Category: Systems

Requirements in Digital Environments

Symbolic environment (National Gallery, Canberra, Australia).

Preamble

Beyond varying names, requirements have often been classified into four basic categories:

  1. Process requirements deal with organization and business processes independently of the part played by supporting systems.
  2. Application requirements deal with the part played by supporting systems in the realization of processes requirements..
  3. Quality of Service requirements deal with users experience independently of symbolic contents.
  4. Technical requirements deal with the implementation of systems functions independently of users experience.
A customary requirements taxonomy

Yet, regardless of the soundness of these categories, their effectiveness varies with contexts, and contexts have been drastically disrupted with enterprises immersion in digital environments.

Digital Disruption

With the generalization of digital environments and the ensuing intermingling of business processes and IT two established distinctions are losing their grip, first between processes and applications, and then between users and systems.

Before and after digital disruption

For processes, the blurring is to concern non deterministic operations (heuristics, non modal logic, learning, …) that used to be the prerogative of humans but are now commonly carried out by artificial brains set in applications (a), user interface (d), or elsewhere (b). As a corollary, user interfaces are losing their homogeneity, as single systems with established codes of conduct are being replaced by an undefined number of unidentified agents (c, d).

Lest they drive enterprises into dead ends requirements have to map their systems according to the new digital territories. Not surprisingly, that can be best achieved using the symbolic/non symbolic distinction.

Requirements associated with symbolic contents.. Given that symbolic expressions can be reformulated, the granularity of these requirements can always be adjusted as to fall into single domains and therefore under the authority of clearly identified owners or stakeholders.

Requirements not dealing with symbolic contents. Since they cannot be uniquely tied to symbolic flows between systems and business contexts, nothing can be assumed regarding the identity of stakeholders. Yet, as they target systems features and behaviors, they can still be associated with architecture levels: enterprise, functional, technical.

Functional Requirements

As commonly understood, functional requirements cover business concerns and the part supported by systems; as such they can be aligned with enterprise architecture capabilities, symbolic (roles, business entities, business logic), and non symbolic (physical objects and locations, time-frames, events, processes execution).

In order to deal with the blurring induced by digital flows, requirements should ensure the transparency and traceability of interactions:

  • Transparency: users should be continuously aware of the kind of agent in charge behind the screen.
  • Traceability: users should be able to ask for explanations about every outcome.

As noted above, such requirements cannot be circumscribed to users interfaces or even applications as they involve the whole of the knowledge architecture . To that end functional requirements should be organized in relation to enterprise architecture capabilities, and include the necessary extensions for knowledge architecture:

  • When agents/roles assignments remain open requirements should include communication (natural, symbolic, or digital) and cognitive capabilities.
  • Assuming that requirements are not limited to modeled information, the distinction between data, information, and knowledge should be explicit.
  • Likewise for non deterministic reasoning used in business logic.
Functional requirements and Capabilities

Requirements concerning the digital capabilities of entry-points and time-frames of processes execution are to be added in order to associate functional and quality of service requirements.

Non Functional Requirements

Non functional requirements (NFRs) are meant to encompass whatever remain which cannot be tied to symbolic representations.

As should be expected for leftover categories, non functional requirements are by nature a mixed bag of overlapping items straddling the line between systems and applications depending on whether they directly affect users experience (quality of service), or are of the sole concern of architects and engineers (technical requirements).

The heterogeneity of non functional requirements is compounded by the mirror impact of the digital transformation on functional ones when business requirements (e.g high-frequency trading) combine performances with “intelligent” computing (e.g. machine learning capabilities).

Quality of Service and Capabilities

Yet, that is not to say that the distinction is arbitrary; in fact it conveys an implicit policy regarding architecture capabilities: defining elapse time as functional means that high-frequency traders will be supported by their own communication network and workstations, otherwise they will be dependent upon the company technical architecture, managed by a separate organizational unit, governed by its own concerns and policies.

On that account the digital transformation may help to clarify the issue of non functional requirements because all requirements, functional or otherwise can now be framed uniformly and therefore discriminate more easily.

FURTHER READING

Semantic Interoperability: Stories & Cases

Preamble

For all intents and purposes, digital transformation has opened the door to syntactic interoperability… and thus raised the issue of the semantic one.

