Before we start to break architecture down into its core concepts, let’s first categorize the different types of architectures and figure out what they share in common, as well as what makes them unique.
For the sake of this discussion, we are defining and focusing on three types of architecture:
- Physical architecture
- Conceptual architecture (which includes digital architecture)
- Logical architecture
Physical Architecture
Physical architecture involves the design and construction of tangible, visible, and touchable structures and spaces, such as houses, office buildings, or landscapes.
Physical structures interact with the physical environments around them, facilitating flows such as traffic or energy flows.
This is what most of us think of when we think of the general concept of architecture.
We think about the proverbial architect designing buildings and creating blueprints that can be used both in the design, construction, maintenance, or future modifications and enhancements of a physical structure.
Of the three types of architecture that we will be discussing, physical architecture is the “easiest” to grasp because it’s a concrete concept (no pun intended).
The other types of architecture - conceptual and logical - are not as concrete.
Logical and conceptual architectures - including digital architectures - require high levels of abstract thinking, but also follow many of the same principles as physical architecture.
Conceptual Architecture
Conceptual architecture deals with the design and implementation of more abstract structures and flows.
These structures may not be tangible, visible, or touchable but we interact with them every day.
These structures are known to us but might not be observable or obvious.
This could include anything from communication structures, to organizational structures, to market structures.
Digital structures are, by nature, conceptual.
We can see the physical components that make up the underlying hardware platforms that run software applications, but we can’t see the 1’s and 0’s being passed along throughout the circuits within, let’s say, a laptop computer.
We have to imagine and hold the concept of what these 1’s and 0’s are supposed to do, the various paths they take through a system, and the data structures they form, represented to human users in the form of human-centric interfaces.
We’re talking about the flows of digital communications and information, the 1’s and 0’s, through digital architectures run on tangible, physical hardware architectures.
Examples of conceptual architectures include:
- Enterprise architecture
- Business architecture
- Software architecture
- Data architecture
- Cloud architecture
- Application architecture
- Information architecture
- Knowledge architecture
…and many more.
Logical Architecture
Logical architecture combines elements of both physical and conceptual architectures.
Logical architecture exists to explain the connections and groupings of these elements in a consolidated and cohesive manner.
These elements can be from various disciplines or applications, both physical and conceptual.
A great example of logical architecture is the concept of solutions architecture.
Solutions architecture, at its most abstract level, is about designing systems or services that solve business challenges.
It’s neither the specific business challenges nor the specific technologies applied that actually matter.
It’s the way in which those elements are logically organized and structured to address a specific problem, communicate complex concepts, or define domains and boundaries in new ways from different perspectives.
Logical architecture exists within many physical and conceptual architectural disciplines.
I’ll use three concrete examples to demonstrate the concept of logical architecture:
- The OSI model
- Cloud architecture
- Design patterns and conceptual frameworks
…just to name a few common examples.
OSI Model
The OSI model is a well-known conceptual architecture for standardizing network communications. It’s been around for decades.
The OSI model is divided into seven layers, each deeply interconnected with the layer above and below it.
For example, the Physical Layer (Layer 1) is the foundational layer responsible for the physical connections between devices; the remaining six layers build on top of this layer.
Another example, the Transport Layer (Layer 4) enables the transfer of data between systems using protocols such as TCP and UDP, which themselves have their own conceptual architectures.
Can TCP and UDP function outside of the OSI model? Absolutely.
The OSI model is conceptual in nature; there is no physical, tangible entity to bind to or be dependent on.
These layers make it easier for us to grasp complex concepts and technologies by logically grouping them and visualizing their interactions and dependencies in a familiar and easy-to-understand structure.
Cloud Architecture
Cloud architecture represents the abstraction of underlying infrastructure components into a more flexible and scalable logical structure.
Cloud architecture hides the complexity of traditional physical infrastructure by providing services at various levels of abstraction, including concepts such as:
- Infrastructure-as-a-Service (IaaS)
- Platform-as-a-Service (PaaS)
- Software-as-a-Service (SaaS)
Design Patterns and Conceptual Frameworks
Sometimes the problems we face have already been addressed and solved before.
In some cases, flexible and reusable solutions have emerged for common problems we face.
These generalized best practices are referred to as design patterns.
We can think of design patterns as one-off templates for solving known problems, but how these patterns get implemented is ultimately up to us.
In other cases, entire models have been established to provide prescriptive guidance for approaching and solving complex institutional problems.
These models are referred to as frameworks.
Some frameworks are more prescriptive than others.
For example, TOGAF (The Open Group Architecture Framework) includes a methodology and a set of tools and best practices for implementing and managing enterprise architecture.
While TOGAF provides guidance on how to approach and solve a number of problems, it is flexible and can be adapted to the needs and context specific to a given organization or implementation.
On the other hand, frameworks such as SAFe (Scaled Agile Framework) tend to be more prescriptive in that they provide detailed step-by-step instructions for the rigid implementation of Agile practices by dictating the roles, ceremonies, and artifacts to be adopted by the organization.