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Topic Review
Parallel Tree Contraction
In computer science, parallel tree contraction is a broadly applicable technique for the parallel solution of a large number of tree problems, and is used as an algorithm design technique for the design of a large number of parallel graph algorithms. Parallel tree contraction was introduced by Gary L. Miller and John H. Reif, and has subsequently been modified to improve efficiency by X. He and Y. Yesha, Hillel Gazit, Gary L. Miller and Shang-Hua Teng and many others. Tree contraction has been used in designing many efficient parallel algorithms, including expression evaluation, finding lowest common ancestors, tree isomorphism, graph isomorphism, maximal subtree isomorphism, common subexpression elimination, computing the 3-connected components of a graph, and finding an explicit planar embedding of a planar graph Based on the research and work on parallel tree contraction, various algorithms have been proposed targeting to improve the efficiency or simplicity of this topic. This article hereby focuses on a particular solution, which is a variant of the algorithm by Miller and Reif, and its application.
  • 514
  • 16 Nov 2022
Topic Review
Touhou Hisōtensoku
Touhou Hisōtensoku ~ Chōdokyū Ginyoru no Nazo wo Oe (東方非想天則 ～ 超弩級ギニョルの謎を追え, lit. "Lacking Perception of the Rule of Heaven in the East: Chase the Enigma of the Superdreadnought Guignol") is a versus fighting game in the Touhou Project game series. The game, by Twilight Frontier and Team Shanghai Alice, can be played as a standalone game or as an expansion pack for the previous fighting game Scarlet Weather Rhapsody. In the Touhou Project overall, it is labeled as the 12.3rd Touhou game.
  • 509
  • 06 Oct 2022
Topic Review
Incompatible Timesharing System
Incompatible Timesharing System (ITS) is a time-sharing operating system developed principally by the MIT Artificial Intelligence Laboratory, with help from Project MAC. The name is the jocular complement of the MIT Compatible Time-Sharing System (CTSS). ITS, and the software developed on it, were technically and culturally influential far beyond their core user community. Remote "guest" or "tourist" access was easily available via the early ARPAnet, allowing many interested parties to informally try out features of the operating system and application programs. The wide-open ITS philosophy and collaborative online community were a major influence on the hacker culture, as described in Steven Levy's book Hackers, and were the direct forerunners of the free and open-source software, open-design, and Wiki movements.
  • 509
  • 04 Nov 2022
Topic Review
Multi-Environment Real-Time
Multi-Environment Real-Time (MERT), later renamed UNIX Real-Time (UNIX-RT), is a hybrid time-sharing and real-time operating system developed in the 1970s at Bell Labs for use in embedded minicomputers (especially PDP-11s). A version named Duplex Multi Environment Real Time (DMERT) was the operating system for the AT&T 3B20D telephone switching minicomputer, designed for high availability; DMERT was later renamed Unix RTR (Real-Time Reliable). A generalization of Bell Labs' time-sharing operating system Unix, MERT featured a redesigned, modular kernel that was able to run Unix programs and privileged real-time computing processes. These processes' data structures were isolated from other processes with message passing being the preferred form of interprocess communication (IPC), although shared memory was also implemented. MERT also had a custom file system with special support for large, contiguous, statically sized files, as used in real-time database applications. The design of MERT was influenced by Dijkstra's THE, Hansen's Monitor, and IBM's CP-67. The MERT operating system was a four-layer design, in decreasing order of protection: The standard supervisor was MERT/UNIX, a Unix emulator with an extended system call interface and shell that enabled the use of MERT's custom IPC mechanisms, although an RSX-11 emulator also existed.
  • 506
  • 27 Oct 2022
Topic Review
Predictive Modeling of Student Dropout in MOOCs
The features of massive open online courses (MOOCs), such as internet-based massiveness, openness, and flexible learning, create a unique blend of a large number of learners, making the prediction of learner success (as well as providing support based on these predictions) particularly challenging. 
  • 505
  • 20 Oct 2023
Topic Review
Medical Data Breach
Medical data, including patients' identity information, health status, disease diagnosis and treatment, and biogenetic information, not only involve patients' privacy but also have a special sensitivity and important value, which may bring physical and mental distress and property loss to patients and even negatively affect social stability and national security once leaked. However, the development and application of medical AI must rely on a large amount of medical data for algorithm training, and the larger and more diverse the amount of data, the more accurate the results of its analysis and prediction will be. However, the application of big data technologies such as data collection, analysis and processing, cloud storage, and information sharing has increased the risk of data leakage. In the United States, the rate of such breaches has increased over time, with 176 million records breached by the end of 2017. There have been 245 data breaches of 10,000 or more records, 68 breaches of the healthcare data of 100,000 or more individuals, 25 breaches that affected more than half a million individuals, and 10 breaches of the personal and protected health information of more than 1 million individuals.
