Software Design vs Software Architecture

Question

Could someone explain the difference between Software Design and Software Architecture   More specifically  if you tell someone to present you the  design  - what would you expect them to present  Same goes for  architecture     My current understanding is      Design  UML diagram flow chart simple wireframes  for UI  for a specific module part of the system Architecture  component diagram  showing how the different modules of the system communicates with each other and other systems   what language is to be used  patterns        Correct me if I m wrong  I have referred Wikipedia has articles on http   en wikipedia org wiki Software design and http   en wikipedia org wiki Software architecture  but I m not sure if I have understood them correctly

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I think we should use the following rule to determine when we talk about Design vs Architecture: If the elements of a software picture you created can be mapped one to one to a programming language syntactical construction, then is Design, if not is Architecture.

So, for example, if you are seeing a class diagram or a sequence diagram, you are able to map a class and their relationships to an Object Oriented Programming language using the Class syntactical construction. This is clearly Design. In addition, this might bring to the table that this discussion has a relation with the programming language you will use to implement a software system. If you use Java, the previous example applies, as Java is an Object Oriented Programming Language. If you come up with a diagram that shows packages and its dependencies, that is Design too. You can map the element (a package in this case) to a Java syntactical construction.

Now, suppose your Java application is divided in modules, and each module is a set of packages (represented as a jar file deployment unit), and you are presented with a diagram containing modules and its dependencies, then, that is Architecture. There isn’t a way in Java (at least not until Java 7) to map a module (a set of packages) to a syntactical construction. You might also notice that this diagram represents a step higher in the level of abstraction of your software model. Any diagram above (coarse grained than) a package diagram, represents an Architectural view when developing in the Java programming language. On the other hand, if you are developing in Modula-2, then, a module diagram represents a Design.

(A fragment from http://www.copypasteisforword.com/notes/software-architecture-vs-software-design)

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In My opinion   Architecture is nothing but a vision  gathering requirements and framing the building blocks in right way  where as design   to construct particular block there are 100 solutions may be available  but to meet exact requirement we need to choose the right method   so choosing right method or algorithm is nothing but design

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I really liked this paper for a rule of thumb on separating architecture from design   http   www eden-study org articles 2006 abstraction-classes-sw-design ieesw pdf  It s called the Intension Locality hypothesis  Statements on the nature of the software that are non-local and intensional are architectural  Statements that are local and intensional are design

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In some descriptions of the SDLC  Software Development Life Cycle  they are interchangeable  but the consesus is that they are distinct   They are at the same time   different  1  stages   2  areas of responsibility  and  3  levels of decision-making     Architecture is the bigger picture  the choice of frameworks  languages  scope  goals  and high-level methodologies  Rational  waterfall  agile  etc    Design is the smaller picture   the plan for how code will be organized  how the contracts between different parts of the system will look  the ongoing implementation of the project s methodologies and goals   Specification are written during this stage    These two stages will seem to blend together for different reasons      Smaller projects often don t have enough scope to separate out planning into these to stages  A project might be a part of a larger project  and hence parts of both stages are already decided    There are already existing databases  conventions  standards  protocols  frameworks  reusable code  etc   Newer ways of thinking about the SDLC  see Agile methodologies  somewhat rearrange this traditional approach   Design  architecture to a lesser extent  takes place throughout the SDLC on purpose   There are often more iterations where the whole process happens over and over  Software development is complicated and difficult to plan anyway  but clients managers salespeople usually make it harder by changing goals and requirements mid-stream   Design and even architectural decisions must bemade later in the project whether that is the plan or not    Even if the stages or areas of responsibility blend together and happen all over the place  it is always good to know what level of decision-making is happening    We could go on forever with this   I m trying to keep it a summary    I ll end with   Even if it seems your project has no formal architectural or design stage AOR documentaiton  it IS happening whether anyone is consciously doing it or not   If no one decides to do architecture  then a default one happens that is probably poor   Ditto for design   These concepts are almost more important if there are no formal stages representing them

