{"id":25531,"date":"2021-07-01T10:54:15","date_gmt":"2021-07-01T08:54:15","guid":{"rendered":"https:\/\/cesam.community\/?p=25531"},"modified":"2023-01-20T11:44:49","modified_gmt":"2023-01-20T10:44:49","slug":"5-1-why-understanding-what-does-the-system","status":"publish","type":"post","link":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/","title":{"rendered":"5.1 Why Understanding What Does the System?"},"content":{"rendered":"

5.1 Why Understanding What Does the System?<\/h2>

Functional architecture, or equivalently functional analysis, intends to describe precisely the different functions of a system and their relative interactions1<\/a><\/sup>And also how these functions are connected to missions. This point \u2013 even if important \u2013 will however not addressed in this pocket guide since it can be easily addressed through a suitable allocation matrix<\/span>. The core motivation of functional architecture is to start understanding and specifying in details the system, but only in terms of behaviors \u2013 i.e. in other terms, to understand and specify what does the system \u2013 and not of concrete structure, i.e. in its functional nature \u2026 as one would have easily guessed! It is indeed important to have first a functional description of a system, and not to dig immediately in the technique, if one wants to be able to rationally manage trade-offs between different options2<\/a><\/sup>Functional architecture allows in particular to make early cost analysis as soon as one have an idea of the average cost of an elementary function (see also the Constructive Cost Model for Systems \u2013 COSYSMO \u2013 [79]). Such a feature is especially interesting for trade-offs that may also be done at functional level (in order to choose between two competing functional architectures for a given system).<\/span>. Functional architecture is indeed usually independent of the technological choices3<\/a><\/sup>The car function \u201cProduce torque\u201d is for instance totally independent of the technology: it exists on a car either with a thermic, or an electrical engine. <\/span> \u2013 at least at some level of abstraction \u2013 which means that functionally reasoning \u2013 of course at the good level of abstraction4<\/a><\/sup>As a consequence of that simple remark, functional architecture is absolutely of NO USE if its analyses go too much in the detail. Detailed functional architecture indeed 1) either overlaps with constructional architecture as soon as detailed functions identify with the high level functions of the components of the considered system, 2) or be totally misaligned with its constructional architectural (which means that the identified functions do not naturally map with components). In the first case, functional architecture overlaps with constructional architecture since the two analyzes do provide exactly the same semantics. In the second case, functional architecture is dangerous since its results \u2013 which have here no concrete value \u2013 may mislead the system designers. In the two case, it is therefore a waste of time and money<\/span> \u2013 on a system allows to reason at the same time on many different constructional options that we will be able to compare and to evaluate later (see Chapter 7 dedicated to these trade-off analyses). One must indeed understand that skipping functional analysis by directly going to technical design is a very bad practice, even if widespread in engineering organizations, since it just means that one makes a very strong design choice without even being conscious of that choice. As a consequence, one will just be glued in that choice, without being able to move to radically different options that may be more adapted.<\/p>\n

We must also stress that functional architecture is absolutely fundamental to capture emergence and transversal behaviors that can only be modeled using its tools. By definition, all emergent behaviors can indeed not been captured by constructional architecture since they are functional properties of an integrated system (we refer to subsection 0.2 for more details). One must hence use functional architecture to describe and model such properties. As an immediate consequence, functional architecture is key tool to structure transversal collaboration in an engineering organization whose purpose is indeed just to manage efficiently the emergent transversal behaviors of a system.<\/p>\n

Last, but not least, functional architecture also allows to organize a system in functionally decoupled \u2013 as much as possible \u2013 sub-systems. This is very important if one wants to avoid too many impacts when there is a change in a system design5<\/a><\/sup> See the first case study of Chapter 6 to see what can unfortunately happen in case of a design evolution \u2026<\/span>. This idea gives rise to layered functional architectures where each functional layer is strictly functionally segregated from the other ones by rigid standard functional interfaces that are managed in configuration. This architectural functional segregation \/ decoupling principle provides huge flexibility: in an ideal world, one will indeed be able to change a function in one layer without any impact on the other layers, as soon as the functional interfaces between layers are respected. We refer to the concrete examples of systems organized according to such a principle \u2013 that is to say computers, mobile phones or communication networks \u2013 that are provided in the functional architecture subsection of section 2.2<\/p>\n<\/div>

