An improved version of UML in Embedded System
Abstract in the post-PC era, an increasing number of areas that require the support of embedded systems, the traditional means of embedded systems development can no longer satisfy the growing complexity and quality requirements; and UML in the software field for the tremendous achievements made by embedded system development brings hope. Therefore, how the UML-based software as a common and comprehensive approach to embedded system cited the field of eight will be an urgent need to consider and solve.
Key words post-PC embedded system software engineering, UML
With computer technology, network technology and the rapid development of communication technologies, the current information society has had a traditional personal computer era entered the post-PC era; and then the main features of the PC era is the widespread application of embedded systems and development marked by of.
With regard to the definition of embedded systems while there are many, but the generally accepted definition of home is: application-centric, computer technology, hardware and software can be cut, right of Taiwan's application system functionality, reliability, cost, size and reactive power consumption requirements of a dedicated computer system.
Embedded systems is the use of micro chips and curing of the software embedded in other systems, so as to achieve other intelligence or information systems, real-time control purposes.
At present, the embedded system in industrial control, aerospace, defense and information appliances such as a wide range of application areas, and has played an important role, but more and more areas of the urgent need for the support of embedded systems. However, since the embedded system hardware, software, application of the different environment, so the current embedded technology with limited staff time and energy spent on familiar with the different major hardware, software and code development. This will not only result in the embedded system development efficiency and quality can not be guaranteed, but also severely constrained embedded technical staff to carry out a higher level of research and development. All of these have become increasingly complex rapid development of embedded system bottlenecks.
1 UML into the feasibility of embedded systems
The 20th century, the sixties and seventies, the software industry faced a crisis. The reason is the increasingly large and complex software, and software quality and productivity are becoming less and less. This has promoted the birth of software engineering, software development makes the standardization and efficiency have been greatly improved. 90s in the 20th century, with the development of object-oriented technology, software engineering to automation, intelligent direction, and its stand out from the UML standard is the emergence and development. Subsequently, a lot of hardware and software manufacturers have developed a number of standards-based CASE tool for UML. Since then the development of software can make use of UML-CASE tool to complete the transition from software analysis, design, implementation to test a series of software engineering process, greatly improving the reusability of software development and efficiency, reducing in the process of software development rework rate.
UML is a prominent feature of object-oriented analysis and design point of view developed by the system, which each of the system functions as a module (the "Class" to that). In UML, using use-case view, logical view, component view, concurrent views, and expand the view to the respective needs of the software analysis, design, implementation, integration and testing process; and each view is a series of plans to include specific the realization of the above 5 categories, including the use case view map, class diagram, object diagram, state diagram, sequence diagram, collaboration diagram, activity diagram, component diagram and plan to start. Among them, the use case diagram, class diagram, object diagram, component diagram and launched plans are static maps, from the static aspects of systems analysis and modeling; and state diagram, sequence diagram, collaboration diagram and activity diagram is from the dynamic aspects of systems analysis, simulation of the dynamic interaction.
2001, UML2. O marks the release of UML technology to further mature and has been an increasing number of hardware and software vendor support, which also makes UML broader development prospects. The face of the UML-based software engineering field in the software's great achievements in the possibility of the UML into the development of embedded systems to be used to change the current low efficiency of embedded systems development today? Discovered through research and analysis, UML Application the existence of the embedded system is mainly the following problems:
① embedded system includes two parts, hardware and software, different hardware from different manufacturers, in a chip embedded in the software to run correctly in another on embedded hardware platforms may not be able to operate normally.
② embedded systems software platform is also different, their respective requirements for the development of a larger difference.
③ most embedded systems for real-time demanding.
④ embedded software platform instead of using object-oriented language developed mainly in c language or assembly language preparation.
All these characteristics result in practical embedded systems difficult to build a UML model. Even if the mountain to build the model, its accuracy, real-time performance is also difficult to verify and guarantee.
In spite of this, the researchers and developers for the introduction of the UML in the embedded systems have made unremitting efforts and achieved some results, including:
① In order to make the correctness of the resulting model can be verified, it was suggested that the use of formal methods. For example, William and H. C. Cheng model using VHDL as a formal description language, through the analysis of UML class diagram model and state diagram of embedded systems has been described in VHDL, the system structure and behavior, and model validation. Scholars have used finite state automata and UML to complete the combination of systems analysis, design and verification.
