EA: Legacy & Latency

 “For things to remain the same, everything must change”

Lampedusa, “The Leopard”


Whatever the understanding of the discipline, most EA schemes implicitly assume that enterprise architectures, like their physical cousins, can be built from blueprints. But they are not because enterprises have no “Pause” and “Reset” buttons: business cannot be put on stand-by and must be carried on while work is in progress.

Refactored Legacy (E. Lusito)

Systems & Enterprises

Systems are variously defined as:

  • “A regularly interacting or interdependent group of items forming a unified whole” (Merriam-Webster).
  • “A set of connected things or devices  that operate  together” (Cambridge Dictionary).
  • “A way of working, organizing, or doing something which follows a fixed plan or set of rules” (Collins Dictionary)
  • “A collection of components organized to accomplish a specific function or set of functions” (TOGAF from ISO/IEC 42010:2007)

While differing in focus, most understandings mention items and rules, purpose, and the ability to interact; none explicitly mention social structures or interactions with humans. That suggests where the line should be drawn between systems and enterprises, and consequently between corresponding architectures.

Architectures & Changes

Enterprises are live social entities made of corporate culture, organization, and supporting systems; their ultimate purpose is to maintain their identity and integrity while interacting with environments. As a corollary, changes cannot be carried out as if architectures were just apparel, but must ensure the continuity and consistency of enterprises’ structures and behaviors.

That cannot be achieved by off-soil schemes made of blueprints and step-by-step processes detached from actual organization, systems, and processes. Instead, enterprise architectures must be grown bottom up from actual legacies whatever their nature: technical, functional, organizational, business, or cultural.

EA’s Legacy

Insofar as enterprise architectures are concerned, legacies are usually taken into account through one of three implicit assumptions:

No legacy assumptions ignore the issue, as if the case of start-ups could be generalized. These assumptions are logically flawed because enterprises without legacy are like embryos growing their own inherent architecture, and in that case there would be no need for architects.

En Bloc legacy assumptions take for granted that architectures as a whole could be replaced through some Big Bang operation without having a significant impact on business activities. These assumptions are empirically deceptive because, even limited to software architectures, Big Bang solutions cannot cope with the functional and generational heterogeneity of software components characterizing large organizations. Not to mention that enterprise architectures are much more that software and IT.

Piecemeal legacies can be seen as the default assumption, based on the belief that architectures can be re-factored or modernized step by step. While that assumption may be empirically valid, it may also miss the point: assuming that all legacies can be dealt with piecemeal rubs out the distinction pointed above between systems and enterprises.

So, the question remains of what is to be changed, and how ?

EA as a Work In Progress

As with leopard’s spots and identity, the first step would be to set apart what is to change (architectures) from what is to carry on (enterprise).

Maps and territories do provide an overview of spots’ arrangement, but they are static views of architectures, whereas enterprises are dynamic entities that rely on architectures to interact with their environment. So, for maps and territories to serve that purpose they should enable continuous updates and adjustments without impairing enterprises’ awareness and ability to compete.

That shift from system architecture to enterprise behavior implies that:

  • The scope of changes cannot be fully defined up-front, if only because the whole enterprise, including its organization and business model, could possibly be of concern.
  • Fixed schedules are to be avoided, lest each and every unit, business or otherwise, would have to be shackled into a web of hopeless reciprocal commitments.
  • Different stakeholders may come as interested parties, some more equal than others, possibly with overlapped prerogatives.

So, instead of procedural and phased approaches supposed to start from blank pages, EA ventures must be carried out iteratively with the planning, monitoring, assessment, and adjustment of changes across enterprises’ businesses, organizations, and systems. That can be represented as an extension of the OODA (Observation, Orientation, Decision, Action) loop:

  • Actual observations from operations (a)
  • Data analysis with regard to architectures as currently documented (b).
  • Changes in business processes (c).
  • Changes in architectures (d).
EA decision-making as an extension of the OODA loop

Moreover, due to the generalization of digital flows between enterprises and their environment, decision-making processes used to be set along separate time-frames (operational, tactical, strategic, …), must now be weaved together along a common time-scale encompassing internal (symbolic) as well as external (actual) events.

It ensues that EA processes must not only be continuous, but they also must deal with latency constraints.

