Why do you need an architecture repository?

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How to manage the structure and behaviour of business systems if you don’t know that structure or behaviour?

How to plan changes that are optimal for the enterprise (rather than suboptimal and localized) if you have no enterprise-wide repository of the system estate?

On the other hand, why is building and maintaining an enterprise-wide architecture repository more challenging than CASE tool vendors tell you?

(CASE = Computer-Aided System Engineering).


Why do you need an architecture repository?. 1

Three thing to bear in mind about repository maintenance. 2


Why do you need an architecture repository?

Some enterprises employ an enterprise architect when managers realize things are out of control – the enterprise is not governing its assets as well as it should.

Managers don’t know what the enterprise owns, what it is today.

So their main interest is the current or baseline state.

You, the newly-appointed enterprise architect, have a mission simply to know and understand the scale and complexity of the current estate.


Other enterprises employ an enterprise architect to help them plan ahead – to define their business, IS or IT strategy – to define what they aim to become.

They are interested not only in the current baseline state, but also a future target state and the migration from the former to the latter.

Both kinds of enterprise need some kind of architecture repository to store/view descriptions of the enterprise and its systems.

An architecture description is a model of a system – it is a restricted view of reality - it does not tell you everything.

But it should tell you what you need to know to make well-informed judgements about where change is needed and the impact of change.


You can be sure that things will change.

·         The business will be reorganised.

·         Enterprises are driven to change by various pressures.

·         They are increasingly driven to make big changes, fast changes, and look for dramatic cost reductions.

·         Enterprises frequently divide and merge.

·         Giving old assets away is easy.

·         Integrating new assets is hard.

·         Mergers can and do founder on the difficulty of consolidating the various information systems used by the formerly distinct enterprises.


You can draw some inspiration from the fact that successful change will require the knowledge of the enterprise that you (enterprise architect) manage.

Some enterprise architecture purposes

You will want to:

·         Record and show the current estate

·         Record and show strategic business and technology goals and directions.

·         Demonstrate that planned IT changes relate those goals

·         Demonstrate that planned IT changes result in simplifications and cost reductions

·         Enable IT assets to be evaluated, managed, and changed.

·         Enable enterprise transformations to be made with minimal costs and risks to business operations.

Some enterprise architecture processes

You are employed to manage the structure of an enterprise’s assets, and to plot transformations from a current state to a future state.

You expect to get involved in:

·         Understanding the structure of the baseline and target architecture states.

·         Planning the transformation: plotting the most effective transformation path from the current state to the future state.

·         Helping programme/project managers to govern the transformation: manage the transition.

·         Developing and maintaining the enterprise architecture and providing technical/design assurance for all enterprise initiatives/projects against it.

Enterprise architecture repository purposes

A repository should help you:

·         Understand the system described: Building and displaying a model of complex structures helps people to understand them.

·         Relate IT to business: You can do traceability analysis, to show which assets relate to which goals, requirements and constraints.

·         Identify potential changes: You can do gap analysis and cluster analysis, to spot areas where changes are desirable.

·         Plan changes: You can define a target or vision architecture by manipulating elements of the baseline architecture,

·         Manage changes: You can do impact analysis following any change proposal.

Three thing to bear in mind about repository maintenance

First, if the repository is not internally cohesive and coherent, people will distrust it.

Second, you’ll need to understand the relationships in the repository meta model.

And practice, you won’t manage to capture all the architecturally significant entities and relationships in one repository.

The importance of repository coherence

Solution architects often document architecture descriptions in diagrams and documents, and that can be enough for small and/or short-term projects.

They can use Power Point or Visio to draw the diagrams.

And use spreadsheets or MS Access to maintain the repository of system elements.


Larger and longer-term projects and programmes require a more flexible form of documentation - that can be manipulated by several architects and presented in a variety of ways.

They need a repository from which up-to-date views can be generated.

Views help you manage a complex repository.

It is hard to understand a complex structure all at once.

You can better understand a partial view that suppresses details shown in other views.

Dividing a complex model into loosely-coupled parallel structures makes it easier to understand and change each on its own.


You should select the views and models to suit your target audiences.

Graphical representation helps you understand a view.

It usually assists understanding and manipulation of a view, and hence of the underlying repository.

But views are superficial; the architecture is in the repository


The repository should help you to add or remove views at will.

Given a migration with 10 stages and an architecture repository with 10 view points, there are at least 100 potential views.

But you do not have to maintain and present all those views if the underlying data is stored for when you need it.


The repository matters more than the pictures.

To manage a complex transformation you need a coherent architecture repository more than pretty pictures.


The repository must be coherent across all views.

An architecture repository relates elements in different views to each other.

An enterprise architecture repository must be maintained in a repository that underpins any and all views.


The repository must be coherent across all stages.

Planning a transformation means plotting how structures change over time.

Migration can involve transition through several intermediate states.

The architecture repository must remain coherent and consistent over time, as well as over views.

The importance of the architecture meta model

In the philosopher’s “eternal golden braid” there are things, descriptions of things, and descriptions of descriptions.

An architecture description contains a collection of artifacts that are related to each other directly or indirectly.

You simply cannot manage a large and complex architecture description without describing the description itself.


The description of description, or model of a model, is known here as a meta model.

A meta model can help you manage documentation in Word and Excel.

But if you store your description in a CASE tool, then the meta model is not just helpful, it is essential.

You must understand the meta model - must understand the model of the architecture repository, even if the readers of any given view do not.

The importance of repository integration

Ideally, you can identify one CASE tool repository as being your central architecture repository.

But in practice, what is documented about enterprise systems usually spans several physical repositories.


Where does your enterprise record its business goals, its balanced score card, and financial data relating to assets or projects?

For example, a US federal government department has to answer queries regarding its investments.

Some do this using templates and functions available in specialized project/investment management tools such as Clarity and Prosight.


“One government department I have worked with

·         stores its architecture models in a CASE tool repository, and

·         publishes its architecture documents (pdf and Word) in a Knowledge Management portal.

Each division stores mandatory model information in the enterprise-wide CASE tool repository, but each has its own portal for architecture documents.

Some documents are linked to models; some are not.

Another tool is used to record fine-grained investment reports (although the CASE tool meta model was modified to record high level investment information).” Steve Else PhD.


In short, people use:

·         CASE tools to maintain diagrams and system element definitions used in architecture descriptions.

·         Knowledge management/portal tools to store architecture deliverable documents

·         Other tools to maintain more management-oriented information.


Linking between repositories presents configuration management challenges.

It is important that your central repository supports every kind of change at every level of change management.

See the related paper for discussion of this.


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