Home > Articles > Software Development & Management > Architecture and Design

The Changing Field of Software Architecture

The authors of Software Architecture in Practice, 3rd Edition discuss how technologies like cloud and edge-dominant systems have changed (and not changed) the field of software architecture in the ten years since the last edition of their book was published.
Like this article? We recommend

The discipline of “software architecture” was not formally studied until about 1990.  Since then the term has become fashionable, and many software professionals now sport some form of “architect” title on their business cards.  Enterprise architects, solution architects, application architects, and others are as common as beans.  But, more significantly, the practice of software architecture has become indispensable technically, and a critical enabler of competitive advantage organizationally. 

What is software architecture?  Definitions abound.  Not surprisingly, we like ours best:

The software architecture of a system is the set of structures needed to reason about the system, which comprise software elements, relations among them, and properties of both.

This definition stands in contrast to many other definitions that talk about the system’s “early” or “major” design decisions.  Many architectural decisions are made early, but not all are. Many decisions are made early that are not architectural. And it’s hard to look at a decision and tell whether or not it’s “major.” So we prefer to focus attention on structures, relationship, and properties.

This focus implies that architecture is an abstraction.  An architecture comprises software elements and how the elements relate to each other.  Our definition, with its emphasis on abstractions—structures and properties—makes it clear that an architecture selects certain details and suppresses others:

  • It omits information about elements that is not useful for reasoning about the system.
  • It omits information that has no ramifications outside of the design and implementation of a single element.
  • It omits private details of elements—details having to do solely with internal implementation.

We humans have finite cognitive capabilities; we can only keep so many details in our heads at once.  But systems know no physical limits—they may become arbitrarily complex, quickly outstripping our abilities to understand them (if “understand” means mastery of every detail of the system).  Thus abstraction is essential to taming the complexity of an architecture.  We simply cannot, and do not want to, deal with all of the complexity all of the time!  Furthermore, by focusing on the abstractions, we can do a substantial amount of planning, design, and analysis before committing enormous amounts of resources to code. This is no different from other mature engineering disciplines: a civil engineer, for example, creates and analyzes blueprints before digging foundations, pouring concrete, and bolting beams together.  This is just plain good common sense.

With the increasing complexity of the systems and systems of systems that envelope our lives these days, architecture has taken an increasingly central role.  It has been almost a decade since the publication of the second edition of Software Architecture in Practice. During that time, the field of software has grown enormously in scope and in its impact on society.  Concurrent with this explosion in software, software architecture has broadened its focus from being primarily internally and technically oriented—addressing problems of how to design, evaluate, and document complex software systems—to including external impacts as well.  It affects your business and its goals; it affects your people and what they do and how they are trained; in some cases it affects the broader technical environment; and in just a few cases it affects society at large (think, for example, of how society has been affected by mobile applications, peer-to-peer networks, social networks, and service computing). Architectures can have a profound effect on your organizational goals, your people, your software development life cycle, and on the way you manage a project. 

The past ten years have also seen dramatic changes in the types of systems being constructed and thus in the types of concerns facing architects.  Large data, social media, and the cloud are all areas that, at most, were embryonic ten years ago and now are not only mature but also extremely influential.  Software has become ubiquitous: in our computers, obviously, but also in our smart phones, our toys, our tools, our refrigerators and rice cookers and cars and thermostats and razors. In fact, software has not just become ubiquitous, but it has become essential in all of these domains (well, maybe not razors) and it has become essential to business success.  Look at the ads for a modern automobile and you will see an enormous emphasis on features enabled by software: anti-lock brakes, adaptive cruise-control, GPS, Bluetooth, anti-theft devices, parking sensors…the list goes on and on.  Without such features, a car simply is not competitive in today’s market.  Getting a head start on your competitors in providing such features can be a huge advantage.  At the heart of it all lies the software architecture; the artifact that mediates between business goals and the achievement of those goals.  Software is at the heart of our lives—the social networks and email and phone calls and instant messages that we exchange, the business-to-business electronic data interchange that keeps our supply chains running, the signaling data that keeps our roadways and airways and trains and power grids operating and cooperating.  And, once again, software architecture lies at the heart of it all. These systems are simply too complex, too business-critical and life-critical to be designed in an ad hoc fashion.

