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Application protocol: System engineering and design | ISO/WD 10303-233 |
For the purposes of this document, the following terms defined in ISO 10303-1 apply:
For the purposes of this document, the following terms defined in ISO 10303-202 apply:
For the purposes of this document, the following terms defined in ISO/TS 10303-1001 apply:
For the purposes of this document, the following terms defined in ISO/TS 10303-1017 apply:
NOTE The same behavior model can produce different execution results if the rules of execution differ between two tools that exchange data. These are the entities that allow recording of the rules used by the tool putting data into the data model.
NOTE An analytical model may be a library model.
NOTE To perform a calculation it is necessary to associate parameters with other elements of equations.
NOTE This is the subclass of property that includes measurable characteristics in normal use. It encompasses the response of the system to excitation by things in its environment. In some other engineering disciplines it is the analysis with differential equations that is called behavior. That is not what is meant here. Here, in AP233, behavior is a model representation of a functional requirement: it is what the system is to do.
EXAMPLE Make a fender is a behavior with several function steps, inputs of sheet steel, power, paint primer, paint and the output of a fender. Ring is the behavior of a bell or tuning fork. The "Q" of the bell or tuning fork is a physical property of the bell and its environment.
NOTE The laws of science and engineering interrelate the values of properties and are used to calculate the values for the whole based on the designed values for the parts.
EXAMPLE As the designers do their work they arrive at design values for the parts. These values will generally differ from the budgeted values because the designers have detailed information unavailable before. It is necessary to calculate the properties of the whole based on these design values to ensure that requirements are satisfied by the proposed design. The mass of the space probe should be 150 pounds or less, based on the design data.
NOTE This is one of the forms of generalization/specialization. This is not inheritance as used in object-oriented software languages. Physical elements of matter and energy do not inherit their properties. Rather they posses the properties of themselves and can be identified by measurement of those properties.
EXAMPLE Explanation: It is categorization that enables us to define alternatives and create taxonomies for libraries.
EXAMPLE the super category is all apples raised on a particular farm. The subcategories are used for sorting and include: good apples, bruised apples, marked apples, rotten apples, and wormy apples.
EXAMPLE the super category is all fruit raised on a particular farm. The subcategories are used for sorting and include: good apples, bruised apples, marked apples, rotten apples, and wormy apples.
EXAMPLE An automobile has in its decomposition tree an engine. For this automobile any of three engines: 140 HP, 180 HP, and 220 HP. The superclass of engine is exhausted by the subclasses and the subclasses are independent.
EXAMPLE All of the automobile engines under current manufacture by GM and its subsidiaries are considered as candidates for three engines that will be used in a new car.
NOTE The constructs regular function port and control function port allow input/output to trigger some function but not others.
NOTE Several different design hierarchues can exist for different purposes. The hierarchy appropriate for manufacturing may conatin more elemnts than the one for engineering design by including materials used in manufacture. The hierarchy for verification of first system built may be different than others because of the need to build parts of the system for early testing to reduce technical risk.
EXAMPLE This definition corresponds to the SC4 convention of separately representing design and realization. SC4 uses the name Part to represent design .
NOTE These include the system, its environment, external systems of interest in the environment, stakeholders, enabling things, things that may cause failure, and all other things of interests.
NOTE Requirements define the domain of the solution; that is, the solution space. The effectiveness measures drive the solution to a particular region in that space. The effectiveness measures are tightly related to stakeholder needs.
EXAMPLE The requirements differences between a PC and a laptop are largely in the laptop optimization conditions for minimum weight, minimum thickness, and maximum battery life. These critiera are some of those that customers (one of the kinds of stakeholder) consider in deciding what to purchase.
NOTE The semantic term element includes matter, energy and information. The term product from ISO 10303-Part 1 STEP definitions defines product as: a thing or substance produced by a natural or artificial process. This part of ISO 10303 needs to define the informational attributes associated with the entity named "product" as defined within ISO 10303-1017 - Product Identification. This entity has attributes that enable one to capture: id, name and description. ISO 10303-1017 provides the definition: A Product is the identification of a product or of a type of product. It is a collector of data common to all revisions of the product. Element appears to be a legitimate subclass of product because this part requires reproducible measurement of element.
EXAMPLE Any thing from microscopic particles to galaxy clusters is an element. Any thing with a finite existence from galaxies with billion-year lives to trans-uranic elements with lifetimes less than nano-seconds. Counter-example: Things like ghosts, devils, the Loch Ness monster, the city of Atlantis are not discernable by reproducible measurement and are excluded. Research and development things that do not yet have reproducible measurements and process control are excluded. For example, silicon for electronic devices would be excluded in 1900.
NOTE It is often possible to limit the parts of the environment needed for development purposes to those external systems that are neighbors to the system.