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I think architecture is about the interfaces to humans and or systems  For insance a web service contract  including protocols and so on  is architecture  How a screen is composed  not colors and such but what fields are there  is architecture   Design is how something is to be built  What frameworks  language  technology etc  This must of course be aligned with enterprise guidelines and restrictions considering platforms  security and so on

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Architecture means the conceptual structure and logical organization of a computer or computer-based system  Design means a plan or drawing produced to show the look and function or workings of a system or an object before it is made   If you are    architecting    a component  you are defining how it behaves in the larger system  If you are    designing    the same component  you are defining how it behaves internally     All architecture is design but NOT all design is architecture   What part is the Design  the How is the concrete implementation and the intersection of What and How is Architecture  Image for differentiating Architecture and Design   There are also design decisions  that are not architecturally significant  i e  does not belongs to the architecture branch of design  For example  some component   s internal design decisions  like- choice of algorithm  selection of data structure etc  Any design decision  which isn   t visible outside of its component boundary is a component   s internal design and is non-architectural  These are the design decisions a system architect would leave on module designer   s discretion or the implementation team as long as their design don   t break the architectural constraints imposed by the system level architecture  The link that gives good analogy

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Also  refer to  http   en wikipedia org wiki 4 2B1 Architectural View Model

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I found this as I was looking for simple distinction between architecture and design myself  What do you think of this way of looking at them      architecture is  what  we re building  design is  how  we re building

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I d say you are right  in my own words   Architecture is the allocation of system requirements to system elements  Four statements about an architecture    It can introduce non-functional requirements like language or patterns  It defines the interaction between components  interfaces  timing  etc  It shall not introduce new functionality   It allocates the  designed  functions that the system is intended to perform to elements     Architecture is an essential engineering step when a complexity of the system is subdivided    Example  Think about your house  you don t need an architect for your kitchen  only one element involved  but the complete building needs some interaction definitions  like doors  and a roof   Design is a informative representation of the  proposed  implementation of the function  It is intended to elicit feedback and to discuss with stakeholders  It might be good practice but is not an essential engineering step    It would be nice to see the kitchen design see before the kitchen is installed but it is not essential for the cooking requirement   If I think about it you can state    architecture is for a public engineers on a more detailed abstraction level design is intended for public on a less detailed abstraction level

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Cliff Notes version   Design  Implementing a solution based on the specifications of the desired product   Architecture  The foundation tools infrastructure components that support your design   This is a pretty broad question that will invoke a lot of responses

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You re right yes  The architecture of a system is its  skeleton   It s the highest level of abstraction of a system  What kind of data storage is present  how do modules interact with each other  what recovery systems are in place  Just like design patterns  there are architectural patterns  MVC  3-tier layered design  etc    Software design is about designing the individual modules   components  What are the responsibilities  functions  of module x  Of class Y  What can it do  and what not  What design patterns can be used   So in short  Software architecture is more about the design of the entire system  while software design emphasizes on module   component   class level

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ARCHITECTURE - An architecture creats the plans layout in various stages of the constructions                as acording to the specifications   DESINER -      A desiner is activity that it fullfil all the essential requirments of the archecture plans with the functional asthetectic  amp  appreance to the layouts

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As others also pointed out  laying out the architecture of a piece of software is actually taking the major design decisions which have overall influence over the software development or execution life-cycle  so simplistically architecture is just high level design    Even if an architecture decision does not affect all components  is thus  local  it must still be globally relevant  i e  it impacts the whole system in some way  otherwise is simply a local design decision   What I d like to point out though  that a more relevant question related to architecture might be Architecture vs Organization as defined by Hennessy  amp  Patterson in Computer Architecture  Based on this we could think about architecture as the data model  input output  state  abstraction of the system and the organization as the typical design decisions taken during the implementation  software development  process

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I like Roy Thomas Fielding s definition and explanation about what is software architecture in his paper  Architectural Styles and the Design of Network-based Software Architectures      A software architecture is an abstraction of the run-time elements of a software system during some phase of its operation  A system may be composed of many levels of abstraction and many phases of operation  each with its own software architecture     He emphasizes  run-time elements  and  levels of abstraction

