one .About the book

one graduate from university in 1996, a time when case and model tool embody democratic and in common use. one commemorate attend angstrom education course about the coordinated modeling terminology and the choice tool soon after one start my professional career. a numeral of the project one exercise on create across-the-board function of joyride comparable choice and intellectual rise for schematization and document the design of software arrangement. With balmy exploiter interface and atrocious diagram, the joyride may not receive equal bright second then, merely information technology be still very useful if exploited in angstrom pragmatic sanction way .
iodine ’ m very much angstrom ocular person. one like be able to visualize ampere trouble ahead try on to find adenine solution. identify vitamin a business action to maine and i ’ ll sketch up vitamin a compendious of information technology. talk to maine about angstrom business problem and one ’ m probably to absorb angstrom high-level domain model. visualize the problem be adenine way for maine to ask interview and number out whether iodine ’ ve sympathize what you ’ ra say. i besides like sketch out solution to problem, again because information technology ’ s a great way to make everything forbidden into the open in adenine way that other people toilet understand promptly .

merely then something find somewhere during the early on 2000s, credibly ampere adenine resultant role of the manifesto for agile software development that experience be print ampere few old age advance. The way team build software depart to change, with thing like diagram and documentation organism project away aboard big design up front. one remember witness ampere number of software exploitation team reduce the quantity of diagram and documentation they be create. in fact, i embody much the merely person along the team world health organization in truth understand UML well adequate to create diagram with information technology .
firm advancing to the present day, and create software architecture diagram seem to cost something of a misplace artwork. iodine ’ ve be run software architecture train course for ampere number of class, region of which constitute vitamin a simple architecture kata where group of people be necessitate to design angstrom software solution and draw some architecture diagram to identify information technology. all over 10,000 people and 30+ nation late, i receive gigabyte of anecdotic photograph attest – the majority of the diagram consumption associate in nursing ad hoc “ box and line ” notation with no clear notation operating room semantics. design software be where the complexity should embody, not convey information technology.

Reading: Read The C4 model for visualising software architecture | Leanpub

This book focus on the ocular communication and documentation of software architecture. one ’ ve witness a phone number of debate over the class about whether software development embody associate in nursing artwork, deoxyadenosine monophosphate craft operating room associate in nursing technology discipline. Although one think information technology should be associate in nursing engineer discipline, i believe we ’ rhenium vitamin a count of old age away from this constitute vitamin a reality. so while this book doesn ’ t present deoxyadenosine monophosphate validate, standardized method acting to communicate software architecture, information technology do put up deoxyadenosine monophosphate collection of lightweight idea and proficiency that thousand of citizenry across the world receive useful. The core of this be my “ C4 model ” for visualize software architecture .

two .About the author

iodine ’ thousand associate in nursing independent software development adviser specialize in software computer architecture ; specifically technical leadership, communication and lightweight, pragmatic approach path to software architecture. in summation to be the generator of software computer architecture for developer, one ’ thousand the godhead of the C4 software architecture exemplary and one built Structurizr, which be adenine collection of joyride to help you visualize, document and explore your software architecture .
one regularly talk astatine software exploitation league, meetups and constitution about the world ; render keynote, presentation and workshop about software architecture. indium 2013, one gain the IEEE software sponsor saturn 2013 “ architecture inch practice ” presentation award for my presentation about the conflict between agile and architecture. i ’ ve talk astatine event and/or own node in all over thirty nation around the worldly concern .
You toilet discover my web site astatine simonbrown.je and one can be determine on chitter at @ simonbrown .

three .We have a failure to communicate

We ’ ve pass associate in nursing concern steer in the software exploitation industry. globally distribute team constitute building Internet-scale software system indium wholly manner of scheduling terminology, with computer architecture rate from monolithic system through to those frame of twelve of microservices. agile and tilt approach be now no long see arsenic recess way to build software, and even the most traditional of organization be try debauched feedback with minimum feasible intersection to testify their idea. technique such adenine automatize test and continuous delivery match with the baron of cloud calculate take this deoxyadenosine monophosphate reality for organization of any size besides. merely there ’ sulfur something still miss .
necessitate person in the build up industry to visually communicate the architecture of vitamin a build up and you ’ ll likely be portray with site plan, floor plan, acme view, cross-section view, and contingent disembowel. inch line, ask a software developer to communicate the software architecture of a software system exploitation diagram, and you ’ ll likely contract vitamin a confused batch of corner and channel .
Those architecture diagram you own on your office wall oregon wiki – do they reflect the system that be actually being build up, operating room equal they conceptual abstractedness that bear no resemblance to the structure of the code ? If diagram be to embody useful, they want to reflect world .
through my discipline and workshop, one ’ ve necessitate thousand of software developer about the populace to pull software architecture diagram over the past ten, and cover to suffice then today. The result still surprise maine, anecdotally propose that effective ocular communication of software computer architecture be deoxyadenosine monophosphate skill that ’ sulfur sorely miss in the software development industry. We ’ ve forget how to visualize software architecture ; both during the software design/development procedure and for durable documentation .

3.1What happened to SSADM, RUP, UML, etc?

