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

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

Event Oriented Analysis & Object Oriented Design

As it’s safe to assume that a primary objective of process analysis is to align business concerns (by nature specific and changing) with enterprise architectures (meant to be shared and stable), events could provide a good starting point.

(F. Handoko)
Event, concerns, processing (F. Handoko)

Business Analysis & Application Design

Taking example from the convincing track record of object oriented approaches for systems architectures and software design, the same principles have been tried for business requirements analysis. While that approach can be credited with significant realizations, success usually depends on some prior alignment of business domains with their system counterpart, in particular on the possibility to uniformly and consistently identify and define business entities as objects independently of operating processes.

Alternatively, when business entities cannot not be readily identified upfront as system objects, analysis may start with organization, entitled agents, activities, and be carried out with the definition of business flows and associated entities.

So, and whatever the approach, the question is how to ensure that the applications under consideration are designed in accordance with architecture capabilities.

System Architecture & Software Design

Words are worth the difference they make: as long as systems were not much more than an assortment of software modules, architecture and design could be understood as one and the same. But nowadays a distinction may be overdue between, on one hand the design of software components run within a single system’s address space and time-frame and, on the other hand, architectures of systems set across different spaces and time-frames.

vvv
Architecture vs Design: words are worth the difference they make

Object oriented solutions (e.g Domain Driven Design) are arguably the option of choice for the former, but services oriented approaches may be a better fit for the latter. Not by chance, events provide a sound conceptual hinge between the two approaches.

Event Oriented Analysis vs Object Oriented Design

Object oriented principles can be streamlined around three core topics: (a) information hiding and coupling between structures and methods; (b) inheritance between types; (c) communication through interfaces and polymorphism.

OO principles can be streamlined along three topics: encapsulation (a), inheritance (b), and communication through interfaces (c).
OO principles can be streamlined around three topics: encapsulation (a), inheritance (b), and communication through interfaces (c).

Of these, encapsulation and inheritance are specific to software design, but communication mechanisms are also at the core of services oriented architectures. Considering messages as the logical system counterparts of business events, event-oriented analysis should help to align business processes with systems capabilities.

From a business processes perspective, events are signaling changes in the states of activities, objects, or expectations. Given that  supporting systems are meant to deal with those changes, the analysis of business requirements could proceed from corresponding events:

  • Business events are defined with regard to time-frames (a) and sources to be authenticated and authorized (b).
  • Triggering changes must be described by messages with regard to their functional (c) and operational (d) scope.
  • Business logic (e) and entities (f) are often shared across applications and therefore better defined independently.
  • Internal changes (same space and time-frame) are hidden.
  • Triggered (external) changes are defined with regard to time-frames (h), processes (d), and devices (g).

A simplified blueprint of Event Oriented Process Analysis
A simplified blueprint of Event Oriented Process Analysis

As it happens, those facets can be aligned with OO design ones, with (c) and (d) for communication, (e) and (f) for encapsulation. On a broader perspective they also fit with the growing focus on event-driven applications and service oriented architectures.

From Event Oriented Process Analysis to Service Oriented Architectures

By moving business logic to the background, event-driven analysis fosters polymorphism at enterprise level with corresponding benefits:

  • With regard to business processes, events come with functional and operational requirements set independently of the business logic that will be carried out: trigger (what has changed), role (who is requesting), and message communication semantics (when the system is supposed to deal with the event).
  • With regard to system capabilities messages can be used to align business (aka external) events with system (aka internal) ones independently of the business entities and logic (what is to be done and how).
  • With regard to architecture and design, that approach is to uphold OO principles by dealing separately with polymorphic requests (interfaces) and business logic (methods).

Those benefits appear clearly when capabilities are realized by services defined with regard to business processes (customers), business objects (messages), business logic (contract), and business operations (policy).

Environment (bold) vs Services (italic)
Environment (bold) vs Services (italic)

It must be reminded that services are part of functional architectures and as a consequence cannot be directly addressed by users or devices.

Events & Action Semantics

With events set as modeling anchors, use cases may provide the modeling glue between processes and functional capabilities:

  • Triggering events (a) map changes in business environments (aka external events) to changes in systems objects (aka internal events).
  • Actors (b) map roles in organization to system users.
  • Messages (c) map the semantics of business processes to the semantics of applications (e) and domains (f).

Use cases (orange) provide a comprehensive and consistent mapping from processes (green) to services (blue).
Use cases (orange) provide a comprehensive and consistent mapping from processes (green) to services (blue).

