{"id":25848,"date":"2021-07-22T15:07:53","date_gmt":"2021-07-22T13:07:53","guid":{"rendered":"https:\/\/cesam.community\/2021\/07\/22\/2-2-the-three-architectural-visions-1-2\/"},"modified":"2022-11-15T11:54:46","modified_gmt":"2022-11-15T10:54:46","slug":"2-2-the-three-architectural-visions-1-2","status":"publish","type":"post","link":"https:\/\/cesam.community\/fr\/2021\/07\/22\/2-2-the-three-architectural-visions-1-2\/","title":{"rendered":"2.2 The three Architectural Visions (1\/2)"},"content":{"rendered":"<div class=\"wpb-content-wrapper\"><section class=\"vc_row wpb_row vc_row-fluid  vc_custom_1627389518372\"><div class=\"wpb_column vc_column_container vc_col-sm-10 vc_col-md-offset-1 col-xs-mobile-fullwidth\"><div class=\"vc_column-inner \"><div class=\"wpb_wrapper\"><div class=\"vc_row wpb_row vc_inner vc_row-fluid\"><div class=\"wpb_column vc_column_container vc_col-sm-9  col-xs-mobile-fullwidth\"><div class=\"vc_column-inner \"><div class=\"wpb_wrapper\"><h2 id=\"0.1\" class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-1\"  style=\"font-weight: 600; color: #000000;\">2.2 The three Architectural Visions<\/h2><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">We are now in position to introduce the three systems architectural visions which will be our first key systems architecting tool for analyzing any system..<\/p>\n<\/div><h3 id=\"0.1\" class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-2\"  style=\"font-weight: 500; color: #01af50;\">2.2.1 Architectural Visions Definition<\/h3><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">The heterogeneity of the environment of a system requires to address it by means of different axes of architectural analysis in order to be able to integrate the whole set of various perceptions of the different system stakeholders<sup class=\"modern-footnotes-footnote \" data-mfn=\"1\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-1\">1<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-1\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"1\">For an electronic toothbrush, these perceptions can be typically the one of the mother who wants good dental hygiene for her children, the one of the stressed business person who wants to clean his\/her teeth as quickly as possible, the one of the dentist who will understand whether the toothbrush is efficient or not with respect to teeth cleaning and the one of the engineer who knows how to construct and how works the electronic toothbrush. <\/span>. Such a consideration naturally leads us to organize these points of views according to different architectural visions that are both necessary due to the variety of any systemic environment, but also useful since they allow decoupling the representations of a given system in different \u201cproperly\u201d interrelated separated views<sup class=\"modern-footnotes-footnote \" data-mfn=\"2\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-2\">2<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-2\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"2\">This way of managing different views on the same system is in fact quite common in usual life. Think for instance of a tourist visiting a city. He\/she will probably use many different views, typically provided by a touristic guide, a metro map and a city map. To find his\/her way, he\/she may for instance first chose the monument to visit in the touristic guide, then move there using the metro map and finally manage the local approach using a city map. In architectural terms, the tourist is thus taking information in different coupled views and integrating them in order to take the \u201cgood\u201d decision! <\/span> which always leads to better clearness and flexibility in terms of system design and development management<sup class=\"modern-footnotes-footnote \" data-mfn=\"3\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-3\">3<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-3\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"3\">A classical difficulty is that such views can correspond with totally \u2013 and even sometimes opposite \u2013 different perceptions on the system, depending on the involved stakeholder.<\/span>.<\/p>\n<p style=\"text-align: justify;\">As a matter of fact, each integrated system S can always be completely analyzed from three different and complementary perspectives that give rise to three generic <em>architectural visions<\/em>, that is to say operational, functional and constructional visions, each of them grouping different types of systemic models, as defined below:<\/p>\n<ul>\n<li style=\"text-align: justify;\"><strong>Architectural vision 1 \u2013 Operational vision<\/strong>: strictly speaking, the operational vision groups only the models of the environment of S \u2013 and not of S itself \u2013 which are involving S. Such operational models are thus describing the interactions of S with its environment.<\/li>\n<li style=\"text-align: justify;\"><strong>Architectural vision 2 \u2013 Functional vision<\/strong>: the functional vision groups all system level models describing the input\/output dynamics of S, without making reference to its concrete components<sup class=\"modern-footnotes-footnote \" data-mfn=\"4\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-4\">4<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-4\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"4\"> That is to say without referring to any technological choice or to any chosen solution.