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Scott Ambler
Glen Little
Mark Lines
Valentin Mocanu
Daniel Gagnon
Michael Richardson
Joshua Barnes

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Strategies for Capturing Quality Requirements

Agile modeling

Quality requirements, also known as non-functional requirements (NFRs), quality of service (QoS) or technical requirements, address issues such as reliability, availability, security, privacy, and many other quality issues.  The following diagram, which overviews architectural views and concerns, provides a great source of quality requirement types (the list of concerns).  Good sources for quality requirements include your enterprise architects and operations staff, although any stakeholder is a potential source for them.

Figure 1. Architectural views and concerns.

Architecture Views and Concerns

Why Are Quality Requirements Important?

Stakeholders will describe quality requirements at any time, but it’s particularly important to focus on them during your initial scoping efforts during Inception as you can see in the goal diagram below for Explore Initial Scope.  Considering quality requirements early in the lifecycle is important because:

  1. Quality requirements drive important architecture decisions. When you are identifying your technical strategy you will often find that it is the NFRs that will be the primary drivers of your architecture.
  2. Quality requirements will drive some aspects of your test strategy. Because they tend to be cross-cutting, and because they tend to drive important aspects of your architecture, they tend to drive important aspects of your test strategy.  For example, security requirements will drive the need to support security testing, performance requirements will drive the need for stress and load testing, and so on. These testing needs in turn may drive aspects of your test environments and your testing tool choices.
  3. Quality requirements will drive acceptance criteria for functional requirements (such as stories).  Quality requirements are typically system-wide thus they apply to many, and sometimes all of your functional requirements.  Part of ensuring that your solution is potentially consumable each iteration is ensuring that it fulfills its overall quality goals, including applicable quality requirements.  This is particularly true with life-critical and mission-critical solutions.

Capturing Quality Requirements

Figure 2 depicts the goal diagram for Explore Scope.  As you can see, there are several strategies for exploring and potentially capturing quality requirements.

Figure 2. The goal diagram for Explore Scope (click to enlarge).

Explore Scope process goal

Let’s explore the three strategies, which can be combined, for capturing quality requirements:

  1. Technical stories.  A technical story is a documentation strategy where the quality requirement  is captured as a separate entity that is meant to be addressed in a single iteration.  Technical stories are in effect the quality requirement equivalent of a user story. For example “The system will be unavailable to end users no more than 30 seconds a week” and “Only the employee, their direct manager, and manager-level human resource people have access to salary information about said employee” are both examples of technical stories.
  2. Acceptance criteria for individual functional requirements.  Part of the strategy of ensuring that a work item is done at the end of an iteration is to verify that it meets all of its acceptance criteria.  Many of these acceptance criterions will reflect quality requirements specific to an individual usage requirement, such as “Salary information read-only accessible by the employee,”, “Salary information read-only accessible by their direct manager”, “Salary information read/write accessible by HR managers”, and “Salary information is not accessible to anyone without specific access rights”.  So in effect quality requirements are implemented because they become part of your “done” criteria.
  3. Explicit list.  Capture quality requirements separately from your work item list in a separate artifact.  This provides you with a reminder for the issues to consider when formulating acceptance criteria for your functional requirements.  In the Unified Process this artifact was called a supplementary specification.

Of course a fourth option would be to not capture quality requirements at all.  In theory this would work in very simple situations but it clearly runs a significant risk of the team building a solution that doesn’t meet the operational needs of the stakeholders.  This is often a symptom of a teams only working with a small subset of their stakeholder types (e.g. only working with end users but not operations staff, senior managers, and so on).

Related Resources

Posted by Scott Ambler on: January 23, 2018 01:17 PM | Permalink | Comments (0)

Should Software Architects Write Code?

Source code
One of the age-old debates in the software world is whether software architects need to write code.  We suspect that as an industry we’ll never reach consensus on this topic. Here are our thoughts on the subject.

Short Answer:

Hell yes!

Detailed Answer:

In the following table we list the advantages, disadvantages, and considerations (when does the strategy makes sense) to compare whether a software architect should write code or not.  You may recognize this approach from our book Disciplined Agile Delivery.