Changes & Latency

Architectures are by nature shared across organizational units (enterprise level) and business processes (system level). As a corollary, architecture changes are bound to introduce mismatches and frictions across business-specific applications. Hence the need of sorting out the factors affecting the alignment of maps and territories:

  • Elapsed time between changes in territories and maps updates (a>b) depends on data analytics and operational architecture.
  • Elapsed time between changes in maps and revised objectives (b>c) depends on business analysis and organization.
  • Elapsed time between changes in objectives and their implementation (c>d) depends on engineering processes and systems architecture.
  • Elapsed time between changes in systems and changes in territories (d>a) depends on applications deployment and technical architectures.

Latency constraints can then be associated with systems engineering tasks and workshops.

EA changes & Latency

On that basis it’s possible to define four critical lags:

  • Operational: data analytics can be impeded by delayed, partial, or inaccurate feedback from processes.
  • Mapping: business analysis can be impeded by delays or discrepancies in data analytics.
  • Engineering: development of applications can be impeded by delays or discrepancies in business analysis.
  • Processes: deployment of business processes can be impeded by delays in the delivery of supporting applications.

These lags condition the whole of EA undertakings because legacy structures, mechanisms, and organizations are to be continuously morphed into architectures without introducing misrepresentations that would shackle activities and stray decision-making.

EA Latency & Augmented Reality

Insofar as architectural changes are concerned, discrepancies and frictions are rooted in latency, i.e the elapsed time between actual changes in territories and the updating of relevant maps.

As noted above, these lags have to be weighted according to time-frames, from operational days to strategic years, so that the different agents could be presented with the relevant and up-to-date views befitting to each context and concerns.

EA views must be set according to contexts and concerns, with relevant lags weighted appropriately.

That could be achieved if enterprises architectures were presented through augmented reality technologies.

Compared to virtual reality (VR) which overlooks the whole issue of reality and operates only on similes and avatars, augmented reality (AR) brings together virtual and physical realms, operating on apparatuses that weaves actual substrates, observations, and interventions with made-up descriptive, predictive, or prescriptive layers.

On that basis, users would be presented with actual territories (EA legacy) augmented with maps and prospective territories.

Augmented EA: Actual territory (left), Map (center), Prospective territory (right)

Composition and dynamics of maps and territories (actual and prospective) could be set and edited appropriately, subject to latency constraints.

Further Reading

Models as Parachutes


The recent paralysis of British Airways world operations (due to a power failure, if officials are to be believed), following the crash of Delta Airlines’ reservation system and a number of similar incidents, once again points to the reliability of large and critical IT systems.

László Moholy-Nagy-para
Models as Parachutes (László Moholy-Nagy)

Particularly at risk are airlines or banking systems, whose seasoned infrastructures, at the cutting edge when introduced half a century ago, have been strained to their limit by waves of extensive networked new functionalities. Confronted to the magnitude and complexity of overall modernization, most enterprises have preferred piecemeal updates to architectural leaps. Such policies may bring some respite, but they may also turn into aggravating factors, increasing stakes and urgency as well as shortening odds.

Assuming some consensus about stakes, hazards, and options, the priority should be to overcome jumping fears by charting a reassuring perspective in continuity with current situation. For that purpose models may provide heartening parachutes.

Models: Intents & Doubts

Models can serve two kinds of purposes:

  • Describe business contexts according to enterprise objectives, foretell evolution, and simulate policies.
  • Prescribe the architecture of supporting systems and the design of software components.

Business analyst figure maps from territories, software architects create territories from maps
Models Purposes: Describe contexts & concerns, Design supporting systems

Frameworks were supposed to combine the two perspectives, providing a comprehensive and robust basis to systems governance. But if prescriptive models do play a significant role in engineering processes, in particular for code generation, they are seldom fed by their descriptive counterpart.

Broadly speaking, the noncommittal attitudes toward descriptive models comes from a rooted mistrust in non executable models: as far as business analysts and software engineers are concerned, such models can only serve as documentary evidence. And since prescriptive models are by nature grounded to systems’ inner making, there is no secure conceptual apparatus linking systemic changes with their technical consequences. Hence the jumping frights.

Overcoming those frights could be achieved by showing the benefits of secure and soft landings.

Models for Secure Landings

As any tools, models must be assessed with regard to their purpose: prescriptive ones with regard to feasibility and reliability of architectures and design, descriptive ones with regard to correctness and consistency. As already noted, compared to what has been achieved for the former, nothing much has been done about the validity of the latter.