NOTE The environment includes not only the external systems that couple with it for useful purposes, but it also includes all external systems that may interact in a manner that causes failure.
EXAMPLE Elements in the environment need not have well defined boundaries as do systems. A laptop computer can connect to a power grid. But for the design of the laptop it is not important to consider the power grid as a system. It is simpler to consider it as an element with an interface that the laptop connects to when needed.
NOTE These functions act as sources and sinks of input/output
NOTE Input/output is associated with one function.
EXAMPLE If function exit is decomposed, there are function exit constructs corresponding to the two exit paths in the higher level function. When one of the exit constructs is encountered, execution of the decomposition is complete and control is passed to the corresponding exit path at the higher level.
NOTE David some word-smithing has been done, please check
NOTE It is a part of behavior. There are several ways to represent function ordering. It may be done with ordering operators and triggering input/output as in classical behavior diagrams or it may be done with events, states, and transitions as done in state machines and state charts. For this fine level of detail it is necessary to intercompare the detailed models in SEDRES with those in the concept model and those emerging from UML 2.0 development.
EXAMPLE A function is activated when all preceeding threads of functions are complete. At this point the function examines its inputs. If all triggering inputs are present the function proceeds to do its work. If one or more triggering inputs is absent, the function waits for them before doing its work. Triggers that arrive while the functions are running are stored in a first in first out queue. Ordinary input/output that arrives while a function is deactivated is stored in a last in first out queue. If the function is running it is discarded. A function is deactivated when it completes its work or is deactivated by input/output.
NOTE It is a part of behavior. This is what functions do in mathematics where the input/output are variables. In software the input/output is data. In systems engineering the input/output are elements, matter, energy, and information. An internal function is a kind of function that is allocated to and implemented by the system/structure. An external function is a kind of function that is allocated to and implemented by elements in the environment.
EXAMPLE The function may be "burn gasses" with an input of two moles of hydrogen and one mole of oxygen. The output will be one mole of water, distinctly different from the inputs and a lot of energy. This function may be followed by a function "cool to 90 degrees centigrade". The input had pressure and volume proportional to temperature; the output is now liquid with a well-defined volume, an isotropic compressibility and a viscosity. If the next function is "cool to ???10 degrees centigrade", then the viscosity goes away and the compressibility becomes a fourth rank tensor relating stress to strain.
NOTE These collections allow an engineer to examine functionality for special purposes, picking those elements needed from the prototypical design and realization views.
EXAMPLE An engineer may wish to study the cooling system of a car engine and require a collection of entities distributed through the prototypical design or realization hierarchies.
NOTE The name input/output or I/O is used because a given I/O entity is generated by one function and consumed by another. It is a part of behavior. In the general case outputs are different things than inputs, and physical properties, behaviors, values, variances and probability distributions can all change. In this general definition "function" is an element of type information and cannot be realized in the physical world except through elements of type matter or energy that exhibit that function. In the physical world things transform other things. It is this fact of reality that results in the allocation of function to structure which is really a statement that this particular structure entity exhibits this particular function and it will be used to provide that transformation. The thought pattern is to think of the desired transformation, function, to consider alternative things that might be used to provide it, and to select among these, using a trade study based on optimization.
EXAMPLE I/O may trrigger functions and it may terminate functions.
NOTE The interconnection may exist for structural reasons without any flow from port to port. The interconnection may exist because functions are assigned to particular assemblies, and the output from one function is an input to the other function. In this case the ports and their interconnection must exist to support flow. The alias for interconnection is interface connection, the term used in AP239.
NOTE It includes the geometric description, input/output description, protocols that must be met, assemblies of parts required to join two ports, allowable defect characteristics, etc.
NOTE Parts interact physically through direct physical contact, exchange of elements, and through forces they exert such as gravity, compression or torque. Thus input/output is bound to ports and described by interfaces. The interface may consist of more than the two ports and may involve an assembly of parts as in the case of two flanges that are assembled with six bolts and an O-ring. The interface may also require detailed description to define what occurs there or how it is maintained.
EXAMPLE For two ports to connect, their interfaces must be compatible. The current carrying capacity of a plug and a socket is a result of the surface area of contact, the contact force, the wiping action on plugging them together, and the surface conductivity of both. This is an emergent property that is not assignable to either port individually.
NOTE For each input/output there are two such functions, one that generates it and one that consumes it.
NOTE Link must be provided in the concept model because a number of application tools use the concept. Links ultimately are fully specified and become a system-assembly.
EXAMPLE In a pumping system it may be useful to define the pumps and tanks while representing the piping as links without detail. At some point in the design detail like diameter, flow impedence, pressure rating, and corrosion resistance must be defined. At his point the link becomes a part.
