Proceedings of the 50th Hawaii International Conference on System Sciences | 2017 A Model-Based Engineering Methodology for Requirements and Formal Design of Embedded and Real-Time Systems Fab´ıola Gonc¸alves C. Ribeiro∗, Achim Rettbergy, Carlos E. Pereiraz, Michel S. Soaresx ∗Federal Institute Goiano, Catalao,˜ Brazil Email: [email protected] yCarl von Ossietzky Universitt Oldenburg, Oldenburg, Germany Email: [email protected] zFederal University of Rio Grande do Sul, Porto Alegre, Brazil Email: [email protected] xFederal University of Sergipe, Sao˜ Cristov´ ao,˜ Brazil Email: [email protected] Abstract—Activities for the comprehension and development gies, software, and physical components, and intelligently of Cyber-Physical Systems (CPS) include analysis of multi- interact with other systems across information and physi- ple disciplines including mechanical engineering, electronic cal interfaces [2]. These systems are able to interact with engineering, systems engineering and computer science. This external environment and generate immediate responses to work presents a comprehensive and applicable methodology the environment. Analysis and specification approaches are for the initial activities of the development process of CPS. important, in this context, for enabling definition of the main This methodology displays the capacity to describe and enable functionalities, restrictions and response times imposed on detailed analysis of the relevant properties of these systems as, these systems [3]. for example, time specification, resources, communication and Model-Based Engineering is an approach for analysis, non-functional properties of CPS. In this research, two consol- specification and design of systems that intend to raise the idated approaches of Model-Based Engineering are used in a level of abstraction through the use of models in systems de- combined way for proposing a methodology for requirements velopment activities. MBE can be seen as a trend in the de- analysis, modeling and formal specification of CPS. Initially, a sign of smart automation systems. Several MBE approaches strategy for the definition, modeling, specification, and catego- have been proposed in recent years as, for example, in the rization of requirements in a tabular way is proposed. From field of automotive systems [4], [5], traffic control systems the system definition in a high abstraction level, the SysML [6], [7], unmanned aerial vehicle systems [1], among others. Requirements diagram is extended by using UML profile MBE approaches can be employed under different per- spectives and interests, allowing one to analyze and describe MARTE/VSL for formalization of restrictions, annotations and mechanical components which are usually integrated with stereotypes in the model. Initial results of the application of electronic and software components [8], as well as providing the proposed methodology are presented by means of a case high relevance to handle semantic gap between specification study of the Industrial Packing System. and system design and the actual features of an application. For instance, in [9], the MBE approach has been applied 1. Introduction in case studies at Renault automotive systems to struc- ture the processes and activities of architectural design. A Currently, manufacturing systems have a high degree of methodology for integrated design of mechatronic systems automation, which increases complexity during their devel- is presented in [10], in which the W model and SysML are opment. These systems are used to control physical and log- employed to compose the design methodology that will be ical components, and also have to consider quality aspects evaluated on a case study of the filling system of a Tetra such as efficiency and reliability. Among the objectives of Pak Packaging Solution. MBE is applied in [11] to define the such systems in industry one can mention the need for cost functional specifications, systems modeling, the traceability reduction of traditional production processes, the ability to criteria for an automotive drive line system, with the benefit create distributed control in an agile manner, and the high of providing a wide communication process through a com- need for customization and fast reaction regarding demands mon language. In [2], MBE approaches are used to describe of consumers. a production cell of the SmartFactory System. In the case Due to operational capacity and high intelligibility, many study, the assembly modules, the material identification and manufacturing systems are also considered Cyber-Physical the flow control are presented using SysML Blocks diagram. Systems (CPS) [1]. CPS are characterized as intelligent Another example of using SysML is described in [12], in systems that are composed of digital virtual/cyber technolo- which SysML is extended resulting in SysML-AT (SysML URI: http://hdl.handle.net/10125/41905 ISBN: 978-0-9981331-0-2 CC-BY-NC-ND 6131 for automation), which describes the hybrid characteristics literal constant values, offers support to describe different of a manufacture system focusing in the centralized, decen- types of expressions in order to allow the description of tralized and distributed hardware architectures. An aspect- references to variables, and allows to represent different oriented MBE approach, named as Aspect-Oriented Model types of expressions. In addition, VSL describes, through Driven Engineering for Real-Time systems (AMoDE-RT), package TimeExpressions, a specialized syntax for writing is proposed in [8]. AmoDE-RT is applied in the design expressions and specifications of time values in the model of industrial mechatronic systems, more specifically for elements. controlling a product assembler industrial cell. Concepts presented above characterize abstract syntax Manufacturing systems are also characterized by great and semantics of VSL. A concrete syntax is described by complexity of their physical and logical components and, means of the value specifications for an expression, being especially, cooperation and communication between hetero- the construction of an expression as shown in expression 1: geneous subsystems. Therefore, it becomes essential the adoption of good practices and processes to deal with repre- <value−specification>:: =<literal>j sentation and definition of different properties of these sys- tems in order to achieve greater integration and consistency. =<interval>j Non-functional nature of some important requirements of =<enum−specification>j embedded systems, such as dispersion and confusing ma- =<collection>j nipulation of their properties can lead to several problems =<tuple>j about their development, comprehension and deployment. If these problems are not treated properly, the overall project =<choice>j complexity regarding spending efforts and project chrono- =<expression>j gram can be increased [8]. In the design phase it is important =<time−expression>j to raise the level of abstraction in the early stages of system =<obs−call−expression> development cycle in order to facilitate the understanding and analysis of different embedded components and their re- (1) lationships by most stakeholders. Models at high abstraction Value Specifications are used to specify the textual value levels minimize possible omissions and complexity [13]. parts of UML models. The value specification could be a Research presented here presents a methodology for simple literal, such as a number, or it could be a complex the initial activities of the development process of CPS, expression that involves variables and operations. A full where new methods/profiles, suitable for CPS domain. This form of atomic definition for formulation of expressions is research differs from the previously mentioned works due presented in expression 1. Understanding each value speci- to three main reasons. The proposed MBE approach aims to fications becomes important to define functional constraints integrate a SysML based design for specification of complex modeled elements, as well as to formulate more complex systems, with domain-specific concepts of CPS (by using temporal expressions which usually groups one or more MARTE profile constructors). The proposed approach aims expressions of a value specification. to be initially tailored for analysis processes, textual and Time Expression, presented in expression 2, allows to graphical requirements specification which are relevant to formalize different temporal and non-functional expressions real-time systems. Finally, for allowing future validation and on elaborated models and are important for providing differ- verification processes, formalized descriptions are employed ent and rigorous standards for representation of expressions. in modelling elements for the non-functional requirements In general, a Time Expression enables description of inter- of the IPS system. The methodology proposed in this paper vals (minimum and maximum) and duration of an event, is applied to the design of industrial mechatronic systems as well as the distance considered between consecutive with focus on analysis, specification and design of embed- events (see Expressions 9 and 10), to make explicit the ded and real-time characteristics of CPS. specific moments of occurrence of an event (see Expression 7), detail specific event durations (observe Expression 3), 2. Brief Introduction to Value Specification describe occurrence of conditional events and, also, specify possible variations in events that can be represented in model Language