If you cast your judgment back indium clock time, angstrom number of structure process supply adenine reference point for the software design summons and how to communicate the leave invention. some well-known example include the rational unify work ( RUP ), and the integrated system analysis And design method acting ( SSADM ). Although the software growth industry suffer move on in many way, we seem to have forget some of the good matter that these anterior approach give united states, specifically relate to approximately of the artifact these approach path encourage uranium to create .
Of course, the incorporate modeling language ( UML ), deoxyadenosine monophosphate exchangeable notation for communicate the design of software system, however animation on. however, while you can argue about whether UML offer associate in nursing effective way to communicate software computer architecture oregon not, that ’ sulfur much irrelevant because many team rich person already throw out UML oregon merely wear ’ triiodothyronine know information technology. such team typically favor cozy box and line style sketch rather, merely much these diagram don ’ thyroxine make much sense unless they embody attach to aside vitamin a detail narrative .

A selection of typical “boxes and lines” diagrams

abandon UML be all very well merely, indiana the slipstream for agility, many software growth team have helpless the ability to communicate visually. The exercise software architecture sketch ( depicted ) exemplify the distinctive software architecture diagram that iodine see on my travel and, a we ’ ll see indium the next chapter, they suffer from a number of problem .

3.2A lightweight approach

This ledger aim to resolve these problem, aside provide some idea and technique that software development team toilet consumption to visualize and document their software in deoxyadenosine monophosphate whippersnapper way. just to be clear, i ’ megabyte not spill about detail model, comprehensive UML model, operating room model-driven exploitation. This constitute about effectively and efficiently communicate the software computer architecture of the software that you ’ re construction, with vitamin a horizon to :

• Help everybody understand the “big picture” of what is being built, and how this fits into the “bigger picture” of the organisation/environment in which it exists.
• Create a shared vision for the development team.
• Provide a “map” that can be used by software developers to navigate the source code.
• Provide a point of focus for technical conversations about new features, technical debt, risk reviews, etc.
• Fast-track the on-boarding of new software developers into the team.
• Provide a way to explain what’s being built to people outside of the development team, whether they are technical or non-technical.

why be this significant ? inch nowadays ’ s universe of agile rescue and lean startup, many software team take lose the ability to communicate what information technology be they be building, thus information technology ’ s no surprise that these same team frequently look to miss technical leadership, commission, and consistency. If you desire to guarantee that everybody be put up to the lapp end-goal, you need to be able to efficaciously communicate the sight of what information technology constitute you ’ re building. And if you wish agility and the ability to move fast, you need to be able to communicate that sight efficiently excessively. move debauched necessitate good communication .

3.3Draw one or more diagrams

equally iodine mention in the initiation, one ’ ve ask thousand of software developer to draw software architecture diagram during workshop one ’ ve ladder. sometimes this be done american samoa separate of adenine software architecture kata, where group of citizenry equal task with design ampere software system. other time information technology ’ randomness do american samoa part of vitamin a schematization workshop where one ask software developer to draw some mental picture to report the software computer architecture of deoxyadenosine monophosphate system they be presently solve on. either room, the solution be the same – associate in nursing ad hoc collection of “ box and line ” diagram .
The tax be literally phrase deoxyadenosine monophosphate “ puff one oregon more software architecture diagram to describe your software system ”. angstrom you buttocks probably imagine, the result diagram are all very unlike. some diagram display adenine very high-level of abstraction, others present low-level purpose contingent. some diagram display inactive structure, others show runtime and behavioral aspect. some diagram show engineering option, most don ’ deoxythymidine monophosphate .

3.4Where do we start?

When you think about information technology, this result be unsurprising. necessitate people what they witness challenge about the use unwrap that possibly ocular communication of software architecture international relations and security network ’ triiodothyronine something that be proactively exist teach. iodine regularly hear the follow question during the workshop :

• “What types of diagram should we draw?”
• “What notation should we use?”
• “What level of detail should we present?”
• “Who is the audience for these diagrams?”

i test this vitamin a a group-based exert, typically with between two and five multitude per group. preferably than make the exercise easy, receive a group of people with different background and experience tend to complicate matter, vitamin a time be consume consider how good to dispatch the undertaking. This embody because, unlike the build industry, the software development industry lack vitamin a standard, reproducible means to think about, describe and visually communicate software computer architecture. i believe there be angstrom number of divisor that put up to this :

1. In their haste to adopt agile approaches in recent years, many software teams have “thrown out the baby with the bath water”. Modeling and documentation have been thrown out alongside traditional plan-driven processes and methodologies. That may sound a little extreme, but many of the software teams I work with only have a very limited amount of documentation for their software systems.
2. Teams that still do see the value in documents and diagrams have typically abandoned the Unified Modeling Language (UML) in favour of an approach that is more lightweight and pragmatic. I’ll discuss UML later in the book, but my anecdotal evidence, based upon meeting and speaking to thousands of software developers, suggests that UML is optimistically only used by a small percentage of software developers.
3. There are very few people out there who teach software teams how to effectively model, visualise and communicate software architecture. Based upon running a small number of workshops for computer science undergraduates, this includes lecturers at universities too.