<\/span>. Such functional models are thus abstractly modeling the behaviors of S.<\/li>\n<li style=\"text-align: justify;\"><strong>Architectural vision 3 \u2013 Constructional vision<\/strong><sup class=\"modern-footnotes-footnote \" data-mfn=\"5\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-5\">5<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-5\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"5\">Other names do classically exist for that vision. One may for instance also speak of structural vision. Some frameworks are also speaking of logical vision to denote the constructional vision in the CESAM meaning<\/span>: the constructional vision groups the natural system level models of S constructed by composition of the lower level models associated with its components. Such constructional models are thus describing the structure of S.<\/li>\n<\/ul>\n<p style=\"text-align: justify;\">An illustration of these three different architectural visions is provided by Figure 20 on the electronic toothbrush example. We sketched there our three different types of models, with their connections (see the last subsection of the current section for more details), each of them illustrating a different architectural vision. One sees that the operational vision is not interested by the toothbrush behavior or structure, but just by describing its interactions with (in this example only some) external systems, which are here Power supply, End-users and Internet. On the other hand, the functional vision gives the main toothbrush behaviors \u2013 i.e. Provide electrical power, Generate brushing power, Provide brushing capability \u2013 that allow producing these external interactions as captured by the operational vision, when the constructional vision shows how to implement concretely these internal behaviors through suitable components, here a base, a body, an head and an embedded software.<\/p>\n<\/div>[vc_single_image image=\u00a0\u00bb25349&Prime; img_size=\u00a0\u00bb450&#215;248&Prime; alignment=\u00a0\u00bbcenter\u00a0\u00bb]<div class=\"last-paragraph-no-margin\"><p style=\"text-align: center;\"><strong><span style=\"font-size: 10pt;\">Figure 20 \u2013 Illustration of the three architectural visions on an electronic toothbrush <\/span><\/strong><\/p>\n<\/div><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">It is also important to point out that the previous architectural visions definitions are consistent. In this matter, the key point is here only to be sure of the existence of functional models as defined above. This is however directly connected to the emergence postulate (see Section 0.2) that claims that the mere knowledge of the models of the components of a system and of their interaction laws is never sufficient to model the system that results from their integration. This fact explains why any system always has purely functional models, whose core fundamental role is to express the emerging behaviors<sup class=\"modern-footnotes-footnote \" data-mfn=\"6\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-6\">6<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-6\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"6\">Unfortunately, this is not a common understanding of the functional vision. When doing \u201cfunctional analysis\u201d, most of people are indeed just modeling the functions of the components of a given system, which is not functional analysis in our meaning since this activity shall focus on describing functions at system level, and not at component level. <\/span> that one will never be able to capture and read within constructional models<sup class=\"modern-footnotes-footnote \" data-mfn=\"7\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-7\">7<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-7\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"7\">To understand this phenomenon, consider the example of a car whose constituent (high-level) systemic components are the car body, powertrain, binnacle, chassis and embedded electronics. The interaction of these components typically allows for features like \u00ab\u00a0obstacle detection\u00a0\u00bb which requires the cooperation of a radar (placed in the car body), an embedded software (within embedded electronics), a LED (positioned in the passenger binnacle), and possibly chassis or powertrain if one wants to act on the brakes and \/ or to reduce engine torque when an obstacle is too close to a car. Such a \u201ctransverse\u201d feature is clearly difficult to catch in a purely constructional car model when one will see the flows exchanged between the various involved components of the vehicle without being able to account for their overall logic. Only a functional model at car level will allow capturing the semantics of such a transverse function.<\/span>.<\/p>\n<\/div><div class=\" vc_custom_1627648101001 last-paragraph-no-margin\"><p style=\"text-align: center;\"><strong>Various Perceptions on a System: the Concorde Case<\/strong><\/p>\n<p style=\"text-align: justify;\">The Concorde supersonic aircraft is a typical example of various \u2013 and often contradictory \u2013 perceptions on the same system. From an engineering perspective, Concorde was indeed an outstanding success. Most British and French engineers are usually very proud of this great technological achievement.