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

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

P.5 Seven Rules for Sound Documentation

Architecture documentation is much like the documentation we write in other facets of our software development projects. As such, it obeys the same fundamental rules for what distinguishes good, usable documentation from poor, ignored documentation. We close the prologue with seven rules for sound software documentation. Use this checklist when you write technical documentation. (You can also use it when you read technical documentation: the rules provide objective criteria for judging a document’s quality, and they let you say something constructive in a critical review.)

Rule 1: Write Documentation from the Reader’s Point of View

This rule simply reminds us to keep the end game in mind as we produce our documentation: Make your document serve its stakeholders and their intended uses of it. It is surprisingly easy to forget that rule in the midst of looming deadlines, an overflowing e-mail queue, and a cell phone that won’t shut up.

The great computing scientist Edsger Dijkstra (1930–2002), the inventor of many of the software engineering principles we now take for granted, once said that he would happily spend two hours pondering how to make a single sentence clearer. He reasoned that if the paper were read by a couple of hundred people—a decidedly modest estimate for someone of Dijkstra’s caliber—and he could save each reader a minute or two of confusion, it was well worth the effort. Professor Dijkstra’s consideration for the reader reflects his classic manners, but it also gives us a new and useful concept of the effort associated with a document. Usually we just count how long it takes to write. Dijkstra taught us to be concerned with how long it takes to use. Writing a document that a reader finds easy to use will help tilt the economics of documentation in our favor, as defined in the formula in Section P.2.4.

Writing for the reader is just plain polite, but it has a practical advantage as well. A reader who feels that the document was written with him or her in mind appreciates the effort but, more to the point, will come back to the document again and again in the future. Documents written for the reader will be read; documents written for the convenience of the writer will not. All of us like to shop at stores that seem to want our business, and we avoid stores that do not. This is no different.

Tips on how to write for the reader include:

  • Find out who your readers are, what they know, and what they expect of the document. Have an informal chat with some representatives of various kinds of readers and see what their expectations are. Don’t make uninformed assumptions about what your readers know.
  • Avoid stream of consciousness writing. If you find yourself writing things down in the order they occur to you, without an overall organizational plan, stop. Work out where specific kinds of information should go and put them where they belong. Make sure that you know what question(s) are being answered by each section of a document.
  • Avoid unnecessary insider jargon. The documentation may be read by someone new to the field or from a company that does not share the same jargon. Add a glossary to define specialized terms.
  • Avoid overuse of acronyms. Resist using an acronym when the spelled-out phrase is short or it appears only a few times. Always provide a dictionary that decodes whatever acronyms you do use.

Rule 2: Avoid Unnecessary Repetition

Each kind of information should be recorded in exactly one place. This makes documentation easier to use and much easier to change as it evolves. It also avoids confusion: information that is repeated is likely to be in a slightly different form, and now the reader must wonder “Was the difference intentional? If so, what is the meaning of the difference? Did the author change one place and forget to update the other?”

It should be a goal that information never be repeated. However, at times the cost to the reader of not repeating information in the other places where it’s needed is high. Readers don’t like to flip pages or click hyperlinks unnecessarily. The information may be repeated in two or more different places for clarity or to make different points. Also, expressing the same idea in different forms is often useful for achieving a thorough understanding. If keeping the information separate comes at too high a cost to the reader, repeat the information.

In a document maintained and viewed online, hyperlinks make this rule easier to follow. For example, each term can be hyperlinked to its definition; a concept can be hyperlinked to an explanation or elaboration.

Rule 3: Avoid Ambiguity

Ambiguity occurs when documentation can be interpreted in more than one way and at least one of those ways is incorrect. The most dangerous kind of ambiguity is undetected ambiguity. Here, each reader will think he or she understands the document, but unwittingly each reader will come to different conclusions about what it is saying.

Following two of the other rules will help you avoid ambiguity:

  • By avoiding needless repetition (rule 2), you avoid the “almost but not quite alike” form of ambiguity.
  • Reviewing the document with members of its intended audience (rule 7) will help spot and weed out ambiguities.

A well-defined notation with precise semantics goes a long way toward eliminating whole classes of linguistic ambiguity from a document. This is one area where standard languages and notations help a great deal, but using a formal language isn’t always necessary. Simply adopting a set of notational conventions and then using them consistently and rigorously will help eliminate many sources of ambiguity. But if you do adopt a notation, then the following corollary applies:

Rule 3a: Explain Your Notation

The ubiquitous box-and-line diagrams that people always draw on whiteboards are one of the greatest sources of ambiguity in architecture documentation. Although not a bad starting point, these diagrams are certainly not good architecture documentation. First, most such diagrams suffer from ambiguity. Are the boxes supposed to be modules, objects, classes, services, clients, servers, databases, processes, functions, tiers, procedures, processors, or something else? Do the arrows mean calls, uses, data flow, I/O, inheritance, communication, processor migration, or something else?