Yet, and contrary to customary beliefs, the rigorous verification of descriptive (aka extensional) models is not a dead-end. Of course these models can never be proven true because there is no finite scope against which they could be checked; but it doesn’t mean that nothing can be done to improve their reliability:

Models must be assessed with regard to their purpose
How to Check for secure landings

  • Correctness: How to verify that all the relevant individuals and features are taken into account. That can only be achieved empirically by building models open to falsification.
  • Consistency: How to verify that the symbolic descriptions (categories and connectors) are complete, coherent and non redundant across models and abstraction levels. That can be formally verified.
  • Alignment: How to verify that current and required business processes are to be seamlessly and effectively supported by systems architectures. That can be managed by introducing a level of indirection, as illustrated by MDA with platform independent models (PIMs) set between computation independent (CIMs) and platform specific (PSMs) ones.

Once established on secure grounds, models can be used to ensure soft landings.

Models for Soft Landings

Set within model based system engineering frameworks, models will help to replace piecemeal applications updates by seamless architectures modernization:

  • Systems: using models shift the focus of change from hardware to software.
  • Enterprise: models help to factor out the role of organization and regulations.
  • Project management: models provide the necessary hinge between agile and phased projects, the former for business driven applications, the latter for architecture oriented ones. Combining both approaches will ensure than lean and just-in-time processes will not be sacrificed to system modernization.

Seamless architectures modernization (a) vs Piecemeal applications updates (b).
Seamless architectures modernization (a) vs Piecemeal applications updates (b).

More generally, and more importantly, models are the option of choice (if not the only one) for enterprise knowledge management:

  • Business: Computation independent models (CIMs), employed to trace, justify and rationalize business strategies and processes portfolios.
  • Systems: Platform specific models (PSMs), employed to trace, justify and rationalize technical alternatives and decisions.
  • Decision-making and learning: Platform independent models (PIMs), employed to align business and systems and support enterprise architecture governance.

And knowledge management is arguably the primary factor for successful comprehensive modernization.

Strategic Decision-making: Cash or Crash

Governance is all about risks and decision-making, but investing on truly fail-safe systems for airlines or air traffic control can be likened to a short bet on the Armageddon, and that cannot be easily framed in a neat cost-benefit analysis. But that may be the very nature of strategic decision-making: not amenable to ROI but aiming at risks assessment and the development of the policies apt to contain and manage them. That would be impossible without models.

Further Reading

2015: A Scraps-Free New Year

As chances are for new years to come with the legacies of past ones, that would be a good time to scrub the scraps.

Sifting through requirements subhodGupta
How to scrub last year scraps (Subhod Gupta)

Legacies as Forced Reuses

As far as enterprise architectures are concerned, sanguine resolutions or fanciful wishes notwithstanding, new years seldom open the door to brand new perspectives. More often than not, they bring new constraints and further curb the possible courses of action by forcing the reuse of existing assets and past solutions. That will call for a review and assessment of the irrelevancies or redundancies in processes and data structures lest they clog the organization and systems, raise entropy, and degrade governance capability.

Architectures as Chosen Reuses

Broadly defined, architectures combine assets (physical or otherwise) and mechanisms (including organizational ones) supporting activities which, by nature, must be adaptable to changing contexts and objectives. As such, the primary purpose of architectures is to provide some continuity to business processes, across locations and between business units on one hand, along time and business cycles on the other hand. And that is mainly to be achieved through reuse of assets and mechanisms.

Balancing Changes & Reuse

It may be argued that the main challenge of enterprise architects is to maintain the right balance between continuity and agility, the former to maintain corporate identity and operational effectiveness, the latter to exploit opportunities and keep an edge ahead of competitors. That may turn to be an oxymoron if architects continuously try to discard or change what was designed to be kept and reused. Yet that pitfall can be avoided if planting architectures and pruning offshoots are carried out independently.

Seasons to Plant & to Prune

Enterprises life can be set along three basic time-scales:

  • Operational: for immediate assessment and decision-making based on full information.
  • Tactical: for periodic assessment and decision-making based on partially reliable information. Periodicity is to be governed by production cycles.
  • Strategic: for planned assessment and decision-making based on unknown or unavailable information. Time-frames are to be governed by business models and risks assessment.

Whereas architecture life-cycles are by nature strategic and meant to span an indefinite, but significant, number of production cycles, trimming redundancies can be carried on periodically providing it doesn’t impact processes execution. So why not doing the house cleaning with the beginning of new years.

