Visual Notation Research Articles

Continuous Evolution of Digital Twins using the DarTwin Notation

AbstractDespite best efforts, various challenges remain in the creation and maintenance processes of digital twins (DTs). One of those primary challenges is the constant, continuous and omnipresent evolution of systems, their user’s needs and their environment, demanding the adaptation of the developed DT systems. DTs are developed for a specific purpose, which generally entails the monitoring, analysis, simulation or optimisation of a specific aspect of an actual system, referred to as the actual twin (AT). As such, when the twin system changes, that is either the AT itself changes, or the scope/purpose of a DT is modified, the DTs usually evolve in close synchronicity with the AT. As DTs are software systems, the best practices or methodologies for software evolution can be leveraged. This paper tackles the challenge of maintaining a (set of) DT(s) throughout the evolution of the user’s requirements and priorities and tries to understand how this evolution takes place. In doing so, we provide two contributions: (i) we develop , a visual notation form that enables reasoning on a twin system, its purposes, properties and implementation, and (ii) we introduce a set of architectural transformations that describe the evolution of DT systems. The development of these transformations is driven and illustrated by the evolution and transformations of a family home’s DT, whose purpose is expanded, changed and re-prioritised throughout its ongoing lifecycle. Additionally, we evaluate the transformations on a laboratory-scale gantry crane’s DT.

Image analysis and polyphenol profiling unveil red-flesh apple phenotype complexity.

The genetic basis of colour development in red-flesh apples (Malus domestica Borkh) has been widely characterised; however, current models do not explain the observed variations in red pigmentation intensity and distribution. Available methods to evaluate the red-flesh trait rely on the estimation of an average overall colour using a discrete class notation index. However, colour variations among red-flesh cultivars are continuous while development of red colour is non-homogeneous and genotype-dependent. A robust estimation of red-flesh colour intensity and distribution is essential to fully capture the diversity among genotypes and provide a basis to enable identification of loci influencing the red-flesh trait. In this study, we developed a multivariable approach to evaluate the red-flesh trait in apple. This method was implemented to study the phenotypic diversity in a segregating hybrid F1 family (91 genotypes). We developed a Python pipeline based on image and colour analysis to quantitatively dissect the red-flesh pigmentation from RGB (Red Green Blue) images and compared the efficiency of RGB and CIEL*a*b* colour spaces in discriminating genotypes previously classified with a visual notation. Chemical destructive methods, including targeted-metabolite analysis using ultra-high performance liquid chromatography with ultraviolet detection (UPLC-UV), were performed to quantify major phenolic compounds in fruits' flesh, as well as pH and water contents. Multivariate analyses were performed to study covariations of biochemical factors in relation to colour expression in CIEL*a*b* colour space. Our results indicate that anthocyanin, flavonol and flavanol concentrations, as well as pH, are closely related to flesh pigmentation in apple. Extraction of colour descriptors combined to chemical analyses helped in discriminating genotypes in relation to their flesh colour. These results suggest that the red-flesh trait in apple is a complex trait associated with several biochemical factors.

Evaluation of Orange data mining software and examples for lecturing machine learning tasks in geoinformatics

AbstractThe study presents the advantages of, and possible uses for, Orange software for data mining in combination with processing spatial data by ArcGIS Pro software in education. To present suitability of Orange software in education, the scientific method of Physics of Notation by D. Moody is used to evaluate the Orange software's visual vocabulary. All nine principles are applied in the presented evaluation. As a result, a high level of effective cognition of the Orange visual vocabulary is proven by this method. Namely, the semantic transparency of visual vocabulary, thanks the explicit inner icons, is semantically immediate. Also, principle of dual coding is used properly by automatic text labels of graphical symbols with the opportunity to rename labels. Renaming is also a way to ensure the partial overloading of symbols found by the first principle of semiotic clarity. The principle of cognitive interaction is partially fulfilled by automatically reorganizing connector lines between symbols to reduce the crossing of lines. A high level of effective cognition is beneficial for students. The evaluation of the visual notation of Orange software is presented to inform teachers and the geoinformatics community of the highly effective cognitive aspects of Orange software. The two practical lectures of processing in Orange and ArcGIS Pro software are shown to the teachers and students of geoinformatics community as examples of machine learning tasks. They are cluster analyses carried out with the density‐based spatial clustering of applications with noise method, first for the location of cafés in Olomouc town and the second example concerns finding similar European towns based on their land use arrangement, using the neural network and following hierarchical clustering. Both examples could provide inspiration for the geoinformatics community to adopt Orange data mining software.