NOTE These measurements are often made when actual parts first become available. They verify that the parts meet their requirements. They also verify the quality of analysis models used during design.
EXAMPLE A part like a turbine blade has a number of important properties critical to the performance of a jet engine, These include aerodynamic efficiency, weight, moment of inertia, vibration spectra, mean time between failure, and corrosion resistance. Important properties are predicted durng design with analysis. Measurement is made as soon as possible.
NOTE Physical properties are represented in equations by parameters.
EXAMPLE In Spice, temperature is a model parameter that may be set at the execution time.
EXAMPLE For a laptop computer weight and thickness are minimized and battery life is maximized.
NOTE Some parameters are left in parametric form and are calculated. Others are supplied values to fully specify the equations.
NOTE Parts have physical properties assigned to them. Many engineering domains think of these as components, but manufacturing thinks of them as assemblies because they build assemblies. Assembly is a standard ISO naming convention. It may be desirable to alias this name.
NOTE Physical properties are budgeted to structure using analysis methods, and the emergent performance is calculated using the same methods. Behavior is allocated to the structure. Form and function are separated conceptually so that the design can be optimized by considering several different structures that can provide the desired emergent behavior and properties.
NOTE These collections allow an engineer to examine physical realizations for special purposes, picking those elements needed from the prototypical system, design and realization views.
EXAMPLE An engineer may wish to study the cooling system of a car engine and require a collection of entities distributed through the prototypical design or realization hierarchies.
NOTE This is the subclass of property that encompasses measurable characteristics that require additional instrumentation to measure them. They cannot be established from responses to the enviropnment alone. All of the "properties" used in analysis with differential equations fall into this category.
EXAMPLE Responses of an element like mass, power consumption, mean time between failure, etc. are critically important and appear in requirements. They are not measured by responses to excitation from their environment.
NOTE Systems interconnect with one another port-to-port. Ports couple to desired things in the environment and also to the ports of things that cause failure, threaten security or safety. The alias for port is interface connection, this is the term that is used in AP239.
NOTE When a system interacts with its environment, the boundary between the system and the environment is the collection of all interacting ports.
EXAMPLE Consider a ultrasonic transmitting transducer coupled to a water tank and a receiver transducer coupled to the tank. The transmitter port connects to a water port and couples sound energy into the water. The intensity at any point is a result of the impedance match between the two ports, the radiation pattern of the transducer, and the attenuation and dispersion in the water. The receiving transducer is attached to another port of the water. The received signal is dependant on the relative impedance of the two ports, the sound distribution in the water, and the radiation pattern of the receiving transducer. This example is often oversimplified as "broadcast" neglecting the port to port conditions and the properties of the medium and neglecting the ports.
NOTE Property is usefully decomposed into several categories ??? the measurable characteristics in normal use, the measurable characteristics that require additional instrumentation for measurement, and the observable characteristics. It is a systems engineering best practice to separate behavior from structure (function from form) and to allocate behavior to structure based on trade studies among alternatives.
EXAMPLE The acceleration of a car is in the first category. behavior. This characteristic can be observed in the normal operation of the car. The weight of the car is not directly observable in the use of the car. It requires that the car be placed on a scale to record the measurable characteristic. The fact that a car has four wheels, a steering wheel on either the left or the right side, and a sun roof are observable characteristics.
NOTE Numeric values, real numbers, can be given as a mean and variance, a probability distribution of values or as a histogram. Many probability distributions are used in systems engineering. These may include: normal, log-normal, Bernoulli, beta, binomial, negative binomial, chi squared, discrete uniformed, erlang, exponential, F, gamma, geometric, laplace, poisson, T, triangular, uniform, weibull.
EXAMPLE Property values are useful in making comparisons and decisions, in verification, and in validation. Comparisons and decisions can only be made if there are both mean values and variances available. Mean values alone are insufficient.
NOTE Triggering input/output is stored in a "first in first out" queue so that the earliest trigger received activates the function. Non-triggering input/output is stored in a "last in first out" queue so that the most recent input is used by the function to ensure the input is fresh.
NOTE Several different realization hierarchies can exist for different purposes. The hierarchy appropriate for manufacturing may conatin more elemnts than the one for maintenance because that discipline emphasizes line replaceable units.
EXAMPLE This definition corresponds to the SC4 convention of saeparately representing design and realization. SC4 uses Product_as_realized to represent realized things.
NOTE The referenced source may be a requirements document, government requirements for safety, security, environmental quality, etc., or a state or federal law
NOTE The constructs regular function port and control function port allow input/output to trigger some function but not others.
NOTE This corresponds to the regularization function used in optimal control design and in statistical optimization of processes.
NOTE Especially useful for distributed systems in which a particular function is realized in many places
NOTE Values that shall be met are stated in requirements. The laws of science and engineering interrelate the values of properties and are used to calculate the values appropriate for the parts based on the required value for the whole.