On that basis, the main objective of event-oriented analysis would be to distinguish between communication and business semantics, the former dealing with interactions, the latter with business logic.

Further Reading

IoT & Real Time Activities

The world is the totality of facts, not of things.

Ludwig Wittgenstein

As the so-called internet of things (IoT) seems to bring together people, systems and devices, the meaning of real-time activities may have to be reconsidered.

Real Time Representation (Lucy Nicholson)
Fact and Broadcast (Lucy Nicholson)

Things, Facts, Events

To begin with, as illustrated by marketed solutions like SIGFOX, the IoT can be described as a fast and stripped-down communication layer carrying not so much things than facts and associated raw (i.e non symbolic) events. That seems to cut across traditional understandings because the IoT is dedicated to non symbolic devices yet may include symbolic systems, and fast communication may or may not mean real-time. So, when applications network requirements are to be considered, the focus should be on the way events are meant to be registered and processed.

Business Environments Cannot be Frozen

Given that time-frames are set according primary events, real-time activities can be defined as exclusive ongoing events: their start initiates a proprietary time-frame perceived from the outside as being without duration, i.e as if nothing could happen until their completion, with activities targeting the same domain supposed to be frozen.

ccc
Contrary to operational timing constraints (left), real-time ones (right) are set against the specific (i.e event driven) time-frames of targeted domain.

That principle can be understood as a generalization of the ACID (Atomicity, Consistency, Isolation, Durability) scheme used to guarantee that database transactions are processed reliably. Along that understanding a real-time business transaction would require that, whatever its actual duration, no change from other transactions would be accepted to its domain representation until the business transaction is completed and its associated outcomes duly committed. Yet, the hitch is that, contrary to systems transactions, there is no way to freeze actual business ones which will continue to be carried out notwithstanding suspended registrations.

Accesses can be fully synchronized within DB systems (single clock), suspended within functional architectures, consolidated within environment.
Accesses can be fully synchronized within DB systems (single clock), suspended within functional architectures, consolidated within environment.

In that case the problem is not so much one of locks on DB as one of dynamic alignment of managed representations with the changing state of affairs in their actual counterpart.

Yoking Systems & Environments

As Einstein famously said, “the only reason for time is so that everything doesn’t happen at once”. Along that reasoning coupling constraints for systems can be analyzed with regard to the way events are notified and registered:

  • Input flows: what happens between changes in environment (aka facts) and their recording by applications (a).
  • Processing: could the application be executed fully based on locally available information, or be contingent on some information managed by systems at domain level (b).
  • Output flows: what happens between actions triggered by applications and the corresponding changes in the environment (c).
vvvv
How to analyze the coupling between environment and system.

It’s important to remind that real-time activities are not defined in absolute time units: they can be measured in microsecond as well as in aeons, and carried out by light sensors or by snails.

A Simple Decision Routine

Deciding on real-time requirements can therefore follow a straightforward routine:

  • Should changes in relevant external objects, processes, or expectations, be instantly detected at system’s boundaries ? (a)
  • Could the interpretation and processing of associated events be carried out locally, or be contingent on information shared at domain level ? (b)
  • Should subsequent actions on relevant external objects, processes, or expectations be carried out instantly ? (c)
vvv
Coupling with the environment must be synchronous and footprint local or locked.

Positive answers to the three questions entail real-time requirements, as will also be the case if access to shared information is necessary.

 What about IoT ?

Strictly speaking, the internet of things is characterized by networked connections between non symbolic things. As it entails asynchronous communication and some symbolic mediation in between, one may assume that the IoT cannot support real-time activities. That assumption can be checked with some business cases given as examples.

Further Readings

External Links

Relating to Functions

Preamble

Functions map inputs with outputs as expected from a performing agent whatever its nature (concrete or abstract) or means (physical, logical, or magical).
They are not to be confused with objectives (which don’t necessarily specify performing agents or detail inputs) nor with activities (which purport to describe concrete execution paths).

simon-fujiwara-empire-clock
Functions and Processes are set along orthogonal dimensions (Simon Fujiwara)

Those distinctions are critical when the aim is to align business processes requirements with systems architecture capabilities.

Functions & Processes

Functions are complete (contrary to objectives) and abstract (contrary to activities) descriptions of what organizations (represented by actors), system architectures (represented by services), or objects (through operations) can do. As such they are akin to interfaces or types, and cannot be instanciated on their own. Processes on the contrary describe how activities are executed, i.e instanciated (#).

