6327868
A schedulable garbage collection for embedded applications in CLI
Common language infrastructure (CLI) has been introduced as a core technology of Microsoft .NET. It enables "writing in multiple languages, running in multiple platforms" by providing virtual execution system (VES), common intermediate language, and common type system etc. The advantages of using CLI, including portability, compactness, and interoperability, could benefit the productivity of application software development and deployment. However, for embedded real-time systems, the applications' time-constraints cannot be satisfied easily due to several features of CLI runtime environment, such as thread priority, thread scheduling, garbage collection etc. In this paper, we aim to have a garbage collection mechanism applicable on real-time applications in CLI and other virtual machine environments. We achieve the goal by making the pause time of garbage collection operations predictable, and the invocation of garbage collection and applications schedulable. A cost model based on measured WCET is established to predict the execution time and overhead of garbage collection operations.
30590203
Efficient State-Saving Architectures for Power-Mode Switching
Time and energy is expended in switching between power modes (e.g., active, hibernate, sleep, etc.). Powering off cache is one major reason for this. When there is a switch in the power-mode involving cache power-off, the system spends time and energy in filling the cache with new data (inherent cache misses). In our technique, before powering off the cache, we save its state in Embedded DRAM and bring it back when the previous power mode is restored. Our experiments have showed that in a majority of cases the cache contents are too valuable to be erased. By saving the contents we can reduce switching speed and energy. We present a heuristic to save the most relevant cache contents so that power and delay overheads are minimized. To measure the area overhead a synthesizable VHDL model was designed.
920212
Resource scheduling in dependable integrated modular avionics
In the recent development of avionics systems, integrated modular avionics (IMA) is advocated for next generation architecture that needs integration of mixed criticality real-time applications. These integrated applications meet their own timing constraints while sharing avionics computer resources. To guarantee timing constraints and dependability of each application, an IMA-based system is equipped with the schemes for spatial and temporal partitioning. We refer the model as SP-RTS (strongly partitioned real-time system), which deals with processor partitions and communication channels as its basic scheduling entities. This paper presents a partition and channel-scheduling algorithm for the SP-RTS. The basic idea of the algorithm is to use a two-level hierarchical schedule that activates partitions (or channels) following a distance-constraints guaranteed cyclic schedule and then dispatches tasks (or messages) according to a fixed priority schedule. To enhance schedulability, we devised heuristic algorithms for deadline decomposition and channel combining. The simulation results show the schedulability analysis of the two-level scheduling algorithm and the beneficial characteristics of the proposed deadline decomposition and channel combining algorithms.
40618061
Transaction Recovery in Distributed DB/DC Systems: A Progressive Approach
10753893
Evaluation of Error Recovery Blocks Used for Cooperating Processes
Three alternatives for implementing recovery blocks (RB's) are conceivable for backward error recovery in concurrent processing. These are the asynchronous, synchronous, and the pseudorecovery point implementations. Asynchronous RB's are based on the concept of maximum autonomy in each of concurrent processes. Consequently, establishment of RB's in a process is made independently of others and unbounded rollback propagations become a serious problem. In order to completely avoid unbounded rollback propagations, it is necessary to synchronize the establishment of recovery blocks in all cooperating processes. Process autonomy is sacrificed and processes are forced to wait for commitments from others to establish a recovery line, leading to inefficiency in time utilization. As a compromise between asynchronous and synchronous RB's we propose to insert pseudorecovery points (PRP's) so that unbounded rollback propagations may be avoided while maintaining process autonomy. We developed probabilistic models for analyzing these three methods under standard assumptions in computer performance analysis, i.e., exponential distributions for related random variables. With these models we have estimated 1) the interval between two successive recovery lines for asynchronous RB's, 2) mean loss in computation power for the synchronized method, and 3) additional overhead and rollback distance in case PRP's are used.
31591898
Scanning the issue - special issue on real-time systems
2382569
Filtering XPath expressions for XML access control
XPath is a standard for specifying parts of XML documents and a suitable language for both query processing and access control of XML. In this paper, we use the XPath expression for representing user queries and access control for XML. And we propose an access-control method for XML, where we control accesses to XML documents by filtering query XPath expressions through access-control XPath expressions. For filtering the access-denied parts out of query XPath expressions, set operations (such as, intersection and difference) between the XPath expressions are essential. However, it is known that the containment problem of two XPath expressions is coNP-hard when the XPath expressions contain predicates (or branch), wildcards and descendant axes. To solve the problem, we directly search XACT (XML Access Control Tree) for a query XPath expression and extract the access-granted parts. The XACT is our proposed structure, where the edges are structural summary of XML elements and the nodes contain access-control information. We show that the query XPath expressions are successfully filtered through the XACT by our proposed method, and also show the performance improvement by comparing the proposed method with the previous work.
46434197
Flow Control Strategy for Flexible Machining and Assembly System
Abstract In this paper an effective flow control strategy for a Flexible Machining and Assembly System is proposed using the concepts of operation-oriented and, combined push and pull control method. The proposed flow control mechanism could meet production demands with a minimum makespan while satisfying assigned due-dates and keeping a low volume of work-in-process at the same time. It also considers machine failures and rush jobs.
21778074
Dream of Mee-Luck: Aspiration for a New Dawn
Many countries in the world are putting much effort for the preservation of cultural assets of their own countries using digital. However, most of the attempts are based on the aspect of preservation science which aims to exquisitely restore cultural assets through historical investigation. Therefore in most cases they are successful in the restoration of shape without incorporating the spirit and meaning of the respective cultural asset. In this regard, we suggest an approach using Responsive Multimedia System which can present legend of Unju Temple as a sequence of events in VE. Users can experience virtual story by manipulating interactive StoryMap displayed on ARTable. In the suggested artwork, we express the uncompleted beauty, which we cannot find out from Unju Temple today.
5961676
Total Data Quality Management: The Case of IRI
Abstract Implementing a Total Data Quality Management (TDQM) program is not a trivial undertaking. Two key steps are (1) to clearly define what an organization means by data quality and (2) to develop metrics that measure data quality dimensions and that are linked to the organization’s goals and objectives. This paper presents the case of Information Resources, Inc., which exemplifies how a company can develop a viable TDQM program.
14475818
Data exchange for machine shop simulation
Manufacturing simulation systems normally provide interfaces for data import and export using proprietary formats. Dependent data interfaces limit simulation applications in the manufacturing industry. This paper describes a mechanism for transferring data between a traditional database and XML files, which represent a machine shop data model developed at the National Institute of Standards and Technology (NIST). The data model is described by XML (eXtensible Markup Language) and UML (Unified Modeling Language). The data transfer mechanism is based on document object model (DOM), XML path language (XPath), and open database connectivity (ODBC) database engines. A prototype implementation is also described in this paper