Strategy Advantages Disadvantages Considerations
Software architects also develop
  • Helps to keep the architects grounded
  • Developers are more likely to respect the architects and follow their advice
  • Architects are able to create working examples of their strategies, increasing the usefulness to developers
  • More people with architecture skills are needed to support your development teams (arguably a good thing)
  • Apply when you have an ample supply of people with architecture skills, or at least are willing to invest in developing sufficient people
  • Apply when it is critical that developers build well-architected solutions
Software architects don’t develop
  • Architects can focus on architecture
  • Architects can support multiple delivery teams
  • Developers are far less likely to follow the advice of such architects, effectively forgoing any benefit the architects could have brought to your organization
  • The architects are forced to create less-effective artifacts such as white papers and models, as compared with working reference architectures, due to lack of coding skills
  • When you have very few people in your organization with architecture skills
  • The software architects should pair with others so as to transfer their architecture skills to them, thereby growing the pool of software architects and thus making it more viable to allow the software architects to code

In the Disciplined Agile (DA) toolkit we’ve made it very clear that we expect Architecture Owners to be actively involved with the development of the solution.  On Disciplined Agile teams the Architecture Owner is effectively a team member with additional responsibilities around leading the team through architecture decisions, in coaching them on architecture skills, and in working closely with your Enterprise Architecture team (if any) to ensure their development team understands and is working towards your organization’s technical roadmap.

We’re often told that it isn’t realistic to expect architects to write code.  Invariably this is coming from people who are currently working in traditional IT organizations that have very well-defined roles, IT organizations that more often than not are struggling to be effective.  Our response is always the same – Really?  Are development teams following your architectural strategy?  Are they eager to work with you, or are they forced to work with you?  This generally leads to a discussion that reveals that things aren’t going so well for these architects in practice, and sometimes leads to a positive discussion as to how we can move towards a more effective approach for them.  They kind of approach described in the Disciplined Agile (DA) toolkit.

 

Additional Reading:

 

Posted by Scott Ambler on: February 08, 2016 11:00 AM | Permalink | Comments (0)

How Enterprise Architecture Enables Agile Software Development

Layered Architecture

Enterprise architecture, when performed in a disciplined agile manner, is an important enabler of agile software delivery.  This is true for several reasons:

  1. Common architecture enables agile teams to focus on value creation.  A common enterprise architecture enables reuse across delivery teams.  When agile teams have high-quality assets – such as micro-services, legacy data sources, and frameworks – available to reuse they are able to focus on creating new value for their stakeholders and not on reinventing new versions of existing assets.
  2. Common technical guidance enables greater consistency between teams.  When team follow effective, common conventions it results in greater quality.   This makes it easier to learn about assets that are new to them, in particular existing source code, and to evolve those assets as needed.  Greater consistency also makes it easier for people to move between teams because it will be easier for them to come up to speed on what the new team is doing and to share their skills with those team members.
  3. Agile architectures enable disaggregation.  When your solutions are built from loosely coupled, highly cohesive components it is easier to spread development work across smaller teams.  This reduces overall risk and organizational complexity, which in turn reduces time-to-delivery.  It also allows agile teams to focus on what they’re building instead of coordinating with other teams or mocking out the (undelivered) work of other teams.
  4. Common infrastructure enables continuous delivery.  When there is a common technical infrastructure to IT delivery teams to deploy into it is easier to deploy.  The easier it is to deploy, the more often it makes sense to deploy.
  5. Enterprise architecture scales agile.  A disciplined agile approach to enterprise architecture enables organizations to scale agile strategies “horizontally” across their entire IT department.

The Disciplined Agile Delivery (DAD) 1.x framework purposefully included the philosophy of enterprise awareness, the need for agile delivery teams to look beyond their immediate needs and consider the long-term needs of their organization.  A common example of this is to work closely with your organization’s enterprise architects.  The Disciplined Agile 2.0 framework, which we are incrementally publishing here at DisciplinedAgileDelivery.com, explicitly addresses Enterprise Architecture so that organizations may see how it fits into the overall strategy to build an agile organization.

Posted by Scott Ambler on: July 06, 2015 11:41 AM | Permalink | Comments (0)

Identifying your Initial Architecture Strategy

When a disciplined agile project or product team starts, one of the process goals which they will likely need to address is Identify Initial Technical Strategy. This is sometimes referred to as initial architecture envisioning or simply initial architecture modeling. This is an important process goal for several reasons. First, the team should think through, at least at a high level, their architecture so as to identify a viable strategy for moving forward into construction.  A little bit of up-front thinking can increase your effectiveness as a team by getting you going in a good direction early in the lifecycle.  Second, the team should strive to identify the existing organizational assets, such as web services, frameworks, or legacy data sources, that they can potentially leverage while producing the new solution desired by their stakeholders.  By doing this you increase the chance of reuse, thereby avoiding adding technical debt into your organizational ecosystem, and more importantly you reduce the time and cost of delivering a new solution as the result of reuse.  You will do this by working with your organization’s enterprise architects, if you have any.  This is an aspect of Disciplined Agile’s philosophy of working in an enterprise aware manner.