Business processes describe sets of execution instances (#). Functions describe what can be expected from enterprise or functional architectures. Business logic describe how the flows are to be processed.
Business processes describe sets of execution instances (#). Functions describe what can be expected from enterprise or functional architectures. Business logic describe how the flows are to be processed.

That understanding provides for a modular approach to business processes:

  • Business processes can be defined with regard to business functions independently of the way they are supported.
  • Business rules can be managed independently of the way they are applied, by people or systems.
  • Business logic can be factored out in functions (business or systems) or set within specific processes.

Yet that would not be possible without some modeling across enterprise architecture layers.

Functions & Models

Functions are meant to facilitate reuse across enterprise architectures, which entails descriptions that are clearly and easily accessible: context, modus operandi, expected outcome. Whatever the modeling method(s) in use, it’s safe to assume that different stakeholders across enterprise architectures will pursue different objectives, to be defined with different concepts. If they are to communicate they will need some explicit and unambiguous semantics for the links between processes, functions, and activities:

  • Functional flows are used between processes and functions (a) or actors (d), or between actors and functions (e).
  • Composition or aggregates are used to specify where the business logic is to be employed, by functions (b) or by processes (c).
  • Documentation references (f) are used between unspecified actors and business logic, in case it would performed by people.

Semantics of connectors: functional flows (a,d,e), aggregates (b) and composition (c), and documentation (f).
Semantics of connectors: functional flows (a,d,e), aggregates (b) and composition (c), and documentation (f).

Finally, the semantics of connectors used between functions will have to be consistent with the one used to connect them to processes and activities.

Combining Functions

Considering that functions are neatly set within the systems modeling realm, one would assume that inheritance and structure connectors can be used to detail and combine them. Yet, since functions cannot be instantiated, some paring down can be applied to their semantics:

  • Traditional structure connectors are set with regard to identification: bound to structure for composition, set independently otherwise. Since functions have no instances that criterion is irrelevant and the same reasoning goes for composition.
  • Likewise, since functions have no states to be considered, inheritance of functions can be represented by aggregates.

ddd
Functions can be combined at will using only aggregates

As far as functions are concerned, structures as well as inheritance connectors can be fully and soundly replaced by aggregate ones, which could significantly improve the mapping of business processes, activities, and supporting functions.

Further Readings

People should not be Confused with their Personas

Confronted with the ubiquity of IT systems and the blurring of traditional fences, enterprises grapple with the management of accesses and authorizations. Hence the importance of a clear distinction between agents, organizational units, and systems users.

(E. Erwitt)
Confusing Mimicry: People Impersonating Personas (E. Erwitt)

What is at stake is best understood by looking at the modeling of users’ access, collective agents, and interoperability.

Users’ Access

Roles (or actors in UML parlance) are meant to provide a twofold description of system users in order to combine two perspectives: organization and business process on one hand, system and applications on the other hand.

That can only be achieved by maintaining a clear distinction between actual agents, able to physically interact with systems, and roles, which are symbolic positions defined by and relative to organizations. Since mapping people and organization with systems users is the primary purpose of access rights management, lumping both sides under a single concept would definitely preclude the modeling of typical access scripts:

  • Anonymous: no authentication or authorization.
  • Registered user (role): user name and password are matched to user record.
  • Identified person: authentication of external identity.
  • Registered person: identification of a user with established external identity.

Security: actors vs actual and symbolic counterparts
Security: actors vs actual and symbolic counterparts

Given that authentication and authorization procedures depend on matching actual agents with their system symbolic representations (authentication) and roles (authorization), ignoring those distinctions would sap the whole security architecture.

Collective Agents

Confusing agents and roles may also prevent a proper management of collective authorizations.

At enterprise level parties can be identified physically as individuals or nominally as groups. But from a system perspective interactions can only be carried out by actors with physical identities, whatever their nature, users, systems, or devices.

Parties and actors are set along orthogonal perspectives, identities for the former, role for the latter.
Parties and actors are set along orthogonal perspectives, identities for the former, roles for the latter.

Managing accesses therefore requires an additional level of complexity, namely the relationship between collective and individual rights:

  • Parties can be intrinsically individual, collective, or contingent on circumstances (a).
  • As far as collective entities are concerned, access rights can directly allocated on behalf of group membership or delegated to named individuals (b).
  • Rights may depend on their origin and compatibility (c).
  • Roles allocation may be conditioned by both entitlements and specific rights on operations and objects (d).

