Enterprise IT System Architecture maintains a holistic view of the system architecture across the organisation in support of the delivery of the IT plans and longer term business strategy.

As well as providing a complete catalog of the existing estate as a baseline for future development, enterprise architecture also aims to provide a view of the future state architecture and associated system strategy that is aligned with the business strategy.

“Enterprise Architecture is the holistic expression of an organisation’s key business, information, application and technology strategies and their impact on business functions and processes” (Meta Group inc.)

“Enterprise Architecture links the business mission, strategy, and process of an organisation to its IT strategy” (preface, Clinger-Cohen Act)

The benefits of Enterprise Architecture include:

• Alignment of IT systems strategy with the business strategy
• More effective solution delivery by providing direction, governance and discipline
• Facilitate consistency, standardisation, re-use and convergence, reducing duplication and total cost of ownership
• Reduce IT system complexity through clear specification based on standard models and design patterns
• More effective IT portfolio management, by considering project scope alignment with strategy

“The value is that they create order out of chaos” (Gartner Research)

Enterprise architecture is concerned with the current state, future state, roadmap and strategy (as per the IT System Architecture Definition), but at a holistic level:

• A comprehensive catalog of the current state applications and supporting platforms
• In a mature environment the current state should be defined by architecture specifications that have been completed as part of ongoing project delivery (see Solution Architecture)
• High level views of potential future states and associated roadmap from the current state
• A definition of strategy in terms of design standards, principles and imperatives to be considered or that must be applied going forward

The enterprise architecture practice also maintains the architecture framework, i.e. the reference models, patterns and methods.

The enterprise architecture needs to be maintained on an ongoing basis, with the following key events triggering change:

• A change in business strategy that indicates the need for new or different IT system capabilities in the future
• Specific business requirements for new or different IT system capabilities that were not previously identified in the business strategy; this is typically as part of IT solution delivery in which case it is necessary to develop the enterprise architecture to support support a specific initiative.
• Review of the current IT system architecture, typically as part of a post-implementation review (PIR) following the delivery of a new solution and/or as part of a regular audit of the IT estate; this may require reconciliation with an views created during solution design

In an environment where the enterprise architecture is immature it may not be practical to develop it independently given the time and effort required to do this, with potentially limited immediate benefits. Instead, a more iterative and organic approach can be adopted whereby the enterprise architecture is developed in response to, and in support of specific initiatives, although it should be noted that this may have some impact on delivery timescales and/or the quality of the enterprise architecture specification.

The enterprise architecture scope can be managed across various domains, where a domain is closely aligned with a particular concern (and therefore a point of view), for example design layer (e.g. applications), function (e.g. customer relationship management), or other concern (e.g. security). Typically more design structure orientated domains form the core practice.

The IT Business Architect is therefore concerned with how the system will support the high level business processing requirements, including:

• Understand the business model, goals, strategy, organisation and operating model
• Definition of how systems support the above and will meet future requirements
• Review and validate business cases for system changes
• Definition of the system architecture models: process, function and information
• Definition of the reference models to describe the above in a common business language

The Business Architect will be the primary face-off to the business stake-holders.

The Information Architect is concerned with how information (including data, content and knowledge) is managed across the system both conceptually and physically, including:

• Understand how information assets are owned and classified by the business
• Definition of the information model, information life-cycle and associated reference models
• Definition of how processes, functions and underlying applications maintain and consume information
• Definition of mechanics of the storage, retrieval and transportation of the information
• Definition of the processes to ensure data is adequately protected according to its classification

The Enterprise Information Architect governs the Corporate Data Dictionary and faces-off to the business information managers. A key reference model is the Information Domain Classification, which describes the various types of information entity at various levels and associated attributes such as ownership, sensitivity, etc.

Solution Architecture is concerned with how Application and Platform Architecture supports the Business and Information Architecture, including:

• Understand the business/system and information architecture
• Determine the non-functional requirements, e.g. relating to performance, availability, operability, etc.
• Definition of the application architecture models; how applications and associated integration support process, function and information
• Definition of the platform architecture models: how software and infrastructure support the delivery of applications
• Definition of the solution security policies, including confidentiality and data protection requirements

Specifically with regard to Platform design there are architecture aspects concerned with:

• Runtime or Execution Architecture: The framework that supports execution of business application services.
• Development Architecture: The framework that supports development of all aspects of the solution.
• Operations Architecture: The framework that supports management and operation of the solution.

Here Solution Architecture is concerned with a high level view of the Platform Architecture across the software technology platform and supporting infrastructure, with the primary focus being on the Runtime Architecture. Domain specific Architects (e.g. Security, Technology, Infrastructure) may be employed to detail the in depth Solution Architecture.

The Enterprise Solution Architect maintains the Application Inventory, which should catalog details of all existing application within the estate including attributes such as: functions supported and users/locations supported, change and running expenses, user and transaction volumes, alignment with strategy and standards, etc.