
Demonstration
The direct observation of an item for unquantified functionality without use of intrusive instrumentation, fixtures, or excitation. Applicable IFF the characteristic specified is externally observable and need not be quantified. In theory, we want to do demonstrations at the highest level of system aggregation for which the function is directly observable (in order to provide... read more
Dendrogram
A connected, acyclic graph. “Connected” means there are no loose parts of the graph. “Acyclic” means that any given node can be reached from any other node by exactly one path. These two properties mean that such graphs look like trees (“Dendron” is the Greek root word for “tree”). Many people use the word “taxonomy”... read more
Derivation
Derivation is the process of identifying topics, parameters, and/or values by way of “reasoning”. The inputs to the reasoning process are: 1) pre-existing characterizations1 (which might, or might not, have been produced in the context of a conceptual design) and 2) new information that was (for whatever reason) not considered when developing those pre-existing characterizations.... read more
Design
As a verb: The act of thinking up (synthesizing) without reference to prior work of the same scope and detail. Modifying something without reference to prior work of the same scope and detail. The act of documenting Engineering intent in a manner sufficiently concrete that unambiguous manufacturing planning can be accomplished to repeatedly produce interchangeable... read more
Design Analysis Cycle (DAC)
The project-specific sequence of design decisions and the analyses used to make them, organized in an iterative loop. The basic premise is that we execute analyses in an iterative manner, improving with each iteration the fidelity of the designs and the models that represent them. Contrast with VAC which, even if it conducts analyses having... read more
Design Approval Engineer (DAE)
An industry engineer authorized by the FAA to make major/minor determinations for proposed changes to an aircraft’s Type Certification data in response to a proposed change in the design. A DAE is paid by the aircraft developer, but has a legal responsibility to the FAA. The term is applicable only in the context of Commercial Aircraft.... read more
Design Certification Review (DCR)
A NASA term, roughly equivalent to FCA plus PCA. NASA developmental techniques were historically geared toward mission-specific hardware, or very small production runs. The review essentially constitutes the point at which the Developer warrants (within the terms of the development contract) an entire system for the intended use.
Design Reference Mission (DRM)
A combination of circumstances and operations used as a guideline for development (or selection) of a Configuration Item (CI). The combination might, or might not, contain one or more sequences. DRM’s can vary widely in their complexity. They might (or might not) be used as a source of significant Functional Analysis for development efforts, and... read more
Design Space
An absurdly abstract topological notion, rarely applied in any useful sense. The notion really requires explicit parameterization and evaluation of the technologically relevant features of every feasible conceptual design (which is likely a superset of the required characteristics) relative to the n-dimensional basis formed by the union of all such mutually feasible1 features. Footnotes i.e.,... read more
Design-to Requirement
A type of development requirement articulating a mandatory characteristic of a CI. Infrequently, referred to as “identification requirement” because the dingus isn’t considered to be the dingus if it doesn’t posses said characteristic correctly.
Designated Engineering Representative (DER)
An industry engineer authorized by the FAA to approve engineering technical data on behalf of the FAA within the limits of his/her specified authority. A DER is paid by the aircraft developer, but has a legal responsibility to the FAA. The term is applicable only in the context of Commercial Aircraft. Contrast with DAE and... read more
Detail Specification
In the MIL-STD-490 context, either of the following: A comprehensive set of technical requirements allocable to a given CI without reference to General Specification(s) A set of requirements uniquely allocable to a given CI (sometimes referred to as a “specification sheet”, although they could take book form) plus references to the applicable General Specification(s)
Developer
The person or organization that develops a product.
Development
The creation of a design for a product, including the generation of data to substantiate the warranty (whether implicit or explicit). read more.
Development Requirement
A technical requirement used to guide (drive) the designers and verification planners during development of a CI. In a perfect world where nothing went wrong, synonymous with Qualification Requirement, except that the final Qualification Requirements might end up not matching the Development Requirements actually used to drive the design. The best ways to use this... read more
Development Specification
A type of detail specification containing the technical requirements for the design and verification of a CI. Contrast with Product/Fabrication Specification.
Deviation
A prior granting of permission to fail before any official attempt (see run for score) to verify compliance with an allocated technical requirement. Use of a deviation avoids giving the appearance of changing the requirement and is, therefore, an important component of an Acquisition Customer’s Pearl Harbor File and (also therefore) much despised by developers.... read more
Device Driver
Device drivers communicate directly with the hardware, typically by writing values to memory locations and/or registers and handling interrupts. Device drivers are typically called by both the operating system and application software as needed. Depending upon the operating system, device drivers can be managed by the operating system or considered part of the operating system.... read more
Differential Algebraic Equation (DAE)
A DAE is a system of differential equations where not all of the terms share any single, continuous independent variable and/or derivatives with respect to it, and where some of the terms are purely algebraic (as opposed to differential). This last constraint means that the Jacobian of the system is singular, so the system of... read more
Digital Computer
A computational device based on (usually more than one) hardware implementation of Boolean algebra. These computers require all problems to be cast in the form of 1’s and 0’s, usually through the use of a compiler. Digital computers are vastly more complicated than the analog computers they have (mostly) replaced, but are also vastly more... read more
Dingus, The
The thing we’re working on or interested in. The focus of our attention. The widget. The Maltese Falcon. More soberly stated, a collection of one or more elements of hardware, software, and operating procedures intended to exhibit or express one or more features on behalf of an End User during operation.