The process goal diagram for Identify Initial Architecture Strategy is shown below. The rounded rectangle indicates the goal, the squared rectangles indicate issues or process factors that you may need to consider, and the lists in the right hand column represent potential strategies or practices that you may choose to adopt to address those issues. The lists with an arrow to the left are ordered, indicating that in general the options at the top of the list are more preferable from an agile point of view than the options towards the bottom. The highlighted options (bolded and italicized) indicate default starting points for teams looking for a good place to start but who don’t want to invest a lot of time in process tailoring right now. Each of these practices/strategies has advantages and disadvantages, and none are perfect in all situations, which is why it is important to understand the options you have available to you.

Develop Initial Architecture Strategy process goal

Let’s consider each process factor:

  • Choose the level of detail.  How much effort should you put into capturing your architectural strategy, if any at all.  A small co-located team may find that a high-level overview captured using whiteboard sketches is sufficient.  A team that is geographically distributed across several locations will find that it needs to at least take digital snapshots of the sketches and share them (perhaps via a wiki) or even capture the diagrams using a drawing tool such as Visio or OmniGraffle.  They may also find that they need to define the details of the interfaces to major components and services, a strategy often referred to as design by contract.  A team in a life-critical regulatory environment may choose to capture more details, even to the point of doing big design up front (BDUF).
  • Explore technology architecture.  Technical aspects of your architecture may be captured via free form layered architecture diagrams, network diagrams, or UML deployment diagrams amongst others.
  • Explore business architecture.  Business or domain aspects may be explored via conceptual domain models, high-level process models, and UML component diagrams amongst others.
  • Explore user interface (UI) architecture.  For end users, the UI is the system.  The implication is that you had better architect it well, and more important ensure that it is usable/consumable.  You may explore the user interface architecture via a UI flow diagram/wireframe model, low-fidelity UI prototypes, or high-fidelity UI prototypes.
  • Consider the future.  A critical thing is for your architecture to be able to accommodate change in the future.  The lean strategy is to consider these changes, and make architectural choices that best enable you to accommodate the changes when and if you need to, but DO NOT overbuild your solution now.  In short, think but wait to act.  To do this you need to consider the potential changes that could occur, often via “what if” discussions.  If you need to capture these potential changes you might decide to write change cases.
  • Apply a modeling strategy(ies).  How will your team go about formulating their architecture?  Will they hold informal modeling sessions in an agile modeling space or formal modeling sessions Joint Application Design (JAD) strategy?  Or both?
  • Select an architecture strategy. Will they identify a single technical strategy or several options which they will hope to explore and eventually choose from (or combine ideas from)?
  • Identify a delivery strategy.  Will the team be building a solution from scratch?  Will they be evolving an existing solution?  Will they be evolving a purchased, commercial off the shelf (COTS) package?  Combinations thereof?

We want to share two important observations about this goal.  First, this goal, along with Explore Initial ScopeCoordinate Activities, and Move Closer to a Deployable Release seem to take the brunt of your process tailoring efforts when working at scale.  It really does seem to be one of those Pareto situations where 20% addresses 80% of the work, more on this in a future blog posting.  As you saw in the discussion of the process issues, the process tailoring decisions that you make regarding this goal will vary greatly based on the various scaling factors.  Second, as with all process goal diagrams, the one above doesn’t provide an exhaustive list of options although it does provide a pretty good start.

We’re firm believers that a team should tailor their strategy, including their team structure, their work environment, and their process, to reflect the situation that they find themselves in.  When it comes to process tailoring, process goal diagrams not only help teams to identify the issues they need to consider they also summarize potential options available to them.  Agile teams with a minimal bit of process guidance such as this are in a much better situation to tailor their approach than teams that are trying to figure it out on their own.  The DA process decision framework provides this guidance.

