To push or not to push: on the rearrangement of movable objects bya mobile robot

We formulate and address the problem of planning a pushing manipulation by a mobile robot which tries to rearrange several movable objects in its work space. We present an algorithm which, when given a set of goal configurations, plans a pushing path to the "cheapest" goal or announces that no such path exists. Our method provides detailed manipulation plans, including any intermediate motion of the pusher while changing contact configuration with the pushed movables. Given a pushing problem, a pushing path is found using a two-phase procedure: a context sensitive back propagation of a cost function which maps the configuration space, and a gradient descent phase which builds the pushing path. Both phases are based on a dynamic neighborhood filter which constrains each step to consider only admissible neighboring configurations. This admissibility mechanism provides a primary tool for expressing the special characteristics of the pushing manipulation. It also allows for a full integration of any geometrical constraints imposed by the pushing robot, the pushed movables and the environment. We prove optimality and completeness of our algorithm and give some experimental results in different scenarios.     

Making C++ objects persistent: The hidden pointers

C++ objects of types that have virtual functions or virtual base classes contain volatile (‘memory’) pointers. We call such pointers ‘hidden pointers’ because they were not specified by the user. If such C++ objects are made persistent, then these pointers become invalid across program invocations. We encountered this problem in our implementation of O++, which is a database language based on C++. O++ extends C++ with the ability to create and access persistent objects. In this paper, we describe the hidden pointers problem in detail and present several solutions to it. Our solutions are elegant in that they do not require modifying the C++ compiler or the semantics of C++. We also discuss another problem that arises because C++ allows base class pointers to point to derived class objects. C++ has emerged as the de facto standard language for software development, and database systems based on C++ have attracted much attention. We hope that the details and techniques presented will be useful to database researchers and to implementors of object-oriented database systems based on C++.     

Patents: to file or not to file?

In the previous paper, the author discussed the three criteria for patentability: novelty, usefulness, and nonobviousness and the practical value of obtaining a patent in terms of discoverability - the ease with which infringement can be determined, and in terms of avoidance - the ease with which a potential user of someone's invention could achieve similar results without using that invention. In this paper, the author continues the discussion of the practical value of a patent. Suppose that you have decided that your invention is novel, useful, and nonobvious. Further, suppose that you have decided that your invention is unavoidable (that is, it is the only reasonable way to do whatever it does), and that infringement would be easily discoverable. The remaining questions as to whether to proceed with a patent application are: Who would be likely to use your invention? Based on your answer to #1, what is the value to you of owning the patent? How much will it cost you to obtain the patent? Will your patent stand up in court if it is challenged?.     

GUI objects with impenetrable borders: Instruction (not practice) makes perfect

Walker and Smelcer (Proceedings of the CHI 90, ACM, New York, 1990, pp. 221–225) found that menus could be selected faster if they were placed against the edge of the screen. Doing so creates an impenetrable border between the menu and the edge of the screen that the mouse cursor cannot penetrate. This changes how users move the mouse, so that selection times quicken compared to menus with a penetrable border. Experiment 1 investigated the effect that practice has on the acquisition of objects with and without impenetrable borders. The findings suggest that excessive practice was not necessary to demonstrate border type differences; thus, the advantage of having impenetrable borders seems to be relatively instantaneous. However, it was not readily apparent whether or not participants would realize the advantages of impenetrable borders without instruction. Thus, the primary purpose of Experiment 2 was to assess whether or not users would discover the benefits of impenetrable borders spontaneously. Participants were assigned to either the penetrable or impenetrable border condition. Additionally, participants received either full instruction concerning the benefits of the target placement, or limited instruction that simply informed the participant about the nature of the task. The results demonstrated that participants receiving limited instruction selected targets with impenetrable borders faster than participants who selected objects with a penetrable border. However, an exploratory comparison suggests that only 50% of participants who received limited instruction actually detected the impenetrable border. An additional comparison suggests that with practice the participants who were successful at detecting the impenetrable border selected the targets as quickly as participants who received full instruction concerning the benefits of impenetrable borders. The findings suggest that with full instruction, all users will perform reduced selection times. Given that not all participants discovered the impenetrable border it suggests that, whenever possible, users should receive instruction pertaining to the benefits of the impenetrable borders.     

Web services are not distributed objects

Web services are frequently described as the latest incarnation of distributed object technology. This misconception, perpetuated by people from both industry and academia, seriously limits broader acceptance of the true Web services architecture. Although the architects of many distributed and Internet systems have been vocal about the differences between Web services and distributed objects, dispelling the myth that they are closely related appears difficult. Many believe that Web services is a distributed systems technology that relies on some form of distributed object technology. Unfortunately, this is not the only common misconception about Web services. We seek to clarify several widely held beliefs about the technology that are partially or completely wrong. Within the distributed technology world, it is probably more appropriate to associate Web services with messaging technologies because they share a common architectural view, although they address different application types. Web services technology will have a dramatic enabling effect on worldwide interoperable distributed computing once everyone recognizes that Web services are about interoperable document-centric computing, not distributed objects.     

