Tuesday, December 31, 2019
The Challanges of Marijuana Legalization Essay - 1855 Words
The use of marijuana for medical purposes has stimulated debate for many years. Some people find it beneficial, and believe it is the best way to relieve their chronic pain. There are a growing number of people who think marijuana is safe and think it should be legalized in small quantities for recreational use. Despite its illegality, marijuana has continued to be used by many people. Though some discount it as a harmful substance, there are many others who worry about increased criminal behavior, addiction and other health problems that can arise from its use. But more importantly they are concerned about the message teenagers would get if marijuana was legalized for recreational use. Since marijuana is a natural product many people mayâ⬠¦show more contentâ⬠¦As more responsibilities are heaped on teenagers, they are prone to find a way to deal with it, possibly drugs. It does not help that many people in authority, including some of our Presidents, have admitted to using ma rijuana at one time in their life. This acceptance of marijuana coupled with the pressures teens face on a daily basis is one reason that more teens are using marijuana. Because of the widespread use and acceptance of this substance, as well as the passage of several state medical marijuana laws, several research studies were conducted. These studies were analyzing whether new medical marijuana laws were causing an increase in teen use. The data from the research showed there was an increase in teen use over the last four years. One such study even revealed that it had increased in the youngest age group studied, eighth grade students (Anonymous). This increase in teen use is discussed in an article from Target News Reports that states ââ¬Å"one in every fifteen high school seniors today is smoking pot on a daily basisâ⬠(Marijuana). These studies show a growing trend in teenage use of marijuana. It also indicates that legalizing marijuana, even for medicinal purposes, may pla y a role in increased teen use.However, there is some conflicting evidence from National Institute on Drug Abuse that demonstrate research over a period of ten years, 2001-2010, indicating that there has not been a
Monday, December 23, 2019
The Disease Of Alzheimer s Disease Essay - 1482 Words
Alzheimerââ¬â¢s disease is a degenerative brain disease that is seen in the elderly. It is the most common form of dementia, which is a general term for memory loss and other intellectual abilities serious enough to interfere with daily life (Alzheimerââ¬â¢s Disease Dementia). Alzheimerââ¬â¢s is one of the leading causes of death in America. Dementia and Alzheimerââ¬â¢s have been around for centuries, but Alzheimerââ¬â¢s disease wasnââ¬â¢t first described until 1906 by Dr. Aloysius Alzheimer. In the past, there was a stigma for elderly people with the disease and people with dementia and Alzheimerââ¬â¢s were seen as a burden on society. Society has only recently accepted and cared for people with the disorder. There are now treatments and research being done for dementia and Alzheimerââ¬â¢s, but no cure remains and many individuals still suffer from the disease. Future treatments for the disease include taking aim at significant aspects of the disease like fi ghting beta-amyloid plaques, recruiting the immune system, reducing brain cell inflammation, and studying the heart-head connection (Alzheimerââ¬â¢s Treatments: Whatââ¬â¢s on the Horizon?). There are other ways to possibly treat the disease in the future as well. Hopefully from looking at the history of the disease, how the disease affects the brain and body, and future treatments, Alzheimerââ¬â¢s disease and dementia will be a thing of the past. In the past, people with dementia and Alzheimerââ¬â¢s were locked away in institutions or shunned from society (Batsch).Show MoreRelatedThe Disease Of Alzheimer s Disease1421 Words à |à 6 Pagesengulfed by a mysterious disease. The neurons being cut off and destroyed by two abnormal structures. First memory is affected gradually getting worse. Then one is unable to think properly, reason, and lacks of self control. Gaps are formed in the brain s ventricles, due to the amount of dead tissue. In the end, it will lead to death. All of this may sound like something from a science fiction movie but infact its very real. These are all known possible symptoms of a common disease that affects aboutRead MoreThe Disease Of Alzheimer s Disease1677 Words à |à 7 Pagesone thing Alzheimer s cannot take away, and that is love. Love is not a memory - it s a feeling that resides in your heart and soul.â⬠(Fade to Blank). The human brain is a remarkably complex organ that processes, stores, and recalls information. ââ¬Å"Alzheimer s disease (AD) is a slowly progressive disease of the brain that is characterized by impairment of memory and eventually by disturbances in reasoning, planning, language, and perception. Many scientists believe that Alzheimer s disease resultsRead MoreAlzheimer s Disease And Disease935 Words à |à 4 Pageswith Alzheimerââ¬â¢s disease. This disease is commonly found in the elderly. This explains why people assume older people have a bad memory. Alzheimerââ¬â¢s does not occur in a short period of time, it typically takes months to develop. It involves gradual memory loss due to two specific protein fragments that spread to different parts of the brain killing brain cells as they go. As mentioned in the article