Posted by Scott Ambler on: February 10, 2014 07:28 AM | Permalink | Comments (0)

Strategies for Verifying Non-Functional Requirements

Early in the lifecycle, during the Inception phase, disciplined agile teams will invest some time in initial requirements envisioning and initial architecture envisioning. One of the issues to be considered as part of requirements envisioning is to identify non-functional requirement (NFRs), also called quality of service (QoS) or simply quality requirements. The NFRs will drive many of your technical decisions that you make when envisioning your initial architectural strategy. These NFRs should be captured someone and implemented during Construction. It isn’t sufficient to simply implement the NFRs, you must also validate that you have done so appropriately. In this blog posting I overview a collection of agile strategies that you can apply to validate NFRs.

A mainstay of agile validation is the philosophy of whole team testing. The basic idea is that the team itself is responsible for validating its own work, they don’t simply write some code and then throw it over the wall to testers to validate. For organizations new to agile this means that testers sit side-by-side with developers, working together and learning from one another in a collaborative manner. Eventually people become generalizing specialists, T-skilled people, who have sufficient testing skills (and other skills).

Minimally your developers should be performing regression testing to the best of their ability, adopting a continuous integration (CI) strategy in which the regression test suite(s) are run automatically many times a day.  Advanced agile teams will take a test-driven development (TDD) approach where a single test is written just before sufficient production code which fulfills that test.  Regardless of when tests are written by the development team, either before or after the writing of the production code, some tests will validate functional requirements and some will validate non-functional requirements.

Whole team testing is great in theory, and it is strategy that I wholeheartedly recommend, but in some situations it proves insufficient.  It is wonderful to strive to have teams with sufficient skills to get the job done, but sometimes the situation is too complex to allow that.  There are some types of NFRs which require significant expertise to address properly: NFRs pertaining to security, usability, and reliability for example.  To validate these types of requirements, worse yet even to identify them, requires skill and sometimes even specialized (read expensive) tooling.  It would be a stretch to assume that all of your delivery teams will have this expertise and access to these tools.

Recognizing that whole team testing may not sufficiently address validating NFRs many organizations will supplement their whole team testing efforts with parallel independent testing  .  With this approach a delivery team makes their working builds available to a test team on a regular basis, minimally at the end of each iteration, and the testers perform the types of testing on it that the delivery team is either unable or unlikely to perform.  Knowing that some classes of NFRs may be missed by the team, independent test teams will look for those types of defects.  They will also perform pre-production system integration testing and exploratory testing to name a few.  Parallel independent testing is also common in regulatory compliance environments.

From a verification point of view some agile teams will perform either formal or informal reviews.  Experienced agilists prefer to avoid reviews due to their inherently long feedback cycle, which increases the average cost of addressing found defects, in favor of non-solo development strategies such as pair programming and modeling with others.  The challenge with non-solo strategies is that managers unfamiliar with agile techniques, or perhaps the real problem is that they’re still overly influenced by disproved traditional theories of yesteryear, believe that non-solo strategies reduce team productivity.  When done right non-solo strategies increase overall productivity, but the political battle required to convince management to allow your team to succeed often isn’t worth the trouble.

Another strategy for validating NFRs code analysis, both dynamic and static.  There is a range of analysis tools available to you that can address NFR types such as security, performance, and more.  These tools will not only identify potential problems with your code many of them will also provide summaries of what they found, metrics that you can leverage in your automated project dashboards.   This strategy of leveraging tool-generated metrics such as this is a technique which IBM calls Development Intelligence and is highly suggested as an enabler of agile governance in DAD. Disciplined agile teams will include invocation of code analysis tools from you CI scripts to support continuous validation throughout the lifecycle.

Your least effective validation option is end-of-lifecycle testing, in the traditional development world this would be referred to as a testing phase.  The problem with this strategy is that you in effect push significant risk, and significant costs, to the end of the lifecycle.  It has been known for several decades know that the average cost of fixing defects rises the longer it takes you to identify them, motivating you to adopt the more agile forms of testing that I described earlier.  Having said that I still run into organizations in the process of adopting agile techniques that haven’t really made embraced agile, as a result still leave most of their testing effort to the least effective time to do such work.  If you find yourself in that situation you will need to validate NFRs in addition to functional requirements.

To summarize, you have many options for validating NFRs on agile delivery teams.  The secret is to pick the right one(s) for the situation that you find yourself in.  The DA toolkit helps to guide you through these important process decisions, describing your options and the trade-offs associated with each one.

Related Resources

 

Posted by Scott Ambler on: October 23, 2012 07:49 AM | Permalink | Comments (0)
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