Low-code development using requirements and knowledge representation models

Low-Code Development is a new software development paradigm which is typically used to generate web applications from high-level visual notations. These notations allow to express the User Interface and Application Logic (usersystem interactions) in a way which is understandable by the end-users. Using certain model-driven approaches, the low-code environments allow for generating the front-end layer and basic CRUD operations in the back-end. Yet still, non-standard domain logic (data processing) operations still necessitate the use of traditional programming. In this article we present a visual language, called RSL-DL that can be used to represent such non-standard domain logic in a visual form. It allows to capture domain knowledge with complex domain rules aligned with requirements models. The language synthesises and extends approaches found in knowledge representation (ontologies) and software modelling language engineering. The development environment of RSL-DL enables fully automatic generation of domain logic code by reasoning over and reusing domain knowledge. The environment includes a dedicated model editor and a transformation engine. The language?s abstract syntax is defined using a meta-model expressed in MOF. Its semantics is expressed with several translational rules that map RSL-DL models onto typical programming language constructs. The article presents a list of these rules in an informal way, and then introduces their formalisation using a graphical transformation notation. The RSL-DL environment includes an inference engine that enables processing queries to domain models and selecting appropriate invocations to generated code. It was also initially validated through studies that involve understandability, operability and complexity assessment. Based on these results, we conclude that declarative knowledge representations can be successfully used to produce imperative backend code with non-trivial logic.

Sound Drawing and Dhol Notation: A Methodological Approach to Visualising Drum Sounds

The research introduces ‘Sound Drawing’ as an engaging instructional activity to develop a visual dhol notation system. In contrast to the conventional reliance on spoken language for dhol instruction, this research involves developing a visual notation system that effectively bridges the auditory intricacies of the dhol drum with corresponding visual representations. Through a methodical examination of sound drawings collaboratively generated by participants, this study critically assesses the effectiveness of sound drawing as an active and inclusive pedagogical instrument within the domain of dhol learning. The outcomes demonstrate how participants’ visual interpretations of dhol sounds led to creating a notation system. This system reflects a diverse range of auditory perceptions and offers a new avenue for cultural engagement and learning in music education. By introducing sound drawing as an immersive instructional activity, this research aspires to advance dhol pedagogy, rendering it more accessible to diverse cultures and communities, thus transcending linguistic barriers. This study pioneers the incorporation of sound drawing as an innovative pedagogical activity for the collective development of a visual dhol notation system, thereby instigating a transformation in pedagogical paradigms and fostering cross-cultural engagement within the rich musical tradition of the dhol.

Study of models of formal description of knowledge about information systems’ functional requirements using EER-diagram

The object of research is a formal description of knowledge about the functional requirements for the information system. In processes that work with requirements, the basis for modeling requirements for an information system is often the representation of these requirements at the level of information, expressed in the form of their textual descriptions or visual models. Such processes can be considered as successive transformations of representations of requirements in the form of data, information and knowledge during the identification and formulation of requirements for an information system in accordance with the chosen methodology of information system development. However, such an approach leaves open the question of the type of representations of individual requirements for the information system, the methods and methods of forming these representations and transforming these representations into themselves and into each other. Therefore, conducting research on solving this issue is relevant from a theoretical and applied point of view. Usually, the ER diagram and the class diagram are used to describe information support and software of information system, respectively. But during development, in some cases, the problem of compatibility of information support and software arises because the diagrams are made only from such points of view of the corresponding types of support for which the visual descriptions were created. This problem is proposed to be solved by the unification of these descriptions and the development of a formal apparatus that uses a frame model to display the description of functional requirements at the level of knowledge using a class diagram and an ER diagram. Visual notations of functional requirements describing the architecture of information support (ER-diagram and EER-diagram) and software support (class diagram) were studied. According to the results of the study of the common elements of the diagrams and the proposed network of frames, it was found that the network of frames can reflect the description of functional requirements at the level of knowledge in the EER diagram. The obtained result makes it possible to define a visual model (EER-diagram), which will be used for the formal apparatus of visual display of descriptions of the functional requirements for the information system at the level of knowledge, and to propose a mechanism for transforming this visual model into an ER-diagram and a class diagram, which, respectively, describe architectures of information support and software of information system.

