Characterizing Efficacy of Alternative Media for Requirements Expression

Kolligs, Jason; Thomas, Lawrence Dale

doi:10.3390/systems13050314

Open AccessArticle

Characterizing Efficacy of Alternative Media for Requirements Expression

by

Jason Kolligs

¹

and

Lawrence Dale Thomas

^2,*

¹

Strategic Technology Consulting (STC), Chantilly, VA 20151, USA

²

Department of Industrial and Systems Engineering & Engineering Managemnt, College of Engineering, University of Alabama in Huntsville, Huntsville, AL 35899, USA

^*

Author to whom correspondence should be addressed.

Systems 2025, 13(5), 314; https://doi.org/10.3390/systems13050314

Submission received: 3 February 2025 / Revised: 15 April 2025 / Accepted: 18 April 2025 / Published: 25 April 2025

(This article belongs to the Section Systems Engineering)

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Abstract

:

Requirements are most commonly expressed in natural language, but alternative media can be employed. Previous research has established the viability of model diagrams and engineering drawings for requirements expression. To move beyond viability, three (3) factors—Cognition, Quality, and Accountability—were developed to assess the potential impact of using alternate media requirement expressions in systems engineering. The alternate media candidates were evaluated against the factors and their subfactors, which determined that the inclusion of alternate media may be expected to positively impact requirements expression in all three areas. For Cognition, improved communication is predicted as alternate media are situationally preferable based on their inherent context offerings and systematically shorter comprehension times for spatial information, which potentially reduces the cognitive burden on the reader. For Quality, alternate media are predicted to improve the appropriateness of requirement expressions within a specification. For Accountability, improvement is predicted within a project as alternate media can mitigate ambiguity, improve feasibility, and enhance verification and validation efforts. The contribution of this research is the establishment of a conceptual basis for creating multi-media requirement documentation that amplifies the desired characteristics of requirement expressions to better communicate stakeholder information.

Keywords:

alternate media requirement expressions; requirements engineering; systems requirements; systems engineering; model-based systems engineering

1. Introduction

Low-quality requirements are among the first potential mistakes of an engineering project, and their effects are felt downstream in the form of increased costs and schedule overruns [1,2,3,4]. Natural language is the most commonly employed means of expressing requirements in systems engineering because of the low barrier to entry, i.e., most people know how to write sentences [5,6]. The use of natural language to express requirements constitutes the verbal model of a system. In von Bertalanffy’s seminal work, General Systems Theory, from 1967, two (2) cases are put forth for natural language or verbal models of a system: they are better than (i) no model or (ii) a mathematical model being forced into an unfit situation [7]. Although natural language is perceived as the default technique for expressing requirements in system acquisition scenarios due to the emphasis on legal accountability and contract law [8], it does not have to be the default means for expressing requirements in general. Natural language requirement specification ambiguity has been addressed with patterns by Tjong et al. [9] and improved structure by Carson [10], but neither suggests changing the medium altogether. Likewise, this research does not suggest abandoning sentences but rather supplementing sentences with alternate media to serve as requirement expressions in conjunction with requirement sentences.

The definition of requirements can be challenging, with literature offering multiple definitions and some systems engineering communities overloading the term to be interchangeable with the abstraction of a need or want, an individual requirement expression, or a specification document [11,12,13]. A comprehensive analysis of the relevant literature, including professional society standards and guidelines, determined that requirements are based on the concepts of (i) the solution to a problem and (ii) accountability, and resulted in the following basis for requirement expression [14]:

Requirement expressions exist to capture an instance of a want or need of the following:

A requesting external stakeholder that serves as the contractually obligated origin of a problem that a project agrees to solve;
A requesting intra-project authority stakeholder that represents an iteration toward a solution to which the receiving intra-project group is accountable.

The term requirement expression is used intentionally in this paper and is adapted from Ryan and Wheatcraft’s assertion that “a requirement statement is the result of a formal transformation of one or more needs into an agreed-to obligation for an entity to perform some function or possess some quality (within specified constraints)” [15]. Whereas the requirement statement implies a natural language medium (e.g., sentences), the term requirement expression allows for other media options that conform to the foregoing basis of a requirement expression. The concepts of requirements, requirement expressions, and sets of requirement expressions exist in multiple engineering disciplines [16]. Conceivably, requirement expressions can include requirement sentences, model diagrams, engineering drawings, and other alternate media, such as mathematical models, as illustrated in Figure 1.

The use of Systems Modeling Language (SysML) diagrams to represent natural language requirements has been established in the literature [17,18]. In a laboratory setting, subsequent experimental research revealed that model-based requirements expressed as SysML diagrams outperform natural language requirements in the four measured variables of applicability, bounding, necessity, and completeness [19]. The viability of alternative media, including model diagrams and engineering drawings for requirements expression, has been established using the International Council on Systems Engineering (INCOSE) characteristics for individual requirements and sets of requirements [6] in comparison with the characteristics for model diagrams per Object Management Group (OMG) guidelines [20] and the characteristics for engineering drawings per American Society of Mechanical Engineers (ASME) guidelines [21,22]. The assessment concluded that requirement sentences, model diagrams, and engineering drawings share fundamental characteristics, and the differences are attributable to their respective capabilities to represent abstraction [23]. The differences in representing abstraction explain the dominance of requirement statements early in the life cycle when system trades are being explored, and options must be kept open versus the dominance of engineering drawings later in the life cycle when ambiguity is particularly undesirable. An analogous assertion can be made for the location in the requirements hierarchy, where abstraction is more desirable in the higher levels of the requirements hierarchy and less desirable and necessary in the lower levels of the requirements hierarchy.

To illustrate, consider the pointing requirements of a scientific spacecraft. At the top level, the pointing requirement is simply to be sufficiently stable to allow data acquisition by the instrument, which is quite ambiguous. It is noted that this requirement will originate early in the system life cycle and likely remain unchanged as the system life cycle progresses. As the life cycle progresses, the scientific spacecraft design fidelity increases, the components become better characterized, and parameters such as structural stiffness are estimated such that other parameters, such as reaction wheel torques, can be estimated. The estimation of a coherent set of technical parameters allows the expression of requirements for the components of the scientific spacecraft, which are lower-level requirements and inherently less ambiguous. Such an iterative refinement continues forward in time and downward in the requirements hierarchy until the scientific spacecraft, including all components, is fully specified.