Alzheimerââ¬â¢s Disease Fact Sheet (2015), Dr. Alois Alzheimer first discovered the disease by noticing somethingRead MoreThe Disease Of Alzheimer s Disease1304 Words à |à 6 Pagesperson knows well, or asking questions continuously can be signs of a more serious problem. It is a disease of the brain that started slowly and gets worse as the time progresses. Alzheimerââ¬â¢s is a progressive destroying of brain tissue that primarily strikes people over the age of 65. Brain functions such as memory, comprehension, and speech deteriorate. The term first introduced by Dr. Alois Alzheimers in 1906. Memory is lost first. As days passes, attention tends to distracted, simple calculationsRead MoreThe Disease Of Alzheimer s Disease1172 Words à |à 5 PagesAlzheimerââ¬â¢s Disease Alzheimerââ¬â¢s disease is the 6th leading cause of death in America. It kills more than breast cancer and prostate cancer combined. Alzheimerââ¬â¢s accounts for 70-80% of dementia cases. By the age of 65, 1 in 9 people are diagnosed and by the age of 85, 1 in 3 people will have the disease. According to the Alzheimer Association, 5 million people in American have Alzheimerââ¬â¢s. Alzheimerââ¬â¢s starts to form 20 years prior to being diagnosed. Learning about Alzheimerââ¬â¢s can help familiesRead MoreAlzheimer s Disease : Disease1759 Words à |à 8 Pages Alzheimerââ¬â¢s Disease Madison Lollar Psychology 1030-C62 Volstate Community College Word Count: 1,589 Alzheimerââ¬â¢s Disease: When it comes to Alzheimerââ¬â¢s, I know firsthand how it affects individuals and their families. My great grandfather had Alzheimerââ¬â¢s for many years before his passing late last year, at age 92. Alzheimerââ¬â¢s is a disease that many individuals suffer with each year, but yet with all the advancements in modern medicine we still have no cure for it. There are differentRead MoreThe Disease Of Alzheimer s Disease1385 Words à |à 6 PagesThe disease stem cells could fix is called Alzheimerââ¬â¢s Disease (AD). The reason I chose this topic is because I have seen first hand how badly someone who suffers from Alzheimerââ¬â¢s Disease is affected in their daily lives. This disease completely takes over their lives and they turn into a completely different person who can hardly function. AD is very tough on the loved ones of the person suffering from it because that person, most of the time has no idea what is going on or who their loved onesRead MoreAlzheimer s Disease : A Disease1304 Words à |à 6 Pages10, 2015 Alzheimerââ¬â¢s Disease Alzheimerââ¬â¢s is a disease in the brain that affects a personââ¬â¢s memory, thinking, and behavior. It is the most common form of dementia and is common in adults older than 65. More than five million Americans are being affected by Alzheimerââ¬â¢s at this moment. Alzheimerââ¬â¢s comes in three stages; early, middle, and advanced. The disease is caused by the shrinking of the brain due to many risk factors and genetics. Dementia and Alzheimerââ¬â¢s disease are often confused becauseRead MoreThe Disease Of Alzheimer s Disease2364 Words à |à 10 Pages1. Introduction Alzheimerââ¬â¢s disease is a prominent brain disease that effects a massive amount of individuals in the United States. Alzheimerââ¬â¢s disease (AD) is the sixth leading cause of death in the United States, accounting for 60-80% of dementia cases, with no chance of being cured, prevented or decelerating over time (Alzheimerââ¬â¢s Association, 2014). AD is the most well-known form of dementia, causing complications in brain function in the areas of memory, thinking, and behavior (Alzheimerââ¬â¢sRead MoreThe Disease Of Alzheimer s Disease2246 Words à |à 9 PagesINTRODUCTION Alzheimerââ¬â¢s Disease has been one of the top leading causes of death in our country. It is understood that this disease is identified as an excess of the protein amyloid-ß within an increase of plaque (Seneff, Wainwright, and Mascitelli, 2010). Additionally, as the brain ages, it gets used to the inflammation and oxidative stress, so it is important to take the right amount of antioxidant micronutrients like vitamin C and vitamin E as well as anti-inflammatory macronutrients such as
Sunday, December 15, 2019
Mobile Query and Processing in Mobile Database Environment Free Essays
string(78) " all data that is highly related and likely to be queried in the near future\." MOBILE QUERY AND PROCESSING IN MOBILE DATABASE ENVIRONMENT Agustinus Borgy Waluyo1 1 Bala Srinivasan1 David Taniar2 School of Computer Science and Software Engineering, Monash University, Australia {Agustinus. Borgy. Waluyo, Bala. We will write a custom essay sample on Mobile Query and Processing in Mobile Database Environment or any similar topic only for you Order Now Srinivasan}@infotech. monash. edu. au. 2 School of Business Systems, Monash University, Australia David. Taniar@infotech. monash. edu. au Abstract Mobile database is a new context of database application in wireless environment. It introduces unique type of queries, and query-processing strategies that are different to traditional databases. We classify mobile database query into two categories, especially context-awareness query and adhoc query. Context-awareness query is further classified into location dependent, context dependent, and hybrid query. As for the query processing, we define three strategies namely mobile client, on air, and server strategy. Mobile client and on air strategy relates to caching strategy and broadcast strategy respectively. Finally, we include some challenges in mobile databases. 