Background: Urban mobility management faces growing challenges that require the analysis and optimization of sustainable solutions. Digital twins (DTs) have emerged as innovative tools for this assessment, but their implementation requires standardized procedures and languages; Methods: As part of a broader methodology for continuous DT validation, this study focuses on the conceptual validation phase, presenting a conceptualization approach through formalization using Specification and Description Language (SDL), agnostic to simulation tools. The conceptual validation was achieved through stakeholder engagement in the Bolzano context, producing 41 SDL diagrams that define both elements common to different urban realities and specific local data collection procedures; Results: The feasibility of implementing this stakeholder-validated conceptualization was demonstrated using Simulation of Urban MObility (SUMO) for traffic simulation and optimization criteria calculation, and its framework SUMO Activity GenerAtion (SAGA) for generating an Activity-Based Modeling (ABM) mobility demand that can be improved through real sensor data; Conclusions: The SDL approach, through its graphical representation (SDL/GR), enables conceptual validation by enhancing stakeholder communication while defining a framework that, while adapting to the monitoring specificities of different urban realities, maintains a common and rigorous structure, independent of the chosen implementation tools and programming languages.

Abstract The objective of the paper is to present a methodology that can be used to translate a model from one formalism to another allowing model reuse and cross‐verification. With the use of formal languages, the model specifications can be expressed in a rigorous and univocal way, and the model can be validated against the specifications or conceptual model. Expressing the same model in different formal languages opens the conceptual model validation to a varied number of specialists. Also, in the context of modeling a new system, where there is no data to perform validation against a real system, having pairs of models can be used to perform cross‐model verification to ensure that the model specifications or conceptual models are correctly implemented by comparing the results produced by both models. Specifically, a method is presented to translate a model conceptualized on specification and description language (SDL) to discrete event system specification (DEVS). The transformation mechanism between SDL and DEVS formalisms is described. The methodology is exemplified with a disease spread model for COVID‐19, and it is shown how the results obtained by the two models can be used for cross‐verification.

Specification and Description Language (SDL) is a language that can represent the behavior and structure of a model completely and unambiguously. It allows the creation of frameworks that can run a model without the need to code it in a specific programming language. This automatic process simplifies the key phases of model building: validation and verification. SDLPS is a simulator that enables the definition and execution of models using SDL. In this paper, we present a new library that enables the execution of SDL models defined on SDLPS infrastructure on a HPC platform, such as a supercomputer, thus significantly speeding up simulation runtime. Moreover, we apply the SDL language to a social science use case, thus opening a new avenue for facilitating the use of HPC power to new groups of users. The tools presented here have the potential to increase the robustness of modeling software by improving the documentation, verification, and validation of the models.

Industries like telecommunications, medical, automotive, military, avionics, and aerospace use complex real-time systems. Specification and Description Language (SDL) is one of the leading domain specific languages that is formally defined by international standards and well established in describing such systems. To check system properties abstracted model of the system is prepared in selected modeling language. We use Spin (Simple Promela Interpreter) model checker that is one of the leading tools for verification of complex concurrent and reactive systems. This paper focuses on modeling the SDL timer construct. It is one of the SDL constructs that is not easily modeled with Promela, but is present in many SDL systems. After an overview of the related work we propose a new Discrete Time Model for Promela (DTMP) that is seamlessly integrated in our framework for modeling SDL systems and can be used with the mainstream version of the Spin tool. To the best of our knowledge, this is not possible with the existing solutions. We describe how DTMP can be used to model SDL systems that use timers. Experimental results demonstrate its applicability to non-SDL systems with Fischer’s mutual exclusion protocol and the Parallel Acknowledgment with Retransmission that were used in prior studies. We compare state-space requirements with one of the existing solutions DT Promela and DT Spin. With that, virtues and shortcomings of this high-level solution are exposed. We have shown that DTMP is effective when an extensive range of timer expiration values are used, which is usually the case in real-life SDL systems.