Given the viability of alternative media for requirement expression, the question then turns to preference: which media should be used in what circumstances to best express requirements? This question is the focus of this paper. The suitability of requirement statements very early in the life cycle is reflected by their dominance in practical applications for expressing top-level requirements. Likewise, the suitability of engineering drawings late in the life cycle is reflected by their dominance in practical applications for expressing detailed requirements. However, what about the requirements between the high and low levels and the phases in the life cycle between the early and late? In particular, this paper will describe evidence to suggest specific engineering media—model diagrams and engineering drawings are two options considered for this research—can better communicate specific information types, e.g., abstract and empirical, compared to other media. The factors involved in using different media will be identified and evaluated to investigate the evidence for using different media in systems engineering. Prior research has established the content of requirement expressions [14] and the viability of media other than natural language to express requirements [23]. The objective of this research is to establish a theoretical basis for determining the best media for requirement expression, acknowledging that the best media to express a given requirement is influenced by both its location in the requirements hierarchy and the relevant phase of the system life cycle.

The remainder of this paper is organized as follows.

Section 2 provides a scenario to illustrate the need for using alternative media for requirements expression and provides the context for the research described in the remainder of the paper; the scenario will be revisited in Section 4.
Section 3 describes the research methodology, including the sources used in the implementation and validation of the methodology.
Section 4 analyzes alternative media for requirement expression, including requirement sentences, model diagrams, and engineering drawings, using the factors and impact ratings described in Section 3. The last subsection of Section 4 returns to the scenario presented in Section 2.
Section 5 summarizes the key findings of the research, describes the limitations of the findings, and identifies areas for further research.

2. Scenario

The following example of a requirement sentence and a potential model diagram are provided to illustrate the alignment of information between the alternative media. The Leader Radio (LR) Performance Requirements Document (PRD) from 2019 provides a relatively straightforward requirement sentence that defines the components of an ordered (i.e., purchased) LR set. The LR PRD is a publicly released document seeking the procurement of a two-channel radio system in handheld and mounted (M-LR) variants [24]. The LR PRD includes several sections that establish a capability and component hierarchy using only the requirement sentences. No alternate media are offered to complement these hierarchies, even as supplemental, i.e., non-requirement expression, material in the LR PRD. Figure 2 presents a SysML block definition diagram that depicts the composition of the LR ordered set described in natural language in Table 1 [23]. The equivalence of the two requirement expressions is intuitive, and one could reasonably argue the superiority of either the natural language expression or the schematic (SysML Block Definition Diagram) expression.

Now, consider additional sections of the LR PRD that further describe the capability and component hierarchy, again using only requirement sentences, as given in Table 2 and Table 3. In contrast to the previous instance, it is very difficult for a reader to understand the hierarchy described by the natural language requirements, and arguably, most readers would manually draw a diagram as an aid to do so. What makes a textual requirement expression adequate in one instance and inadequate in another instance? This question will be explored in the subsequent sections of this paper, and this scenario will be revisited in Section 4.5.

3. Materials and Methods

The evidence suggesting that specific engineering media may better communicate specific information types than requirement sentences is based on the impact of media-type factors identified in this research. The subsequent methodology identifies these factors and their potential impacts if alternate media were used. This research includes cognitive psychology, which addresses factors related to media and media-human interactions [25]. This method consists of two phases. The first phase has been described in prior research and is briefly described in the following paragraph for context [14,23]. However, the focus of the first phase in prior research was the identification of the characteristics of requirement media, including natural language, diagrams, and drawings, whereas this research extends that systematic literature review to identify factors to be used to characterize the impacts of alternative media for requirements expression [26,27]. The second phase applies the identified factors to media types to identify the potential impacts of the use of certain media on those factors.

To gather information on the premise of requirements, topics were researched using online databases, focusing on journal databases such as Google Scholar, INCOSE, and IEEE Xplore. The keywords used to begin this research included: “requirements”, “stakeholder needs”, “stakeholder wants”, “customer needs”, “customer wants”, “purpose”, “origins”, “theoretical”, “basis”, and their amalgamations. Relevant works, i.e., those pertaining to the theoretical need for requirements, were selected, and their bibliographies were further investigated. While the terms “stakeholder” and “customer” differ in meaning, with the customer being a subset of stakeholder, they are both used regularly in systems engineering writings [11,12] and so both terms were included in the keyword list. The literature provides a common theme justifying the development of requirements—accountability. The literature also provides a common theme of quality, characterized by various terms such as necessary, singular, conforming, appropriate, and correct [6]. Three additional themes emerged from the literature review:

Communication—communication of quality requirements to establish accountability between the customer and the supplier;
Creativity—the ability to express quality requirements;
Cognitive Burden—the difficulty in forming accurate cognitive representations or mental models of requirement expressions.

This research considers these three themes to be aspects of cognition. These three themes—Quality, Accountability, and Cognition–comprise the factors used to identify the potential impacts of the use of alternative media.

3.1. Factor Identification

As previously described in Section 1. Introduction: Requirement expressions exist to convey a needed or desired solution and to provide accountability. Communication is the means to accomplish these ends, where communication involves different types of information, such as findings, analyses, relationships, calculations, and so forth, between the organizational echelons supporting the project. Communication goes beyond writing or capturing symbols, as it “presupposes the achievement of intended effects of verbal action upon the addressee, while speaking and writing do not” [28]. Communication can occur through various mediums and occurs when mutual comprehension is achieved. Any means used for communication falls under the umbrella of linguistics, which includes a number of fields, such as pragmatics, cognitive psychology, logic, and semantics [28]. The evidence suggesting that specific engineering media may better communicate specific information types is based on the impact of media-type factors to be identified, as described subsequently.

3.1.1. Quality and Accountability Factors

The INCOSE Guide for Writing Requirements contains two (2) key elements used to derive their characteristics: formal transformation and agreed-to obligation [6]. This research adapts these elements into two factors—a quality factor and an accountability factor. The INCOSE key element of formal transformation refers to the capturing of one or more needs and, for an individual requirement expression, leads to the characteristics Necessary, Singular, Conforming, Appropriate, Correct, and Conforming” [6]. The same key element (formal transformation) for a requirement expression set applies to the Consistent characteristic [6]. As these characteristics address the quality of the formal transformation of the need in any requirement expression, they constitute subfactors that comprise a Quality Factor.

The second key element of the agreed obligation refers to the clarity of the agreement between the customer and provider, which comprises an Accountability Factor [6]. Likewise, the INCOSE characteristics that constitute subfactors for an individual requirement expression derived from the agreed-to obligation key element are Unambiguous, Complete, Feasible, and Verifiable [6]. For a set of requirement expressions, the Accountability characteristics are Complete, Feasible, Comprehensible, and Able to be Validated [6]. Table 4 captures the alignment of the factors and subfactors from INCOSE, along with the other analogous characteristics for Unified Modeling Language diagrams per OMG guidelines [20] and engineering drawings per ASME guidelines [21,22]. From Table 4, it is observed that the gathering, alignment, and comparison of the characteristics of requirement sentences, model diagrams, and engineering drawings revealed a similarity among the different media for what constitutes the proper use of each. Most of the characteristics used the same vocabulary to either state or describe the characteristic, such as Unambiguous, Clear, and Concise, and applied to both individual requirement expressions and sets of requirement expressions. The differences in the lists and alignments are discussed in the analysis results in Section 4.3.3.