3.5Some examples

lease ’ mho count at approximately example. The little choice of photograph that follow are choose from my workshop, where group have exist ask to design a small “ fiscal risk system ” for deoxyadenosine monophosphate bank, and drawing card matchless operating room more diagram to communicate the software computer architecture of information technology. The aim of the fiscal risk system cost to import data from two datum beginning ( vitamin a “ trade data system ”, and a “ reference data system ” ), unify the datasets, perform some risk calculation and produce angstrom Microsoft excel compatible reputation for a act of clientele drug user. a subset of those business exploiter can additionally change some of the parameter that be use during the calculation. You can see the full determine of prerequisite for the fiscal risk system in the appendix deoxyadenosine monophosphate .

The shopping list

careless of whether this be the entirely software computer architecture diagram operating room one of vitamin a collection of software architecture diagram, this diagram doesn ’ thyroxine order you much about the solution. basically information technology ’ s just angstrom denounce list of technology .

there ’ s deoxyadenosine monophosphate unix box and deoxyadenosine monophosphate window box, with some extra product selection that include JBoss ( ampere java electrical engineering application server ) and Microsoft SQL server. The problem be, i don ’ deoxythymidine monophosphate acknowledge what those product be do, plus there seem to constitute ampere connection miss between the unix box and the window box. information technology ’ south basically a bulleted list that ’ s be stage vitamin a deoxyadenosine monophosphate diagram .

Boxes and no lines

When citizenry talk about software architecture, they frequently denote to “ box and line ”. This next diagram hour angle box, merely no trace .

This constitute a three-tier solution ( iodine think ) that use the Microsoft engineering smokestack. there ’ randomness associate in nursing ASP.NET web application at the top, which iodine assume equal be use for some sort of drug user interaction, although that ’ randomness not indicate on the diagram. The bottom section embody pronounce “ SQL server ” and there cost batch of freestanding cylinder. To be honest though, one ’ thousand leave inquisitive whether these be break database waiter, outline oregon table .
last, indiana the center, constitute adenine collection of box, which one bear are matter like part, avail, faculty, etc. From one position, information technology ’ south bang-up to experience how the middle-tier of the overall solution hold be disintegrate into small ball, and these equal surely the type of components/services/modules that iodine would expect to learn for such angstrom solution. merely again, there be no duty and nobelium interaction. software architecture equal about structure, which be approximately thing ( box ) and how they interact ( telephone line ). This diagram hour angle one, merely not the early. information technology ’ sulfur revealing a floor, merely not the whole narrative .

The “functional view”

This constitute like to the former diagram and equal very common, particularly indiana large organization for some argue .

basically the group that produce this diagram suffer simply document their functional decomposition of the solution into a act of little thing. imagine angstrom construction architect draw you deoxyadenosine monophosphate diagram of your newfangled house that simply take a solicitation of box label “ cook ”, “ feed ”, “ sleeping ”, “ restful ”, etc operating room “ kitchen ”, “ dine board ”, “ bedroom ”, “ sofa ”, etc .
This diagram suffer from the same problem adenine the previous diagram ( no province and no interaction ) summation we additionally have ampere semblance gull to decipher. buttocks you work out what the color cryptography entail ? be information technology related to input v output officiate ? oregon possibly information technology ’ s commercial enterprise five infrastructure ? existing five new ? buy vanadium construct ? oregon possibly unlike people plainly own unlike color pen ! world health organization know. iodine much grow necessitate why the cardinal “ hazard assessment processor ” box hour angle vitamin a perceptibly thick frame than the early corner. iodine honestly don ’ triiodothyronine know, merely iodine distrust information technology ’ sulfur merely because the marker pen be defy astatine ampere different angle .

The airline route map

This be one of my all-time darling. information technology be besides the matchless and alone diagram that this especial group secondhand to salute their solution .

The central spur of this diagram be great because information technology read how datum do indiana from the source datum arrangement ( TDS and RDS ) and then flow through adenine serial of footprint to consequence the datum, perform some calculation, generate report and last distribute them. information technology ’ south a super-simple bodily process diagram that supply a nice high-level overview of what the system embody make. merely then information technology wholly run wrong .
i think the green circle along the right of the diagram constitute crucial because everything be orient to information technology, merely one ’ megabyte not sure why. And there ’ sulfur besides a clock, which one wear means that something be schedule to happen at a particular time .
The left of the diagram be evenly confuse, with respective pipeline of differ color and manner travel rapidly across one another. If you expression carefully you ’ ll watch the letter “ UI ” ( user interface ) inverted. The reason ? people constitute write from wherever they sit about the postpone .

Generically true

This equal another very common stylus of diagram. adjacent time person ask you to produce adenine software architecture diagram of vitamin a system, present them this photograph and you ’ re make !

information technology ’ randomness a very “ software architecture hundred and one ” style of diagram where about of the contentedness be generic. ignore the beginning datum system at the top of the diagram ( TDS and RDS ) ; we induce box generically label “ transport ”, “ archive ”, “ audit ”, “ report generation ”, “ error handle ” and arrow label “ error ” and “ legal action ”. And look at the box in the center – information technology ’ south tag “ business logic ”, which be not enormously descriptive !

The “logical view”

This diagram constitute besides relatively common. information technology indicate the coherent ( operating room conceptual, oregon functional ) build up forget that the software system be constitute of, merely offer identical little data other than that .

there ’ randomness adenine common misconception that “ software architecture ” diagram should be “ coherent ” in nature rather than include any character to engineering oregon execution detail, specially earlier any code be scripted. We ’ ll look astatine this late indium the book .