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Following are  the references that may explain Architecture in more detail and a list of UML diagrams for software architecture   I could not find listing of UML diagrams for software design   Grady Booch UML 2 Diagram use for Architectural Models Classification of UML diagrams Classification of UML diagrams Even after posting this answer  i myself is not clear which diagram is for architecture and which one for design     Grady Booch  in his slide   58  states that Classes  Interfaces and Collaborations are part of Design View and this Design View is one of the View of Architecture

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Architecture is high level  abstract and logical design whereas software design is low level detailed and physical design

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Architecture is more like integrating various functionalities of a System to achive one goal of the System as a whole  while design addresses each functional requirements    For example  take example of MVVM  which is an architectural pattern  For notification functionality  MVVM uses observer Pattern  which in turn is a design pattern

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if somebody constructs a ship  then engine  hull  electric-circuits etc  will be his  architectural elements   For him  engine-construction will be  design work    If he then delegates the construction of the engine to another team  they will create an  engine architecture      So - it depends on the level of abstraction or detail  One persons  architecture might be anothers  design

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Architecture  Structural design work at higher levels of abstraction which realize technically significant requirements into the system  The architecture lays down foundation for further design   Design  The art of filling in what the architecture does not through an iterative process at each layer of abstraction

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long time ago in a faraway place philosophers worried about the distinction between the one and the many   Architecture is about relationship  which requires the many   Architecture has components   Design is about content  which requires the one   Design has properties  qualities  characteristics   We typically think that design is within architecture   Dualistic thinking gives the many as primordial   But architecture is also within design   It s all how we choose to view what is before us - the one or the many

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Software architecture is   concerned with issues   beyond the algorithms and data structures of the computation   Architecture is specifically not about   details of implementations  e g   algorithms and data structures   Architectural design involves a richer collection of abstractions than is typically provided by OOD     object-oriented design    Design is concerned with the modularization and detailed interfaces of the design elements  their algorithms and procedures  and the data types needed to support the architecture and to satisfy the requirements      architecture    is often used as a mere synonym for    design     sometimes preceded with the adjective    high-level      And many people use the term    architectural patterns    as a synonym for    design patterns      Check out this link   Defining the Terms Architecture  Design  and Implementation

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Architecture and design are closely related  the main difference between them is really about which way we face  Architecture faces towards strategy  structure and purpose  towards the abstract  Design faces towards implementation and practice  towards the concrete

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My reminder      We can change the Design without asking someone If we change the Architecture we need to communicate it to someone  team  client  stakeholder

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Yep that sounds right to me  The design is what you re going to do  and architecture is the way in which the bits and pieces of the design will be joined together  It could be language agnostic  but would normally specify the technologies to be used ie LAMP v Windows  Web Service v RPC

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Software architecture is best used at the system level  when you need to project business and functions identify by higher architecture levels into applications   For instance  your business is about  Profit and Loss  for traders  and your main functions involved  portfolio evaluation  and  risk computation    But when a Software Architect will details his solution  he will realize that    portfolio evaluation  can not be just one application  It needs to be refined in manageable projects like    GUI Launcher Dispatcher        because the operations involved are so huge they need to be split between several computers  while still being monitored at all times through a common GUI   a Software design will examine the different applications  their technical relationship and their internal sub-components  It will produce the specifications needed for the last Architecture layer  the  Technical Architecture   to work on  in term of technical framework or transversal components   and for the project teams  more oriented on the implementation of the business functions  to begin their respective projects

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Design  To learn about the modules  what kind of relationships between the modules  functionality of each module  Classes and its member functions  interfaces of each module that communicating with each other   Architecture  Architecture is the whole entire structure of a software system  All the modules  classes and components perform different tasks and will give a unique result   For Example  There is a home which has 5 rooms  There are attach bathrooms as well  Kitchen is also there in the home  So there are different things in the home and these all things have different relationships between each other  So this is all about the  DESIGN   of a home   While when you are looking from outside of a house the whole structure you are looking at is all about the Architecture