3.1.2. Cognition Factor

Requirement expressions are the interfaces between requirement writers and requirement readers. From a cognitive perspective, reading “is the ability to construct linguistic meaning from written representations of language” [25]. When reading, humans begin to construct mental representations of the subject. From psychology, “formal rules theories assume that humans construct propositional representations of arguments” [29]. These mental models provide the foundation for spatial deduction applied by reading other statements [28,29]. Mental representations and processes underlie deductive reasoning and are the same “irrespective of an argument’s symbolic representation”, i.e., sentences or diagrams [29]. Hence, regardless of how information is processed, it is represented as a mental model. Research has begun to address the concept that project teammates may have different mental models [30,31].

Mental representations and processes also “consider working memory load as a fundamental source of difficulty in deductive reasoning [and] logical structure is a critical factor affecting working memory” [29]. Boudreau and Pigeau’s experiment showed that the impact of logical structure indicated significant differences between premises displayed as diagrams and premises displayed as sentences [29]. The term diagram refers to “a drawing that shows arrangement and relations” [32] or any structural or schematic representation beyond sentence structures, which this research designates as alternate media. Boudreau and Pigeau’s experiment used “sentences or diagrams to represent the relations among entities, and nouns or images to represent entities” [29]. The participants in the experiment received a premise set and were asked to validate the stated relative location between entities. Premises inspection times, responses, and response times were collected. The comprehension times associated with alternate media were found to be systematically shorter than those associated with sentences, where the term systematically shorter indicated greater ease in creating mental representations from alternate media than from sentences [29].

Similarly, Cognitive Load Theory claims that “human cognitive processing is heavily constrained by our limited working memory, which can only process a limited number of information elements at a time” [33,34]. Simplifying information provides the greatest opportunity for understanding, and ease of information processing helps create understanding. Since individuals create cognitive representations or mental models, communication may be more efficient and effective, i.e., requiring less working memory load to convey information using alternate media than words or sentences.

Different media inherently possess different capabilities for providing context or, alternatively, reducing ambiguity. When unburdened by arbitrary constraints, sentences carry the most flexibility to communicate requirements anywhere on the spectrum of abstraction, from conceptual to empirical [25]. This is consistent with the INCOSE Guide for Writing Requirements, which acknowledges that sentences are the most flexible media and that flexibility covers a wide range of contexts [6]. However, this flexibility is created by a lack of inherent context in the media; that is, a sentence provides no inherent context and is, therefore, more flexible. Conversely, model diagrams, including formal logic, provide spatial context and relationships between their components, which allow engineers and problem solvers to better understand what is being conveyed [20,35]. Likewise, engineering drawings focus on scale, and the ensuing accuracy allows components to be manufactured within tolerances [21], thereby providing a high level of context. Since more context is preferable in communication [25] and visual context reduces cognitive load [33], it can be conjectured that higher-context-offering media are potentially preferable in communication, which will be assessed subsequently in Section 4. Table 5 provides a ranking of media by contextual offering, where a higher context or more details offered by a medium is associated with a higher ranking.

Other constraints are frequently applied to requirement expressions in practice, especially requirement sentences [14]. A common constraint is the use of the canonical form, which structures requirement sentences to a general form:

<subject> shall <outcome to be accomplished> <relational operators> <level of performance> <condition> [11].

Such constraints have an impact on creativity as they pertain to problem-solving [36]. The requirement sentence constraints qualify as both product constraints, which limit possible solutions, and process constraints, which limit possible approaches [36]. Constraints can have positive and negative effects on creativity, but overall, “process constraints were more likely to inhibit creativity” [36].

Table 5. Media ranked by contextual offering.

Rank	Media	Context Offered	Rank Rationale
1	Engineering Drawings	Scaled lines and position provide detailed context of components [21]	The precision of context offered in an engineering drawing is ready for manufacture [21]
2	Modeling Diagrams	Lines and position provide relational or spatial context between components [35,37]	This context supports functional definitions and hierarchical block definitions that can be turned into software systems or engineering drawings [20]
3	Natural Language Sentences	“There is no limitation on the concepts that can be expressed.” [6]	Provides context when other media would be more cumbersome otherwise, e.g., “if quantitative information to be conveyed consists of one or two numbers, it is more appropriate to use written language than tables or graphs” [38].

3.1.3. Factor Identification Summary

The cognition factor is comprised of communication, creativity, and cognitive burden, which represent potential areas of impact and constitute the subfactors for alternate media requirement expressions. The cognition, quality, and accountability factors and their respective subfactors are listed in Table 6. These factors provide an objective basis for the qualitative assessment of the relative utility of requirement sentences, model diagrams, and engineering drawings for requirements expression by identifying the potential impacts of the use of particular media on these factors in specific contexts.

3.2. Factor Evidence and Impact Assessment

The Quality, Accountability, and Cognition factors will be evaluated for model diagrams and engineering drawings against requirement sentences based on both the strength of the evidence from the literature for determining the impact and the magnitude of the impact on the respective factor. Both evidence and impact will be assessed using four-tiered rating scales, listed in Table 7 and Table 8, along with a brief description of each rating level.

3.3. Validation

The qualitative research principles of data authenticity and transparent analysis provide the basis for the validity of this analysis [39]. The quality and authenticity of the data were addressed using reputable sources. The transparency in the analysis is documented in this paper to provide rationale and repeatability.

4. Analysis

This section describes the analysis of the requirement sentences, model diagrams, and engineering drawings using the factors and impact ratings described in the preceding section. Each subsection describes the current practices, proposed change(s), and theorized impacts. The Cognition factor is assessed first, and the impact assessment for each Cognition subfactor is described for illustration. The Quality and Accountability factor assessments describe only the positive or negative impacts of the respective Quality and Accountability subfactors for brevity.

4.1. Potential Impacts Related to Cognition

Recall that the Cognition factor, for the purpose of this research, is comprised of communication, creativity, and cognitive burden. Each of these concept areas is applied to the three (3) media options—requirement sentences, model diagrams, and engineering drawings—to identify potential impacts. Each section addresses current practices, proposed changes, theorized impacts, and potential challenges. The findings are summarized in Table 9 to highlight the potential impacts.

4.1.1. Potential Impacts to Communication

Based on the theoretical basis for the requirements in Section 1, the primary purpose of the requirements expressions is to iterate toward a solution. This is accomplished by properly communicating findings or analyses, such as relationships and calculations, among the organizational echelons supporting the project. An experienced requirement developer knows that the requirement expression needs to provide as much context as possible in a language the reader understands to improve communication [25]. The literature review identified two (2) concepts that apply to context and media: (i) coreference and (ii) inherent context provided by media choice. These concepts were identified through an analysis of the types of information (per Hertz and Rubenstein [40]) conveyed by the requirements. One finding of that analysis was that the requirement element “Technical Terms and Data Definitions” exists to provide clear definitions in order to reduce confusion and allow requirements to be expressed more simply [41]. Technical Terms and Data Definitions within requirement expressions are employed to establish coreference. The concept of inherent context was previously discussed in Section 3.1.2.