Direct Incorporation
Inclusion of the exact text of one document into another, placing the content under the unilateral Configuration Control of the latter – that is, creating a stream of future changes applicable to the new document that is independent from the stream of future changes in the original reference. This represents a fork in the road... read more
Directed Design
A condition in which the acquisition customer provides contractual direction with regard to one or more design features in addition to those written into the development specification. Sometimes this happens because the customer wants to make best use of technical thoughts they’ve had; other times it happens because the System Engineering theoreticians try to avoid... read more
Disposal
The action taken at the end of a CI’s life. The disposal issue is often ignored during system development, even though doing so can have serious consequences for your children and grand-children (see, for example, Yucca Mountain).
Disposition
A decision made with respect to some formally identified, formally managed issue. The issue can be any of many forms (e.g., Review Item Discrepancy or Non-Conformance).
Distal Cause
A distal cause that is an event or circumstance that is remote to the point or time of an event or condition, having precipitated other events or circumstances leading to the result. Contrast with proximate cause, root cause, and causal factor. For distal causes where the separation factor is time alone, see latent1. Footnotes Causes... read more
DLL Hell
A predicament in which multiple versions of a Dynamic Linked Library (dll) must be present in order to support multiple linking operations at run-time, couple with an incompletely managed system of defining their applicability by the various pieces of Application Software. The term is actually specific to a certain dominant OS, the concept is broadly applicable.
DoD Directive 5000.1R (Acquisition System)
The granddaddy document for how the Department of Defense is supposed to acquire systems, forming the formal context for most of our System Engineering efforts.
Domain
In Functional Analysis (mathematics): the set of permissible inputs for a function. In the internet: a cluster of internet addresses, all subordinate to some common node of autonomy, authority, or control.
Drawing
An engineering document (which can be in digital form) that discloses, whether directly or by reference, the physical and/or functional requirements for an item. In this business, the term “drawing” is synonymous with “Engineering Drawing” as defined by ASME Y14.24. The alert reader will note that the definition above, which is adapted from the referenced... read more
Effectivity
A type of accession identifier indicating an individual unit (or range) for an End Item, usually assigned during the contractual planning stage for any particular production run or series. Contrast with Serial Number and Line Number: Effectivity represents a contract planning sequence of an order being placed, S/N represents a manufacturing planning sequence, and L/N... read more
Embedded Software
Software that is dedicated to the control of (and usually hosted within) hardware which itself has one or more functions allocated on the basis of a specific End Use. Such hardware is typically not “general purpose”; true embedded software has no functionality other than that required to ensure the correct operation of the hardware (including,... read more
Emulation
I use “emulate” to model the behavior of an item without modeling the causes and effects that produce it. This is more useful in specifying requirements than when characterizing an actual design. Sometimes, I refer to this concept as “Fun With Numbers”. Contrast with simulation.
End Item
An item (usually a CI) explicitly indicated as completing some specific delivery provision. The provision can involve more than one delivery of the subject item (see Effectivity). See also CEI and PEI.
End User
The abstract concept of the person who uses an item to accomplish some operationally relevant task. Being abstract, this term is uniformly applied to mean both operational users of the product, and some duly recognized organization representing them. The parameterization of the task may, or may not, be directly related to that of the design’s features.... read more
Endian
In computing, the order in which data are stored: whether “least significant bit”is on the left or right end of a memory address. The two orders are referred to as (you guessed it!) “Big Endian” and “Little Endian”. Some computers do it one way, some do it the other. If we want them to communicate,... read more
Engineering Change Proposal (ECP)
A proposal to the Acquisition Customer for the purpose of considering changes to the technical baseline of a program or project. In the early phases of development, an ECP is typically limited to technical requirement changes, although it is possible that small-scale changes to SoW and/or T&C will be necessary in order to effect the... read more
Engineering Release Unit (ERU)
The impartial third party within an Engineering outfit that holds onto the “released” documentation so that the originating group has no opportunity to violate any of the four rules by re-writing history to hide any errors. The concept of an ERU is intrinsic to demonstrating process integrity, rather than just claiming it. An ERU also... read more
Envelope Drawing (ED)
A type of PCD used when the procuring authority wishes to stipulate certain design features without themselves completing the design. An ED is usually created as the first in a chain of drawings when some or all of the design Engineering effort is to be procured.
Environment
The circumstances, objects, or conditions by which an item is surrounded. read more.
Evaluate
In the System Engineering context, the process of specifying the actual collection of points for a value, rather than the criteria for their selection. The abstraction is borrowed from database design theory.
Executable (software)
An image of 1’s and 0’s that is loaded into RAM and actually processed (“executed”) by a digital computer. Contrast with Source Code and Object Code.
Exogenous
Meaning “to arise from outside”: sourced externally to the subject of discussion.
Experimental Uncertainty
There being no such thing as a perfect measurement, Experimental Uncertainty expresses the result of analytically propagating measurement “errors”1 from the instrument to a final, integrated result. Propagation is often not simple, and often depends on the detailed physics relationship between properties than can be instrumented and properties that cannot be instrumented. The National Institute of... read more
External Change Control
The situation where changes require authorization from the customer. See also Class I Change (a priori permission) and Class II Change (ex post facto concurrence), both of which are forms of “external” control during the production phase. Contrast with Internal Change Control.