The spread of the SARS-CoV-2 modeling is a challenging problem because of its complex nature and lack of information regarding certain aspects. In this paper, we explore a Digital Twin approach to model the pandemic situation in Catalonia. The Digital Twin is composed of three different dynamic models used to perform the validations by a Model Comparison approach. We detail how we use this approach to obtain knowledge regarding the effects of the nonpharmaceutical interventions and the problems we faced during the modeling process. We use Specification and Description Language (SDL) to represent the compartmental forecasting model for the SARS-CoV-2. Its graphical notation simplifies the different specialists’ understanding of the model hypotheses, which must be validated continuously following a Solution Validation approach. This model allows the successful forecasting of different scenarios for Catalonia. We present some formalization details, discuss the validation process and present some results obtained from the validation model discussion, which becomes a digital twin of the pandemic in Catalonia.

In the light of standardization, the model-driven engineering (MDE) is becoming increasingly important for the development of DSLs, in addition to traditional approaches based on grammar formalisms. Metamodels define the abstract syntax and static semantics of a DSL and can be created by using the language concepts of the Meta Object Facility (MOF) or by defining a UML profile.Both metamodels and UML profiles are often provided for standardized DSLs, and the mappings of metamodels to UML profiles are usually specified informally in natural language, which also applies for the static semantics of metamodels and/or UML profiles, which has the disadvantage that ambiguities can occur, and that the static semantics must be manually translated into a machine-processable language.To address these weaknesses, we propose a new automated approach for deriving a UML profile from the metamodel of a DSL. One novelty is that subsetting or redefining metaclass attributes are mapped to stereotype attributes whose values are computed at runtime via automatically created OCL expressions. The automatic transfer of the static semantics of a DSL to a UML profile is a further contribution of our approach. Our DSL Metamodeling and Derivation Toolchain (DSL-MeDeTo) implements all aspects of our proposed approach in Eclipse. This enabled us to successfully apply our approach to the two DSLs Test Description Language (TDL) and Specification and Description Language (SDL).

Based on a SEIRD model (Susceptible, Exposed, Infective, Recovered and Deceased) for COVID-19 infection with a new parametrization using a high infection rate, and a low fatality, we define the model in System Dynamics, Python, and Specification and Description Language (SDL). The different implementations obtained can be improved depending on the capabilities of the approach and, more interestingly, can be used to improve the Validation and Verification processes. In this paper, we are focused on describing how this comparison with other models’ validation processes allows us to find the parameters of the system dynamics model, hence the parameters of the pandemic. This is a crucial element, specifically in this case, because the data are not complete or validated for different reasons. We use using existing data from Korea and Spain and showing that the proposed method and the obtained parametrization for the model fit with the empirical evidence. We discuss some implications of the validation process and the model parametrization. We use this approach to implement a Decision support system that shows the current pandemic situation in Catalonia.

On Formal Modeling and Validation of Signaling Protocols for Web Real-Time Communications using SDL

The definition of a Life Cycle Assesment (LCA) for a building or an urban area is a complex task due to the inherent complexity of all the elements that must be considered. Furthermore, a multidisciplinary approach is required due to the different sources of knowledge involved in this project. This multidisciplinary approach makes it necessary to use formal language to fully represent the complexity of the used models. In this paper, we explore the use of Specification and Description Language (SDL) to represent the LCA of a building and residential area. We also introduce a tool that uses this idea to implement an optimization and simulation mechanism to define the optimal solution for the sustainability of a specific building or residential.

This article proposes a methodology to assess building behaviour, whilst taking its life cycle into account. Understanding of the system can be obtained by combining well-known energy consumption calculation engines (TRNSYS) with co-simulation processes defined using Specification and Description Language (SDL). In this instance, to find the best comfort, energy and cost scenarios for energy rehabilitation, Co-simulation is conducted in two phases: the best scenes of passive systems are found, those presented as a priority; and, the active systems are made with ‘brute force analysis’. The article provides the results for a case study: a single-family home built between 1991 and 2007 and located in Mediterranean climate zone. The methodology provides a set of passive energy efficiency measures, to improve until two scales in the building energy labelling system. Using the methodology and the proposed model has enabled us to dramatically reduce the run time until 75% and therefore.