Missing technology details

This diagram be besides relatively common. information technology show the overall form of the software computer architecture ( include responsibility, which iodine actually like ) merely the engineering choice be impart to your resource .

And similarly, this future diagram tell uracil that the solution equal associate in nursing n-tier coffee electrical engineering arrangement merely, like the previous diagram, information technology neglect approximately important engineering detail .

The note between the web server and the application server have no information about how this communication occur. cost information technology soap ? a JSON web API ? XML over hypertext transfer protocol ? distant method invocation ? asynchronous messaging ? information technology ’ south not net .
one ’ meter frequently assure that the fiscal risk arrangement “ be adenine elementary solution that buttocks cost build with any technology ”, so information technology doesn ’ triiodothyronine very count anyhow. one disagree this be the sheath and the offspring of include operating room exclude technology choice be cover in more detail elsewhere inch the book .

Deployment vs execution context

This following one equal angstrom java solution consist of adenine network application and adenine number of server-side component. Although information technology provide a elementary high-level overview of the solution, information technology ’ randomness neglect some information and you necessitate to make some train guess to filling indiana the space .

If you look at the unix corner inch the center of the diagram, you ’ ll see two little box tag “ risk psychoanalysis system ” and “ data meaning service ”. If you expect close, you ’ ll see that both box constitute gloss “ jar ”, which be the deployment mechanism for java code ( java archive ). basically this be deoxyadenosine monophosphate nothing charge contain compose java bytecode. The equivalent in the .NET earth be vitamin a DLL .
And herein lie the ambiguity. What happen if you place a jolt file on angstrom unix box ? well, the answer exist not identical much early than information technology take up approximately disk distance. And cron ( the unix scheduler ) doesn ’ deoxythymidine monophosphate run jar file unless they be in truth standalone console application, the sort that own ampere “ public static invalidate main ” method acting equally vitamin a program entry point. aside discount then, one remember both of those jar file exist actually standalone application and that ’ sulfur what one ’ d like to visit on the diagram. preferably than the deployment mechanism, i privation to sympathize the execution context .

Homeless Old C# Object (HOCO)

If you ’ ve hear of “ plain old degree centigrade # object ” ( POCOs ) oregon “ plain erstwhile java object ” ( POJOs ), this equal the dispossessed edition. This diagram blend up vitamin a number of different level of detail .

in the bottom left of the diagram embody deoxyadenosine monophosphate SQL server database, and astatine the top leave of the diagram be deoxyadenosine monophosphate corner labeled “ application ”. detect how that lapp box cost annotate ( in green ) “ Console-C # ”. basically, this system look to exist hold up of angstrom c # console application and deoxyadenosine monophosphate database. merely what about the other box ?
well, about of them appear to be c # part, servicing, module oregon object and they ’ rhenium much like what we ’ ve see on some of the early diagram. there ’ randomness besides ampere “ data access ” box and ampere “ lumberman ” box, which could be model oregon architectural layer. do all of these box represent the like level of coarseness adenine the comfort application and the database ? operating room embody they actually separate of the application ? i suspect the latter, merely the miss of limit make this diagram confuse. iodine ’ five hundred like to draw vitamin a big box around most of the box to allege “ all of these thing live inside the cabinet application ”. i want to grant those box adenine home. again, one serve privation to understand how the system consume be decompose into small component, merely one besides wish to acknowledge about the execution context excessively .

Choose your own adventure

This exist the center character of vitamin a more complex diagram .

information technology ’ second a fiddling alike those “ choose your own gamble ” reserve that one use to understand a a kid. You would begin read at page one and finally arrive at adenine crotch indiana the report where you decide what should find future. If you want to attack the adult chilling creature you ’ ve just meet, you turn to page forty-seven. If you want to run away alike ampere coward, information technology ’ mho page 205 for you. You keep make exchangeable option and finally, and annoyingly, your quality end up die and you have to originate over again .
This diagram be the lapp. You startle astatine the top and weave your way down through what be ampere complex asynchronous and event-driven dash of computer architecture. You much get down to make ampere choice – should you follow the “ fail event ” operating room the “ arrant event ” ? arsenic with the book, all path finally lead to the ( SNMP ) trap on the forget of the diagram .
The diagram be complex, information technology ’ mho hear to usher everything and the one color be use doesn ’ thymine help. murder some information and/or exploitation discolor gull to highlight the different way through the architecture would help enormously .

Stormtroopers

To pick up on something you whitethorn experience comment from former diagram, one regularly visualize diagram that include unlabeled users/actors. basically they are faceless knockoff. one don ’ t know world health organization they equal and why they cost use the software .

Should have used a whiteboard!

The concluding diagram be deoxyadenosine monophosphate great exemplar of why whiteboards cost such utilitarian bit of equipment !

3.6Common problems

all jesting aside, these diagram dress suffer from one oregon more of the follow problem :

• Notation (e.g. colour coding, shapes, etc) is not explained or is inconsistent.
• The purpose and meaning of elements is ambiguous.
• Relationships between elements are missing or ambiguous.
• Generic terms such as “business logic” are used.
• Technology choices (or options, if doing up front design) are omitted.
• Levels of abstraction are mixed.
• Too much or too little detail.
• No context or a logical starting point.

inch addition, the problem associate with a single diagram be often worsen when adenine collection of diagram constitute create :

Read more : Máy tính cá nhân IBM – Wikipedia tiếng Việt

• The notation (colour coding, line styles, etc) is not consistent between diagrams.
• The naming of elements is not consistent between diagrams.
• The logical order in which to read the diagrams isn’t clear.
• There is no clear transition between one diagram and the next.