Cooked Semantics (Urs Fisher)

To put the issue in perspective, languages combine four levels of interpretation:

  • Syntax: how terms can be organized.
  • Lexical: meaning of terms independently of syntactic constructs.
  • Semantic: meaning of terms in syntactic constructs.
  • Pragmatic: semantics in context of use.
Languages levels of interpretation

At first, semantic networks (aka conceptual graphs) appear to provide the answer; but that’s assuming flat ontologies (aka thesaurus) within which all semantics are defined at the same level. That would go against the objective of bringing the semantics of business domains and systems architectures under a single conceptual roof. The problem and a solution can be expounded taking users stories and use cases for examples.

Crossing stories & cases

Beside the difference in perspectives, users stories and use cases stand at a methodological crossroad, the former focused on natural language, the latter on modeling. Using ontologies to ensure semantic interoperability is to enhance both traceability and transparency while making room for their combination if and when called for.

Set at the inception of software engineering processes, users’ stories and use cases mark an inflexion point between business requirements and supporting systems functionalities: where and when are determined (a) the nature of interfaces between business processes and systems components and, (b) how to proceed with development models, iterative or model based.

Users’ stories are part and parcel of Agile development model, their backbone, engine, and fuel. But as far as Agile is concerned, users’ stories introduce a dilemma: once being told stories are meant to be directly and iteratively put down in code; documenting them in words would bring back traditional requirements and phased development. Hence the benefits of sorting out and writing up the intrinsic elements of stories as to ensure the continuity and consistency of engineering processes, whether directly to code, or through the mediation of use cases.

To that end semantic interoperability would have to be achieved for actors, events, and activities.

Actors & Events

Whatever architectures or modeling methodologies, actors and events are sitting on systems’ fences, which calls for semantics common to enterprise organization and business processes on one side of the fence, supporting systems on the other side.

To begin with events, the distinction between external and internal ones is straightforward for use cases, because their purpose is precisely to describe the exchanges between systems and environments. Not so for users stories because at their stage the part to be played by supporting systems is still undecided, and by consequence the distinction between external and internal events.

With regard to actors, and to avoid any ambiguity, a semantic distinction could be maintained between roles, defined by organizations, and actors (UML parlance), for roles as enacted by agents interacting with systems. While roles and actors are meant to converge with analysis, understandings may initially differ across the fence between users stories and use cases, to be reconciled at the end of the day.

Representations should support the semantic distinctions as well as trace their convergence.

That would enable use cases and users stories to share overlapping yet consistent semantics for primary actors and external events:

  • Across stories: actors contributing to different stories affected by the same events.
  • Along processes: use cases set for actors and events defined in stories.
  • Across time-frames: actors and events first introduced by use cases before being refined by “pre-sequel” users stories.

Such ontology-based representations are to support full iterative as well as parallel developments independently of the type of methods, diagrams or documents used by projects.

activities

Users’ stories and use cases are set in different perspectives, business processes for the former, supporting systems for the latter. As already noted, their scopes overlap for events and actors which can be defined upfront providing a double distinction between roles (enterprise view) and actors (systems view), and between external and internal events.

Activities raise more difficulties because they are meant to be defined and refined across the whole of engineering processes:

  • From business operations as described by users to business functions as conceived by stakeholders.
  • From business logic as defined in business processes to their realization as defined in diagram sequences.
  • From functional requirements (e.g users authentication or authorization) to quality of service.
  • From primitives dealing with integrity constraints to business policies managed through rules engines.

To begin with, if activities have to be consistently defined for both users’ stories and use cases, their footprint should tally the description of actors and events stipulated above; taking a leaf from Aristotle rule of the three units, activity units should therefore:

  • Be triggered by a single event initiated by a single primary actor.
  • Be located into a single physical space with all resources at hand.
  • Timed by a single clock controlling accesses to all resources.

On that basis, the refinement of descriptions could go according to the nature of requirements: business (users’ stories), or functional and quality of service (use cases) .

Activities (execution units) should be tally with roles, events, and location.
Use cases wrap computation independent activities into transactions.