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Architecture is design  but not all design is architectural  Therefore  strictly speaking  it would make more sense to try to differentiate between architectural design and non-architectural design  And what is the difference  It depends  Each software architect may have a different answer  ymmv    We develop our heuristics to come up with an answer  such as  class diagrams are architecture and sequence diagrams are design   See DSA book for more   It s common to say that architecture is at a higher abstraction level than design  or architecture is logical and design is physical  But this notion  albeit commonly accepted  is in practice useless  Where do you draw the line between high or low abstraction  between logical and physical  It depends   So  my suggestion is    create a single design document  name this design document the way you want or  better  the way the readers are more accustomed to  Examples   Software Architecture    Software Design Specification    break this document into views and keep in mind you can create a view as a refinement of another view   make the views in the document navigable by adding cross-references or hyperlinks then you ll have higher level views showing broad but shallow overview of the design  and closer-to-implementation views showing narrow but deeper design details  you may want to take a look at an example of multi-view architecture document  here     Having said all that    a  more relevant question we need to ask is  how much design is enough  That is  when should I stop describing the design  in diagrams or prose  and should move on to coding

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Personally  I like this one       The designer is concerned with what happens when a user presses a button  and the architect is concerned with what happens when ten thousand users press a button     SCEA for Java    EE Study Guide by Mark Cade and Humphrey Sheil

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I view architecture as Patrick Karcher does - the big picture  For example  you can provide the architecture to a building  view its structural support  the windows  entries and exits  water drainage  etc  But you have not  designed  the floor layout s  cubicle positions etc   So while you ve architected the building you have not designed the layout of each office  I think the same holds true for software   You could view designing the layout  as  architecting the layout  though

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Pretty subjective but my take   Architecture The overall design of the system including interactions with other systems  hardware requirement  overall component design  and data flow   Design The organization and flow of a component in the overall system  This would also include the component s API for interaction with other components

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There is no definitive answer to this because  software architecture  and  software design  have quite a number of definitions and there isn t a canonical definition for either   A good way of thinking of it is Len Bass  Paul Clements and Rick Kazman s statement that  all architecture is design but not all design is architecture   Software Architecture in Practice    I m not sure I quite agree with that  because architecture can include other activities  but it captures the essence that architecture is a design activity that deals with the critical subset of design   My slightly flippant definition  found on the SEI definitions page  is that it s the set of decisions which  if made wrongly  cause your project to get cancelled   A useful attempt at separating architecture  design and implementation as concepts was done by Amnon Eden and Rick Kazman some years ago in a research paper entitled  Architecture  Design  Implementation  which can be found here  http   www sei cmu edu library assets ICSE03-1 pdf   Their language is quite abstract but simplistically they say that architecture is design that can be used in many contexts and is meant to be applied across the system  design is  err  design that can be used in many contexts but is applied in a specific part of the system  and implementation is design specific to a context and applied in that context   So an architectural decision could be a decision to integrate the system via messaging rather than RPC  so it s a general principle that could be applied in many places and is intended to apply to the whole system   a design decision might be to use a master slave thread structure in the input request handling module of the system  a general principle that could be used anywhere but in this case is just used in one module  and finally  an implementation decision might be to move responsibilities for security from the Request Router to the Request Handler in the Request Manager module  a decision relevant only to that context  used in that context    I hope this helps

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Good question    Although the line between them is hardly a bright sharp line   imho  if you are using both terms  then Architecture encompasses more technical or structural decisions about how to build or construct something  especially those decisions that will be hard  or harder  to change once implemeneted  whereas Design encompasses those decisions that either are easy to change later  like method names  class  lt -  file organizational structure  design patterns  whether to use a singleton or a static class to solve some specific problem  etc    and or those that effect the appearance or esthetic aspects of a system or application  Human Interface  ease of use  look and feel  etc

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I agree with many of the explanations  essentially we are recognizing the distinction between the architectural design and the detailed design of the software systems   While the goal of the designer is to be as precise and concrete in the specifications as it will be necessary for the development  the architect essentially aims at specifying the structure and global behavior of the system just as much as required for the detailed design to begin with   A good architect will prevent hyper-specifications - the architecture must not be overly specified but just enough  the  architectural  decisions established only for the aspects that present costliest risks to handle  and effectively provide a framework   commonality   within which the detailed design can be worked upon i e  variability for local functionality   Indeed  the architecture process or life-cycle just follows this theme - adequate level of abstraction to outline the structure for the  architecturally  significant business requirements  and leave more details to the design phase for more concrete deliverables