Formally defined Specification and Description Language (SDL) is used for the design and specification of complex safety-critical systems. Each change in the specification of the product should be immediately checked formally against the requirements' specification. This paper presents semi-automated system abstraction, automated model extraction, simulation, and formal verification of real-life complex SDL specification. Sound algorithms implemented in our sdl2pml automated model extraction tool preserve all properties of the SDL system. Sdl2pml includes our model of discrete time, abstraction, and support for all relevant SDL functionality and constructs such as dynamic process creation, rational data types, and communication with more than one process instance. To the best of our knowledge, most of them are not supported by any other known approach. We use our SpinRCP tool for simulation and formal verification of the extracted model with the Spin model checker. We demonstrate the applicability of our approach on ISDN User adaptation protocol from SI3000 Softswitch. The extracted Promela model is the largest one ever processed by Spin. We have shown that Spin simulation and model checking can be applied successfully to such huge models.

Discrete Event System Specification (DEVS) is one of the main widely used formal languages to represent simulation models, while Specification and Description Language (SDL) is a graphical ITU-T standard language, commonly used in telecommunication and engineering areas. In this paper, we present an algorithm, and a simulation infrastructure that implements this algorithm, to transform a simulation model represented using the DEVS formalism to the SDL standard language. The algorithm can be viewed as a mechanism to represent graphically DEVS models. In addition, because of the transformation, one can use SDL tools in order to implement DEVS models. To implement the algorithm, we propose an Extensible Markup Language representation for the DEVS and SDL models. For practical application of the algorithm, it is implemented in a simulation infrastructure named the Specification and Description Language Parallel Simulator that allows defining the models with both formalisms.

Passenger flow simulation in a hub airport: An application to the Barcelona International Airport

In order to guarantee the high rate, high throughput and low latency and reliable service provided by TD-LTE system under various mobility conditions, handover (HO) procedure and its performance are of high importance. Based on research on structure of TD-LTE system and RRC (Radio Resource Control) layer, this paper proposed intra-system handover procedure in RRC layer of UE side. Simulation of the proposed design and implementation on SDL (Specification and Description Language) /TTCN (Tree and Tabular Combined Notation) verified its conforming to 3GPP conformance protocol specification. Finally, proposed design was verified on the chip ARM1176JZF-S with the corresponding software.

This paper addresses the problem of formally modeling processes related to the operation of surgical pavilions and an anesthesia unit in a Chilean hospital. To perform this modeling, we used Specification and Description Language (SDL), which resulted in a graphic layout consisting of one system, 11 blocks, 52 processes, 135 channels of communication, and 137 information signals. The model includes as system environment to the emergency units, clinical services, and support units. The model was created to document and understand the tacit knowledge of the personnel working in the anesthesia and pavilion surgical units. The aim of the proposed methodology was to design a model that can represent the system in a modular and standard way and that will also assist with hospital management and facilitate simulation.

Coming wireless communication standards like Long Term Evolution (LTE) promise to bring a drastic increase in data rate for the end user. To facilitate this evolution, sophisticated technology for the mobile equipment is required. Most research focuses on the signal processing in the physical layer whereas the computational capabilities for protocol processing are neglected. This paper describes novel software architecture and load balancing for the LTE protocol stack that allows concurrent execution on a multi-core processor and thus allows for exploiting all the advantages like higher performance through parallelism at low power consumption. The layered protocol is developed using Specification and Description Language (SDL). In addition, the LTE protocol stack is parallelized and executed on a multi-core processor, by employing the SDL processes concurrency. Moreover, the LTE system is scheduled on multi-core by customizing the SDL scheduler to implement a data pipeline scheduler. Furthermore, a new load balancer scheme is proposed by moving the load balancer to the modem subsystem’s layer and using the SDL process migration concept. The performance of the LTE protocol implementation using the new scheme beats the classic thread migration scheme by more than 50% on single as well as multi-core platforms. The data throughput using the new scheme increases on two, three, or four cores, compared to single core, by about 195%, 290%, and 360%, respectively, and thus shows an excellent scalability for up to three cores and still giving reasonably good results for four cores.

