Home > Articles

  • Print
  • + Share This
This chapter is from the book

Architectural Decisions

If you ask software practitioners what the most visible output is from architectural activities, many will likely point to a fancy diagram that highlights the key components and their interactions. Usually, the more color and complexity, the better. The diagram is typically too difficult to read on a normal page and requires a special large-scale printer to produce. Architects want to look smart, and producing a complex diagram shows that the architect can solve extremely difficult problems! Though such diagrams give the authors and readers the false sense of being in control, they normally have limited impact on driving any architectural change. In general, these diagrams are rarely understood in a consistent manner and provide limited insight without a voiceover from the diagram’s author. In addition, diagrams are hard to change, which ends up in a divergence from the code running in the production environment that adds confusion when making architectural decisions.

This brings us to the question, What is the unit of work of an architect (or architectural work)? Is it a fancy diagram, a logical model, a running prototype? Continuous Architecture states that the unit of work of an architect is an architectural decision. As a result, one of the most important outputs of any architectural activity is the set of decisions made along the software development journey. We are always surprised that so little effort is spent in most organizations on arriving at and documenting architectural decisions in a consistent and understandable manner, though we have seen a trend in the last few years to rectify this gap. A good example is the focus on architectural decision records in GitHub.5

In our original book,6 we discussed in detail what an architectural decision should look like. Following are the key points:

  • It is important to clearly articulate all constraints related to a decision—architecture is, in essence, about finding the best (i.e., good enough) solution within the constraints given to us.

  • As stated in principle 2, Focus on quality attributes, not on functional requirements, it is important to explicitly address quality attribute requirements.

  • All options considered and rationale for coming to the decision have to be articulated.

  • Tradeoff between the different options and impact on quality attributes should be considered.

Finally, the following information is critical for an architectural decision: Who made this decision, and when? Appropriate accountability increases the trust in the decisions being made.

Making and Governing Architectural Decisions

Let us look at the different types of architectural decisions in an enterprise. Figure 2.3 demonstrates our recommended approach to making architectural decisions in a typical enterprise.7

Figure 2.3

Figure 2.3 Levels of architectural decisions

If we assume that an enterprise has set up governance bodies that ratify decisions, it is only natural that the higher up you go, the fewer decisions are made and the fewer reviews are conducted. For example, enterprise architecture boards make far fewer decisions than product-level governance boards. Note that the scope and significance of architectural decisions also increase with scale. However, most decisions that can impact an architecture are driven on the ground by development teams. The closer you get to implementation, the more decisions are made. Although they tend to be of a more limited scope, over time, these decisions significantly impact the overall architecture. There is nothing wrong with making more decisions at this level. The last thing we recommend is to create unnecessary burden and bureaucracy on development teams that need to be agile; they must quickly make decisions to deliver their software system. From a Continuous Architecture perspective, two elements enable us to take advantage of aligning agile project teams to wider governance around architectural decisions:

  • Guidelines: In reality, the probability of development teams compromising the architecture is greatly reduced if they are given clear guidelines to adhere to. For example, if there are clear guidelines around where and how to implement stored procedures, then the risk of creating a brittle architecture by writing stored procedures in random parts of the architecture can be avoided.8 If you go back to Figure 2.3, you see that the main job of higher governance bodies is not to make decisions but to define guidelines. The recommended approach is that there should be fewer principles the higher you go in the organization.

  • Visibility: As stated before, we do not want to stop teams from making decisions aligned with their rhythm of delivery. At the same time, we do not want the overall architecture of a system or enterprise compromised by development team decisions. To go back to our stored procedure example, we can imagine a scenario where teams put a stored procedure here and there to meet their immediate deliverables. In some cases, even the existence of these stored procedures can be forgotten, resulting in a brittle architecture that is expensive to refactor. Creating visibility of architectural decisions at all levels of the organization and sharing these decisions among different teams will greatly reduce the probability of significant architectural compromises occurring. It is not technically difficult to create visibility; all you need to do is agree on how to document an architectural decision. You can use a version of the template presented in our original book or utilize architectural decision records. You can utilize existing communication and social media channels available in the organization to share these decisions. Though technically not difficult, creating the culture for sharing architectural decisions is still difficult to realize, mainly because it requires discipline, perseverance, and open communication. There is also a natural tension between having your decisions visible to everyone but at the same time close to the team when working (e.g., checked into their Git repository).