Powertypes (2) are introduced to manage categories of roles, operations, and objects.
Powertypes (2) are introduced to manage categories of roles, operations, and objects.

That will not be possible without modeling separately entities identified by organizations (collectively or individually) and their personas while interacting with systems.

Interoperability

From smartphones to dumb appliances, things are unceasingly moving around networks and swapping places with people. Given the number, diversity, and turnover of interacting parties, systems are in no position to keep tabs on what is happening to agents behind the roles. Interoperability is therefore fully subordinate to the reliability and versatility of actors’ functional capabilities with regard to agents (organization) and applications (systems):

  • Agents identified externally are classified with regard to communication capability: users (natural language, digital, analog), systems (digital), and devices (analog).
  • Applications are classified with regard to their communication requirements (services, users interfaces, RT interfaces, …).
  • Actors are used to map agents to applications.

vvvvv
Actors can be used to characterize communication mechanism between actual agents and applications.

That formal distinction between agents and actors comes to be critical when access rights are to be checked for peer-to-peer transactions carried out across multiple participants.

Postscript

Besides its benefits, the validity of this perspective is borne out by its congruence with enterprise architecture layers (business, systems functionalities, platforms technologies) and model driven engineering (e.g computation independent, platform independent, and platform specific models).

Further Reading

External Links

Enterprise Systems & the OS Kernel Paradigm

Preamble

Given the ubiquity of information and communication technologies on one hand, the falling apart of technical fences between systems, enterprises, and business environments on the other hand, applying the operating system (OS) paradigm to enterprise architectures seems a logical move.

Users and access to services (Queuing at a Post Office in French West Indies)

Borrowing the blueprint of computers operating systems, enterprise operating systems (EOS) would  be organized around a kernel managing shared resources (people, hardware and software) and providing services to business, engineering or operational processes.

Gerrymandering & Layers

When IT was neatly fenced behind computer screens managers could keep a clear view on organization, roles, and responsibilities. But with physical hedges replaced by clouded walls, the risk is that IT may appear as the primary constituent of enterprise architecture. Given the lack of formal arguments against what may be a misguided understanding, enterprise architects have to rely on pragmatic answers. Yet, they could prop their arguments by upending the very principles of IT operating systems and restore the right governance footprint.

To begin with, turfs must be reclaimed, and that can be done if the whole of assets and services are layered according to the nature of problems and solutions: business processes (enterprise), supporting functionalities (systems), and technologies (platforms).

Problems and solutions must be set along architecture layers
EA must separate and federate concerns along architecture layers

Then, reclaiming must also include governance, and for that purpose EOS are to rely on a comprehensive and consistent understanding of assets, people and mechanisms across layers:

  • Physical assets, including hardware.
  • Non physical assets, including software.
  • Agents (identified people with organizational responsibilities) and roles.
  • Events (changes in the state of objects, processes, or expectations) and activities.

Mimicking traditional OS, that could be achieved with a small and compact conceptual kernel of formal concepts bearing out the definitions of primitives and services for the whole of enterprise processes.

EOS’s Kernel: 12 concepts

A wealth of definitions may be the main barrier to enterprise architecture as a discipline because such profusion necessarily comes with overlaps, ambiguities, and inconsistencies. Hence the benefit of relying on a small set of concepts covering the whole of enterprise systems:

  • Six for individuals actual (objects, events, processes) and symbolic (surrogates objects, activities, roles) elements.
  • One for actual (locations) or symbolic (package) containers.
  • One for the partitioning of behaviors (branch) or surrogates (power type).
  • Four for actual (channels and synchronization) and symbolic (references and flows) connectors.

Semantics
Governance calls for comprehensive and consistent semantics

Considering that nowadays business entities (enterprise), services (systems), and software components (technology) share the same distributed world, these concepts have to keep some semantic consistency across layers whatever their lexical avatars. To mention two critical examples, actors (aka roles) and events must be consistently understood by business and system analysts.

Those concepts are used to describe enterprise systems building blocks which can be combined with a small set of well known syntactic operators:

  • Two types of connectors depending on target: instances (associations) or types (inheritance).
  • Three types connections for nondescript, aggregation, and composition.

UMLSharp_syntax
Syntactic operators are meant to be applied independently of targets semantics

Again, Occam’s razor should be the rule: just like semantics are consistently defined across architecture layers, the same syntactic operators are to be uniformly applied to artifacts independently of their semantics.