1. Introduction Recent advances in wireless technology have led to mobile computing, a new dimension in data communication and processing. Many predict a new emerging, gigantic market with millions of mobile users carrying small, battery-powered terminal equipped with wireless connection [1,2,10]. The mobile computing environment provides database applications with useful aspects of wireless technology, which is known as mobile databases. This advance technology has created a new age of nomadic database users. Basically, these users are simply accessing a database through a network. However, the network is now applied in wireless environment, and has several novel properties, which include userââ¬â¢s locations are constantly changing, the likelihood of losing connections is much greater than in a traditional network, and asymmetric communication environment in which the wireless bandwidth for uplink communication is smaller than downlink communication [11]. In general, mobile user communicates with a Mobile Base Station (MBS) to carry out any activities such as transaction and information retrieval. MBS has a wireless interface to establish communication with mobile client and it serves a large number of mobile users in a specific region called cell. In mobile environment architecture, each MBS is connected to a fixed network as illustrated in Figure 1(a). Mobile units or mobile clients in each cell can connect to the fixed network via wireless radio, wireless Local Area Network (LAN), wireless cellular, or satellite. Each of the wireless networks provides a different bandwidth capacity. However, the wireless bandwidth is too small as compared to the fixed network such as ATM (Asynchronous Transfer Mode) can provide speed up to 155Mbps [7]. 55 Wireless Network Mobile Base Station Mobile Base Station Wireless Network High speed Wired Network Fixed Host Fixed Host Crossing Crossing Mobile Client Query Query Processing Strategy Data Repository Query Result 2 Mobile Base Station Mobile Base Station Query Taxonomy = Mobile Client = Wireless Network 1 (a) Mobile Environment Architecture (b) Query Application in Mobile Environment Figure 1. Mobile Environment Architecture and Query Processing Figure 1(b) depicts the query processing in mobile databases. Mobile client initiates a query, and retrieve the data from data repository. The data repository is available in the fixed network. The query is transmitted through wireless channel, and the result is obtained using certain query processing strategies. As can be seen in Figure 1b, a sign of number 1, and 2, which is attached in query taxonomy, and query processing strategy respectively, correspond to the main content of this paper. Driven by differences between wired and wireless environment results in differences of type of queries, query processing mechanisms as well as communication technology. It is the aim of this paper to provide comprehensive query taxonomy, and processing strategy in mobile databases. Figure 2 shows a detailed structure of this paper. Subsequent sections in this paper are organized as follows. Section 2 describes query taxonomy in mobile databases. Section 3 contains the query processing strategies, and section 4 discusses some challenges in mobile databases. Finally, section 5 concludes the paper. In this paper, the term mobile client, mobile device, mobile user, user and client are used interchangeably Location D ependent Q ueries C ontext Aw areness Taxonomy C ontext D ependent Q ueries Hybrid Q ueries A d Hoc Q ueries M obile Q uery and Processing M obile C lient Processing Strategy O n Air Server Figure 2. Structure of Paper 56 2. Query Taxonomy In this section, we classify type of queries in mobile databases. The queries can be entirely new and specifically applied in the wireless environment, while the other can be a common type of query in traditional databases. 2. Context Awareness The word ââ¬Ëcontextââ¬â¢ implies a variety of aspects. [14] defines the word context into three categories namely computing context, user context, and physical context. Computing context relates to computing resources such as network connectivity, bandwidth, printer, and workstations. User context associates with userââ¬â¢s needs, preferences, roles, profile, and alike. Physical co ntext involves environment issue, which include lighting, noise, traffic, temperature, and humidity. [5] adds another category of context called ââ¬Ëtime contextââ¬â¢, which refers to time of a day, week, month, year, etc. 6] defines context as either the aspect of physical world or condition and activities in the virtual world. It is further described that context information can either be transient when the context associates with the environment at a point of time or persistent when the context involves a history of transient context. In simple words, we can always define that context relates to who, when, where, and what. Context awareness creates a new class of applications in mobile computing. With context awareness, mobile device is expected to adapt constantly in a wide range of dynamically and continually changing situations. It is important for the device to be able to aware of the situation, environment, and tasks that the mobile client is performing as well as will be performing in the near future. The utilisation of context information in an application minimises the amount of user involvement in a service by providing related information. Having known the context of the query enables