A challenge often discussed in the realms where multiple media are used as information sources is coreference [35]. Coreference is “determining when parts of the text and diagram refer to the same subject” [35]. This is also a current challenge in today’s requirement sentences, as multiple requirement sentences may refer to the same object and, therefore, must ensure syntactical accuracy among themselves [6,42]. This is addressed as part of the Conformity desirable requirement expression characteristic [6] and is also used to reduce complexity by ensuring that the terms are agreed upon [43]. Such an impact would vary immensely based on the size of the project, the number of requirement developers, organizational policy, and available requirements engineering tools. The inclusion of alternate media requirement expressions does not inherently address the source of the coreference challenges, which is a human component of systems engineering. A human error of coreference can occur in requirement sentences, model diagrams, or engineering drawings. Therefore, based on the lack of direct evidence, this research categorizes the impact of alternate media on coreference as not applicable.

Referring to Table 5, the increased inherent context provided by model diagrams and engineering drawings relative to requirement sentences implies that each is potentially preferable in communication to sentences based on the level of context needed or wanted to be conveyed. While direct evidence is limited, the incorporation of alternate media may have a positive impact.

4.1.2. Potential Impacts to Creativity

Section 3.1 discussed how creativity could be enhanced by the imposition of product constraints that provide constraints against the semantics of requirement expressions, namely, the canonical form [36]. These constraints challenge the pragmatics, or what is meant to be conveyed, of the requirement expression by adding another layer of complexity and ambiguity. For example, if a requirement developer operating within the constraints employs creativity to develop a requirement expression, the reader must then try to understand the requirement through creativity, constraints, and media constructs. This goes against the importance of communication [25] and the law of parsimony, i.e., Occam’s razor [44].

It is a common practice in today’s requirements engineering to supplement specifications with diagrams and tables to provide clarity to requirement sentences [37]. This is also practiced in formal logic [45]. This practice acknowledges the shortcomings of the constraints imposed on requirement developers. It also acknowledges the challenges of abiding by constraints and properly conveying the intended communication. Another arbitrary constraint is the mandatory use of the term shall. If the only purpose of using shall in requirement sentences is to distinguish them from other sentences within a specification, there is no need to continue its use, as requirement expressions are distinguished by other attributes, primarily a unique identifier [46]. Removing the arbitrary constraints on both requirement sentences and requirement expressions would provide less need for creativity and, therefore, improve communication based on a clearer conveyance of information from developer to reader. While the indirect evidence supports a potentially positive impact, that is, the removal of arbitrary constraints, the removal or relaxation of constraints can also be applied to the requirement sentences; therefore, this impact is not applicable.

4.1.3. Decrease Cognitive Burden for Readers

The literature review from Section 3.1 described two (2) concepts that relate to improving spatial reasoning for readers: (i) comprehension times associated with alternate media were found to be systematically shorter compared to sentences [29], and (ii) Cognitive Load Theory, which claims that “human cognitive processing is heavily constrained by our limited working memory which can only process a limited number of information elements at a time” [33,34]. These concepts are further explored in relation to alternate media in the subsequent paragraphs.

The systematically shorter comprehension times for alternate media indicate greater ease or decreased cognitive burden when creating mental representations from alternate media than from sentences [29]. The application of this finding is related to the information being conveyed, i.e., when conveying spatial information, alternate media are better suited than sentences. This is consistent with the contextual ranking of alternate media in Table 2, which outlines how different media inherently provide different degrees of context. For example, an engineering drawing containing measurements that are depicted accurately and to scale is easier to comprehend than a series of sentences in which each sentence must maintain reference points to support the building of a mental model of the component. This represents limited and direct evidence. The limited direct evidence of Boudreau and Pigeau [29] supports the potentially positive impact of alternate media on conveying spatial data in support of reader comprehension.

Cognitive Load Theory describes how information overload increases the cognitive load or cognitive burden on a reader and decreases the level of understanding [33,34]. Current systems engineering practices include a multitude of engineering products that support system development, such as fault trees, system architectures, and process flow diagrams [11]. These engineering products contain alternate media as needed to ensure maximum context and convey their intended information to the expected audience. Often, these engineering products are included in specifications to complement requirement sentences [11,46], which could also be interpreted as information overload. If engineering products are included because they provide more or better context, then the requirement sentences repeating the information are superfluous. Likewise, alternate media may represent data more concisely than requirement sentences. For example, a large data set can be graphed. This potential reduction in specification content, without the loss of specification information, serves as indirect evidence to potentially decrease the cognitive burden on the reader, thereby providing a potentially positive impact on understanding. This could represent a significant resource saving in terms of effort and schedule, as the derivation of requirement sentences from engineering products could be partially omitted from projects.

4.1.4. Cognition Factor Impact Summary

This section explores the cognition factor for the potential impact of using alternate media requirement expressions in systems engineering. The Communication and Cognitive Burden components are closely related, as communication is improved when the cognitive load is eased, and the cognitive load is eased when information is clearly communicated [25,33,34]. The assessment results ranged from potentially positive impact to not applicable, with no potentially negative impacts identified. These assessments are primarily based on limited direct supporting evidence, with additional indirect evidence considerations. The level of evidence is limited to support the overall claim that alternate media would provide a potentially positive improvement to the communication factor. Alternate media requirement expressions could provide inherent context that potentially improves communication and may decrease cognitive burden by reducing cognitive overload and improving comprehension time. These findings are summarized in Table 9.

Table 9. Cognition factor impact assessment.

Cognition Subfactor	Impact Rating	Evidence Rating	Rationale
Communication	Potential Positive	Limited Direct Support	Alternate media are situationally preferable based on their inherent context offerings [35,42,43].
Creativity	Not Applicable	Indirect Support	Removing arbitrary constraints would positively impact any requirement media [36,37,45,46].
Cognitive Burden	Potential Positive	Limited Direct and Indirect Support	Alternate media have systematically shorter comprehension times for spatial information [29] and would potentially reduce cognitive burden, which, according to Cognitive Load Theory, improves understanding [33,34].

4.2. Potential Impacts Related to Quality

Assessing quality within natural language documentation is a challenge in current practices. Even with formal document quality indicators, such as the work of Arthur and Stevens [47], the process is human-based and, therefore, arduous and subjective. Semi-formal and formal languages, such as SysML or formal logic, provide machine-supported opportunities for quality checking [26]. Digital tools are available that provide conformity to engineering products based on selected standards [48,49]. Conformity checks for modeling languages can be automated using some Model-Based Systems Engineering (MBSE) tools. While natural language processing is starting to support conformity checks for requirement sentences, it is still limited and requires review by the requirement developer [50]. The Quality factor corresponds directly to the subset of the INCOSE Guide for Writing Requirements characteristics, as listed in Table 4. Each subfactor was assessed, and the findings are compiled in Table 10. Each quality subfactor was assessed, but only those with potentially negative or positive impacts were included for brevity.