Kernel’s Functions

Continuing with the kernel analogy, based on a comprehensive and consistent description of resources, the traditional OS functions can be reinterpreted with regard to architecture capabilities implemented across layers:

  • What: memory of business objects and operations (enterprise), data base logical entities (systems), data base physical records (platforms).
  • Who: roles (enterprise), logical interfaces (systems), and physical entry points (platforms).
  • When: business events and processes (enterprise), transaction management (systems), and middleware (platforms).
  • Where: sites (enterprise), logical processing units (systems), network architecture (platforms).
  • How: business processes (enterprise), applications (systems), and programs (platforms).

Traceability of Capabilities across architecture layers

That fits with the raison d’être of a kernel which is to combine core functions in order to support the services called by processes.

Services

Still milking the OS analogy, a primary goal of an enterprise kernel is to support a seamless integration of services:

  1. Business driven: the definition of services must be directly and unambiguously associated to business ends and means across enterprise layers.
  2. Traceability: they must ensure the transparency of the tie-ups between organization and processes on one hand, information systems on the other hand.
  3. Plasticity: they must facilitate the alignment of changes in business objectives, organization and supporting systems.

A reasoned way to achieve these objectives is to classify services with regard to the purpose of calling processes:

  • Business processes deal with the transactions between the enterprise and its environment.
  • Engineering processes deal with the development of enterprise resources independently of their use.
  • Operational processes deal with the management of enterprise resources when directly or indirectly used by business processes.

Enterprise Operating System: Layers & Services
Enterprise Operating System: Layers & Services

That classification can then be crossed with architecture levels:

  • At enterprise level services are bound to assets to be used by business, engineering, or operational processes.
  • At systems level services are bound to functions supporting business, engineering, or operational processes.
  • At platform level services are bound to resources used by business, engineering, or operational processes.

As services will usually rely on different functions across layers, the complexity will be dealt with by kernel primitives and masked behind interfaces.

Services called by processes can combine different functions directly (basic lines) or across layers (dashed lines).

Finally, that organization of services along architecture layers may be aligned with governance levels: strategic for enterprise assets, tactical for systems functionalities, and operational for platforms and resources.

Further Reading

Business Processes & Use Cases

Summary

As can be understood from their theoretical basis (Pi-Calculus, Petri Nets, or State Machines), processes are meant to describe the concurrent execution of activities. Assuming that large enterprises have to keep a level of indirection between operations and business logic, it ensues that activities and business logic should be defined independently of the way they are executed by business processes.

Communication Semantics vs Contexts & Contents (G. Winogrand)

For that purpose two basic modeling approaches are available:  BPM (Business Process Modeling) takes the business perspective, UML (Unified Modeling Language) takes the engineering one. Yet, each falls short with regard to a pivotal conceptual distinctions: BPM lumps together process execution and business logic, and UML makes no difference between business and software process execution. One way out of the difficulty would be to single out communications between agents (humans or systems), and specify interactions independently of their contents and channels.

vvv
Business Process: Communication + Business Logic

That could be achieved if communication semantics were defined independently of domain-specific languages (for information contents) and technical architecture (for communication channels). As it happens, and not by chance, the outcome would neatly coincide with use cases.

Linguistics & Computers Parlance

Business and functional requirements (see Requirements taxonomy) can be expressed with formal or natural languages. Requirements expressed with formal languages, domain-specific or generic, can be directly translated into some executable specifications. But when natural languages are used to describe what business expects from systems, requirements often require some elicitation.

When that challenge is put into a linguistic perspective, two school of thought can be considered, computational or functional.

The former approach is epitomized by Chomsky’s Generative Grammar and its claim that all languages, natural or otherwise, share an innate universal grammar (UG) supporting syntactic processing independently of their meanings. Nowadays, and notwithstanding its initial favor, that “computer friendly” paradigm hasn’t kept much track in general linguistics.

Alternatively, the functionalist school of thought considers linguistics as a general cognitive capability deprived of any autonomy. Along that reasoning there is no way to separate domain-specific semantics from linguistic constructs, which means that requirements complexities, linguistic or business specific, have to be dealt with as a lump, with or without the help of knowledgeable machines.

In between, a third approach has emerged that considers language as a functional system uniquely dedicated to communication and the mapping of meanings to symbolic representations. On that basis it should be possible to separate the communication apparatus (functional semantics) from the complexities of business (knowledge representation).

Processes Execution & Action Languages

Assuming the primary objective of business processes is to manage the concurrent execution of activities, their modeling should be driven by events and their consequences for interactions between business and systems. Unfortunately, that approach is not explicitly supported by BPM or UML.