the device to pre-fetch all data that is highly related and likely to be queried in the near future. You read "Mobile Query and Processing in Mobile Database Environment" in category "Papers" With this query, client only initiates a single request and all related data will be retrieved implicitly. This technique avoids client to have multiple request that result in energy efficiency. Example: To find restaurants information in current region. The query will result of retrieving restaurants based on userââ¬â¢s preferences such as Italian, Chinese or fast food as well as pre-fetching maps, traffic and weather condition, which is likely to be queried next. Most applications have been focusing on location awareness rather than context awareness as a whole. Thus, we classify mobile database queries into location dependent queries, context dependent queries, and the combination thereof. 2. 1. Location Dependent Queries Location dependent query is a class of queries that are motivated by mobile clients. In this type of query, the location of the mobile client is a parameter of the query. The value of the location parameter can be provided by the client or a global positioning system (GPS). An example of this query is a travelerââ¬â¢s information system that provides information on hotels, restaurant, bars and the like, to motorists. Processing of queries must be based on knowledge of the userââ¬â¢s location. For queries services that are ahead of the current route, direction of motion and speed are necessary to be taken into account. Recent technology provides a new feature in automobiles, which offers 57 navigational aids as a built-in feature. In general, each location updates generate two direct costs, particularly transmission cost, which refers to the cost to inform the server of the new location, and server processing cost, which corresponds to the cost of updating the system containing the location of the mobile unit. The location parameter can be in any objects, such as taxis, trucks, and helicopters. This class of query can be further classified into two categories: (i) Continuous query, and (ii) On-demand query. Continuous query The continuous type of query includes real-time monitoring of mobile objects. This is different compared with conventional queries, which are based on an instant of the database at some moment in time. Real-time monitoring queries are continuous for monitoring purposes [3, 13]. Examples: (i) To request information about nearby tourist attractions, hotels, or shopping center while traveling. With this type of query, users only need to send a query once and notification of the updated information about nearby tourist attractions, hotels, or shopping center will be sent automatically as they move to different regions. ii) This query also helps tourists whenever they are close to a certain situation such as dangerous zone or traffic jam by providing some alerts to mobile user. Figure 3 shows an illustration of real-time query monitoring. In this application, the system must be able to provide the accurate query results and update them in real time whenever some mobile cl ients enters or exits the region defined by the query. This class of query can be referred as range-monitoring queries. The range-monitoring queries are removed from the system only when the user explicitly ends the query. Server End Query Query i Response i New Region Updated response i Region 1 Mobile Client 1 Moves to Region 2 Mobile Client 1 Figure 3. Continuous Query On demand query The on demand location dependent query is different from continuous query in a way that its database management does not manage the query but only the location of each mobile units in specified regions. Figure 4 illustrates on demand query. Every mobile unit is registered under one location server that manages the user profiles and is called the home location server. Location information of mobile clients can be stored at predefined sites like the userââ¬â¢s home location server in a network. Consequently, the search space for a userââ¬â¢s location can be reduced. However, when a mobile user crosses any boundaries of a cell, the information at the predefined site has to be updated accordingly. This type of query does not have to specify when to end the query since the server does not keep the query but the location [12]. Examples: To retrieve nearby hospital, police station or petrol station in the area. 58 Server Q uery i R esponse i Q uery j R esponse j Region 1 M obile C lien t 1 M oves to Region 2 M obile C lien t 1 Figure 4. On Demand Query When the parameter is an object, and mobile client requests an object that satisfies location criteria, then the situation becomes different. Figure 5 illustrates on demand query with location object parameter [8,15]. Examples: (i) Taxi operator wants to see how many free taxis are currently in a certain region. They can find free taxis and allocate them to another region that require more taxis or send them directly to the nearby customer. (ii) Tourists who come to the country, where there are no designated busââ¬â¢ stops, nor timetable. They can utilize mobile device to retrieve incoming buses within a pre-defined time. Server Object Query Object Result Location Tracking Location Info Mobile Client Object Figure 5. On Demand Query with Location Object Parameter 2. 1. 