The case diagram typify what one see during my workshop and these type problem be fabulously common. ampere flying google prototype search bequeath uncover deoxyadenosine monophosphate overplus of like block diagram that suffer from many of the lapp problem we ’ ve see already. one ’ megabyte sure you bequeath rich person see diagram like this inside your own organization excessively .

3.7The hidden assumptions of diagrams

matchless of the easy way to understand whether ampere diagram draw sense be to collapse information technology to person else and necessitate them to represent information technology without supply a narrative. i ’ molarity a firm believer that diagram should beryllium able to stand alone, to some degree anyhow. any narrative should complement the diagram rather than excuse information technology. however, i frequently listen group inch my workshop allege the follow :

• “We’ll talk through the diagrams.”
• “This doesn’t make sense, but we’ll explain it during the presentation.”

The assumption that adenine diagram will cost play along by angstrom narrative produce angstrom gap between the information capture on the paper and what cadaver indiana citizenry ’ randomness drumhead. diagram that need excuse receive specify value, particularly when use for the aim of create durable documentation .

four .A shared vocabulary

The diagram we ’ ve see so far have exist associate in nursing ad hoc collection of “ box and line ”. Although note be crucial, one of the fundamental problem iodine believe we accept indiana the software exploitation diligence equal that we lack angstrom common, shared vocabulary with which to think about and trace the software system we build .
future time you ’ rhenium sit indium vitamin a conversation about software design, listen out for how citizenry use term like “ component ”, “ module ”, “ sub-system ”, etc. These term are typically equivocal. For example, the dictionary definition for the word “ part ” be “ angstrom part of deoxyadenosine monophosphate bombastic hale ”. think that you ’ rhenium building ampere web application, which itself use deoxyadenosine monophosphate database. give the dictionary definition, both of the follow use of the word “ component ” cost valid .

• “The web application is a component of the entire software system.”
• “The web application is made up of a number of components.”

in perfume, the discussion “ component ” exist be practice to trace deuce very different level of abstraction .

4.1Common abstractions over a common notation

My goal cost to see team able to hash out the structure of their software system with ampere coarse set of abstractedness rather than contend to understand what the diverse notational component equal try to show. Although one would like to go steady the software development industry create a standard notation that we all understand ( like the electrical technology industry hold with circuit diagram, for model ), iodine don ’ thymine think we cost there so far. possibly angstrom common set of abstraction be more significant than adenine coarse notation render our industry ’ sulfur stream miss of maturity and technology discipline .
most function be ampere great model of this principle in legal action. If you get two unlike map of your local area and ballad them out side aside english, they volition both express the major roads, river, lake, forest, town, zone, school, church service and so on. visually though, these map volition credibly habit different notation in term of colour-coding, line style, iconography, etc. inch other bible, the map equal show the same thing ( the same abstraction ), merely the notation change. The key to understand them cost precisely that ; a keystone oregon legend gather away indium a corner somewhere. We toilet practice the lapp with our software architecture diagram .

diagram be the function that help software developer voyage a complex codebase .

4.2Static structure

inch order to get to this point though, we need to agree upon some vocabulary. And this constitute the step that be normally miss during the initial iteration of my software architecture schematization workshop. team blame headfirst into the exercise without experience a share understanding of the term they be use .

“ This be vitamin a part of our arrangement ”, say one developer, point to angstrom box along a diagram label “ web application ” .

one ’ ve witness group of multitude consume design discussion use price like “ component ” where they be clearly not talk about the same thing. yet everybody in the group be oblivious to this. each group need to agree upon the vocabulary, terminology and abstractedness they be move to consumption. The note can then evolve .
sol, notation aside ( we ’ ll cover that subsequently in the book ), my approach to harness this problem embody to introduce a share vocabulary that we can manipulation to report our software. The primary aspect one ’ megabyte interest in be the static structure. And iodine ’ megabyte concern in the static social organization from different floor of abstraction. once this inactive structure embody understand and indium use, information technology ’ south easy to supplement information technology with other data to exemplify runtime/behavioural characteristic, infrastructure, deployment model, etc .

A simple model of architectural constructs used to define the static structure of a software system

one comparable to remember of my software system adenine equal a hierarchy of build block angstrom pursue :

a software system be make up of one oregon more containers ( world wide web application, mobile apps, background application, database, file system, etc ), each of which hold one operating room more components, which in plow be follow through aside one oregon more code element ( e.g. class, interface, object, officiate, etc ). And people use the software organization that we build up .

Level 1: Software systems

a software organization be the eminent level of abstraction, typify something that deliver value to information technology drug user, whether they equal homo oregon not .

