What is an architecture?

Introduction

Welcome to this series of articles on Introduction in Enterprise Architecture. The series is structured into four articles, each of them answering one of the following questions:

1. What is an Architecture?
2. What is an Enterprise Architecture?
3. Which benefits are provided by an Enterprise Architecture?
4. Which benefits are provided by Enterprise Architecture Frameworks?

The intended audience are all of you, being affected by the topic of Enterprise Architecture. Such as a decision maker, who wants to understand a topic being highly relevant for many companies and organizations. As well as an architect, who already knows about the complexity of Enterprise Architecture and is looking for conclusive and consistent suggestions on how to answer the questions mentioned before.

A definition of Architecture

Have you ever listened to or even participated in a discussion on Enterprise Architecture? You might have recognized that the participants in the discussion had no common sense on the meaning of Architecture to start with, more often than not without even being aware about this lack of common sense.

Reasons are often not a lack of individual expertise but a lack of common expertise and common terminology. Consequently discussions on Enterprise Architecture either tend to be wasted time or not effective since a great amount of time needs to be invested to get a common understanding on expertise and terminology.

In order to prevent discussions without the needed common fundamentals and terminology I recommend you to start with the definition of architecture as provided by ISO 42010:2007.

The fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution.

Following this definition, an architecture provides information on the fundamental organization of a system (without providing a definition of system), structured in

• its components,
• their relationship to each other and the environment
• as well as the principles governing its design and evolution.

Following the definition of ISO it can be concluded, that inherently every system consists of an architecture, since every system

• has an organization,
• can be structured in its components and their relationship to each other and
• follows some principles on its design and evolution.

Consequently the ISO definition is a good starting point for a common understanding on architecture but does not provide guidance on the difference between the system inherent architecture and its formal description, typically the nice diagrams being created by architects in some kind of modeling software.

In order to avoid misconception other sources and technical literature such as “The open group architecture framework” (TOGAF) extend the definition of architecture.

A formal description of a system, or a detailed plan of the system at component level to guide its implementation.

and

… structure of components, their inter-relationships, and the principles and guidelines governing their design and evolution over time.

Comparing the definition provided by ISO with the definition provided by TOGAF you might recognize, that TOGAFs second definition applies to what ISO defines as an architecture.

TOGAFs first definition on the other side extends ISOs definition by the formal description of the system in terms of diagrams and models created by architects to describe the system, its components and all the relationships and associations.

The advantage of TOGAFs approach on architecture definition is that in a discussion participants need only to agree on which aspect of architecture the discussion is about, on architecture itself or on its formal description. The disadvantage of TOGAFs approach is the semantic overload of the term architecture.

In order to avoid confusion it can be beneficial to make a difference between the architecture (following the definition of ISO or TOGAFs second definition) and the architecture model, defined as the formal description of the architecture following TOGAFs first definition.

An architecture model does not necessarily reflect the complete architecture but only the relevant aspects regarding the concrete context and demands. Given the organizational structure as the relevant aspect of the architecture, the model might provide org-charts and hierarchy diagrams. Given the system interrelationships as the relevant aspect of the architecture, the architecture model might provide system and wiring diagrams.

Most important is the understanding that an architecture is system inherent by definition and the architecture model is the formal description of the relevant aspects of the architecture.

Conclusion

In the context of this article I did provide you the definition of architecture referencing to ISO 42010 and TOGAF as the inherent structure of a system,

• its components,
• their interrelationship to each other and the environment as well as
• its principles on design and evolution.

Following an other aspect of TOGAFs definition of architecture and to avoid confusion in the difference between the architecture and its formal description, the term architecture model was introduced.

Architecture model is defined as the formal description of the relevant aspects of the architecture regarding a specific context.

Using the information provided in this article, the next article is discussing a definition of Enterprise Architecture.