A visual notation for succinct program traces

Program traces are a widely used representation for explaining the dynamic behavior of programs. They help to make sense of computations and also support the location and elimination of bugs. Unfortunately, program traces can grow quite big very quickly, even for small programs, which compromises their usefulness. In this paper we present a visual notation for program traces that supports their concise representation. We explain the design decisions of the notation and compare it in detail with several alternatives. An important part of the trace representation is its flexibility and adaptability, which allows users to transform traces by applying filters that capture common abstractions for trace representations. We also present an evaluation of the trace notation and filters on a set of standard examples. The results show that our representation can reduce the overall size of traces by at least 79%, which suggests that our notation is an effective improvement over the use of plain traces in the explanation of dynamic program behavior.

Echoic Re-Presencing

This paper considers listening as a method in media archaeology—a cluster of technology-oriented approaches to the past that attend to “dead end” inventions outside teleological narratives of progress. In particular, Wolfgang Ernst’s media-archaeological ear advances a materialist approach which favors listening to “the technical signifier rather than […] the acoustic or musical signified.” However, this perspective is subject to recurrent critiques from feminist scholars who highlight the lack of regard for the asymmetrical power structures that undergird technical objects and their exclusion from historical narratives. As a case study, and interrogation of the possibilities for a feminist media archaeology, this paper examines the work of Daphne Oram, a British composer whose contributions to electronic music have been routinely overlooked, and the excavation of her work in Oramics: Atlantis Anew (2011), a film by Aura Satz. The archival vestiges of Oram’s composition technique, in which visual notations on celluloid are sonified by her Oramics Machine, align with, and demand consideration beyond, Ernst’s “ascetic approach to signals.” Through a close reading of Satz’s film, I suggest that her simultaneous attention to the material processes of sound technologies and the erasure of women’s labor posits a necessary extension to this mode of enquiry. Considering recent feminist interventions in media archaeology, as well as critiques in sound studies that drawn on feminist STS to challenge the presumed universality of listening, this paper proposes a framework of media-archaeological listening as echoic re-presencing. Oram’s work, and Satz’s re-prescencing of it, therefore open up possibilities for listening otherwise to the sonic past.

Just scratching the surface: Post-fire engravings as semasiographic writing in the ancient Andes

We present analyses of post-fire engravings (PFEs), scratched markings made in the surface of ceramic vessels, from the sites of Atalla (800–500 BCE) and Huari (600–1000 CE), Peru. We compare engraved motifs, the vessel forms on which they appear, their placement on vessels, and the contexts in which they were found at Atalla and Huari to other examples mentioned in the Andean and international archaeological literature. These comparisons elucidate both regional and site-level spatial patterns that suggest that these markings constitute intentional visual notations created by the vessel users. Drawing upon the Quechua concept of quillca as “the creation of meaningful markings,” we argue that Andean PFEs are meaning-laden signs whose use was comparable to writing. Our analyses also reveal that PFEs appear most frequently on serving wares, such as bowls and cups, vessel forms that were used in commensal events. Semasiographic writing is particularly useful in multilingual contexts, and we highlight that the archaeological data support a correlation between the use of PFEs and historical moments of increasing intercultural interaction in the pre-Hispanic Andes. We present a case for this alternative form of literacy and suggest that this form of semasiographic writing played a role in multilingual commensal events.

AStar: A modeling language for document-oriented geospatial data warehouses

A Geospatial Data Warehouse (GDW) is an extension of a traditional Data Warehouse that includes geospatial data in the decision-making processes. Several studies have proposed the use of document-oriented databases in a GDW as an alternative to relational databases. This is due to the ability of non-relational databases to scale horizontally, allowing for the storage and processing of large volumes of data. In this context, modeling the manner in which facts and dimensions are structured is important in order to understand, maintain, and evolve the Document-oriented GDW (DGDW) through visual analysis. However, to the best of our knowledge, there are no modeling languages that support the design of aggregated data as facts and dimensions, that can be represented as referenced or embedded documents, partitioned into one or more collections. To overcome this lack, we propose Aggregate Star (AStar), a Domain-Specific Modeling Language for designing DGDW logical schemas. AStar is defined from a concrete syntax (graphical notation), an abstract syntax (metamodel), and static semantics (well-formedness rules). In order to describe the semantics of the concepts defined in AStar, translational semantics map the graphical notation to the metamodel and the respective code, to define the schema in MongoDB (using JSON Schema). We evaluate the graphical notation using Physics of Notations (PoN), which provides a set of principles for designing cognitively effective visual notations. This evaluation revealed that AStar is in accordance with seven of the nine PoN principles, an adequate level of cognitive effectiveness. As a proof of concept, the metamodel and well-formedness rules were implemented in a prototype of Computer-Assisted Software Engineering tool, called AStarCASE. In its current version, AStarCASE can be used to design DGDW logical schemas and to generate their corresponding code in the form of JSON Schemas.