Contrary to the “simplex” mapping of business information into corresponding data models (e.g using Relational Theory), models of business and systems processes (e.g Petri Nets or State Machines) have to be set in a “duplex” configuration as they are meant to operate simultaneously. Neither BPM nor UML are well equipped to deal with the task:

  • The BPM perspective is governed by business logic independently of interactions with systems.
  • Executable UML approaches are centered on software processes execution, and their extensions to action semantics deal essentially on class instances, features value, and objects states.

Such shortcomings are of no serious consequences for stand-alone applications, i.e when what happens at architecture level can be ignored; but overlooking the distinction between the respective semantics of business and software processes execution may critically hamper the usefulness, and even the validity, of models pertaining to represent distributed interactions between users and systems. Communication semantics may help to deal with the difficulty by providing relevant stereotypes and patterns.

Business Process Models

While business process models can (and should) also be used to feed software engineering processes, their primary purpose is to define how concurrent business operations are to be executed. As far as systems engineering is concerned, that will tally with three basic steps:

  1. Dock process interactions (aka sessions) to their business context: references to agents, business objects and time-frames.
  2. Specify interactions: references to context, roles, events, messages, and time related constraints.
  3. Specify information: structures, features, and rules.

Communication with systems: dock to context (1), interactions (2), information (3).
Communication with systems: dock to context (1), interactions (2), information (3).

Although modeling languages and tools usually support those tasks, the distinctions remain implicit, leaving users with the choice of semantics. In the absence of explicit guidelines confusion may ensue, e.g between business rules and their use by applications (BPM), or between business and system events (UML). Hence the benefits of introducing functional primitives dedicated to the description of interactions.

Such functional semantics can be illustrated by the well known CRUD primitives for the creation, reading, updating and deletion of objects, a similar approach being also applied to the design of domain specific patterns or primitives supported by functional frameworks. While thick on the ground, most of the corresponding communication frameworks deal with specific domains or technical protocols without factoring out what pertains to communication semantics independently of information contents or technical channels.

Communication semantics should be independent of business specific contents and systems architectures.
Communication semantics should be independent of business specific contents and systems architectures.

But that distinction could be especially productive when applied to business processes as it would be possible to fully separate the semantics of communications between agents and supporting systems on one hand, and the business logic used to process business flows on the other hand.

 Communication vs Action Semantics

Languages have developed to serve two different purposes: first as a means to communicate (a capability shared between humans and many primates), and then as a means to represent and process information (a capability specific to humans). Taking a leaf from functional approaches to linguistics, it may be possible to characterize messages with regard to action semantics, more precisely associated activity and attendant changes:

  • No change: messages relating to passive (objects) or active  (performed activity) states.
  • Change: messages relating to achievement (no activity) or accomplishment (attendant on performed activity).

Basic action semantics for interactions between users (BPM) and systems (UML)

Communication semantics can then be fully rounded off by adding changes in agents’ expectations to the ones in the states of objects and activities, all neatly modeled with state machines.

Communication semantics: changes in expectations, objects, and activities.

It must also be noted that factoring out the modeling of agents’ expectations with regard to communications is in line with the principles of service oriented architectures (SOA).

Additionally, transitions would have to be characterized by:

  • Time-frame: single or different.
  • Address space : single or different.
  • Mode: information, request for information, or request for action.

Organizing business processes along those principles, would enable the alignment of BPMs with their UML counterpart.

Use Cases as Bridges between BPM & UML

Use cases can be seen as the default entry point for UML modeling, and as such they should provide a bridge from business process models. That can be achieved by if use cases are understood as a combination of interactions and activities, the former obtained from communications as defined above, the latter from business logic.

Use Cases are best understood as a combination of interactions and business logic
Use Cases are best understood as a combination of interactions and business logic

One step further, the distinction between communication semantics and business contents could be used to align models respectively to systems and software architectures:

Last but not least, the consolidation of models contents at architecture level would be congruent with modeling languages, BPM and UML.

Further Reading

External Links

Use Cases Shouldn’t Know About Classes

Summary

Uses cases are meant to describe how users interact with systems, classes are meant to describe software components, including those executing use cases. It ensues that classes are introduced with the realization of use cases but are not supposed to appear as such in their definition.