Transversal Behaviors are Crucial to Master: the Airport Radar Case<\/strong><\/p>\n

ALTHEIS is a leading airport radar company in the world. They developed a new airport radar on the basis of a modular generic functional architecture, each generic functional module being devoted to a certain part of a radar treatment chain and managed by a dedicated engineering team. The idea was to replace development, when dealing with a specific radar deployment, by parametrization. Each generic functional module had thus to be specifically parametrized when instantiated on a given concrete airport application.
\nHowever the overall amount of parameters to manage was quite high: around one million elementary parameters that could be organized in around 50.000 high level parameters, each of them with a specific business meaning, were indeed managed by the development engineers. This huge complexity lead initially to what could have become a real industrial disaster: when a radar was parametrized and put in service, it happened that the radar never stabilized since bugs were permanently appearing on the field which regularly obliged the radar to go back to the factory to be reparametrized, which could only be done by the development team due to the technicity of the parametrization. This situation was terribly uncomfortable and clearly economically not sustainable6<\/a><\/sup>A radar business model is indeed based on first a fixed initial price that just covers the development costs and secondly yearly maintenance fees on which the constructor is making its benefit. One can thus easily understand that permanent bugs are just destroying the radar business model.<\/span>.<\/p>\n

CESAMES was appointed to analyze and to try to solve that issue. It appeared that its root cause was connected to the lack of a shared and explicit radar functional architecture. When the parametrization was initially done, each team in charge was indeed not conscious at all of its functional interdependence \u2013 through transversal functions \u2013 with the other teams. As a consequence, each parametrization done locally at the level of one team was in conflict with the other parametrizations, which lead to the observed problems.
\nThe solution \u2013 provided by CESAMES \u2013 was to architecture all parameters in alignment with the radar Functional Breakdown Structure (FBS), by clustering the parameters according to the different functions of the FBS. A parameter architecture team \u2013 managed by a functional architect \u2013 was then created to manage, guarantee and maintain among time the functional coherence of each of all these parameter clusters.<\/p>\n<\/div>

Case study 7 \u2013 The Airport Radar Case\u00a0<\/span><\/strong><\/p>\n<\/div>NEXT PAGE<\/i><\/a><\/div><\/div><\/div>

TABLE OF CONTENTS<\/h2>[vc_wp_custommenu nav_menu=\u00a0\u00bb132″]

REFERENCES<\/h2>

[79] Valerdi R., The Constructive Systems Engineering Cost Model (COSYSMO), Quantifying the Costs of Systems Engineering Effort in Complex Systems, VDM Verlag Dr. Muller, 2008 <\/span><\/p>\n<\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/section>\n<\/div>","protected":false},"excerpt":{"rendered":"