Evaluation of Visual Notations as a Basis for ICS Security Design Decisions

For making informed security decisions during the design of industrial control systems (ICS), engineers need to process large amounts of security-relevant information outside their area of expertise. This problem moves the presentation of the security-relevant information into focus: security-relevant engineering information must be presented to security decision-makers in a way that enables them to decide upon security measures to build a defensible system. Visual representations have the potential to effectively convey suchlike information, thus saving the engineers’ brain capacity for the security decision-making. However, research shows that this potential is only realized if the visualizations are carefully constructed for cognitive effectiveness. As a prerequisite for constructing a visual language for security engineering in the future, this paper explores two scientific questions: 1) what are the requirements for visualizing security-relevant engineering information in a way that enables engineers to make security decisions during ICS design? and 2) which existing visual languages meet (parts of) these requirements? The evaluation of existing visualizations reveals that there is a need for an improved, specialized visual language for security engineering that builds upon established engineering visualizations like piping and instrumentation diagrams and network maps, represents all security-relevant information as icons to achieve semantic transparency, and includes filtering mechanisms to reduce the complexity of each single diagram. The paper finishes with defining the main pillars of a future visual language that should allow ICS engineers to quickly capture security-relevant information and guide them through the process of selecting the right security measures to design a defensible ICS.

Visual notations in container orchestrations: an empirical study with Docker Compose

Container orchestration tools supporting infrastructure-as-code allow new forms of collaboration between developers and operatives. Still, their text-based nature permits naive mistakes and is more difficult to read as complexity increases. We can find few examples of low-code approaches for defining the orchestration of containers, and there seems to be a lack of empirical studies showing the benefits and limitations of such approaches. We hypothesize that a complete visual notation for Docker-based orchestrations could reduce the effort, the error rate, and the development time. Therefore, we developed a tool featuring such a visual notation for Docker Compose configurations, and we empirically evaluated it in a controlled experiment with novice developers. The results show a significant reduction in development time and error-proneness when defining Docker Compose files, supporting our hypothesis. The participants also thought the prototype easier to use and useful, and wanted to use it in the future.

Visual Notation a Movement Route and Time Spectrum Mapping Approach of Visual Field Quantified Tool Based on Space Syntax-The Case Study of Evacuation Behavior in a Fire Scene

本文目的在於探究使用者視覺資訊變化與其逃生行為（如移動之快慢／停滯／繞道…等）兩者之關係。本研究以空間型構理論（Space Syntax）之視野量化工具Isovist為基礎，將受測者逃生模擬過程以固定時間段紀錄，使之成為具備時間因子的移動路徑再導入量化可見視野之分析參數-視覺範圍值（Visual Area）與可判讀是否繞道之分析參數－位移程度（Range），量化分析受測者之視野資訊變化與逃生移動行為模式，並佐以空間視覺資訊圖譜與行為移動戳記等記錄形式記錄分析之，得以檢視其逃生過程中移動速度變化、停滯和繞道行為。因而以『視覺譜記』為本文標題。本研究透過虛擬實境（Virtual Reality，VR）火場情境模擬實驗蒐集了54個有效樣本數據。初步推斷，受測者產生停滯與繞道地點之空間特徵為視覺範圍值（Virtual Area）與整體空間視覺相對互視程度（Relative Visibility, Visual Integration-HH）落差較大處，即雖位於視野搜尋量大之空間場域，但卻無法從局部區域判讀整體的空間組構，最終做出錯誤之逃生移動決策。The purpose of this article is to explore the relationship between user's visual information difference and evacuation behavior, such as fast or slow movement, stagnation and detour. This research is based on the Space Syntax's visual field tool, Isovist. The simulation process is recorded in a fixed period of time, making it a route with time factor, and then we employ analytical parameter, Visual Area and the Range, quantitatively to analyze the subject's visual information and behavior patterns, to clarify stagnation and detour behavior during the process. This paper records and analyzes usage behaviors in the form of spatial visual information maps and behavioral movement stamps as well, so it is named as ''visual Notation''. In this study, 54 valid sample data were collected through the VR fire scene simulation experiment. It is preliminarily inferred that the spatial characteristics of the subject's stagnation and detour locations are the large gap between Virtual Area and Relative Visibility, Visual Integration-HH. Even the location is in the high visual search volume, it's hard to interpret the overall spatial configurations from local area, and ultimately make a wrong movement decision.