  • 502
  • 25 Nov 2022
Topic Review
Characterizations of the Category of Topological Spaces
In mathematics, a topological space is usually defined in terms of open sets. However, there are many equivalent characterizations of the category of topological spaces. Each of these definitions provides a new way of thinking about topological concepts, and many of these have led to further lines of inquiry and generalisation.
  • 501
  • 19 Oct 2022
Topic Review
CALL (DOS Command)
This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built into the command interpreter, others existed as external commands on disk. Over the several generations of DOS, commands were added for the additional functions of the operating system. In the current Microsoft Windows operating system, a text-mode command prompt window, cmd.exe, can still be used.
  • 500
  • 10 Oct 2022
Topic Review
Functional Database Model
The functional database model is used to support analytics applications such as financial planning and performance management. The functional database model, or the functional model for short, is different from but complementary to the relational model. The functional model is also distinct from other similarly named concepts, including the DAPLEX functional database model and functional language databases. The functional model is part of the online analytical processing (OLAP) category since it comprises multidimensional hierarchical consolidation. But it goes beyond OLAP by requiring a spreadsheet-like cell orientation, where cells can be input or calculated as functions of other cells. Also as in spreadsheets, it supports interactive calculations where the values of all dependent cells are automatically up to date whenever the value of a cell is changed.
  • 498
  • 17 Oct 2022
Topic Review
Country Code Top-Level Domains with Commercial Licenses
Country code top-level domains with commercial licenses are Internet country code top-level domain that have adopted a policy for worldwide commercial use. Some of the world's smallest countries have opened their country code domain to worldwide registrations for commercial purposes. For example, Tuvalu and the Federated States of Micronesia, small island-states in the Pacific, have partnered with VeriSign and FSM Telecommunications respectively, to sell domain name registrations using the TV and fm TLDs to television and radio stations. Some commercially available ccTLDs are in demand for use outside their home countries because their name can provide a component of a meaningful word or phrase. These are sometimes referred to as vanity ccTLDs.
  • 498
  • 16 Nov 2022
Topic Review
Serial Number Arithmetic
Many protocols and algorithms require the serialization or enumeration of related entities. For example, a communication protocol must know whether some packet comes "before" or "after" some other packet. The IETF (Internet Engineering Task Force) RFC 1982 attempts to define "Serial Number Arithmetic" for the purposes of manipulating and comparing these sequence numbers. This task is rather more complex than it might first appear, because most algorithms use fixed size (binary) representations for sequence numbers. It is often important for the algorithm not to "break down" when the numbers become so large that they are incremented one last time and "wrap" around their maximum numeric ranges (go instantly from a large positive number to 0, or a large negative number). Unfortunately, some protocols choose to ignore these issues, and simply use very large integers for their counters, in the hope that the program will be replaced (or they will retire), before the problem occurs (see Y2K). Many communication protocols apply serial number arithmetic to packet sequence numbers in their implementation of a sliding window protocol. Some versions of TCP use protection against wrapped sequence numbers (PAWS). PAWS applies the same serial number arithmetic to packet timestamps, using the timestamp as an extension of the high-order bits of the sequence number.
  • 497
  • 11 Oct 2022
Topic Review
Monoculture (Computer Science)
In computer science, a monoculture is a community of computers that all run identical software. All the computer systems in the community thus have the same vulnerabilities, and, like agricultural monocultures, are subject to catastrophic failure in the event of a successful attack.
  • 494
  • 25 Nov 2022
Topic Review
Microsoft Realtime Compression Interface
DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the user could store on disks by transparently compressing and decompressing data on-the-fly. It is primarily intended for use with hard drives, but use for floppy disks is also supported. This feature was removed in Windows XP and later.
  • 493
  • 22 Nov 2022
Topic Review
Cloud Digital Forensics
Cloud computing technology is rapidly becoming ubiquitous and indispensable. Despite the multiple advantages the cloud offers, organizations remain cautious about migrating their data and applications to the cloud due to fears of data breaches and security compromises.