4.2.1. Appropriate

According to INCOSE, the “specific intent and amount of detail of the requirement is appropriate to the level (level of abstraction) of the entity to which it refers” [6] and in canonical form that is prior to the action shall) [11]. Best practices dictate that system specifications should be maintained at one (1) system hierarchy [11]; however, it is common to see requirement sentences addressing subsystems within a system specification [4]. These subsystem requirement sentences can be difficult to follow as they can be under a common subsystem header or throughout the document under the theme of the requirement sentence, such as environmental or safety. Conveying a requirement at a particular level of abstraction can be achieved using media types that align with the intended abstraction level.

Model diagrams often present hierarchies, such as block definition diagrams or internal block diagrams [51], and connectivity, such as a Department of Defense Architectural Framework (DoDAF) System Viewpoint Systems Interface Description (SV-1) [52]. This hierarchical structure and relational connectivity define the appropriateness of the model diagram [51,52]. Engineering drawings as requirement expressions provide scale and position to support appropriateness [22]. Because of the visual representation of alternate media, inherent context, and reduced comprehension times, the inclusion of inappropriately leveled requirements would be more evident when operating in alternate media. Therefore, based on indirect evidence, the inclusion of alternate media requirement expressions would have a potentially positive impact.

4.2.2. Quality Factor Impact Summary

The Quality factor, comprised of quality characteristics, shows a potentially positive impact if alternate media requirement expressions are included in systems engineering, including no potentially negative impacts identified. Four (4) of the six (6) subfactors, Necessary, Correct, Conforming, and Consistent, are not applicable to a media change. The Singular subfactor had no evidence identified and was therefore not assessable. The Appropriate characteristic carries the potential for a positive improvement rating based on indirect evidence of the visual representation of alternate media. The findings are summarized in Table 10, along with an abbreviated rationale.

4.3. Potential Impacts Related to Accountability

The accountability provided by requirement expressions can exist both within a team and between a team and its external stakeholders. The accountability factor corresponds directly to a subset of the INCOSE Guide for Writing Requirements characteristics, as listed in Table 4. This section also addresses the blank entries in Table 4. Each subfactor was assessed, and the findings are presented in Table 11. The subfactors that comprise the accountability factor are similar for individual requirement expressions and requirement sets; therefore, they are addressed simultaneously. Each accountability subfactor was assessed, but only those with potentially negative or positive impacts were included for brevity.

4.3.1. Unambiguous (Individual) and Comprehensible (Set)

Ambiguity continues to be a challenge in requirements engineering [6,29,35]. Ambiguity is directly related to semantics and pragmatics, which, along with context, guide the reader to the interpretation intended by the requirement developer [25]. Section 3.1 describes an added layer of ambiguity due to the canonical form constraint for requirement sentences [29], which can create an increased cognitive burden [33,34]. Section 3.1 also discussed shorter comprehension times for alternate media compared to requirement sentences [29]. The concepts of coreference and hybrid inference systems also apply to ambiguity and comprehensibility.

Ambiguity is also related to the type of information being conveyed. The results described in Section 3.1.2 show that different media types possess different capabilities to represent varying abstraction levels or information subtypes. Applying well-suited alternate media to specific information types is an opportunity to mitigate ambiguity. Model diagrams and engineering drawing literature omit a set of characteristics related to comprehensibility. Because each model diagram and engineering drawing can represent multiple requirement sentences, the individual characteristics potentially address the same amount of information as a set of requirement sentences. It can also be asserted that if lower-level representations are unambiguous, then the collective set is unambiguous [24].

Accountability is improved when ambiguity is reduced, as it ensures that both parties understand what is expected of one another. Ambiguity is attributable to the requirement developer, and this holds for any media. However, the inherent context, as per Section 3.1, provided by some alternate media supports both the development and reading of requirement expressions. As ambiguity, comprehension, and communication are directly linked, the potential impact on these characteristics, if alternate media requirement expressions are used is the same as the assessment for the cognition factor: potentially positive, based on limited direct evidence.

4.3.2. Feasible (Individual and Set)

For requirement sentences, feasibility is related to ambiguity, as ensured by the restraint of the requirement developer [37,42]. While model diagrams are characterized as realistic, engineering drawings do not have the characteristic of matching feasible individuals or sets of drawings. Many engineering drawing types depict components ready for manufacture and are therefore bound to physical laws, which inherently provide feasibility [16]. The level of abstraction of the information dictates the media that can be used to represent it. However, being able to diagram or draw a concept speaks to its feasibility. If a component or concept can be diagrammed or drawn, the ability of the concept to be realized as part of the solution is shown to be more feasible. Therefore, based on indirect evidence, alternate media provide a potentially positive benefit regarding the determination of feasibility for requirement expression.

4.3.3. Verifiable (Individual) and Able to Be Validated (Set)

The concepts of verifying and validating requirements have multiple considerations. First, there are the characteristics of the requirement sentences and their specifications. There are two (2) other considerations: legality and configuration management. The characteristics address the accountability contained in the requirement sentences and requirement sets, while the legal aspect addresses the accountability beyond the engineering team, and configuration management addresses the accountability within the team.

The requirement sentence characteristics ensure that the requirement can be realized at the level of abstraction described in [6]. For a requirement set, the characteristic ensures that the set achieves the goal of the originating stakeholder [6]. Currently, requirement developers gather verification information from appropriate stakeholders, such as the test group, to ensure that requirement sentences are verifiable [37,42]. These concepts provide accountability within the requirement sentence. These characteristics are enhanced by configuration management practices.

Recall from Section 3.1 that no matching characteristics existed for model diagrams or engineering drawings for the requirement sentence characteristics of verifiable for a single requirement or able to be validated for a requirement set. Verifying an engineering drawing can be a straightforward process of inspection or measurement of the compliance of the component as produced in the drawing. This does not imply that all drawings are verifiable, as it is possible to draw a component that cannot be realized. However, a proper drawing that is complete with tolerances and other characteristics is inherently more verifiable because of the empirical information provided. Conversely, requirement sentences, because of their flexibility to capture abstractions and the ambiguity tied to natural language [25], are at risk of being unverifiable and, therefore, require a contingency to ensure that the author accounts for verification. An example would be capability requirements that capture concepts from a Concept of Operations (CONOPS) document while deliberately maintaining an implementation-agnostic position, as described in the INCOSE Systems Engineering Handbook [46].