Further Reading

Modernization & The Archaeology of Software

The past is not dead. In fact, it’s not even past. –
William Faulkner


Retrieving legacy code has something to do with archaeology as both try to retrieve undocumented artifacts and understand their initial context and purpose. The fact that legacy code is still well alive and kicking may help to chart their structures and behaviors, but it may also confuse the rationale of initial designs.

Legacy Artifact: Was the bowl intended for turkeys ? at thanksgiving ? Why the worm ?

Hence the importance of traceability and the benefits of a knowledge based approach to modernization organized along architecture layers (enterprise, systems, platforms), and processes (business, engineering, supporting services).

Model Driven Modernization

Assuming that legacy artifacts under consideration are still operational (otherwise re-engineering would be pointless), modernization will have to:

  • Pinpoint the deployed components under consideration (a).
  • Identify the application context of their execution (b).
  • Chart their footprint in business processes (c).
  • Define the operational objectives of their modernization (d).
  • Sketch the conditions of their (re)engineering (e) and the possible integration in the existing functional architecture (f).
  • Plan the re-engineering project (g).

Modernization Road Map

Those objectives will usually not be achieved in a big bang, wholly and instantly, but progressively by combining increments from all perspectives. Since the different outcomes will have to be managed across organizational units along multiple engineering processes, modernization would clearly benefit from a model based approach, as illustrated by MDA modeling layers:

  • Platform specific models (PSMs) should be used for collecting legacy artifacts and mapping them to their re-engineered counterparts.
  • Since platform independent models (PIMs) are meant to describe system functionalities independently of implementations,  they should be used to consolidate the functionalities of legacy and re-engineered artifacts.
  • Since computation independent models (CIMs) are meant to describe business processes independently of supporting systems, they should be used to reinstate, document, and validate re-engineered artifacts within their business context.

Model Driven Modernization

Corresponding phases can be expressed using the archaeology metaphor: field survey and collection (>PSMs), analysis (PSMs/PIMs), and reconstruction (CIMs/PIMs).

Field Survey

The objective of a field survey is to circumscribe the footprint of the modernization and collect artifacts under consideration:

  • Given targeted business objects or activities, the first step is to collect information about locations, distribution and execution dependencies.
  • Sites can then be searched and executable files translated into source ones whose structure and dependencies can be documented.
  • The role of legacy software can then be defined with regard to the application landscape .

Analysis (with regard to presentation, control, persistency, and services)

It must be noted that field survey and collection deal with the identification and restoration of legacy objects without analyzing their contents.


The aim of analysis is to characterize legacy components, first with regard to their architectural features, then with regard to functionalities. Basic architectural features take into account components’ sharing and life-cycle.

The analysis of functionalities can be achieved locally or at architecture level:

  • Local analysis (a) directly map re-factored applications to specific business requirements, by-passing functional architecture. That’s the case when targeted applications can be isolated, e.g by wrapping legacy code.
  • Global analysis (b) consolidate newly supported applications with existing ones within functional architecture, possibly with new functionalities.

Analysis (with regard to presentation, control, persistency, and services)

It must be noted that the analysis of legacy components, even when carried out at functional architecture level, takes business processes as they are.


The aim of reconstruction is to set legacy refactoring within the context of enterprise architecture. That should be done from operational and business perspectives:

  • As the primary rationale of modernization is to deal with operational  problems or bottlenecks, its benefits should be fully capitalized at enterprise level.
  • Re-factored applications usually make room for improvements of users’ experience; that may bring about further changes in organization and business processes.


Hence, modernization is not complete until potential benefits of re-factored applications are considered, for business processes as well as for functional architecture.

From Workshops to Workflow

As noted above, modernization can seldom be achieved in a big bang and should be planned as a model based engineering process. Taking a leaf from the MDA book,  such a process would be organized across four workshops:

  • Technical architecture (deployment models): that’s where legacy components are collected, sorted, and documented.
  • Software architecture (platform specific models): where legacy components are put in local context.
  • Functional architecture (platform independent models): where legacy components are put in shared context.
  • Enterprise architecture (computation independent models): where legacy components are put into organizational context.

Modernization & MBSE Workshops

Those workshops would be used to manage the outcomes of the modernization workflow:

  1. Collect and organize legacy code; translate into source files.
  2. Document legacy components.
  3. Build PSMs according basic architecture functional patterns.
  4. Map to PIMs of system functional architecture.
  5. Consolidate enterprise architecture.

Modernization Workflow

With the relevant workflows defined in terms of model-based systems engineering, modernization can be integrated with enterprise architecture.

Further Reading

External Links