Functional architecture, or equivalently functional analysis, intends to describe precisely the different functions of a system and their relative interactions. The core motivation of functional architecture is to start understanding and specifying in details the system, but only in terms of behaviors \u2013 i.e. in other terms, to understand and specify what does the system \u2013 and not of concrete structure, i.e. in its functional nature \u2026 as one would have easily guessed! It is indeed important to have first a functional description of a system, and not to dig immediately in the technique, if one wants to be able to rationally manage trade-offs between different options…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[158],"tags":[157],"yoast_head":"\n5.1 Why Understanding What Does the System? - 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\/01\/5-1-why-understanding-what-does-the-system\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"5.1 Why Understanding What Does the System? - Cesam Community\" \/>\n<meta property=\"og:description\" content=\"Functional architecture, or equivalently functional analysis, intends to describe precisely the different functions of a system and their relative interactions. The core motivation of functional architecture is to start understanding and specifying in details the system, but only in terms of behaviors \u2013 i.e. in other terms, to understand and specify what does the system \u2013 and not of concrete structure, i.e. in its functional nature \u2026 as one would have easily guessed! It is indeed important to have first a functional description of a system, and not to dig immediately in the technique, if one wants to be able to rationally manage trade-offs between different options...\" \/>\n<meta property=\"og:url\" content=\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\" \/>\n<meta property=\"og:site_name\" content=\"Cesam Community\" \/>\n<meta property=\"article:published_time\" content=\"2021-07-01T08:54:15+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2023-01-20T10:44:49+00:00\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@cesamcommunity\" \/>\n<meta name=\"twitter:site\" content=\"@cesamcommunity\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\"},\"author\":{\"name\":\"admin\",\"@id\":\"https:\/\/cesam.community\/fr\/#\/schema\/person\/1698618e5539e0eadd3578d29281a505\"},\"headline\":\"5.1 Why Understanding What Does the System?\",\"datePublished\":\"2021-07-01T08:54:15+00:00\",\"dateModified\":\"2023-01-20T10:44:49+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\"},\"wordCount\":1484,\"publisher\":{\"@id\":\"https:\/\/cesam.community\/fr\/#organization\"},\"keywords\":[\"Article\"],\"articleSection\":[\"CESAM Systems Architecting Method\"],\"inLanguage\":\"fr-FR\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\",\"url\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\",\"name\":\"5.1 Why Understanding What Does the System? - Cesam Community\",\"isPartOf\":{\"@id\":\"https:\/\/cesam.community\/fr\/#website\"},\"datePublished\":\"2021-07-01T08:54:15+00:00\",\"dateModified\":\"2023-01-20T10:44:49+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#breadcrumb\"},\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Accueil\",\"item\":\"https:\/\/cesam.community\/fr\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"CESAM Systems Architecting Method\",\"item\":\"https:\/\/cesam.community\/fr\/category\/cesam-systems-architecting-method-en\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"5.1 Why Understanding What Does the System?\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/cesam.community\/fr\/#website\",\"url\":\"https:\/\/cesam.community\/fr\/\",\"name\":\"Cesam Community\",\"description\":\"La communaut\u00e9 CESAM\",\"publisher\":{\"@id\":\"https:\/\/cesam.community\/fr\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/cesam.community\/fr\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"fr-FR\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/cesam.community\/fr\/#organization\",\"name\":\"CESAM Community\",\"url\":\"https:\/\/cesam.community\/fr\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\/\/cesam.community\/fr\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/cesam.community\/wp-content\/uploads\/2021\/04\/cesam_community_logo_v4.png\",\"contentUrl\":\"https:\/\/cesam.community\/wp-content\/uploads\/2021\/04\/cesam_community_logo_v4.png\",\"width\":7310,\"height\":1018,\"caption\":\"CESAM Community\"},\"image\":{\"@id\":\"https:\/\/cesam.community\/fr\/#\/schema\/logo\/image\/\"},\"sameAs\":[\"https:\/\/x.com\/cesamcommunity\",\"https:\/\/www.linkedin.com\/company\/community-cesam\/about\/\"]},{\"@type\":\"Person\",\"@id\":\"https:\/\/cesam.community\/fr\/#\/schema\/person\/1698618e5539e0eadd3578d29281a505\",\"name\":\"admin\",\"sameAs\":[\"https:\/\/cesam.community\"]}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"5.1 