Simulation with active objects: an approach to combined modelling

This paper concerns the combined modelling approach developed for evaluation of performability of large scale computer systems. It presents how to combine queuing networks and Generalised Stochastic Petri Nets in a single model, taking advantages of common abstract features. The main objective of this paper is to present a solution concept involving simulation with active objects that clearly reflects the logic of the simulated objects. Therefore an initial outline of the active objects and their properties, services and structures, which together serve to provide a combined modelling, is given.     

Online train disposition: To wait or not to wait?

We deal with an online problem arising from bus/tram/train disposition problems. In particular, we look at the case in which the delay is unknown and the vehicle can only wait in a station so as to minimize the passengers waiting time.     

To lock, or not to lock: That is the question

Mechanisms to control concurrent access over project artefacts are needed to execute the software development process in an organized way. These mechanisms are implemented by concurrency control policies in version control systems that may inhibit (i.e. ‘to lock’) or allow (i.e., ‘not to lock’) parallel development. This work presents a novel approach named Orion that analyzes the project's historical changes and suggests the most appropriate concurrency control policy for each software element. This suggestion aims at minimizing conflict situations and thus improving the productivity of the development team. In addition, it identifies critical elements that do not work well with any of these policies and are candidates to refactoring. We evaluated Orion through two experimental studies and the results, which indicated it was effective, led us to a prototype implementation. Apart from the Orion approach this paper also presents the planning, execution, and analysis stages of the evaluation, and details of prototype internals.     

Software flaws, to tell or not to tell?

In October, GreyMagic, an Israeli Web application company, warned the public of security flaws that could make Internet Explorer vulnerable to malicious hacking. While the warning itself was of some interest, even more fascinating was the software giant's response. Microsoft publicly chided the firm for divulging the bugs' existence before Microsoft could fix them. For its part, GreyMagic told the media that its past efforts to notify Microsoft before a public disclosure had yielded no meaningful results. This is not the only recent incident in which Microsoft has tussled over the issue of disclosure. Last year the Finnish firm Oy Online Solutions spotted an Internet Explorer bug and talked with Microsoft about the problem. Oy Online agreed to give the software giant time to fix the big but eventually went public anyway, saying Microsoft was endangering users' data by failing to produce a timely patch. These incidents spotlight an issue that has long simmered in the software world. When should software bugs be made public? Should software makers get a chance to fix these problems before the general public is informed? If so, how much time should they have? Are standards needed to govern this arena?.     

To Intervene or not to Intervene: The Dilemma of Management by Exception

Future air traffic management architectures propose to give aircraft more flight path autonomy and turn the air traffic controller into a manager of exceptions. This article reports on one experiment in a series of studies that empirically explored the cognitive work underlying management by exception in air traffic control. Active practitioners (controllers, pilots, dispatchers) were prepared on the rules of the envisioned system and presented with a series of future incidents, each of which they were required to jointly resolve. Management by exception turns out to trap human controllers in a double bind, where intervening early seems appealing but is difficult to justify (airspace throughput) and carry out (controller workload problems). Late interventions are just as difficult, since controllers will have to take over in the middle of a potentially challenging or deteriorating situation. Computerised decision support that flags exceptions migrates the decision criterion into a device, creating a threshold crossing that is typically set either too early or too late. This article lays out the intertwined trade-offs and dilemmas for the exception manager, and makes recommendations for cooperative human–machine architectures in future air traffic management.     

基于条件效果的对象动态可变图规划

主要研究了基于条件效果的对象动态可变的规划问题．提出了相关元件、无关元件、创建／删除对象元件和普通元件等概念，把带有条件效果的动作和不带有条件效果的动作都元件化，并采用了对象命题化的思想．给出了新的基于目标驱动的规划图扩展算法和前向搜索有效规划算法，并给出了相应的后向传播互斥的定义，使得规划图的规模比较小，减少了搜索空间，大大提高了求解有效规划的效率．由于算法中的动作创建的效果是依赖于上下文的描述，这更加符合现实需要，使处理的问题更接近于真实的世界状态，因而此算法比以往的算法应用性更强，更具有现实意义．     

Extraction of embedded and/or line-touching character-like objects

This paper presents a novel method of circle scanning to detect intersection regions and to extract embedded/line-touching character objects. After the unembedded/not line-touching character objects are trivially extracted, the big line structure is broken down into character-like and line-like segments. Connected component analysis is applied and character-like segments are separated from line-like segments. The character-like segments then pick up the belonging intersection patches to produce character-like objects, leaving the other intersection patches to the line-like segments. Thus the problem of extracting embedded/line-touching character-like objects are addressed.     

Simulated annealing — to cool or not

The optimization algorithm simulated annealing is considered. Presented is a class of problem instances and ‘neighbor selection’ matrices for which no monotone decreasing temperature sequence is optimal with respect to certain natural performance criteria. An algorithm called ‘threshold random search’ is introduced, and use is made of the fact that simulated annealing is a randomized version of threshold random search with deterministic thresholds.