As far as ontologies are concerned, the objective is to ensure the continuity and consistency of representations independently of modeling tools and methodologies. For activities appearing in users stories and use cases, that would require:

  • The description of activities in relation with their business background, their execution in processes, and the corresponding functions already supported by systems.
  • The progressive refinement of roles (users, devices, other systems), location, and resources (objects or surrogates).
  • An unified definition of alternatives in stories (branches) and use cases (extension points)

The last point is of particular importance as it will determine how business and functional rules are to be defined and control implemented.

Knitting semantics: symbolic representations

The scope and complexity of semantic interoperability can be illustrated a contrario by a simple activity (checking out) described at different levels with different methods (process, use case, user story), possibly by different people at different time.

The Check-out activity is first introduced at business level (process), next a specific application is developed with agile (user story), and then extended for variants according to channels (use case).

Semantic interoperability between projects, domains, and methods.

Assuming unfettered naming (otherwise semantic interoperability would be a windfall), three parties can be mentioned under various monikers for renters, drivers, and customers.

In a flat semantic context renter could be defined as a subtype of customer, itself a subtype of party. But that option would contradict the neutrality objective as there is no reason to assume a modeling consensus across domains, methods, and time.

  • The ontological kernel defines parties and actors, as roles associated to agents (organization level).
  • Enterprises define customers as parties (business model).
  • Business unit can defines renters in reference to customers (business process) or directly as a subtype of role (user story).
  • The distinction between renters and drivers can be introduced upfront or with use cases’ actors.

That would ensure semantic interoperability across modeling paradigms and business domains, and along time and transformations.

Probing semantics: metonymies and metaphors

Once established in-depth foundations, and assuming built-in basic logic and lexical operators, semantic interoperability is to be carried out with two basic linguistic contraptions: metonymies and metaphors .

Metonymies and metaphors are linguistic constructs used to substitute a word (or a phrase) by another without altering its meaning, respectively through extensions and intensions, the former standing for the actual set of objects and behaviors, the latter for the set of features that characterize these instances.

Metonymy relies on contiguity to substitute target terms for source ones, contiguity being defined with regard to their respective extensions. For instance, given that US Presidents reside at the White House, Washington DC, each term can be used instead.

Metonymy use physical or functional proximity (full line) to match extensions (dashed line)

Metaphor uses similarity to substitute target terms for source ones, similarity being defined with regard to a shared subset of features, with leftovers taken out of the picture.

Metaphor uses similarity to match descriptions

Compared to basic thesaurus operators for synonymy, antonymy, and homonymy, which are set at lexical level, metonymy and metaphor operate at conceptual level, the former using set of instances (extensions) to probe semantics, the latter using descriptions (intensions).

Applied to users stories and use cases:

  • Metonymies: terms would be probed with regard to actual sets of objects, actors, events, and execution paths (data from operations) or mined from digital environments.
  • Metaphors: terms for stories, cases, actors, events, and activities would be probed with regard to the structure and behavior of associated descriptions (intensions).

Compared to the shallow one set at thesaurus level for terms, deep semantic interoperability encompasses all ontological dimensions, from actual instances to categories, aspects, and concepts. As such it can take full advantage of digital transformation and deep learning technologies.

further reading

Squared Outline: Actors


UML Actors (aka Roles) are meant to provide a twofold description of interactions between systems and their environment: organization and business process on one hand, system and applications on the other hand.

That can only be achieved by maintaining a conceptual distinction between actual agents, able to physically interact with systems, and actors (aka roles), which are their symbolic avatars as perceived by applications.

As far as the purpose is to describe interactions, actors should be primary characterized by the nature of language (symbolic or not), and identification coupling (biological or managed):

  1. Symbolic communication, no biological identification (systems)
  2. Analog communication, no biological identification (active devices or equipments)
  3. Symbolic communication, biological identification (people)
  4. Analog communication, biological identification (live organisms)

While there has been some confusion between actors (or roles) and agents, a clear-cut distinction is now a necessity due to the centrality of privacy issues, whether it is from business or regulatory perspective.

FURTHER READING

Squared Outline: States

States are used to describe relevant aspects in contexts and how the changes are to affect systems representations and behaviors.

On that account, events and states are complementary: the former are to notify relevant changes, the latter are to represent the partitions (²) that makes these changes relevant. Transitions are used to map the causes and effects of changes.

  1. State of physical objects.
  2. State of processes’ execution.
  3. State of actors’ expectations.
  4. State of symbolic representations.