Likewise, model diagrams can be verified using various strategies that span the differences between requirement sentences and engineering drawings. Similar to drawings, model diagrams allow objective verification strategies, including executable models [53,54,55]. Executable models can be used to capture and communicate requirement expressions among stakeholders and allow systems engineers to “forecast success in meeting the expectations of users and the acquirer, as well as to provide feedback to identify and correct performance deficiencies before implementation [56]” [57,58]. The use of executable models is outside the scope of this assessment and is analogous to the test equipment used to verify other requirement expressions. More akin to requirement sentences, subjective approaches include visual inspection by subject-matter experts, although this method benefits from model diagrams providing more context than requirement sentences [45]. Overall, there is indirect evidence to support the claim of a potentially positive impact based on the concept that alternate media are more verifiable based on their visual representations.

4.3.4. Accountability Factor Impact Summary

Based on the limited direct evidence regarding the precedents of model diagrams and engineering drawings, alternate media requirement expressions do not need to establish new processes and accountability practices. The assessment results for the subfactors ranged from potentially positive impact to not applicable, with no potentially negative impacts identified. These findings are summarized in Table 11, along with an abbreviated rationale.

4.4. Factor Impact Analysis Summary

The evidence available for this assessment ranged from no supporting evidence for the “Singular” component of the Quality factor to numerous iterations of limited, direct evidence. None of the assessments were rated as being well supported by the available evidence. The limitation of evidence implies a need to further investigate the direct impacts of these factors and their components on systems engineering in the context of allowing alternate media requirement expressions. This limitation is addressed in Section 5.2 of this paper.

The foregoing assessment, based on a limited literature foundation and inference, considered 13 factor components within the three (3) factors: Cognition, Quality, and Accountability. The factor component ratings included six (6) potentially positive impacts, one (1) not assessable, six (6) not applicable, and zero (0) potentially negative assessments. Each factor has a potentially positive impact. The Cognition factor had a potentially widespread impact, as the concepts of Communication and Cognitive Burden, each of which were individually assessed as potentially positive impacts, were applied to multiple other factor components within the assessment. The primary benefit of alternate media, based on limited direct evidence, is the inherent context that can be harnessed to better convey specific abstraction levels and information types. This has a potentially positive effect on Communication, Cognitive Burden, Appropriateness, Ambiguity, and Feasibility.

4.5. Illustration of Factor Analysis

Recall the Leader Radio (LR) component hierarchy, as described textually in Table 2 and Table 3 in Section 2. Model diagrams present an opportunity to convey the relational context between components and should be a strong candidate media to represent this information [35,37]. Figure 3 provides a notional Block Definition Diagram view of a system model created using the LR PRD excerpts and their list of thresholds, i.e., “(T)”, requirement expressions. From the foregoing factor analysis, one could expect the model diagram to offer potential improvements relative to the set of natural language expressions provided in Table 2 and Table 3. Specifically, potentially positive impacts for a requirement set would be anticipated for the Cognition Factor (Communication and Cognitive Burden) and Accountability Factor (Complete, Feasible, Comprehensible, and Able to be Validated); recall that while the Quality Factor had multiple subfactors for which potential positive impacts were determined for individual requirement expressions, there were none for a requirement expression set.

From Figure 3, the improved context reveals noteworthy ambiguities and inconsistencies that are arguably more noticeable in the SysML diagram than in the requirement sentences in Table 2 and Table 3.

At the top right of Figure 3, in the LR Case, an Electronic block can be seen with no relationships. This is likely a case of inconsistency within the LR PRD database. The LR set list (Table 2, lines 814–826) includes an LR Case and the LR ordered set excluded component list (Table 2). Lines 836–841) cite an “LR Case, Electronic”. While it can be assumed that these are references to the same component, the lack of coreference injects ambiguity into the LR PRD.
Similarly, at the bottom left of Figure 2, the “M-LR Installation Kit Ancillaries and Capabilities” block also has no relationships with other blocks. While this could simply be another coreference failure, reading Table 3 does not provide a clear understanding of the M-LR Installation Kit.
As shown in Figure 2 and stated in Table 3 (line 971), the M-LR Ordered Set includes the LR Set. This infers that the M-LR Ordered Set includes four (4) components that are not listed in the M-LR Set: LR Talk Group Selector Capability, LR Earphone, LR Mission Module Capability, and LR Case. This is a feasible proposition, but the LR PRD does not provide a rationale to support this digression from the intuition that the M-LR Ordered Set would be a subset of components of the M-LR Set, which would be consistent with the LR Set and LR Ordered Set relationship.

These ambiguities can create doubt in the Completeness and Correctness of the LR PRD or the reader’s comprehension. No observations are evident regarding the Feasible and Able to be Validated subfactors of Accountability. The inherent capability of the model diagram to convey structure and hence depict hierarchical relationships also eases the Cognitive Burden in forming a mental model of the LR and M-LR component sets and, as such, potentially improves the Communication of the component hierarchy. All these observations are consistent with the expectations established previously in Section 4 that the use of alternate media requirement expressions would potentially lead to more efficient and effective systems engineering of the LR.

5. Discussion

A summary of the key findings of this research, the limitations of the research, and suggested future research directions are discussed in the following subsections.

5.1. Conclusions

Model diagrams and engineering drawings as alternative media were compared to requirement sentences using cognition, quality, and accountability factors, where each factor comprised several subfactors. The assessment focused on the inherent ability of alternate media to impact these factors. Each factor included subfactors that were assessed for the positive or negative impacts of using alternate media to express requirements.

The cognition factors included communication, creativity, and cognitive burden subfactors. The primary benefit of alternate media comes from their inherent context, which can be harnessed to better communicate specific abstraction levels and information types. The creativity component was found to be media agnostic, though this research recommends the removal of arbitrary constraints on requirements development, regardless of media, as it adds a layer of ambiguity. Alternate media significantly reduce the cognitive burden on readers performing spatial reasoning or dealing with cognitive load issues. The findings indicate that alternate media provide very positive improvements in cognition within an engineering effort.

The INCOSE requirement and requirement set characteristics were assigned to Quality and Accountability factors. The Quality factor was composed of Necessary, Appropriate, Singular, Correct, Conforming, and Consistent. This research determined Necessary” and Correct to be media-agnostic characteristics, and the concept of Singular was addressed by the cognition factor. Alternate media better convey appropriateness through structure in a hierarchy that is not inherent in a sentence and was assessed as a very positive improvement. This limited finding shows an improvement in the requirement quality by including alternate media options in systems engineering.

The accountability factor comprised a characteristic consolidation that addressed both individual requirement expressions and their sets: Unambiguous and Comprehensible, Complete, Feasible, Verifiable, and Able to be Validated. The communication improvements provided by the inherent context in alternate media provide an improvement to reduce ambiguity and address comprehensibility issues in requirement expression. Many alternate media provide inherent feasibility; if a component or concept can be diagrammed or drawn, the ability of the concept to be realized as part of the solution is shown to be more feasible. Each of these component assessments indicates that alternate media could provide positive improvement to accountability within requirements engineering.