<br \/>\nBut from a business and societal perspective, it was a total disaster. The supersonic aircraft was typically not able offering a real service to the end-customer. Concorde was indeed the fastest, but also the most expensive aircraft, with very few destinations offered (only ParisNew York &amp; Paris-Rio de Janeiro) and at the end, a quality\/price ratio which was strongly non-optimal. Due to chemical and noise pollution, it was also not an environmental-friendly aircraft, which blocked it during a long time to get the landing authorization in New York city as a consequence of the opposition of many neighbors\u2019 protection organizations.<br \/>\nWhen possible, which is not always the case as taught by the final failure of the Concorde story, the role of the systems architect is to find the best architectural balance between all these different competing points of views<\/p>\n<\/div><div class=\" vc_custom_1627648129790 last-paragraph-no-margin\"><p style=\"text-align: center;\"><strong><span style=\"font-size: 10pt;\">Case study 3 \u2013 Various perceptions on a system: the Concorde case <\/span><\/strong><\/p>\n<\/div><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">We can thus now understand why it is necessary to have three different types of models in order to model in practice a real system: the operational vision indeed captures the external viewpoint while functional and constructional views do capture the internal perspective, by modeling respectively firstly the emergent behaviors and secondly the concrete constitution of the considered system.<br \/>\nAs we will see more in details in the sequel, architectural visions are of course key for in a systems architecting perspective: the first job of any systems architect will indeed always be to classify the modeling information according to our three architectural visions<sup class=\"modern-footnotes-footnote \" data-mfn=\"8\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-8\">8<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-8\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"8\">That will be segregated more precisely according to a systemic analysis grid and organized in different abstraction levels, as we will see further in this pocket guide.<\/span>, so as to obtain homogeneous system models each of them capturing a well-defined view.<\/p>\n<\/div><h3 id=\"0.1\" class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-3\"  style=\"font-weight: 500; color: #01af50;\">2.2.2 Architectural Visions Overview<\/h3><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">Let us thus now present more in details the three different \u2013 operational, functional &amp; constructional \u2013 architectural visions that we introduced in the last section.<\/p>\n<\/div><h3 id=\"0.1\" class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-4\"  style=\"font-weight: 500;\">2.2.2.1 Operational Vision<\/h3><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">The operational vision provides \u201cblack box\u201d models of a given system where one does not describe the system of interest, but rather its interactions and its interfaces with its environment. Its core motivation is to understand in that way the motivation \u2013 that is to say the \u201cWhy\u201d \u2013 of the system.<\/p>\n<\/div>[vc_single_image image=\u00a0\u00bb25355&Prime; img_size=\u00a0\u00bb400&#215;222&Prime; alignment=\u00a0\u00bbcenter\u00a0\u00bb]<div class=\" vc_custom_1627648483246 last-paragraph-no-margin\"><p style=\"text-align: center;\"><strong><span style=\"font-size: 10pt;\">Figure 21 \u2013 Operational vision \u2013 Mission Breakdown Structure (MBS) of an electronic toothbrush <\/span><\/strong><\/p>\n<\/div><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">In this matter, the key point to understand is that an operational analysis manipulates concepts at environment level, which are mixing \u2013 by definition \u2013 both the system of interest and its external systems. The operational concept of \u201cmission of a system\u201d is a typical example of such a situation. Formally speaking, a <em>mission<\/em> for a given system S can indeed be defined as a function of the environment of reference Env(S) of that system<sup class=\"modern-footnotes-footnote \" data-mfn=\"9\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-9\">9<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-9\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"9\">In other terms, Mission(S) \u2261 Function(Env(S)) for every system S.<\/span>. When one analyzes for instance the function \u201cTo guarantee dental hygiene\u201d<sup class=\"modern-footnotes-footnote \" data-mfn=\"10\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-10\">10<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-10\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"10\">Due to the functional nature of a mission, we do recommend to name it as a verb in infinitive form (cf. next subsection).