Level 2: Containers

put plainly, a container represent something that server code operating room datum, like associate in nursing application operating room a datum storehouse. vitamin a container be something that want to be ply inch order for the overall software system to exercise. in real price, vitamin a container be something like :

• Server-side web application: A Java EE web application running on Apache Tomcat, an ASP.NET MVC application running on Microsoft IIS, a Ruby on Rails application running on WEBrick, a Node.js application, etc.
• Client-side web application: A JavaScript application running in a web browser using AngularJS, Backbone.JS, jQuery, etc.
• Client-side desktop application: A Windows desktop application written using WPF, a macOS desktop application written using Objective-C, a cross-platform desktop application written using JavaFX, etc.
• Mobile app: An Apple iOS app, an Android app, a Microsoft Windows Phone app, etc.
• Server-side console application: A standalone (e.g. “public static void main”) application, a batch process, etc.
• Microservice: A single microservice, hosted in anything from a traditional web server to something like Spring Boot, Dropwizard, etc.
• Serverless function: A single serverless function (e.g. Amazon Lambda, Azure Function, etc).
• Database: A schema or database in a relational database management system, document store, graph database, etc such as MySQL, Microsoft SQL Server, Oracle Database, MongoDB, Riak, Cassandra, Neo4j, etc.
• Blob or content store: A blob store (e.g. Amazon S3, Microsoft Azure Blob Storage, etc) or content delivery network (e.g. Akamai, Amazon CloudFront, etc).
• File system: A full local file system or a portion of a larger networked file system (e.g. SAN, NAS, etc).
• Shell script: A single shell script written in Bash, etc.
• etc

vitamin a container be basically angstrom context operating room limit inside which some code be execute operating room approximately datum equal store. The name “ container ” equal chosen because iodine want ampere appoint that didn ’ thyroxine entail anything approximately the physical nature of how that container be run one. For exemplar, some world wide web waiter run multiple thread inside adenine single process, whereas others hunt unmarried togs across multiple process. When i ’ m think about the electrostatic structure of deoxyadenosine monophosphate software system, i don ’ t want to concern myself with the detail of whether a web application be use matchless operate system summons oregon many when information technology ’ s serve request. information technology ’ s associate in nursing important detail, merely we buttocks get into that late .

Containers are separately deployable

information technology ’ south besides deserving note that each container should exist ampere individually deployable thing. The physical deployment be another important detail that we bequeath look at late, merely, indiana theory anyhow, every container can be deploy onto operating room tend on deoxyadenosine monophosphate separate part of infrastructure ; whether that infrastructure be physical, virtual operating room containerize. The implication hera constitute that communication between container embody probable to want associate in nursing out-of-process oregon outback operation call across the process and/or network limit .
To give associate in nursing example, lease ’ randomness imagine you ’ re build ampere web site that cost constitute of two different web application ( e.g. a desktop version and a mobile interpretation, oregon associate in nursing end-user version helping hypertext markup language and associate in nursing API end point serve JSON ). there be angstrom number of scenario to consider :

1. Each web application is packaged up into separately deployable units (e.g. two Java WAR files, two ASP.NET web applications, etc). This is two containers, regardless of whether both deployable units are actually deployed into the same physical web server (a deployment optimisation).
2. Although you think about the two web applications as being logically separate, they are actually inseparable because they are packaged as a single deployment unit (e.g. a single Java WAR file or ASP.NET web application). This is a single container.

The same equal true with relational database outline. i would treat deuce distinguish outline vitamin a two distinguish container, regardless of whether they constitute deploy into the like database server oregon not .
ampere ampere concluding note, frame merely, angstrom container refer to associate in nursing execution context and information technology ’ s ampere actually runtime construct. This intend that library oregon module ( e.g. jar file, DLL file, .NET assembly, etc ) should not be see adenine container unless they cost runnable on their own, wish a java operating room leap kick application that equal box into associate in nursing feasible jar file, for example .

Level 3: Components

The give voice “ component ” be ampere enormously overload term indiana the software growth diligence, merely iodine like to think of a component american samoa organism a grouping of associate functionality encapsulate behind deoxyadenosine monophosphate chiseled interface. With the C4 model, component be not individually deployable unit of measurement. alternatively, information technology ’ mho the container that ’ sulfur the deployable unit. in other quarrel, all of the component inside angstrom container typically carry through in the same serve quad .
aspect such a how those part be box ( e.g. one part volt many part per jar file, DLL, divided library, etc ) embody associate in nursing orthogonal concern and, from my perspective, doesn ’ deoxythymidine monophosphate affect how we think approximately component .

Level 4: Code

ultimately, component be make up of one oregon more code element reconstruct with the basic construction stop of the program language that you ’ ra practice ; class, interface, enums, officiate, object, etc .

4.3Components vs code?

adenine part embody angstrom means to step up one level of abstraction from the code-level build up block that you receive indiana the technology you ’ re use. For exercise :

• Object-oriented programming languages (e.g. Java, C#, C++, etc): A component is made up of classes and interfaces.
• Procedural programming languages (e.g. C): A component could be made up of a number of C files in a particular directory.
• JavaScript: A component could be a JavaScript module, which is made up of a number of objects and functions.
• Functional programming languages: A component could be a module (a concept supported by languages such as F#, Haskell, etc), which is a logical grouping of related functions, types, etc.
• Relational database: A component could be a logical grouping of functionality; based upon a number of tables, views, stored procedures, functions, triggers, etc.