2 Context Dependent Queries This type of query requires maintenance of an internal representation of userââ¬â¢s needs, preferences, roles, profile, etc. With these parameters, application will be able to decide the situation and task that a user is currently performing, and adapt to change of user needs and roles. This enables mobile device not to just retrieve the required information but also some other information that is highly relevant [6,8]. Examples: (i) Tourist wants to see list of restaurants in a town. Rather than retrieving the entire list of restaurants, the query retrieves the restaurants based on userââ¬â¢s preferences and need such as cuisine preference, price, occasion, etc. (ii) A business person wants to check the closest meeting schedule. The query retrieves the time as well as previous history of the meeting, people involved, client accounts, meal preferences, required data, etc. 9 2. 1. 3 Hybrid Queries Hybrid queries represent a combination of location dependent and context dependent queries. This type of query requires the system to maintain all parameters of context-awareness queries including location parameter. Examples: (i) A Traveler wants to find restaurants in the region that he/she will enjoy and within 10 minutes of current travel distance, (ii) A teenager wa nts to check movies in the nearby cinemas that he/she will like, and the show time can be met while considering current travel distance. These queries are very useful for nomadic users since it not only considers the usersââ¬â¢ preferences and needs but also the location of the user. More sophisticated application utilizes a variety of sensors to monitor the environment as well as userââ¬â¢s action in order to provide assistance of the tasks being performed by the user. This application requires the ability to process data streams in real-time, analyze and interpret it precisely. The main point in context awareness query is to accurately analyze the environment and userââ¬â¢s intention, regardless of where the context information is obtained from. It is a difficult challenge since there is a possibility of conflicting data, and the need to have efficient processing to provide a useful application to the user. 2. 2 Ad Hoc Queries Ad Hoc queries are commonly utilised queries in traditional DBMS. This type of query explicitly mentions the required information in the query statement, and does not involve any context awareness information. Thus, the query result is only based on the actual query itself. Examples: (i) University student wants to retrieve his/her academic record or personal details. ii) Travelling sales person inquires about product availability, price, etc. 3. Query Processing Strategy We divide query-processing strategy for mobile databases into three parts, namely: (i) mobile/client strategy, (ii) on-air strategy and, (iii) server strategy. Mobile/clients strategy relates to how client manipulates and maintains the data in its cache efficiently and effectively. On-air strategy corresponds to data broadcasting stra tegies. With this strategy, the number of mobile users does not affect the query performance. Server strategy relates to designing techniques for the server to accommodate multiple requests so that the request can be processed as efficiently as possible. We claim that query processing for mobile databases is very much centered around the issues of caching, broadcasting, and scheduling. Figure 6 shows the architecture of query processing in mobile databases. 60 C Strategies lient OA n ir Strategies Server Strategies Figure 6. Query Processing in Mobile databases 3. 1 Mobile Client Strategy Mobile clientââ¬â¢s strategy defines a number of strategies to maintain cached data items in clientsââ¬â¢ local storage. As stated earlier, wireless communication channel in general suffers to narrow bandwidth while it is also inherently asymmetric communication, in which the downstream communication bandwidth from a server to the mobile client is much larger than the upstream communication bandwidth from clients back to server. Due to the above reason, caching of frequently accessed data items in a clientââ¬â¢s local storage becomes important for enhancing the performance and data availability of data access queries. Another advantage of caching is the ability to handle fault tolerance. This is related to the characteristics of mobile computing in which each mobile client connects or disconnects from the network frequently. In some situation, the MBS may not be accessible due to problem like signal distortion. However, a query can still be partially processed from caches and at least some of the query results can be returned to the user [9]. Three main issues characterize a caching mechanism. These issues include caching granularity, caching coherence strategy, and caching replacement policy. Caching granularity relates to determining a physical form of cached data items. Caching coherence strategy or invalidation strategy involves cache invalidation and update schemes to invalidate and update an out-dated cached item [4]. Caching replacement policy is needed to retain the frequently accessed database items in a clientââ¬â¢s local storage. The more effective a caching replacement policy in keeping the frequently accessed items, the better a query will perform and the more queries could be served during disconnection situation. 