<\/span> , whose functional behavior consists in transforming dirty teeth into healthy teeth and\/or maintaining teeth in an healthy state, one can see that a toothbrush can clearly not achieve alone this feature, which also requires at least an end-user, toothpaste and water plus may be a dentist. Such function can thus only be allocated to the environment of the toothbrush, considered as a system in the meaning of Section 2.1, and not to the toothbrush alone. In other words, \u201cTo guarantee dental hygiene\u201d is hence not a function of the electronic toothbrush, but a function of its environment, which means that it shall be interpreted as a mission \u2013 and again not a function<sup class=\"modern-footnotes-footnote \" data-mfn=\"11\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-11\">11<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-11\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"11\">The role of functional analysis is in particular to extract, strictly speaking, the functions of a system of interest which are hidden within its missions, that is to say the internal behaviors of the considered system that are only involving the system and nothing else around it (and thus also only partially contributing to the missions). For an electronic toothbrush, we may for instance analyze that the toothbrush is only achieving the function \u201cTo brush teeth\u201d, which basically only provide brushing forces, as a partial contribution to the mission \u201cTo guarantee dental hygiene\u201d. To illustrate this subtle distinction, we may take the other classical example of the cigarette system. Most of people will probably say that the core function of a cigarette is \u201cTo smoke\u201d, but again it is easy to see that one cannot smoke without at least a smoker, a source of fire and air, plus probably also an ashtray. \u201cTo smoke\u201d can hence be only allocated to the environment of a cigarette and it shall be interpreted as a mission \u2013 and not a function \u2013 of a cigarette. One may indeed understand that \u201cTo smoke\u201d is a complex protocol requiring first a smoker, a cigarette and a source of fire to provide its own function \u201cTo deliver fire\u201d, passing then through a loop where smoker \u201cinspires pure air\u201d, cigarette \u201cpropagates fire\u201d &amp; \u201cdelivers tar\u201d and smoker \u201cexpires dirty air\u201d up to arriving to the cigarette consumption, with a final request by the smoker of the ashtray function \u201cTo keep ashes\u201d applied to the burned cigarette. This analysis shows that the underlying cigarette functions \u2013 or in other terms the intrinsic behaviors of a cigarette \u2013 are here \u201cTo propagate fire\u201d and \u201cTo deliver tar\u201d. <\/span> \u2013 of the toothbrush according to our above definition.<\/p>\n<p style=\"text-align: justify;\">The operational vision relies on other operational concepts such as life cycle, operational contexts, operational scenarios or operational objects (cf. Section 2.4 for more details). All these concepts may also be managed at different levels of abstraction \/ grain. Figure 21 shows for instance the<em> Mission Breakdown Structure<\/em> (MBS) of an electronic toothbrush where its core missions are put in a hierarchy according to the fact that a high level mission needs the lower levels missions to be achieved.<br \/>\nThe operational vision can also be seen as a natural interface between engineering and non-technical people. Typical examples of operational models are indeed for instance development, assembling or maintenance models (that specify how a product system will be managed by the associated design, manufacturing or support systems), but also marketing or usage models (that describe how a product system will be seen by the market or used the end-users) and business models (which explain how the constructing company will earn money with a product system). In this matter, the role of the operational vision is to express the information contained in these different business models within a language that can be understood by the system designers and used in the development process.<\/p>\n<\/div><h3 id=\"0.1\" class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-5\"  style=\"font-weight: 500;\">2.2.2.2 Functional Vision<\/h3><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">The functional vision provides \u201cgrey box\u201d models of a given system of interest where one begins to apprehend the inside of the system, but only in terms of input\/output abstract<sup class=\"modern-footnotes-footnote \" data-mfn=\"12\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-12\">12<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-12\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"12\"> That is to say independent of any technological implementation.<\/span> behaviors and not of concrete implementation choices, in order to begin understanding more deeply what does the system, without however knowing at this point how it is concretely structured. Its core motivation is to elicit in that way the behavior \u2013 that is to say the \u201cWhat\u201d \u2013 of the system. The core notion of the functional vision is of course the notion of \u201cfunction of a system\u201d, which refers to an input\/output behavior of the considered system. In other terms, a function associated with a given system models a transformation process \u2013 which can be achieved by physical, software or even \u201chumanware\u201d resources \u2013 that transforms a given series of inputs into a given series of outputs. This explains why a common pattern to name a function is a verb followed by a complement, the generic patterns being typically \u201cTo do something\u201d or \u201cTo transform inputs into outputs\u201d. In any case, one shall always check when defining a function whether it expresses such a transformational behavior.