Service Discovery Protocol (SDP) is important in ubiquitous applications, where a large number of devices and software components collaborate unobtrusively and provide numerous services without user intervention.Existing service discovery schemes use a service matching process in order to offer services of interest to the users.Potentially, the context information of the users and surrounding environment can be used to improve the quality of service matching.We propose a C-IOB (Context-Information, Observation and Belief) based service discovery model, which deals with the above challenges by processing the context information and by formulating the beliefs based on the basis of observations.With these formulated beliefs the required services will be provided to the users.In this work, we present an approach for automated validation of C-IOB based service discovery model in a typical ubiquitous museum environment, where the external behavior of the system can be predicted and compared to a model of expected behavior from the original requirements.Formal specification using SDL (Specification and Description Language) based system has been used to conduct verification and validation of the system.The purpose of this framework is to provide a formal basis for their performance evaluation and behavioral study of the SDP.

The IEEE 802.16 standard for mobile broadband wireless access specifies a contention based handover (HO) procedure for its mobile users. There are many HO parameters defined by the standard, which need a fine tuning in order to achieve a satisfactory communication performance. This article presents a precise mathematical model for calculating the impact of handover parameters and an error-prone radio channel over the performance of IEEE 802.16 handover procedure which uses Code Division Multiple Access (CDMA) ranging codes. We analytically analyze the handover latency and handover connection dropping probability. The results are compared with experimental measurements conducted on a protocol prototype developed by using Specification and Description Language (SDL). The following parameters are investigated: values of the minimal and maximal contention window size, number of transmission allocations per frame, number of available CDMA ranging codes, timers and maximum retransmission limits used in the processes of ranging, basic capabilities negotiation and registration. We have found that all parameters need to be carefully adjusted in accordance to the network conditions: number of stations performing handover at a same time, WiMAX physical layer working parameters, and frame-error rate in the uplink and downlink radio channel.

FlexRay is a new standard of network communication system which has been developed for future automotive applications. It was devised by automotive manufacturers and semiconductor vendors. FlexRay provides a high speed serial communication, time triggered bus and fault tolerant communication between electronic devices for automotive applications. In this paper, FlexRay system is first designed using SDL (Specification and Description Language). For hardware implementation, FlexRay system is designed using Verilog HDL based on the SDL design result. The disigned system is synthesized using Synopsys Design Compiler with the Hynix 0.18 ?m cell library. For constructing a FlexRay communication network, the active is used since active star systems can provide high speed data transmission up to 10 Mbps. The performance of the active star network is tested using one transmitter node and two receiver nodes.

This paper gives a contribution in the efforts of Semantic web ontology development. We have developed the core ontology for Specification and Description Language (SDL),an object-oriented, formal language defined by the International Telecommunications Union Telecommunications Standardization Sector (ITU-T) as recommendation Z.100. The language is intended for the specification of complex, event-driven, real-time, and interactive applications involving many concurrent activitiesthat communicate using discrete signals. Using SDL formal model for system specification we bridge the gap between ideas in our minds and the actual implementation of the system. Being visually appealing SDL provides us with a simple tool for communication either between the softwaredevelopers or between non-experts without advanced engineering skills. In this paper we propose the ontology for the basic SDL system and process elements. We also propose a formal framework of SDL Markup Language as a medium for translating SDL model to SDL ontology.