TurkAutomat
Users are not supposed to know about surrogates

The Case for Use Cases

Use cases (UCs) are the brain child of Ivar Jacobson and often considered as the main innovation introduced by UML. Their success, which largely outdoes UML’s footprint, can be explained by their focus and simplicity:

  • Focus: UCs are meant to describe what happens between users and systems. As such they are neatly bounded with regard to their purpose (UCs are the detailed parts of business processes supported by systems) and realization (UCs are implemented by software applications).
  • Simplicity: while UCs may eventually include formal (e.g pre- and post-conditions) and graphical (e.g activity diagrams) specifications, they can be fully defined and neatly circumscribed using stick actors (for the roles played by users or any other system) and ellipses (for system behaviors).

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Use Cases & UML diagrams

As it often happens to successful innovations, use cases have been widely interpreted and extended; nonetheless, the original concepts introduced by Ivar Jacobson remain basically unaltered.

The Point of Use Cases

Whereas focus and simplicity are clearly helpful, the primary success factor is that UCs have a point, namely they provide a conceptual bridge between business and system perspectives. That appears clearly when UCs are compared to main alternatives like users’ stories or functional requirements:

  • Users’ stories are set from business perspective and lack explicit constructs for the parts supported by systems. As a consequence they may flounder to identify and describe business functions meant to be shared across business processes.
  • Conversely, functional requirements are set from system perspective and have no built-in constructs linking business contexts and concerns to their system counterparts. As a consequence they may fall short if business requirements cannot be set upfront or are meant to change with business opportunities.

Along that understanding, nothing should be done to UCs that could compromise their mediating role between business value and system capabilities, the former driven by changes in business environment and enterprise ability to seize opportunities, the latter by the continuity of operations and the effective use of technical or informational assets.

Business Objects vs Software Components

Users’ requirements are driven by concrete, partial, and specific business expectations, and it’s up to architects to weld those diverse and changing views into the consistent and stable functional abstractions that will be implemented by software components.

Users' requirements are driven by concrete, partial, and specific concerns
Users’ requirements are driven by concrete, partial, changing and specific concerns, but supported by stable and fully designed software abstractions.

Given that double discrepancy of objectives and time-scales, business analysts should not try to align their requirements with software designs, and system analysts should not try to second-guess their business counterparts with regard to future business objects. As a consequence, respective outcomes would be best achieved through a clear separation of concerns:

  • Use cases deal with the business value of applications, mapping views on business objects to aspects of classes.
  • Functional architectures deal with assets, in particular the continuous and consistent representation of business objects by software components as described by classes.

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How to get best value from assets

As it happens, that double classification with regard to scope and purpose should also be used to choose a development model: agile when scope and purpose can be united, phased approach otherwise.

Further Reading

 

Ergonomy, Fingertips Errors & Automated Testing

Objective

When interacting with systems, users do things they aren’t supposed to do and walk along irrelevant, even unthinkable, paths that can put tests designers at a loss. This apparent chink between users’ conscious self and their fingertips can be explained by the way humans assess situations and make decisions. Curtailing it is the aim of ergonomics.

Errors at fingerstips (Rembrandt)
Anatomy of Errors: from brain to fingers (Rembrandt)

Taking a leaf from A. Tversky and D. Kahneman (who received the 2002 Nobel Prize in Economics), decision-making relies on two cognitive mechanisms:

  1. The first one “operates automatically and quickly, with little or no effort and no sense of voluntary control”. It’s put in use when actual situations must be assessed and decisions taken rapidly if not instantly.
  2. The second one “allocates attention to the effortful mental activities that demand it, including complex computations”. It’s put in use when situations can be assessed with regard to past experience in order to support informed decisions making.

That distinction can be directly applied to users’ behaviors interacting with systems:

  1. Intuitive behavior: decisions are taken on the basis of the visual context and options as presented by users interfaces before taking into account underlying business contents and logic.
  2. Rational behavior: decisions are taken on the basis of business contents and logic disregarding supporting systems interfaces.

Set in context, that distinction can be put in parallel (but not confused) with the one between domain and functional requirements, the former dealing rationally with business objects and logic, the latter putting the former to use through interactions with supporting systems.

Functional requirements describe the part played by supporting systems
Functional requirements describe the part played by supporting systems

Assuming that business logic should not be contingent on supporting systems interfaces, the best option would be to test its implementation independently of users interactions; moreover, tests targeting intuitive behaviors (i.e not directly based on domain specific contents), could then be generated automatically.

Looking for Errors

Given that testing is meant to find flaws in deliverables, tests are certainly more effective when designers know what they are looking for.