EXAMPLE A requirement may state that a space probe shall weigh no more than 150 pounds. In that case the masses of the subsystems must add up to no more than 150 pounds. It is best practice to budget values to the subsystems for guidance of the engineers working on the subsystems.
EXAMPLE There exists some number of missiles available to a missile battery available for the function "Shoot".
EXAMPLE The function "transmit message" may be allocated to a satellite system, a fiber optic line, a microwave link, etc. Each of these alternatives has some value of the property "bandwidth" that may be used by the function.
NOTE Stakeholders include; for example, the producers, owners, operators, users, and maintainers of the system.
NOTE At the top level of development these needs drive the requirements for the system and the optimization criteria for its development.
NOTE Physical properties are budgeted to structure using analysis methods, and the emergent performance is calculated using the same methods. Behavior is allocated to the structure. Form and function are separated conceptually so that the design can be optimized by considering several different structures that can provide the desired emergent behavior and properties.
EXAMPLE In a real example of optimization the engineer examines not just the maximum or minimum, but looks at the trend in data in that region to be sure the solution is robust. That is, the design solution must not degrade rapidly with small variances in the variables of design.
NOTE A system is composed of interacting systems. The emergent behaviors and properties of a system are the result of the properties and behaviors of the sub-systems and their interactions. These interactions may be highly nonlinear.
NOTE Systems decompose hierarchically; they are systems of systems.
EXAMPLE A car has a well defined boundary with respect to its environment, and the relationships are both static and dynamic. Similarly the engine has the same kinds of relationships and so does the fuel injector of the engine.
NOTE These collections allow an engineer to examine subsystems for special purposes, picking those elements needed from the prototypical system, design and realization views.
EXAMPLE An engineer may wish to study the cooling system of a car engine and require a collection of entities distributed through the prototypical design or realization hierarchies.
NOTE Requirements are derived from requirements in a many-to-many relationship.
NOTE Engineers involved in specification, design, manufacturing and maintenance need a particular collection of information to do their work. An engineer working on the cooling system of an engine needs information about a particular set of parts, behaviors and properties that are particular to that engineering problem. The set of possibly useful system views is very large.
NOTE As a designer considers several alternatives to meet ysystem requirements, it is necessary to carry along temporary property values to accomplish the design work.
EXAMPLE A designer may have been budgeted 40 pounds for his subsystem. He may find a design solution that weighs 38 pounds. In the design process he may consider alternatives that turn out to weigh 36 , 38, 41, and 43 pounds. These are temporary targets. When he examines other budgets he must meet for the subsystem, the designer may conclude that the 38 pound alternative is the best found.
NOTE Many probability distributions are used in systems engineering. These may include: normal, log-normal, Bernoulli, beta, binomial, negative binomial, chi squared, discrete uniformed, erlang, exponential, F, gamma, geometric, laplace, poisson, T, triangular, uniform, weibull.
NOTE Several different standards of units are in use around the world. It is essential to state the standard in use.
EXAMPLE Failure is assured when different groups use different units without making the necesaary transformations.
NOTE This is a requirement on the development organization and not on the system.
NOTE The procedures may include stakeholder and market surveys, and test marketing
NOTE This is to confirm that the requirements are suitable for the marketplace.
EXAMPLE Proctor and Gamble recently acquired an electric toothbrush product, SpinBrush, from four cleveland area entrepreneurs. Out of a panel of twenty four consumers, twenty three raved about the product. Sales have been sufficient to boost Proctor and Gamble to number 1 position in US oral care.
NOTE Entire new product lines have been abandoned after completed development because of unsatisfactory consumer panel responses and unsatisfactory test marketing
EXAMPLE For a complex digital system the procedure may require the application of a suite of test vectors to the digital system along with environmental tests involving temperature stress and vibration.
EXAMPLE For a complex metal system the the procedure may require the application of several nondestructuve tests to ensure that there are no flaws preset that will cause failure
NOTE This is a requirement on the development organization and not on the system.
NOTE This is performed to confirm that the deployed system will meet the requirements
EXAMPLE For a complex digital system the procedure may require the application of a suite of test vectors to the digital system along with environmental tests involving temperature stress and vibration. The result describes the test coverage and the tests passed and failed
NOTE Weights are often expressed in a numerical form.
EXAMPLE They fix the relative importance in trade off weight, thickness, and battery life. How many minutes of battery life are worth how many tenths of a pound in weight.
For the purposes of this document, the following abbreviations apply:
AAM | application activity model |
AP | application protocol |
ARM | application reference model |
MIM | module interpreted model |
PICS | Protocol Implementation Conformance Statement |
URL | uniform resource locator |
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