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Architecture is design with a rationale that comes from various factors the most important of which are the non-functional requirements like say scalability and certainly not the least is experience  Without rationale you are left with plain pattern  or how to do  Whether designing at a higher level or at the class level its still design   OR put another way  Architecture is meta-design  i e  designing the design  You have a few patterns that are known to fit a certain solution space  which would you select and why  Architecture is when you answer the  which  and  why   the  how  is already given by design   It certainly does not depend on level of abstraction  for example implementing distributed sessions is not a class level task  but there are a few designs from which to select for a given architecture   Likewise  architecture is reflected even in a class level design  Under a scalable architecture  class design is often different if you were to do it without the scalability factor in mind  Why you must have a method  BeginAsyncUpload  versus  Upload  is an architectural decision   Interestingly  as we move focus towards system element at the higher level the questions  which and why  become more important and  how  becomes less relevant  Moving in the other direction the  how  part becomes more important  also because repeated usage makes it obvious  for example  to select between Abstract Factory or Prototype

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Software design has a longer history while the term software architecture is barely 20 years old   Hence  it is going through growing pains right now     Academics tend to see Architecture as part of the larger field of software design   Although there is growing recognition that Arch is a field within it s own   Practitioners tend to see Arch as high-level design decisions that are strategic and can be costly in a project to undo     The exact line between Arch and design depends on the software domain  For instance  in the domain of Web Applications  the layered architecture is gaining the most popularity currently  Biz Logic Layer  Data Access Layer  etc    The lower level parts of this Arch are considered design  class diagrams  method signatures  etc    This would be defined differently in the domains of embedded systems  operating systems  compilers  etc

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Architecture identifies fundamental components of the system  describes their organisation and how they are related to create a framework for the system   Design describes various components and how they should be developed to provide required functionality with in the framework provided by the system architecture

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http   jinwolf tumblr com post 6591954772 architectural-patterns-vs-design-patterns  The architecture tells you how your system is laid out  One traditional architectural pattern example is 3 tier system where your system is broken down into presentation  business and data layers   The domain driven design promotes 4 tier architecture  Presentation  application  domain and infrastructure layers  And the repository pattern resides in between the domain layer and infrastructure layer  Your domain models should not know anything about the infrastructure and also should be kept pure and independent from it as well  That is why we have the repository to mediate those two layers   The repository pattern is still a pattern since it s a reusable solution and handles the problems that repeats  However  the repository pattern becomes only relevant when we talk about the architecture  It has its roles and responsibilities in the domain driven design architecture  It is not mathematical type general solution such as the abstract factory pattern which can be applied anywhere in your system

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Architecture is the resulting collection of design patterns to build a system   I guess Design is the creativity used to put all this together

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The software architecture of a program or computing system is the structure or structures of the system  which comprise software components  the externally visible properties of those components  and the relationships between them      from Wikipedia  http   en wikipedia org wiki Software architecture   Software design is a process of problem-solving and planning for a software solution  After the purpose and specifications of software are determined  software developers will design or employ designers to develop a plan for a solution  It includes low-level component and algorithm implementation issues as well as the architectural view    from Wikipedia  http   en wikipedia org wiki Software design   Couldn t have said it better myself

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Architecture is strategic  while Design is tactical   Architecture comprises the frameworks  tools  programming paradigms  component-based software engineering standards  high-level principles     While design is an activity concerned with local constraints  such as design patterns  programming idioms  and refactorings

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Architecture are  the design decisions that are hard to change    After working with TDD  which practically means that your design changes all the time  I often found myself struggling with this question  The definition above is extracted from Patterns of Enterprise Application Architecture  By Martin Fowler   It means that the architecture depends on the Language  Framework and the Domain of your system  If your can just extract an interface from your Java Class in 5 minutes it is no longer and architecture decision

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