Saturday, May 22, 2010

Domain specific patterns

One way to become a recognized expert in your line of work is to become versed in your organization's domain specific design patterns. You will gain an exponential level of recognition if you contribute to codifying these patterns. Be proactive in documenting and sharing design patterns specific to your problem (business) domain. Few organizations invest resources into codifying the non-standard design patterns even though they are implemented often (hence the name). If you're the one recognizing and documenting domain specific design patterns you'll become a recognized expert.

By now many organizations have internal wiki-like collaboration tools. That’s the best place for you to start documenting these domain specific design patterns. Use that collaboration space to involve others. To be effective select an existing (or create your own) framework for describing design patterns. Many frameworks and approaches exit, pick one that works and modify as you go along. Just remember that design patterns apply to different level of design granularity.

Why is this important? Reuse at architectural level. Further, domain patterns may lead to reference architectures. This will help you and your organization reuse design concepts. Reference architecture (specific to your domain) may then result in an implementation framework (again, specific to your domain) that may contribute to development of product lines.


Constantin Kostenko
Firebrand Architect®
SoftwareArchitectures.com
FirebrandArchitect.com

Have a clear exit strategy

When are you done architecting? How long should the architecting phase take? These are very common questions that often don’t have a common answer. Your answer depends on what you’re trying to achieve and your operating environment.

The first step is to understand your environment and your constraints. Both technical and organizational. As Fred Brooks said in his new book The Design Of Design: “constraints are friends.” Constraints bound you and the scope of your work. You must still understand and feel the difference between a real constraint and a perceived constraint (often political) and a requirement.

The second step is to define your exit strategy. This must and can be defined shortly after you understand the general nature of the problem and your role in defining a solution. This requires understanding the role of downstream designers and implementers (even if you may be playing those roles as well). Without clearly defining the success (and failure) criteria before you invest your time your work is never going to be good enough. It’s a given fact that your success criteria and your exit strategy may change through the design process, but having a baseline will make it easier for you to handle changes in the future. But most importantly you’ll know when you’re done.


Constantin Kostenko
Firebrand Architect®
SoftwareArchitectures.com
FirebrandArchitect.com

Thursday, May 20, 2010

The most costly defects are design defects

In software the most costly defects are design defects. If you play the role (or carry the title) of a software architect be sure that you’re explicitly architecting your systems versus letting the designs emerge. The design shall emerge whether you want it or not, but you may not like the results. Further, be sure you understand and document your design decisions in the context when they were made. Undisciplined system design is irresponsible and is only appropriate for experimental solutions and throw away prototypes (that are guaranteed to be thrown away).


Constantin Kostenko
Firebrand Architect®
SoftwareArchitectures.com
FirebrandArchitect.com

Wednesday, May 12, 2010

What's this pattern's level of abstraction? It depends.

In building architecture we often easily recognize when one pattern fits into another pattern. Perhaps this is because physical things are easier for us to touch, feel, see, and sense. For example, in A Pattern Language book, Christopher Alexander clearly shows how building and city planning patterns fit with each other. Take the Activity Pockets pattern as an example. The essence of this pattern captures the fact that in order for an open public space to be vibrant and lively it needs to have a set of activity pockets at its edges. As the number of activity pockets expand the whole open space becomes lively. So if an urban designer’s design goal is to create a lively public space he or she may choose to apply this pattern. This pattern (#124) “helps complete the edge of all these larger patterns … Promenade (#31), Small Public Squares (#61), Pedestrian Street (#100), Building Thoroughfare (#101).” At the same time this pattern is further refined by the following downstream patterns: Arcades (#119), Trellised Walk (#174), Sitting Wall (#243), just to name a few. It’s easy to see the granularity level of the Activity Pockets pattern in the context of a city and a building.

The above mentioned pattern makes sense, especially when combined with a topology map, but what about software patterns?

In the software architecture world the granularity of a given pattern is not always obvious. In case of well known patterns, such as client server or its derivative N-tier, everyone knows that they represent a systemic level of abstraction. But less known patterns may confuse architects, especially if some patterns is widely recognized as systemic, but is encapsulated inside of some other systemic pattern. For example, a 3-tier overarching architecture may have a data repository pattern (also known to sit at a systemic level of abstraction) hidden at the next level of decomposition in the data tier.

The key to dealing with potential confusion is to clearly explain (and document) patterns used and why. Further, maintaining a proper perspective (i.e. dynamic, static, or physical), as mentioned in the previous post, is critical when showing how one patterns supports another pattern.



Constantin Kostenko
Firebrand Architect®
SoftwareArchitectures.com
FirebrandArchitect.com


Sunday, May 02, 2010

Don't mix up architectural perspectives

No real world system consists of a single [software] architecture pattern. Most systems are a combination of multiple patterns (a.k.a. styles) that together make up a solution. A common mistake that some architects make, when documenting software architecture, is mismatching different perspectives. For example, showing a layers pattern coupled with a process threads pattern within the same perspective makes no sense since layers is a static perspective and threads are associated with a dynamic perspective. It’s like mixing apples and oranges. In some cases it’s beneficial to show how a static (modules) perspective maps to a dynamic (run time) perspective, but such composition can occur when you already have two other perspectives.


Constantin Kostenko
Firebrand Architect®
SoftwareArchitectures.com
FirebrandArchitect.com

Blockchain learning path for Enterprise Software colleagues

I wrote this post to document my learning path of blockchain concepts and Ethereum technologies while keeping my “new to blockchain” collea...