Beside alignment with events, defining states consistently across objects, processes, and actors is to significantly enhance the traceability and transparency of architectures designs.

FURTHER READINGS

Squared Outline: Cases vs Stories

Use cases and users’ stories being the two major approaches to requirements, outlining their respective scope and purpose should put projects on a sound basis.

Cases & Stories

To that end requirements should be neatly classified with regard to scope (enterprise or system) and level (architectures or processes).

  • Users stories are set at enterprise level independently of the part played by supporting systems.
  • Use cases cut across users stories and consider only the part played by supporting systems.
  • Business stories put users stories (and therefore processes) into the broader perspective of business models.
  • Business cases put use cases (and therefore applications) into the broader perspective of systems capabilities.

Position on that simple grid should the be used to identify stakeholders and pick between an engineering model, agile or phased.

FURTHER READING

Squared Outline: Activity

As far as modeling is concerned a distinction has to be maintained between the symbolic description of activities and the processes describing their actual execution.

Given that distinction, the objective is to align action semantics with the constraints of their execution:

  1. Action on symbolic representations without coupling with the context (no change).
  2. Action on symbolic representations with coupling with context (change in expectations).
  3. Interaction with actual context without direct coupling (change in process status).
  4. Interaction with actual context with direct coupling  (change in objects).

That taxonomy can then be applied to map use cases semantics to architecture capabilities.

Squared Outline: Time-frames

Time-frames are defined by root events and therefore best defined along the same guideline, namely their scope and the nature of coupling. 

Along that understanding, time-frames can be defined with regard to context (symbolic or actual) and coupling (asynchronous or synchronous):

  1. Symbolic, no coupling: time-frames set by internal events, involving a single actor.
  2. Symbolic, coupling: time-frames set by external events, involving a single actor.
  3. Actual, asynchronous: time-frames set by external events, involving different actors without real-time constraint.
  4. Actual, synchronous: time-frames set by external events, involving different actors with real-time constraint.

That taxonomy could be used to align time-frames with processes‘ execution mode.

Squared Outline: Events

In line with the Symbolic Systems paradigm, events are best understood in terms of interactions between systems (or enterprises) and the environment they represent (or live off).

Events with regard to nature and coupling

On that account events are to be associated with four kinds of notifications:

  1. Actual (aka non symbolic) changes in the state of objects.
  2. Actual (aka non symbolic) changes in the state of activities.
  3. Changes in the state of expectations (e.g requests/acknowledgments).
  4. Neutral changes in symbolic representations (e.g messages).

It must be noted that while synchronization constraints (e.g UML’s calls vs signals) characterize events’ communication semantics, they say nothing about events themselves.

That distinction is of a particular importance for the definition of time as a
change in a dedicated physical device, ensuring that, according to Einstein, events don’t happen at once.

FURTHER READINGS

Squared Outline: Requirements

Depending on context and purpose requirements can be understood as customary documents, contents, or work in progress.

  1. Given that requirements are the entry point of engineering processes, nothing should be assumed regarding their form (natural, formal, or specific language), or content (business, functional, non-functional, or technical).
  2. Depending on the language used, requirements can be directly analyzed and engineered, or may have to be first formatted (aka captured).
  3. Requirements taxonomy should be set with regard to processes (business or architecture driven) and stakeholders (business units or enterprise architecture).
  4. Depending on content and context, requirements can be engineered as a whole (agile development models), or set apart as to tally with external dependencies (phased development models).

Further Reading

Squared Outline: Symbolic Systems

“Computer systems, robots, and people are all examples of symbolic systems, agents that use meaningful symbols to represent the world around them so as to communicate and generally act in the world,”

 (Stanford University’s Symbolic Systems Program)

Symbolic Representations Are Concrete Objects (Albert) 

Most of misconceptions about IT systems can be corrected with a proper understanding of symbolic representations:

  1. Symbolic objects are concrete objects pointing to objects (concrete or otherwise), agents (physical or social), or phenomena.
  2. Symbolic representations are symbolic objects built on purpose (artefacts) as to stand for their counterpart.
  3. Surrogates are symbolic representations meant to reflect the state of their counterpart in domains.
  4. Systems are containers used to manage surrogates.

These four simple tenets can be used as the pillars and the wheels of the whole discipline.

FURTHER READING