3. On Air Strategy In this scheme, the server periodically broadcasts the frequently accessed data items to clients through one or more broadcast channels, but the clients may not cache the data item of interest. This situation might occur when the client does not have enough memory or space to cache the required data. The behavior of this channel is unidirectional which means the server disseminates a set of data periodically, via this type of c hannel to a multiple number of users. A complete broadcast file is referred as a broadcast cycle. In this scheme, the client needs to listen to channel and filter the required data over the channel, which is also generally known as push-mechanism. Figure 7 shows on air query processing. 61 The advantage of broadcasting channel is its scalability. The number of users in the cell and the request rate do not affect the performance of the server. Thus, the utilization of bandwidth is better and the server workload is lower as compared with point to point/on-demand communication. Consequently, the power utilization of the client to retrieve information is also improved. However, it is very important to have good strategies to maintain the overall response time of the client to obtain information from the channel or else the advantages of data broadcast will be diminished. B ro ad cast C h an n el = listen in g to th e chan n el = retriev in g th e d esired data M o bile C lie nt Figure 7. On Air Query Processing 3. 3 Server Strategy This strategy considers the problem of pull-based broadcast scheduling where mobile clients send queries to the server through dedicated or point-to-point channel, server process the query, and send the result back to the client. The strategy concerns with broadcast and disk scheduling. Broadcast scheduling is to determine how queries to be served efficiently in the server considering a number of factors such as the length of the query, the wait time and the popularity of the items. Data scheduling is related to how data is placed on the disk that improves the query response time. The possibility of combining these two methods for query processing strategy is an interesting issue to be explored. B road cast server C ach e S erver D isk S erver T r a n sm itte r S erver Figure 8. Broadcast Server Architecture A database server is able to enhance the data retrieval performance by incorporating its own main memory and cache to store those database items frequently accessed by most mobile clients. Figure 62 8 shows architecture of broadcast server. A query can be processed either in the disk server or cache server. If the relevant data items have been retrieved earlier then the query is processed in the cache server. After processing a query, the results are transmitted to the transmitter queue, which subsequently send the data items through the wireless channel. 4. Challenges in Mobile Databases This section discusses some challenges in mobile database environment. The general concept that has been outlined in this paper contains an enormous issue to investigate. However, due to the limitation of page, only a few numbers can be mentioned. Location management is an important issue in mobile database research. Since the number of user population carrying mobile devices increases linearly with the service demand, the communication traffic for locating users also increases accordingly. This situation requires an efficient strategy for location tracking and management. Location management is a very essential factor in providing context awareness services. Context security introduces a new issue to be considered. Since context information may contain a very confidential and private data. It is necessary to ensure privacy issue protection for every user in a network. Caching management strategy, which includes caching granularity, caching coherent issue, and caching replacement strategy, requires a thorough investigation. A good caching management strategy is able to analyse, predict, and adapt to changing of userââ¬â¢s context in order to assist user in performing tasks. As for processing issue, data caching in mobile databases enable clients to obtain a high computing speed as server, by involving a much smaller data items volume. The asymmetric communication in mobile environment has made it a better reason to employ caching strategy. Broadcast scheduling is another issue to investigate. Generally, the more number of data to be broadcast, the more requests will be served from the data broadcast and this will reduce the chance of mobile clients to send the request to the server. However, at a certain point the advantage of the broadcast data will be diminished if there is too many data in the roadcast cycle. Consequently, it will severely affect the query response time since mobile users have to wait for considerably long delay before they receive the desired data. Therefore, it is essential to decide what data to be broadcast that serves most of the requests since the query access pattern is changed dynamically. 5. Conclusions Recent emergence of w ireless technology enables people to conduct activities, business, or transactions anywhere and anytime without any attachment to stationary computer like used to be. Nomadic people are now able to access email, news, weather, and query to the central database server using wireless devices. Mobile database focuses on the query issue that is the dominant operation in mobile computing. Since mobile database is a new dimension of database application, the type of query, query processing strategy, and communication technology that involves in the application are different than what applies in traditional databases. We have defined query taxonomy as well as query processing strategy in mobile databases. Query in mobile databases are categorized into context-awareness query and ad-hoc query. Context- 63 awareness query is further classified into location dependent, context dependent, and hybrid query. Query processing in mobile databases includes mobile client, on air, and server strategy. Mobile client and on air strategy corresponds to caching strategy and broadcast strategy respectively. Finally, we discuss a few challenges that open enormous opportunities for research in mobile databases. 