For that purpose phased approaches rely on sequences of differentiated tests dealing successively with programming (unit tests), functional requirements (integration tests), and business requirements (acceptance tests).  The unfortunate downside of those policies is that the most wide-ranging flaws are the last to be looked for, with the risk of being found after cascading and costly consequences for functionalities and programs.

Phased and Iterative approaches to tests
Phased and Iterative approaches to tests

Conversely, agile approaches follow iterative policies, with each development cycle combining the definition, programming, and tests of software products. When properly implemented those policies significantly improve the early detection and correction of errors whatever their origin. Yet, since there is no explicit management of intermediate outcomes, it’s difficult to differentiate the tests according the kind of errors to look for, e.g faulty business rules implementation or flawed user interface.

Architecture driven approaches may provide an answer, with requirements unambiguously sorted out depending on their architectural footprint: business contents or system functionalities. As a corollary, tests could also be designed along the same lines, targeting business rationale or human behavior.

Errors in Mirrors

Acceptance tests being performed with regard to requirements, they should be designed along requirements taxonomy, respectively for business logic, users’ interactions, quality of services, and components implementation. Being aligned on requirements, those tests can be neatly defined with regard to closed sets of specifications, functional or otherwise.

Functional tests have to expect the unexpected
Functional tests have to expect the unexpected

But that’s not the case for users’ interactions because people behaviors are not fully predictable; hence, while tests can be systematically designed with regard to the set of users’ actions framed by business and functional requirements, there is no way to comprehensively and unambiguously check for all and every possible behavioral contingencies. That will make for three levels of functional tests:

  1. Implementation of business logic: tests should be designed directly from business requirements, independently of interactions with users.
  2. Implementation of scenarii: while interactions are defined in reference to business logic, their validation should focus on the presentation of contents and dialog control.
  3. Users exceptions: in addition to inputs validity, already checked with business logic, and users’ actions, supposedly secured by interaction scenarii, it is necessary to check that unexpected behaviors have been properly considered .

How to check that unexpected behaviors have been properly considered ?
How to check that unexpected behaviors have been properly considered ?

In other words, functional tests will have to look simultaneously for errors in software (defined with regard to a finite set of requirements), and for users’ mistakes (set in an open range of behaviors). As if tests designers were to mirror users errors in order to look for software ones. So, assuming that errors in business logic and interactions have been considered, what should still be checked, and how ?

Fingertips Errors

When faced with choices, users bank on mental maps combining graphical and business layers, with the implicit assumption that maps’ contexts and concerns are kept up to date. Those maps combine three communication mechanisms:

  • Languages, natural or specific, use syntax and semantics to define business contents, logic, and operations.
  • Icons use similarity for the visual representation of business operations or functional primitives (e.g create, delete, etc).
  • Signals use proximity to draw users’ attention to predefined events (e.g sounds for operations completion or incoming emails).

While language-based interactions are supposedly fully covered by business and functional tests, icons and signals make room for “fingertips” reactions which cannot be directly framed within business logic or functional scenarii, and therefore cannot be comprehensively checked for erroneous behaviors.

Icons and signal based communication can trigger unexpected behaviors.
Icons and signal based communication can trigger unexpected behaviors.

Yet, if instinctive reactions preclude rational considerations, decisions may be swayed by analogies and associations before being informed by the relevant business contents. To prevent that risk, test scenarii built on business logic and functional interactions should be extended in order to take into account the intuitive aspects of users’ behaviors.

Mental Maps & Automated Tests

As noted above, mental maps are built on three layers, one deep (language semantics) and two shallow (icons and signals). While the shallow layers are supposed to reference the deep one, icons and signals may induce instinctive behaviors independently of the referenced business logic. Those behaviors can be triggered by two kinds of mechanisms:

  • Analogy: users will look for similarities and familiar configurations.
  • Proximity: users will look for continuity with regard to scope and operations.

Clearly, lapses in such behaviors will normally escape tests designed for business and functional requirements; yet, by being driven by self-contained mechanisms, intuitive behaviors can be checked independently of references to business contents. And that may open the door to automated tests generation.

With regard to similarities, tests should look for possible confusion between:

  • Objects with common representation but specific features (inheritance).
  • Operations with shared semantics but different scope (polymorphism).
  • Sequences with shared operations but different timing .

With regard to proximity, tests should look for possible confusion between:

  • Objects and their parts, or between their parts (structural proximity).
  • Operations usually associated into the same activity (functional proximity).
  • Operations usually executed successively (chronological proximity).

Scripts for such tests could be generated through pattern-matching and run by wizard applications.

Further Reading

External Links