Why Understanding What Does the System? - Cesam Community","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/","og_locale":"fr_FR","og_type":"article","og_title":"5.1 Why Understanding What Does the System? - Cesam Community","og_description":"Functional architecture, or equivalently functional analysis, intends to describe precisely the different functions of a system and their relative interactions. The core motivation of functional architecture is to start understanding and specifying in details the system, but only in terms of behaviors \u2013 i.e. in other terms, to understand and specify what does the system \u2013 and not of concrete structure, i.e. in its functional nature \u2026 as one would have easily guessed! It is indeed important to have first a functional description of a system, and not to dig immediately in the technique, if one wants to be able to rationally manage trade-offs between different options...","og_url":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/","og_site_name":"Cesam Community","article_published_time":"2021-07-01T08:54:15+00:00","article_modified_time":"2023-01-20T10:44:49+00:00","author":"admin","twitter_card":"summary_large_image","twitter_creator":"@cesamcommunity","twitter_site":"@cesamcommunity","twitter_misc":{"\u00c9crit par":"admin","Dur\u00e9e de lecture estim\u00e9e":"6 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#article","isPartOf":{"@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/"},"author":{"name":"admin","@id":"https:\/\/cesam.community\/fr\/#\/schema\/person\/1698618e5539e0eadd3578d29281a505"},"headline":"5.1 Why Understanding What Does the System?","datePublished":"2021-07-01T08:54:15+00:00","dateModified":"2023-01-20T10:44:49+00:00","mainEntityOfPage":{"@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/"},"wordCount":1484,"publisher":{"@id":"https:\/\/cesam.community\/fr\/#organization"},"keywords":["Article"],"articleSection":["CESAM Systems Architecting Method"],"inLanguage":"fr-FR"},{"@type":"WebPage","@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/","url":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/","name":"5.1 Why Understanding What Does the System? - Cesam Community","isPartOf":{"@id":"https:\/\/cesam.community\/fr\/#website"},"datePublished":"2021-07-01T08:54:15+00:00","dateModified":"2023-01-20T10:44:49+00:00","breadcrumb":{"@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#breadcrumb"},"inLanguage":"fr-FR","potentialAction":[{"@type":"ReadAction","target":["https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/cesam.community\/fr\/2021\/07\/01\/5-1-why-understanding-what-does-the-system\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Accueil","item":"https:\/\/cesam.community\/fr\/"},{"@type":"ListItem","position":2,"name":"CESAM Systems Architecting Method","item":"https:\/\/cesam.community\/fr\/category\/cesam-systems-architecting-method-en\/"},{"@type":"ListItem","position":3,"name":"5.1 Why Understanding What Does the System?"}]},{"@type":"WebSite","@id":"https:\/\/cesam.community\/fr\/#website","url":"https:\/\/cesam.community\/fr\/","name":"Cesam Community","description":"La communaut\u00e9 CESAM","publisher":{"@id":"https:\/\/cesam.community\/fr\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/cesam.community\/fr\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"fr-FR"},{"@type":"Organization","@id":"https:\/\/cesam.community\/fr\/#organization","name":"CESAM Community","url":"https:\/\/cesam.community\/fr\/","logo":{"@type":"ImageObject","inLanguage":"fr-FR","@id":"https:\/\/cesam.community\/fr\/#\/schema\/logo\/image\/","url":"https:\/\/cesam.community\/wp-content\/uploads\/2021\/04\/cesam_community_logo_v4.png","contentUrl":"https:\/\/cesam.community\/wp-content\/uploads\/2021\/04\/cesam_community_logo_v4.png","width":7310,"height":1018,"caption":"CESAM Community"},"image":{"@id":"https:\/\/cesam.community\/fr\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/x.com\/cesamcommunity","https:\/\/www.linkedin.com\/company\/community-cesam\/about\/"]},{"@type":"Person","@id":"https:\/\/cesam.community\/fr\/#\/schema\/person\/1698618e5539e0eadd3578d29281a505","name":"admin","sameAs":["https:\/\/cesam.community"]}]}},"_links":{"self":[{"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/posts\/25531"}],"collection":[{"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/comments?post=25531"}],"version-history":[{"count":7,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/posts\/25531\/revisions"}],"predecessor-version":[{"id":33371,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/posts\/25531\/revisions\/33371"}],"wp:attachment":[{"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/media?parent=25531"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/categories?post=25531"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cesam.community\/fr\/wp-json\/wp\/v2\/tags?post=25531"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}