Visual notations for viewing RDF constraints with UnSHACLed

The quality of knowledge graphs can be assessed by a validation against specified constraints, typically use-case specific and modeled by human users in a manual fashion. Visualizations can improve the modeling process as they are specifically designed for human information processing, possibly leading to more accurate constraints, and in turn higher quality knowledge graphs. However, it is currently unknown how such visualizations support users when viewing RDF constraints as no scientific evidence for the visualizations’ effectiveness is provided. Furthermore, some of the existing tools are likely suboptimal, as they lack support for edit operations or common constraints types. To establish a baseline, we have defined visual notations to represent RDF constraints and implemented them in UnSHACLed, a tool that is independent of a concrete RDF constraint language. In this paper, we (i) present two visual notations that support all SHACL core constraints, built upon the commonly used visualizations VOWL and UML, (ii) analyze both notations based on cognitive effective design principles, (iii) perform a comparative user study between both visual notations, and (iv) present our open source tool UnSHACLed incorporating our efforts. Users were presented RDF constraints in both visual notations and had to answer questions based on visualization task taxonomies. Although no statistical significant difference in mean error rates was observed, all study participants preferred ShapeVOWL in a self assessment to answer RDF constraint-related questions. Furthermore, ShapeVOWL adheres to more cognitive effective design principles according to our performed comparison. Study participants argued that the increased visual features of ShapeVOWL made it easier to spot constraints, but a list of constraints – as in ShapeUML – is easier to read. However, also that more deviations from the strict UML specification and introduction of more visual features can improve ShapeUML. From these findings we conclude that ShapeVOWL has a higher potential to represent RDF constraints more effective compared to ShapeUML. But also that the clear and efficient text encoding of ShapeUML can be improved with visual features. A one-size-fits-all approach to RDF constraint visualization and editing will be insufficient. Therefore, to support different audiences and use cases, user interfaces of RDF constraint editors need to support different visual notations.

Using systems thinking to increase understanding of the innovation system of healthcare organisations.

This paper applies systems thinking modelling to enhance the dynamic understanding of how to nurture an innovative culture in healthcare organisations to develop the innovation system in practice and speed up the innovative work. The model aims to provide a holistic view of a studied healthcare organisation's innovation processes, ranging from managerial values to its manifestation in improved results. The study is based on empirical material from a healthcare unit that, within a few years, changed from having no innovations to repeatedly generating innovations. The study uses the modelling language of causal loop diagrams (CLDs) in the system dynamics methodology to identify the key important aspects found in the empirical material. The proposed model, based on the stories of the interviewees, explores the dynamics of inertia when nurturing an innovative culture, identifying delays attributed to the internal change processes and system relationships. These findings underscored the need for perseverance when developing an innovative culture in the entrepreneurial phases. The approach of using systems thinking to make empirical healthcare research results more tangible through the visual notations of CLDs and mental simulations is believed to support exploring complex phenomena to induce and nurture both individual and organisational learning. The results from this approach provide deepened analysis and provoke the systems view to explain how the nurturing of the culture can accelerate the innovation processes, which helps practitioners and researchers to further expand their understanding of their healthcare contexts.

Acid Patterns: How people are sharing a visual notation system for the Roland TB-303 to create and recreate acid house music

This article discusses the use of an accessible visual notation system that represents the melodic component of an electronic music composition in acid house music, based on programming the Roland TB-303 bassline synthesiser’s sequencer. This notation system can be used for sharing, composition, collaboration and archival purposes. This system is called an acid pattern. The article analyses a variety of different approaches to communicate acid patterns. It examines the requirements and visual elements used and how they relate directly to the functionality of the Roland TB-303’s sequencer. Through content analysis of images, text and audio data gathered from various music community websites this article furthers the understanding of how the practices and cultures of acid house music composition, notation and archiving are shared online and how they, enabled by web-based technologies, can build communities. This article suggests important possibilities for communities of practice-based around a shared cultural identity, accessible notation systems, and the creation and recreation of music in both online and offline contexts.