  • 493
  • 18 Jan 2024
Topic Review
AutoPatcher
AutoPatcher is an offline updater and alternative to Microsoft Update that can be used for installing software patches, service packs and other updates for certain Microsoft Windows systems. It allows these to be downloaded on a different machine or in advance, and then installed without an internet connection. By doing this, system updates can be automated and scripted, time and bandwidth required to download relevant updates is reduced, and exposure of unsecured systems online can be avoided. AutoPatcher also allows installation of some common additional software, registry settings, and patches for other Microsoft software, notably Microsoft Office. AutoPatcher currently exists for Windows 2000, XP, Vista, 7, 8, 10 and some server equivalents (Windows 2003 and 2008). For some years it did not provide support for Windows 7 or older systems, nor for some 64 bit operating systems; updates are now possible for some of these in the 2014 version of Autopatcher. Originally software patches were distributed with AutoPatcher but, following legal complaints the software was modified in 2007. It now downloads all patches to a local hard drive from Microsoft's servers (ensuring the files are original and unmodified) and then allows their offline use as before.
  • 492
  • 12 Oct 2022
Topic Review
Spacetime Symmetries
Spacetime symmetries are features of spacetime that can be described as exhibiting some form of symmetry. The role of symmetry in physics is important in simplifying solutions to many problems. Spacetime symmetries are used in the study of exact solutions of Einstein's field equations of general relativity. Spacetime symmetries are distinguished from internal symmetries.
  • 491
  • 28 Nov 2022
Topic Review
BOSH
BOSH is an open-source software project that offers a toolchain for release engineering, software deployment and application lifecycle management of large-scale distributed services. The toolchain is made up of a server (the BOSH Director) and a command line tool. BOSH is typically used to package, deploy and manage cloud software. While BOSH was initially developed by VMware in 2010 to deploy Cloud Foundry PaaS, it can be used to deploy other software (such as Hadoop, RabbitMQ, or MySQL for instance). BOSH is designed to manage the whole lifecycle of large distributed systems. Since March 2016, BOSH can manage deployments on both Microsoft Windows and Linux servers. A BOSH Director communicates with a single Infrastructure as a service (IaaS) provider to manage the underlying networking and virtual machines (VMs) (or containers). Several IaaS providers are supported: Amazon Web Services EC2, Apache CloudStack, Google Compute Engine, Microsoft Azure, OpenStack, and VMware vSphere. To help support more underlying IaaS providers, BOSH uses the concept of a Cloud Provider Interface (CPI). There is an implementation of the CPI for each of the IaaS providers listed above. Typically the CPI is used to deploy VMs, but it can be used to deploy containers as well. Few CPIs exist for deploying containers with BOSH and only one is actively supported. For this one, BOSH uses a CPI that deploys Pivotal Software's Garden containers (Garden is very similar to Docker) on a single virtual machine, run by VirtualBox or VMware Workstation. In theory, any other container engine could be supported, if the necessary CPIs were developed. Due to BOSH indifferently supporting deployments on VMs or containers, BOSH uses the generic term “instances” to designate those. It is up to the CPI to choose whether a BOSH “instance” is actually a VM or a container.
  • 490
  • 28 Nov 2022
Topic Review
Keyword-Based Trust Management System for Fog Computing
Many companies have seen dramatic changes because of cloud computing. This is particularly true given the rapid increase in the use of enormous data sets. Meanwhile, there has been a meteoric increase in demand for private services. The proliferation of Internet of Things (IoT) devices and the increasing demand for low-latency applications have led to the rise of fog computing as a solution for decentralized data processing. Malicious nodes, unauthorized access, and data breaches can compromise the integrity and reliability of data processing. Therefore, there is a solid motivation to address these gaps in trust management and enhance the overall security of fog computing. Optimizing network performance and reducing latency is crucial to ensuring a seamless user experience in fog computing. Improving the efficiency of data transmission and communication among fog nodes can significantly enhance the performance of fog computing networks.
  • 490
  • 18 Aug 2023
Topic Review
Microsoft DoubleSpace BPB
DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the user could store on disks by transparently compressing and decompressing data on-the-fly. It is primarily intended for use with hard drives, but use for floppy disks is also supported. This feature was removed in Windows XP and later.
  • 489
  • 24 Oct 2022
Topic Review
Congruence (General Relativity)
In general relativity, a congruence (more properly, a congruence of curves) is the set of integral curves of a (nowhere vanishing) vector field in a four-dimensional Lorentzian manifold which is interpreted physically as a model of spacetime. Often this manifold will be taken to be an exact or approximate solution to the Einstein field equation.
  • 488
  • 04 Nov 2022
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