6. References 1. 2. 3. 4. 5. 6. 7. 8. 9. ACHARYA S. , ALONSO R. , FRANKLIN M. AND ZDONIK S. Broadcast Disks: Data Management for Asymmetric Communication Environments, Proceedings of ACM Sigmod, pp. 199-210, May, 1995. BARBARA D. , Mobile Computing and Databases-A Survey, IEEE TKDE, 11(1):108-117, January/February, 1999. CAI Y. AND HUA K. A. , An Adaptive Query Management Technique for Real-Time Monitoring of Spatial Regions in Mobile Database Systems, 21st IEEE IPCCC, pp. 259-266, 2002. CHAN B. Y. , SI A. and Leong H. V. , Cache Management for Mobile Databases: Design and Evaluation, Proceedings of the International Conference on Data Engineering (ICDE), pp. 4-63, 1998. CHEN G. AND KOTZ D. , A Survey of Context-Aware Mobile Computing Research, Technical Report TR2000381, Department of Computer Science, Dartmouth College, November, 2000. EBLING R. M. , HUNT H. D. G. AND LEI H. , Issues for Context Services for Pervasive Computing, Proceedings of Middlewareââ¬â¢01 Advanced Workshop on Middleware for Mobile Computing, Heidelberg, November, 2001. ELMASRI R. AND NAVATHE S. B. , Fundamentals of Database Systems, 3ââ¬â¢rd Edition, Addison W. , U. S. A. , 2000. FRANKLIN J. M. , Challenges in Ubiquitous Data Management, Informatics, pp. 4-33, 2001. GODFREY P. AND GRYZ J. , Semantic Query Caching for Heterogeneous Databases, Proceedings of the 4th Knowledge Representation meets Databases Workshop (KRDB), pp. 61-66, April, 1997. 10. IMIELINSKI T. AND VISWANATHAN S. , Adaptive Wireless Information Systems, Proceedings of SIGDBS (Special Interest Group in Database Systems) Conference, pp. 19-41, October, 1994. 11. IMIELINSKI T. , VISWANATHAN S. AND BADRINATH B. R. , Data on Air: Organisation and Access, IEEE TKDE, 19(3): 353-371, May/June, 1997. 12. KOTTKAMP H. -E. AND ZUKUNFT O. Location-Aware Query Processing in Mobile Database Systems, ACM Symposium on Applied Computing, pp. 416-423, February, 1998. 13. KUBACH U. AND ROTHERMEL K. , A Map-Based Hoarding Mechanism for Location-Dependent Information, Proceedings of Second Mobile Data Management (MDM), pp. 145-157, January, 2001. 14. SCHILIT B. , ADAMS N. AND WANT R. , Context-Aware Computing Applications, Proceedings of IEEE Workshop on Mobile Computing Systems and Applications, pp. 85-90, December, 1994. 15. WOLFSON O. , ET AL, Databases for Tracking Mobile Units in Real Time, Proceedings of ICDTââ¬â¢99, pp. 169186, 1998. 64 How to cite Mobile Query and Processing in Mobile Database Environment, Papers
Saturday, December 7, 2019
Dahl on Democracy free essay sample
What Underlying Conditions Favour Democracy? Page 145-165 We face two questions: How can we account for the establishment of democratic institutions in so many countries in so many parts of the world, and how can we explain its failure? A full answer is impossible; two interrelated sets of factors are undoubtedly of crucial importance. FAILURE OF THE ALTERNATIVES During the 20th century, the main alternatives lost out in competition with democracy. The monarchy, open oligarchy, hereditary aristocracy fatally declined in legitimacy and ideological strength. Though replaced by nondemocratic alternatives (fascism, nazism) they flourished briefly due to their defeat in WW2. Military dictatorships, mainly in latin America, fell due to economic, diplomatic and military (Argentina) failures. The main democratic antagonist (USSR) collapsed due to internal decay and external pressures. A final victory for democracy has not been achieved, nor was it close, see China. Middle eastern countries are still not democratic as well as some countries that reverted back to nondemocratic regimes as conditions were not favourable. Favourable conditions: Essential conditions for democracy 1. Control of military and police by elected officials. 2. Democratic beliefs and political culture. 3. No strong foreign control hostile to democracy Favourable conditions for democracy: 4. A modern market economy and society 5. Weak subcultural pluralism FOREIGN INTERVENTION democratic institutions are less likely to develop in a country subject to intervention by another country hostile to democratic government in that country. E. g. Soviet intervention prevented Czechoslovakia, Poland and Hungary from democratizing despite favourable conditions. The US: history of intervening in Latin America, overthrowing democratically elected governments to protect their economic interests in the region, for instance in Guatamala in 1954. With the collapse of the Soviet Union, the US started supporting development of democratic institutions in Eastern Europe. CONTROL OVER MILITARY AND POLICE Unless the military and police forces are under the full control of democratically elected officials, democratic political institutions are unlikely to develop or endure. The most dangerous internal threat to democracy comes from leaders who have access to the means of physical coercion: military and police. Military and police leaders must defer power to democratic officials. In