SoaML cognition and its potential application to Autonomous Driving: An Empirical Study

Recently, the architectural styles of 5G technology started supporting advance vehicle-to-everything (V2X) services. From standardization viewpoint, Service-oriented architecture Model Language (SoaML) specification has been used to model and design services for reusable environments. However, the system designers made less effort in addressing the issues related to visual representations (notations) in SoaML. In this paper, we present a novel evaluation approach to obtain the cognitive effectiveness of SoaML’s visual notations by applying the scientific principles from Physics of Notations (PoNs). Furthermore, we evaluated results of the cognitive effectiveness of SoaML via survey-based empirical study for reference architecture, intra-cloud space, and organizational boundary symbols. Our results indicate the applicability of the new proposed notations and improvements in cognitive effectiveness of the SoaML notation. For future work, we plan to test the proposed architectural improvements for designing V2X service-based use cases.

Toward a Graphical Modeling Tool for Response-Time Requirements Based on Soft and Hard Real-Time Capabilities in Industrial Cyber-Physical Systems

Emerging industrial digitization metaphors such as cyber-physical systems and digital twins increasingly advocate the use of distributed and autonomous modular solutions. This article proposes a visual notation for modeling the timing properties of such modular industrial systems. The proposed work builds upon an existing notation that enables the analysis of the timing properties and requirements of potentially competing automation solutions. It provides a set of symbols that capture, among others, communication networks and devices, I/O interfaces, and industrial controllers. This article extends this preexisting notation by modeling the relation between physical devices and their controlling software in the context of industrial automation applications. The existing notation and its extensions are described and applied to a miniaturized automation system to illustrate its dual usage: as a tool to collect requirements and as a tool to analyze existing systems. The testing scenario highlights the opportunities provided by the extensions in comparison to the preexisting notation, which, for the sake of completeness, is more briefly introduced and described.

Emotionalism Within People-Oriented Software Design

In designing most software applications, much effort is placed upon the functional goals, making a software system useful. However, the failure to consider emotional goals, which make a software system pleasurable to use, can result in disappointment and system rejection even if utilitarian goals are well implemented. Although several studies have emphasised the importance of people’s emotional goals in developing software, there is little advice on how to address these goals in the software system development process. This paper bridges the gap between emotional goals elicitation and the software system design process by proposing a novel technique entitled the Emotional Goal Systematic Analysis Technique (EG-SAT) to systematically analyse people’s emotional goals in cooperation with functional and quality goals. EG-SAT allows in-depth analysis of emotional goals to build a software system and provides a visual notation for representing the analysis, facilitating communication and documentation. EG-SAT provides traceability of emotional goals in system design by connecting the emotional goals to functional and quality goals. To demonstrate the method in use, a two-part evaluation is conducted. First, EG-SAT is used to analyse the emotional goals of potential users of a mobile learning application that provides information about low carbon living for tradespeople and professionals in the building industry in Australia. The results of using EG-SAT in this case study are compared with a professionally developed baseline. Second, we ran a semi-controlled experiment in which 12 participants were asked to apply EG-SAT and another technique to our case study. The outcomes show that EG-SAT helped participants analyse emotional goals and gain valuable insights about the functional and non-functional goals for addressing people’s emotional goals. The key novelty of the EG-SAT is in proposing an easy to learn and easy to use technique that helps system analysts gain insights on how to address people’s emotional goals. Furthermore, the EG-SAT enables system analysts to convert emotional goals to traditional functional and non-functional goals that existing software engineering methodologies can analyse without demanding excessive effort.

The challenges of visualizing DMLA models

Abstract Multi-layer metamodeling is a metamodeling method that provides great flexibility for domain prototyping, while it also ensures rigid validation of domain rules. Visualization of multi-layer models would be essential in order to promote this new modeling technique in industrial setups; however, the traditional way of representing model entities is not sufficient here. Dynamic Multi-Layer Algebra is a multi-layer metamodeling approach that addressed the challenges of multi-layer modeling, but uses a text-based language to create models. This paper presents Dynamo, a visual notation for Dynamic Multi-Layer Algebra, which is also applicable to other multi-layer metamodeling approaches. The paper elaborates the graphical syntax and the design decisions.