A good example of architecture’s modern role is how architecture is central to the creation of “edge-dominant” systems.  An edge-dominant system is one that depends crucially on the inputs of users for its success.  Think Wikipedia, Facebook, YouTube, Craigslist, Twitter, Flickr, and Pinterest.  YouTube serves up approximately 1 billion videos a day. Twitter boasts that its users tweet 50 million times per day. Facebook reports that it has over 1 billion users and serves up about 30 billion pieces of content each month. Flickr recently announced that users had uploaded more than 6 billion photos.  And edge-dominant systems are not limited to open-content systems. Open-source software has exactly the same model of free contributions by “the crowd,” and it has resulted in some of the most important software in the world, standing at the heart of our business and information technology infrastructure: Linux and Apache run about two thirds of the world’s web servers.  The Android operating system runs more smart phones than all other operating systems combined.  MySQL, Eclipse, JBoss, Joomla, PHP, Firefox, FileZilla, OpenOffice, Hadoop, Wordpress, Twiki…the list of important open source applications is long and impressive and runs much of our personal and corporate lives.

Why do we care about this class of systems? Because the architectures of such systems have some important differences from the architectures that you would build for traditional systems.  In the field of software architecture, we are fond of analogies with traditional architecture; designing a complex piece of software has much in common with designing a building. By way of contrast, we call this new class of systems “Metropolis” systems, in that they resemble a city more than a single building, with millions of stakeholders, continuous change, conflicting requirements, and no single planning authority. 

The key architectural choice for a Metropolis edge-dominant system is the distinction between core and edge.  That is, the architecture of these systems is, without fail, bifurcated into

  • a core (or kernel) infrastructure that is designed by a small, coherent team and that defines the system’s basic structure, quality attributes and tradeoffs.  This code is typically highly modular, slow to change, and robust.
  • a set of edge functions or services that are built on the core. These deliver the majority of the function and end-user value and change relatively rapidly.  And these edge functions are typically independent of each other.

The core (often called a platform) is usually implemented as a set of services; complex platforms have hundreds of these.  The functions and services at the edge may number in the thousands or even more (think of the number of apps for Android, the number of plug-ins for Firefox, or the number of applications and drivers for Linux).  Without this key architectural structure, these systems would not be able to grow (seemingly) without bounds. 

All our familiar software development life cycles—waterfall, Agile, iterative, or prototyping-based—are broken in an edge-dominant, crowdsourced world. These models all assume that requirements can be known; software is developed, tested, and released in planned increments; projects have dedicated finite resources; and management can “manage” these resources. None of these conditions is true in the Metropolis.  Requirements emerge from the crowds; the software is perpetually changing, with no notion of a single stable state; project resources come and go with the whims of the crowds; and management can only influence but not control the contributors. 

Another set of architectural technologies that have become important in recent years, and which look to be dominant for many years to come, is cloud-based systems.  The cloud provides an elastic set of resources through the use of virtual machines, virtual networks, and virtual file systems.  Cloud-based architectures provide enormous economies of scale for many businesses. In one sense the cloud is nothing new; we have had time-sharing computers that provided virtualized resources since the 1960s. But cloud-based systems deliver their services ubiquitously (and cheaply!), over the internet.  And the various service models— Software as a Service, Platform as a Service, and Infrastructure as a Service—and deployment options—private cloud, public cloud, hybrid cloud, community cloud—have added a new set of design options (and tradeoffs) for today’s software architect.

The point of these examples is twofold: 1) architecture keeps changing, and you need to stay on top of the latest technologies and their underpinnings to stay relevant in your organization; 2) architecture is architecture is architecture (apologies to Gertrude Stein).  Did we just contradict ourselves?  What we mean is that while technologies like cloud and edge-dominant systems change and bring with them enormous consequences, the fundamentals behind these technologies do not change.  This is good news!  By understanding the design primitives of architecture and the way in which you can create, document, plan, and analyze these artifacts, you can master this critical skill.  Architect on!

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020