central and Latin America, of the 47 governments, two thirds gained power by means other than free and fair elections, most often by a military coup. In contrast, Costa Rica has been a beacon of democracy since 1950. In 1950, Costa Rica eliminated the threat of a military coup by abolishing the military all together. CULTURAL CONFLICTS WEAK OR ABSENT Democratic political institutions are more likely to develop and endure in a country that is culturally fairly homogenous and less likely in a country with sharply differentiated and conflicting subcultures. Cultural conflicts can erupt in the political arena, and they typically do: over religion, language, or even dress-codes in schools. Issues like these pose a special problem for democracy. Cultural problems are often viewed as matters of principle from deep religious convictions, cultural preservation or group survival. They view them too crucial to allow for compromise, nonnegotiable. A peaceful democratic process requires negotiation, conciliation and compromise. In older democracies, they have managed to avoid severe cultural conflicts. Even if these differences exist, they have allowed more negotiable differences (i. e. economic issues). There are some exceptions. Cultural differences have been significant in the US, Switzerland, Belgium, Netherlands and Canada. How have democratic institutions been able to survive in these countries? Assimilation. The American solution, British colonists encountered new waves of settlers from Ireland, Scandinavia, Germany, etc. By 1910, 20% of the population wasnt born in the US. They assimilated their dominant political loyalty and identity and became American. This was mainly voluntary or enforced by social mechanisms (such as shame) that minimized the need for coercion by the state. However, African Americans and Native Americans needed to be coerced to assimilate, if not this was followed by exclusion. This resulted in an irrepressible conflict; the Civil War. Deciding by consensus. Distinctive and potentially conflicting subcultures have existed in Switzerland, Belgium and the Netherlands. Each created political arrangements that required unanimity or broad consensus for decisions made by cabinet and parliament. The principle of majority rule yielded to a principle of unanimity. Consensual systems like these cannot be created or will not work successfully except under very special conditions. These include a talent for conciliation; high tolerance for compromise; trustworthy leaders capable of negotiating sufficient solutions; consensus on basic goals and values; a national identity that discourages demands for separation and a commitment to democratic procedures that exclude violent and revolutionary means. These are uncommon conditions, and may collapse under the pressure of acute cultural conflict (like in Lebanon, 1958). Electoral Systems. Cultural differences often get out of hand because they are used by politicians competing for support (Kenya 2012, Ivory Coast 2010). Politicians may deliberately appeal to members of their cultural group and ignite latent animosities into hatreds that culminate in ââ¬Å"cultural cleansingâ⬠. To avoid this, electoral systems could be designed to change incentives of politicians: make conciliation more profitable than conflict. For instance, no candidates can be elected with the support of only a single group, they would need to gain votes from several major cultural groups. This needs to be included early in the process of democratization. Separation. When cultural cleavages are too deep to be overcome by any of the previous solutions, the final solution may be for cultural groups to separate themselves into different political units within which they possess enough autonomy to maintain their identity and achieve their main political goals (eg: Sudan, Montenegro, Kosovo). The Swiss solution has two requirements: citizens in different subcultures must be already separated along territorial lines, and second the citizens must have a national identity and common goals and values to sustain a federal union. In Canada, French Canadians want independence, however their territory isnt sufficient territorially divided. DEMOCRATIC BELIEFS AND CULTURE. The prospects for stable democracy in a country are improved if its citizens and leaders strongly support democratic ideas, values and practices. A democratic political culture helps to form citizens who believe that democracy and political equality are desirable. A substantial majority of citizens must prefer democracy and its political institutions to any nondemocratic alternative and support democratic leaders who uphold democracy. ECONOMIC GROWTH WITH A MARKET ECONOMY Historically, the development of democratic beliefs and a democratic culture has been closely associated with a market economy; it is a highly favorable condition for the consolidation of democratic institutions. Where most economic enterprises are WHY DEMOCRACY HAS SPREAD THROUGHOUT THE WORLD The 20th century turned out to be the Century of Democratic Triumph. That triumph should be viewed with caution. In many countries the basic political institutions are weak or defective. It is reasonable to wonder whether democratic successes will be sustained in the twenty-first century. The answer depends on how well democratic countries meet their challenges. One of these arises directly from the contradictory consequences of market-capitalism.
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