② For real-time requirements to provide solutions to include: the use of the standard stereotypes of UML and its real-time systems conceptual design, as well as the expansion of UML or UML to transform to meet the requirements of real-time systems.
③ For the issue of language, mainly in the following two solutions: one is the use of object-oriented C++ + + language development, such as SystemC; the other is the use of C language combined with the UML development environment, such as the United States I-Logix Inc. the introduction of the Rhapsody.
From the above we can see three kinds of solutions, UML applications in embedded systems arising from the verifiable, and real-time, and language problems can be solved and therefore the possibility of widespread use of UML to analyze, design and guide the development of embedded systems to address the inefficiencies embedded system development problems.
2 An Improved UML general embedded system programs
As the application of UML in the embedded systems research are often focused on solving a particular aspect of embedded systems, which do not have universal, it is difficult to become the standard modeling of embedded systems. To address the UML in the embedded system modeling problems, this paper, a generic UML for embedded system design solutions.
In order to model embedded systems must consider the following:
◆ time. Described in time sequence chart and its binding information.
◆ concurrency. Category used to describe concurrent activities. The activities of class attributes (such as priority level) can be defined into a category of the label value by type of component version <(Process>> and <<Thread>> will be mapped to the realization of their environment.
◆ asynchronous communication. UML support for asynchronous messages sent between threads.
◆ synchronous communication. The definition of semaphores, monitors or key areas of the category / categories to describe the synchronous version.
Therefore, modeling embedded systems can be drawn of the general process is as follows:
① First, determine the system requirements. Neither at this stage to consider which part of the software, nor to consider which part of the hardware, only on the basis of research and the exchange with the user system should have come to function, and roles and the relationship between the use case shown, so as to arrive at Use Case Diagram final demand and systems.
② into the system design phase, which is based on use cases derived from the demand map design class diagram. This stage to determine which functions need to be completed by the hardware, which functions by software. Software design class diagrams and the basic methods of pure software modeling, as in this will not repeat them. Processing hardware from the hardware to achieve the packaging, hardware packaging to provide access to the hardware interface. Wrapper class to deal with the hardware to the device and the communications equipment of the interruption, through this type of hardware to hide low-level details of the agreement, and very convenient, fast and low-level disruption of the system is converted to the rest of the senior events. Packaging activities are adequate or static type, mainly depends on the properties of the hardware.
③ If the class diagram described in the type of software or hardware complex, indescribable clear, then the object graph can be used to refine, making them more specific and clear.
④ For real-time requirements need to be defined in the sequence and description scarf; If you want to know the link between the different target groups, as well as links to send a message to ask how the object, you can create a collaborative map; through the establishment of a state map, to understand that an object-cho can reach all states, as well as the objects of the object received by the state of the incident and so on.
⑤ Finally, the use of component maps and launched plans to achieve system integration and verification.
Over the course of the environment in the Rhapsody software to achieve, because the software can be commonly used in embedded systems C language, usually closer to the embedded development environment.
3 examples of analysis and discussion
A warning system here as an example to show how to use UML to design embedded systems. An alarm system in general by the sensors (including acoustic sensors, image sensors and thermal sensors), alarm (including the voice of alarm, telephone and alarm light), keyboard, LCD display, the system processor, and used to store system configuration information and log information such as the memory components.
When the sensors receive a signal through the analog / digital conversion of information to the system processor, the system processor set configuration information in accordance with conditions, to determine whether the need for alarm. If necessary, will be issued a warning to the alarm command. Keyboard and LCD display for human-computer dialogue, can be set according to actual needs and means of alarm conditions.
Sequence diagram of the system as shown in Figure 1. From Figure 1 can be seen, the system requests information from the sensor to return to the issue of warning time interval of less than 3s. This is the sequence diagram of embedded real-time systems the time required by a case in point.
In the class diagram of the system processor type activities designed to deal with through the control panel LCD display and user interaction. The control panel can be configured to activate and shut down the system. All the configuration changes are stored in the system configuration information category. System processor to receive sensor information, and it compared with the system configuration information in order to decide whether or not to report to the police. In order to understand the alarm system queries and historical information, the system processor to all the events stored in the log. System processors, sensors and alarms of the simple relationship between the class diagram shown in Figure 2.
Embedded systems for the introduction of a universal, comprehensive UML technology, is bound to the current rapid development of embedded systems have a positive impact on research and development. In this paper, the proposed ideas and methods from the UML for embedded technology in the plight of the area has played a useful role in exploration and recommendations.
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