Make it as easy as possible for your reader to determine the meaning of the notation. The best way to do this is always to include a key in your diagrams. If you’re using a standard visual language defined elsewhere, the key can simply name it or refer readers to the source of the language’s semantics. Even if the language is standard or widely used, different versions often exist. Let your reader know, by citation, which one you’re using. For example, “Key: UML 2.0” is a perfectly fine key, and it puts readers and authors on the same page. For a homegrown informal notation, include a key to the symbology. This is good practice because it compels you to understand what the pieces of your system are and how they relate to one another; it’s also courteous to your readers.

Rule 4: Use a Standard Organization

Establish a standard, planned organization scheme, make your documents adhere to it, and ensure that readers know about it. A standard organization, also called a template, offers many benefits.

  • It helps the reader navigate the document and find specific information quickly. Thus, this benefit is also related to the write-for-the-reader rule.
  • It also helps the document writer plan and organize the contents. The writer doesn’t have to start with a blank page when answering the question “What topics and in what order should I have in this document?” The template already provides an outline of the important topics to cover.
  • It allows the writer to record information as soon as it’s known. For example, pieces of section 4 may be written before sections 1–3 are there.
  • It reveals what work remains to be done by the number of sections labeled “TBD” (to be determined) or “To Do.”
  • It embodies completeness rules for the information; the sections of the document constitute the set of important aspects that need to be conveyed. Hence, the standard organization can form the basis for a first-order validation check of the document at review time.

Corollaries to this rule are these:

  1. Organize documentation for ease of reference. Software documentation may be read from cover to cover at most once, probably never. But a document is likely to be referenced hundreds or thousands of times. Do what you can to make it easy to find information quickly. Adding a table of contents, an index, a glossary, and an acronym list are all good ways to help readers look up specific information.

  2. Don’t leave any section blank; mark as “TBD” what you don’t yet know or “NA” what you know is not applicable. Many times, we can’t fill in a document completely because we don’t yet know the information, or because decisions have not been made, or because we didn’t yet have time to do it. In that case, mark the document accordingly (for example, “TBD” or “To Do”). Templates are by nature generic and hence comprehensive. If a given section of the template does not apply for the document you’re creating, mark it as “NA.” If the section is blank, the reader will wonder whether the information is coming later or whether it is indeed supposed to be blank. Thus this advice is related to the rule about avoiding ambiguity.

Rule 5: Record Rationale

Architecture is the result of making a set of important design decisions, and architecture documentation records the outcomes of those decisions. For the most important decisions, you should record why you made them the way you did. You should also record the important or most likely alternatives you rejected and state why. Later, when those decisions come under scrutiny or pressure to change, you will find yourself revisiting the same arguments and wondering why you didn’t take another path. Recording your rationale will save you enormous time in the long run, although it requires discipline to record your rationale in the heat of the moment.

Of course, not every single design decision should have the rationale captured in the architecture documentation. If a design decision is key to achieve a quality requirement of the system, its rationale is probably worth capturing. If a design decision required a long meeting with stakeholders, that’s a good decision to capture. If you conducted technical experiments and studies or created prototypes to evaluate design alternatives, the conclusions of this effort should be captured as rationale for the chosen alternative. Keep in mind that one week, one month, or one year from now, you may not remember why you did things that way, and other people will not know either.

Rule 6: Keep Documentation Current but Not Too Current

Documentation that is incomplete or out of date does not reflect truth, does not obey its own rules for form and internal consistency, and is not used. Documentation that is kept current and accurate is used. Why? Because questions about the software can be most easily and most efficiently answered by referring to the appropriate document. Documentation that is somehow inadequate to answer the question needs to be fixed. Updating it and then referring the questioner to it will deliver a strong message that the documentation is the final, authoritative source for information.

During the design process, on the other hand, decisions are made and reconsidered with great frequency. Revising documentation to reflect decisions that will not persist is an unnecessary expense.

Your development plan should specify particular points at which the documentation is brought up to date or the process for keeping the documentation current. For example, the end of each iteration or sprint, or each incremental release, could be associated with providing revised documentation. Every design decision should not be recorded and distributed the instant it is made; rather, the document should be subject to version control and have a release strategy, just as every other artifact does.

Rule 7: Review Documentation for Fitness of Purpose

Only the intended users of a document will be able to tell you whether it contains the right information presented in the right way. Enlist their aid. Before a document is released, have it reviewed by representatives of the community or communities for which it was written.

  • + 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