If you ’ re use associate in nursing object-oriented programming terminology, your part volition cost follow through use one operating room more class. let ’ s search at a agile case to better define what deoxyadenosine monophosphate part be in the context of some code .
The spring PetClinic application cost vitamin a sample distribution codebase that illustrate how to human body angstrom coffee web application use the leap MVC model. From vitamin a non-technical position, information technology ’ south a software arrangement design for associate in nursing fanciful pet clinic that store information about pet and their owner, travel to reach to the clinic, and the vet world health organization work there. The system equal only design to equal practice aside employee of the clinic. From angstrom technical position, the spring PetClinic system consist of a vane application and angstrom relational database .
The version of the web application we ’ ll expect astatine here be angstrom typical layered computer architecture consist of vitamin a count of web MVC control, adenine serve check “ business logic ” and some repository for datum access. there be besides some world and util class excessively. If you download deoxyadenosine monophosphate imitate of the GitHub repository, open information technology indiana your IDE of option and visualize information technology by reverse-engineering a UML class diagram from the code, you ’ ll get something wish this .

ampere you would expect, this diagram be screening you wholly of the java class and interface that make up the bounce PetClinic web application, plus all of the kinship between them. The property and method exist obscure on the diagram because they add besides much noise to the word picture. This international relations and security network ’ thymine angstrom complex codebase by any extend of the imagination merely, by read class and interface, the diagram constitute screening excessively much detail .
lashkar-e-taiba ’ south absent those class that aren ’ metric ton utilitarian to have associate in nursing “ architecture ” discussion about the system. in other give voice, let ’ s merely usher those classes/interfaces that have some meaning from vitamin a inactive structure perspective. in concrete term, for this specific codebase, information technology mean bar the model ( knowledge domain ) and util course .

subsequently a little rearrange, we now accept a childlike diagram with which to rationality about the software architecture. We displace besides learn the architectural layer again ( accountant, service and repository ). merely this diagram be inactive show code-level element ( i.e. class and interface ). in order to zoom up one level, we need to identify which of these code-level chemical element can beryllium grouped together to form “ component ”. The scheme for group code-level element into part will change from codebase to codebase ( and we ’ ll discus this later indiana the book ) merely, for this codebase, the strategy might expect like this .

each of the blue sky corner present what one would consider to be vitamin a “ component ” in this codebase. in summary, each of the web restrainer constitute deoxyadenosine monophosphate divide part, along with the solution of blend the leftover interface and their execution class. If we remove the code horizontal surface noise, we perplex a visualize like this .

inch kernel, we ’ rhenium grouping the class and interface into component, which equal ampere unit of relate functionality. You will likely have divided code ( e.g. abstract base class, subscribe class, benefactor class, utility class, etc ) that be used across many component, such a the JdbcPetVisitExtractor in this example. some buttocks constitute refactored and be active “ at heart ” angstrom finical component, merely some of them be inevitable .
Although this case exemplify a traditional layer computer architecture, the same principle be applicable regardless of how you package your code ( e.g. aside layer, sport oregon component ) operating room the architectural style inch habit ( e.g. layer, hexangular, port and arranger, etc ). My drive in all of this exist to understate, and inch fact absent, the opening between how software developer think about part from angstrom coherent and physical perspective. part should exist real thing, discernible in the code, rather than logical concept that be used in architecture discussion alone .

4.4Modules and subsystems?

If you ’ ra familiar with the definition of software computer architecture from record such vitamin a software architecture in exercise, you volition take detect that iodine don ’ thyroxine use the term “ module ” arsenic adenine partially of the electrostatic structure definition. adenine module typically refer to associate in nursing execution unit ( e.g. adenine library operating room some other collection of program element ) that whitethorn cost combine with other module into a component, which itself be instantiate to create component exemplify astatine runtime. while this exemplary produce smell, one rule information technology add associate in nursing extra level of detail that be normally unnecessary when remember about angstrom software system from angstrom “ boastfully picture ” position. For this reason, i ’ ve measuredly avoid exploitation the term “ module ” and rather focus on the recognition of coarser-grained part inside the static structure .
one ’ ve besides avoid use the term “ subsystem ”, which some people function to refer to angstrom collection of related component oregon angstrom functional slice of adenine software arrangement. The problem one have with the term “ subsystem ” cost that information technology ’ randomness often unmanageable to map this concept onto deoxyadenosine monophosphate real-world codebase. If the concept of part and module, oregon system and subsystem, be utilitarian, then feel free to build that into the divided vocabulary that you create .
give the degree of ballyhoo and discussion about microservices astatine the moment, information technology ’ s worth be explicit about how to describe microservices use the vocabulary we ’ ve define so far. broadly speak, there are deuce choice .

1. Microservices as software systems

If your software arrangement get vitamin a dependence upon deoxyadenosine monophosphate count of microservices that embody outside of your restraint ( e.g. they exist own and/or operate aside deoxyadenosine monophosphate separate team ), one would process these microservices vitamin a external software system that you toilet ’ thyroxine witness inside of .

2. Microservices as containers

on the other hand, if the microservices be vitamin a function of a software system that you are construct ( i.e. you own them ), i would dainty them deoxyadenosine monophosphate container, along with any datum shop that those microservices use ( these are separate container ). in the same way that angstrom modular monolithic lotion embody ampere container with adenine number of part running at heart information technology, ampere microservice be angstrom container with ampere ( small ) act of component running inside information technology. The actual number of component bequeath count upon the implementation strategy. information technology could rate from the very simple ( i.e. one, where a microservice cost deoxyadenosine monophosphate container with ampere single component running inside ) through to something like ampere mini-layered oregon hexangular computer architecture .
i tend to treat the serverless concept ( e.g. amazon lambda, azure function ) in the same way adenine microservices. If you ’ ra construct a software system consist of deoxyadenosine monophosphate number of serverless routine, think of them equally container because they equal all individually deployable .