Let us look briefly at how the Continuous Architecture principles help us in dealing with architectural decisions. These principles are aligned with Domain-Driven Design,9 which is an extremely powerful approach to software development that addresses challenges similar to those addressed by Continuous Architecture.

  • Applying principle 4, Architect for change—leverage the “power of small,” results in loosely coupled cohesive components. The architectural decisions within a component will have limited impact on other components. Some architectural decisions will still cut across components (e.g., minimally how to define the components and their integration patterns), but these decisions can also be addressed independently of component-specific decisions.

  • Applying principle 6, Model the organization of your teams after the design of the system you are working on, results in collaborative teams that focus on delivering a set of components. This means that the knowledge sharing of relevant architectural decisions is more natural because the team is already operating in a collaborative manner.

Architectural Decisions in Agile Projects

Let us now investigate architectural decisions within the context of agile development. Most technology practitioners are wary of high-level architectural direction from the ivory tower. The team will make the necessary decisions and refactor them when the need arises. We are supportive of this view. Continuous Architecture emphasizes explicitly focusing on architectural decisions rather than forgetting them in the heat of the battle: architectural decisions should be treated as a key software artifact. Making architectural decisions an explicit artifact is key for agile to scale to and link with the wider enterprise context.

By clearly defining all known architectural decisions, we are basically creating an architectural backlog. This list includes the decisions you have made and the ones you know you have to make. Obviously, the list of architectural decisions will evolve as you make decisions and develop your product. What is important is to have a list of known architectural decisions and decide on which ones you need to address immediately. Remember principle 3, Delay design decisions until they are absolutely necessary.

There are two main ways in which you can integrate your architectural decisions with your product backlog. One option is to keep the architectural decision backlog separate. The second option is to have them as part of your product backlog but tagged separately. The exact approach you take will be based on what works within your context. The key point is to not lose track of these architectural decisions. Figure 2.4 illustrates how the architectural decision backlog logically relates to individual product backlogs.

Figure 2.4

Figure 2.4 Architectural decision and product backlogs

If you take a risk-based approach for prioritization, you will end up focusing on architecturally significant scenarios first. Then your initial set of sprints becomes focused on making key architectural decisions.

If you then make your architectural backlog visible to other teams and relevant architecture groups, then you have created full transparency into how you are evolving your architecture.

Although focusing on architectural decisions is an essential activity, it is still necessary to create a level of architectural description to communicate and socialize the architecture. We believe that more than 50 percent of architecture is communication and collaboration. You need such to be able to train new team members as well as explain your system to different stakeholders. Communication and collaboration are addressed in detail in the original Continuous Architecture.10

As we expand on our case study in subsequent chapters, we highlight key architectural decisions. These are examples and are not meant as a full set of decisions. In addition, we capture only some basic information for each decision, as exemplified in Table 2.1. For most architectural decisions, we expect that more information is captured, including constraints and detail regarding analysis and rationale.

Table 2.1 Decision Log Entry Example

Type

Name

ID

Brief Description

Options

Rationale

Foundational

Native Mobile Apps

FDN-1

The user interface on mobile devices will be implemented as native iOS and Android applications.

Option 1, Develop native applications.

Option 2, Implement a responsive design via a browser.

Better end-user experience. Better platform integration. However, there is duplicated effort for the two platforms and possible inconsistency across platforms.

  • + Share This
  • 🔖 Save To Your Account

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.

Overview


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.

Surveys

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.

Newsletters

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.

Security


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

Children


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

Marketing


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.

Choice/Opt-out


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.

Links


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