Based on the Cognition, Quality, and Accountability factors identified in this research, alternate media requirement expressions categorically improve systems engineering. The specific identification of the relative differences in alternative media for requirements expression is a significant contribution of this research, which proposes that systems engineering should use alternate media to convey requirements based on the level of abstraction needed to communicate the requirement. In this age of digital engineering, this research establishes a definitive basis for creating multi-media requirement documentation that is both more accurate and concise.

5.2. Limitations

This research demonstrates the feasibility and potential impact of using alternate media to express requirements. This research includes a diversity of media to address the assertion that alternate media are viable for requirement expressions; however, this research does not claim to identify all possible applicable media. While the limitation of this research is scoped by media, the respective media are largely distinct, and the application can be generalized, although future research described in Section 5.3 is warranted.

Limited evidence was discovered to directly support the assessment of the identified factors and their components. The qualitative impacts associated with the scoped alternate media were researched using a qualitative analysis approach to scope this research to general impacts. These potential impacts have led to research in the non-engineering fields of cognitive science, pragmatics, and economics. The citations from these fields provide general information that provides limited evidence to allow for alternate media requirement expressions. Qualitative research is limited but well-suited for such generalizations, and a quantitative analysis would better identify impacts and values. Some theories are based on a single source, as that was all that could be found. While this is sufficient to conduct theory crafting, it provides a weak basis that should be expanded. This research theorizes that there are potentially positive impacts of including alternate media requirement expressions in systems engineering [59]. Quantitative studies are recommended in Section 5.3 to more completely identify and better define the impacts.

5.3. Future Research

A qualitative approach was used to scope this research to general impacts based on the limited evidence. Further research is needed to provide more evidence that can be used to better determine the impacts and refine the contextual rankings of additional media types. For instance, a laboratory setting could gather experimental data to measure the impact of different media requirement expressions on cognitive load. A pilot study was recently completed to inform the planning of a comprehensive study, the results of which will be published upon completion. Another example would be to collect project data in a longitudinal fashion to analyze the effort and schedule impacts of using alternate media requirement expressions or using field or test data to identify system effectiveness impacts. These quantitative approaches would provide information to validate and refine the theoretical basis. A quantitative analysis could potentially identify the level of impact and allow for a more value-based approach to benefit from the inclusion of alternate media requirement expressions in systems engineering.

Furthermore, the scope of this research was limited to textual sentences, model diagrams, and engineering drawings as viable media for system requirement expressions due to (1) the availability of guidelines and standards for each and (2) their diversity being representative of alternative media in general to enable the analysis and conclusions. Additionally, there is an opportunity to identify other media for inclusion, which should be explored for support or refinement of the conclusions resulting from this study.

Author Contributions

Conceptualization, J.K. and L.D.T.; methodology, J.K.; validation, J.K.; formal analysis, J.K.; investigation, J.K.; writing—original draft preparation, L.D.T.; writing—review and editing, L.D.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

No new data were created or a No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

Author Jason Kolligs was employed by the company Strategic Technology Consulting (STC). The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Requirement expression terminology illustration.

Figure 2. Potential leader radio ordered set SysML block definition diagram [23].

Figure 3. Potential leader radio structure SysML block definition diagram.

Table 1. Documented leader radio (LR) ordered set component list [24].

828	The LR Set shall include the following components when the LR Set is ordered:
829	3.2.1 (T) LR-RT IAW Para 3.1;
830	3.2.2 (T) LR GPS Antenna;
831	3.2.6 (T) LR Loudspeaker—Microphone, External;
832	3.2.7 (T) LR Talk Group Selector Capability;
833	3.2.8 (T) LR Earphone;
834	3.2.11 (T) LR Mission Module Capability.

Table 2. Documented leader radio set component list [24].

814	The LR Set capability is dependent upon the following components being assembled into a
815	Functional radio set IAW the approved As Build Configuration List (ABCL):
816	LR RT (Para 3.1);
817	LR GPS Antenna (Para 3.2.2);
818	LR Multi-band Antenna (Para 3.2.3);
819	LR VHF Antenna (Para 3.2.4);
820	LR Rechargeable Battery (Para 3.2.5);
821	LR Loudspeaker (Para 3.2.6);
822	LR Talk Group Selector Capability (Para 3.2.7);
823	LR Earphone (Para 3.2.8);
824	LR Case (Radio Pouch) (Para 3.2.9);
825	LR GPS Cable (Para 3.2.10); and
826	LR Mission Module Capability (Para 3.2.11).
827
828	The LR Set shall include the following components when the LR Set is ordered:
829	3.2.1 (T) LR-RT IAW Para 3.1;
830	3.2.2 (T) LR GPS Antenna;
831	3.2.6 (T) LR Loudspeaker—Microphone, External;
832	3.2.7 (T) LR Talk Group Selector Capability;
833	3.2.8 (T) LR Earphone;
834	3.2.11 (T) LR Mission Module Capability.
835
836	The LR Set does not include the following components when the LR Set is ordered:
837	3.2.3 (T) LR Multi-band Antenna(s);
838	3.2.4 (T) LR VHF Antenna(s);
839	3.2.5 (T) LR Rechargeable Battery;
840	3.2.9 (T) LR Case, Electronic (Radio Pouch, Camouflage);
841	3.2.10 (T) LR GPS Cable.

Table 3. Documented mounted-leader radio set component list [24].

953	The Mounted Leader Radio (Mounted-LR or M-LR) set capability is dependent upon the
954	Following components being assembled into a functional radio set, IAW the approved as
955	Build configuration List (ABCL):
956	LR-RT (Para 3.1);
957	LR GPS Antenna (Para 3.2.2);
958	LR Multi-band Antenna (Para 3.2.3);
959	LR VHF Antenna (Para 3.2.4);
960	LR Rechargeable Battery (Para 3.2.5);
961	LR Loudspeaker (Para 3.2.6);
962	LR Talk Group Selector Capability (Para 3.2.7);
963	LR GPS Cable (Para 3.2.10);
964	LR Mission Module Capability (Para 3.2.11);
965	M-LR Case, Electronic (Pouch for R/T and ancillary items) (Para 3.3.2);
966	M-LR Installation Kit (Para 3.3.3) (mount, adapter, amplifiers(s), power
967	Management, and VICTORY integration items)
968	M-LR Environmental Testing (Para 3.3.5); and
969	M-LR Antenna(s) (Para 3.6 Ancillary Items)
970	The M-LR shall include the following components when the M-LR is ordered:
971	3.3.1 (T) Leader Radio Set (LR) IAW para 3.2
972	3.3.3 (T) M-LR Installation Kit (except 3.3.3.5 Antennas)
973	3.3.4 (O) M-LR Install Kit Equipment Reuse
974	3.3.5 (T) M-LR Environmental Testing
975	The M-LR does not include the following components when M-LR is ordered:
976	3.3.2 (T) M-LR Case, Electronic
977	3.3.3.5 (T) Antennas
978	3.3.3.6 (T) M-LR Installation Kit Ancillaries and Capabilities

Table 4. Quality and accountability factors aligned to media characteristics.