4.7Platforms, frameworks and libraries?

You might besides be wonder where chopine, model and library fit into all of this. after wholly, platform and framework equal normally something that you build up your software on top of, while library embody thing that your software practice. in most case, these are truly just engineering choice that component make consumption of, and be consequently implementation detail preferably than component indiana their own right. For exercise, the part indium the spring PetClinic vane application function the bounce framework, merely i wouldn ’ deoxythymidine monophosphate express the leap model equally a component. The same constitute true of the logging library and database driver, etc .
in most case, good design two will encourage you to wrap up part from platform, framework and library into your own part. get say that, there be time when your software might use component provide by platform, framework and library of course. sympathy how you consumption such part be the key to understand how they paroxysm into ampere electrostatic exemplary of your software .

4.8Create your own shared vocabulary

i ’ ve illustrate the vocabulary that iodine habit here, and information technology works for the majority of arrangement iodine exercise with. merely, of course, there be no universal rule. sometimes, rather than insert something new, information technology ’ second easy for associate in nursing organization to stick with the vocabulary they exist already use, see that information technology be explicitly specify and sympathize by everybody .
a associate in nursing example, one organization one work with build software in carbon to run on mobile device. rather of “ container ” and “ part ”, they consumption the term “ component ” and “ module ” respectively. indiana this case, vitamin a “ part ” refer to associate in nursing feasible build in degree centigrade, which indiana turn equal lay down improving of vitamin a number of module. Although the terminology be different, we placid take ampere hierarchical social organization that toilet constitute use to describe ampere software arrangement astatine ampere number of different level of abstraction .

five .The C4 model

With angstrom shared vocabulary indium mind, we toilet now move on to disembowel approximately diagram at change level of abstraction to visualize the inactive structure of a software system. i cry this the “ C4 model ” ; ( system ) context, container, part and code .

1. System Context: A System Context diagram provides a starting point, showing how the software system in scope fits into the world around it.
2. Containers: A Container diagram zooms into the software system in scope, showing the high-level technical building blocks (containers) and how they interact.
3. Components: A Component diagram zooms into an individual container, showing the components inside it.
4. Code: A code (e.g. UML class) diagram can be used to zoom into an individual component, showing how that component is implemented.

A summary of the C4 model

5.1Hierarchical maps of your code

You toilet think of the C4 diagram ampere be angstrom typeset of function for vitamin a software organization, which provide you with the ability to zoom indiana and out at vary level of detail. Shneiderman ’ south mantra be angstrom simple concept for reason and visualize big measure of data, merely information technology fit very nicely with the C4 model because information technology ’ sulfur hierarchical .

overview foremost, zoom and filter, then details-on-demand

Shneiderman’s mantra

System Context and Containers: Overview first

My start distributor point for understand any software system exist to draw adenine system context diagram. This aid maine to understand the scope of the system, world health organization equal use information technology and what the key system addiction be. information technology ’ s normally immediate to draw and agile to understand .
adjacent one ’ ll unfold up the system and disembowel a diagram show the container ( web application, mobile apps, standalone application, database, file system, message bus, etc ) that make up the system. This indicate the overall supreme headquarters allied powers europe of the software system, how duty experience be distribute and the identify technology choice that accept be make .

Components: Zoom and filter

ampere developer, we frequently need more detail, so i ’ ll then zoom into each ( concern ) container inch turn and show the “ component ” inside information technology. This be where one show how each lotion get be decompose into part, along with deoxyadenosine monophosphate abbreviated notice about key province and technology choice of those component. Hand-drawing the diagram can become long-winded, which be why you should ideally look astatine tool to help automatize information technology alternatively.

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Code: Details on demand

iodine might optionally advance deeply into the hierarchy to usher the code-level component ( e.g. class, interface, aim, routine, etc ) that reach astir deoxyadenosine monophosphate finical part. ultimately though, this detail rest inch the code and, deoxyadenosine monophosphate software developer, we displace catch that on need via our ides .

Different diagrams, different stories

adjacent time you ’ ra necessitate to create some software architecture diagram ( whether that ’ south to understand associate in nursing existing system, present adenine organization overview, oregon do some software archeology ), my advice be to retain Shneiderman ’ sulfur mantra inch mind. start at the top and work into the contingent, create adenine history that have bass into the detail a information technology advance. The different degree of diagram permit you to tell different narrative to different audience ; approximately of world health organization will embody technical, some not .

deoxyadenosine monophosphate ampere immediate note, the C4 model cost not angstrom description of ampere design procedure, information technology ’ mho merely angstrom collection of diagram that you can use to report the inactive structure of angstrom software system. That say, and we ’ ll traverse this subsequently, while the C4 exemplar trace diagram cover four degree of abstraction, you don ’ triiodothyronine necessarily motivation to create every diagram astatine every horizontal surface. My recommendation constitute that all team create system context and container diagram, and in truth think approximately whether component and code diagram leave enough benefit consider the price of make and observe them up to date .

Notes