<\/p>\n<p style=\"text-align: justify;\">Contrarily to the operational vision, all functional concepts \u2013 such as functional modes, functional scenarios or functional objects (see Section 2.4 for more details) \u2013 are now uniquely referring to the system of interest, without involving any external system. All these concepts can again be managed at different levels of abstraction \/ grain. Figure 22 shows for instance the <em>Functional Breakdown Structure<\/em> (FBS) of an electronic toothbrush, where its main functions are put in a hierarchy according to the fact that a high level function needs the lower levels functions to be achieved (i.e. the \u201calgorithm\u201d of the high level function involves the lower functions as sub-routines).<\/p>\n<\/div>[vc_single_image image=\u00a0\u00bb25358&Prime; img_size=\u00a0\u00bb400&#215;252&Prime; alignment=\u00a0\u00bbcenter\u00a0\u00bb]<div class=\" vc_custom_1627650020233 last-paragraph-no-margin\"><p style=\"text-align: center;\"><strong><span style=\"font-size: 10pt;\">Figure 22 \u2013 Functional vision \u2013 Functional Breakdown Structure (FBS) of an electronic toothbrush <\/span><\/strong><\/p>\n<\/div><div class=\"last-paragraph-no-margin\"><p style=\"text-align: justify;\">We may now point out that a key difficulty of functional analysis is the identification of <em>transverse functions<\/em> that is to say of functions that cannot be directly allocated to a single component of a given system. Such functions are indeed capturing the emergent behaviors resulting from the cooperation between the different components of a system, which by definition cannot be easily observed at constructional level. It is therefore always important to identify these functions in order to master the integration process since these functions are also telling us where different teams in charge of different components shall work collaboratively<sup class=\"modern-footnotes-footnote \" data-mfn=\"13\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-13\">13<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-13\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"13\">We already provided an illustration on that situation in footnote 80 to which the reader may first refer. Another similar example is the thrust reversing function on an aircraft: this function, which reverts the air flow passing in an aircraft engine to decrease the speed of the aircraft when on ground, is provided by the cooperation of a cylinder that pushes a trap both located in the nacelle, the engine itself and a critical embedded software that coordinates the involved nacelle and engine components when thrust reversing operates. Such a function is typically transverse since distributed on several hardware &amp; software components which are located moreover provided by different suppliers (typically one for the nacelle, one for the engine, one for the embedded system): identifying the function and putting it under control in the aircraft development project is thus totally key to ensure the success of its integration. <\/span>. Within a functional breakdown structure, one may thus normally always find both component functions and transverse functions. Unfortunately most of engineers are often forgetting the transverse functions in their analyses, which leads them to lose the most important value of a complete functional analysis in a systems architecting perspective.<\/p>\n<p style=\"text-align: justify;\">Another key point is that the functional vision is fundamental in systems architecting since it provides the deep invariants of any system. Any communication network will achieve for instance always the same basic functions such as \u201cTo receive messages\u201d, \u201cTo route messages\u201d or \u201cTo deliver messages\u201d, independently of its implementation technology that may either purely manual (think to your snail mail operator) or based on many different techniques (Hertzian waves, twisted cables, copper wires, optical fiber, etc.). In a totally different direction, consider a State as an organizational system: one may observe that it always relies on the core function \u201cTo collect taxes\u201d, consisting in taking money from the citizen pockets and bringing it in the State ones, which is basically invariant among time even if the tax collecting mechanisms evolve a lot from Roman antiquity up to our modern societies. In other words,<em> technology changes but functional architecture remains<\/em>. As a natural consequence, functional architecture always provides a robust basis for architecting a system. It indeed allows the systems architect to reason on a system independently of technology and thus to define, analyze and evaluate different implementation options for a given functional architecture. Such an approach is key to choose the best solution, which cannot be done if one directly works at constructional level where one will be glued in a given technical choice, without possibility of making another.