Factor	Requirement Sentence Characteristic [6]	Model Diagram Characteristic [20]	Engineering Drawing Characteristic [21,22]
Individual Requirement Expression Quality Factor	Necessary	Necessary	Necessary
	Appropriate	Appropriate	Scale
	Singular	(Nearly) Independent	Singular
	Correct	Precision	Accuracy
	Conforming	Self-Consistent	Consistent
Requirement Expression Set Quality Factor	Consistent	Harmonious	Consistent
Individual Requirement Expression Accountability Factor	Unambiguous	Unambiguous	Clear
	Complete	Complete	Complete
	Feasible	Realistic	(blank)
	Verifiable	(blank)	(blank)
Requirement Expression Set Accountability Factor	Complete	Sufficient	Complete
	Feasible	Realistic	(blank)
	Comprehensible	(blank)	(blank)
	Able to be Validated	(blank)	(blank)

Table 6. Alternate media requirement expression factor composition (Note: Ind. refers to individual requirements, and Set refers to requirement sets).

Factor	Cognition	Quality	Accountability
Subfactors	Communication Creativity Cognitive Burden	Necessary Appropriate Singular Correct Consistent (Set)	Unambiguous Complete (Ind. & Set) Feasible (Ind. & Set) Verifiable Comprehensible (Set) Able to be Validated (Set)

Table 7. Factor impact ratings and Descriptions.

Impact Rating	Rating Description
Not Assessable	Insufficient evidence to support a subfactor impact assessment
Potentially Negative Impact	Changing to alternate media provides the opportunity for negative outcomes for the subfactor.
Not Applicable	The subfactor is not impacted by a media change.
Potentially Positive Impact	Changing to alternate media provides the opportunity for positive improvements to the subfactor.

Table 8. Factor Evidence Ratings and Descriptions.

Impact Rating	Rating Description
No Support	No evidence was found to address the factor
Indirect Support	Limited references that do not directly address the factor
Limited Direct Support	Limited references that directly address the factor
Well Supported	Multiple references that directly address the factor

Table 10. Quality factor impact assessment.

Factor	Quality Subfactor	Impact Rating	Evidence Rating	Rationale
Individual Requirement Expression Quality Factor	Necessary	Not Applicable	Limited Direct Support	The concept of necessity is media agnostic [6,37,42].
	Appropriate	Potentially Positive	Indirect Support	Alternate media better convey appropriateness through structure and hierarchy [4,6,11,22,51,52].
	Singular	Not Assessable	No Support	The concept of staying focused on a singular concept may be addressed by the cognition factor [29,33,34].
	Correct	Not Applicable	Limited Direct Support	The concept of correctness is media agnostic [6,37,42].
	Conforming	Not Applicable	Limited Direct Support	It is currently a manual process to ensure conformity in each of the scoped media [6,37,42,48,49,50].
Requirement Expression Set Quality Factor	Consistent	Not Applicable	Limited Direct Support	It is currently a manual process to ensure consistency in each of the scoped media [6,37,42,48,49,50].

Table 11. Accountability factor aligned to scoped media characteristics.

Factor	Accountability Subfactor	Impact Rating	Evidence Rating	Rationale
Individual Requirement Expression Accountability Factor	Unambiguous	Potentially Positive	Limited Direct Support	Ambiguity is mitigated by the communication improvement opportunities provided by alternate media [29,33,34,36].
	Complete	Not Applicable	Limited Direct Support	Media agnostic [37,42].
	Feasible	Potentially Positive	Indirect Support	Many alternate media have inherent feasibility based on the ability to be drawn or adherence to physical law [16,37,42].
	Verifiable	Potentially Positive	Limited Direct and Indirect Support	Many alternate media are inherently verifiable, and modeling tools can verify model diagrams. Alternate media also support legality and configuration management [6,25,45,53,54,55,56,57,58].
Requirement Expression Set Accountability Factor	Complete	Not Applicable	Limited Direct Support	Media agnostic [37,42].
	Feasible	Potentially Positive	Indirect Support	Many alternate media have inherent feasibility based on their ability to be drawn or adherence to physical law [16,37,42].
	Comprehensible	Potentially Positive	Limited Direct Support	Ambiguity is mitigated by the communication improvement opportunities provided by alternate media [29,33,34,36].
	Able to be Validated	Potentially Positive	Limited Direct and Indirect Support	Many alternate media are inherently verifiable, and modeling tools can verify model diagrams. Alternate media also support legality and configuration management.

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Kolligs, J.; Thomas, L.D. Characterizing Efficacy of Alternative Media for Requirements Expression. Systems 2025, 13, 314. https://doi.org/10.3390/systems13050314

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Kolligs, Jason, and Lawrence Dale Thomas. 2025. "Characterizing Efficacy of Alternative Media for Requirements Expression" Systems 13, no. 5: 314. https://doi.org/10.3390/systems13050314

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Kolligs, J., & Thomas, L. D. (2025). Characterizing Efficacy of Alternative Media for Requirements Expression. Systems, 13(5), 314. https://doi.org/10.3390/systems13050314

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Characterizing Efficacy of Alternative Media for Requirements Expression

Abstract

1. Introduction

2. Scenario

3. Materials and Methods

3.1. Factor Identification

3.1.1. Quality and Accountability Factors

3.1.2. Cognition Factor

3.1.3. Factor Identification Summary

3.2. Factor Evidence and Impact Assessment

3.3. Validation

4. Analysis

4.1. Potential Impacts Related to Cognition

4.1.1. Potential Impacts to Communication

4.1.2. Potential Impacts to Creativity

4.1.3. Decrease Cognitive Burden for Readers

4.1.4. Cognition Factor Impact Summary

4.2. Potential Impacts Related to Quality

4.2.1. Appropriate

4.2.2. Quality Factor Impact Summary

4.3. Potential Impacts Related to Accountability

4.3.1. Unambiguous (Individual) and Comprehensible (Set)

4.3.2. Feasible (Individual and Set)

4.3.3. Verifiable (Individual) and Able to Be Validated (Set)

4.3.4. Accountability Factor Impact Summary

4.4. Factor Impact Analysis Summary

4.5. Illustration of Factor Analysis

5. Discussion

5.1. Conclusions

5.2. Limitations

5.3. Future Research

Author Contributions

Funding

Data Availability Statement

Conflicts of Interest

References

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