<\/p>\n<p style=\"text-align: justify;\">Good systems architectures are also based on functional segregation principles. This simply means that some key functional interfaces must be strictly respected at constructional level<sup class=\"modern-footnotes-footnote \" data-mfn=\"14\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-14\">14<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-14\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"14\">In this matter, the role of the systems architect is to guarantee that such interfaces will never be violated in the design.<\/span>. This gives rise to layered architectures where components are clustered in different independent layers connected by functional interfaces. Typical classical examples of such architectures are computer, mobile phone or communication network architectures that are organized in different independent layers, starting from the physical layer up to arriving to service layers (see for instance [90] for more details). One must thus for instance be able on one hand to change a signal processing protocol within the physical layer without any impact on the service layer and on the other hand to implement a new service or a service evolution in the service layer without any impact on the physical layer. Such a result is typically achieved by means of robust functional interfaces that shall also be stable among time, in order to absorb the technological evolutions that will naturally arrive in the life of any system<sup class=\"modern-footnotes-footnote \" data-mfn=\"15\" data-mfn-post-scope=\"00000000000019b60000000000000000_25848\"><a href=\"javascript:void(0)\"  role=\"button\" aria-pressed=\"false\" aria-describedby=\"mfn-content-00000000000019b60000000000000000_25848-15\">15<\/a><\/sup><span id=\"mfn-content-00000000000019b60000000000000000_25848-15\" role=\"tooltip\" class=\"modern-footnotes-footnote__note\" tabindex=\"0\" data-mfn=\"15\"> Another motivation for such functional segregation is abstraction. It would indeed be basically impossible to develop a service if one would access directly to the physical layer of a computer system since the physical world is here usually highly non deterministic with many probabilistic phenomena that must be hidden to a service developer. <\/span>.<\/p>\n<p style=\"text-align: justify;\">It is finally interesting to observe that the standard vocabulary used to discuss of the functional vision is traditionally different, depending whether the considered system is a technical or an organizational system. The term \u201cfunction\u201d is for instance usually reserved for technical systems (that may be of either hardware or software nature), when one rather uses the terms \u201cprocess\u201d, \u201cactivity\u201d or \u201ctask\u201d to express the same behavioral concept when dealing organizational systems. It shall however be clearly understood that processes, activities or tasks are in fact nothing else than functions of a given organizational system, considered at different levels of abstraction.<\/p>\n<\/div><a  href=\"https:\/\/cesam.community\/2021\/07\/30\/2-2-the-three-architectural-visions-2-2\/\" target=\"_self\" class=\"btn pofo-button-1 bg-position-center-center  wow none button-style9  btn-link text-extra-dark-gray text-deep-pink-hover  btn-medium   vc_custom_1627657291558\" >Next page<i class=\"ti-arrow-right   margin-5px-left no-margin-right\" aria-hidden=\"true\"><\/i><\/a><\/div><\/div><\/div><div class=\"wpb_column vc_column_container vc_col-sm-3  col-xs-mobile-fullwidth\"><div class=\"vc_column-inner \"><div class=\"wpb_wrapper\"><h2 class=\"text-medium-gray text-small margin-5px-bottom alt-font text-uppercase heading-style4  heading-6\"  style=\"font-size: 10px; font-weight: 600; color: #000000;\" data-fontsize=\"10px\">TABLE OF CONTENTS<\/h2>[vc_wp_custommenu nav_menu=\u00a0\u00bb132&Prime;]<\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/section>\n<\/div>","protected":false},"excerpt":{"rendered":"2.2 The three Architectural VisionsWe are now in position to introduce the three systems architectural visions which will be our first key systems architecting tool for analyzing any system.. 2.2.1 Architectural Visions DefinitionThe heterogeneity of the environment of a system requires to address it by means of different axes of architectural analysis in order to be able to integrate the whole set of various perceptions of the different system stakeholders . Such a consideration naturally leads us to organize these points of views according to different architectural visions that are both necessary due to the variety of any systemic environment, but also useful since they allow decoupling the representations of a given system in different \u201cproperly\u201d interrelated separated views2This way of managing different views on...","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[158],"tags":[157],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.2 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>2.2 The three Architectural Visions (1\/2) - Cesam Community<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cesam.community\/fr\/2021\/07\/22\/2-2-the-three-architectural-visions-1-2\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"2.2 The three Architectural Visions (1\/2) - 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