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1、,Chapter 29Emerging Database Technologies andApplications,Copyright 2004 Pearson Education,Inc.,Chapter 29-3,Chapter Outline,1 Mobile Databases1.1 Mobile Computing Architecture 1.2 Characteristics of Mobile Environments1.3 Data Management Issues1.4 Application:Intermittently Synchronized Databases2
2、Multimedia Databases2.1 The Nature of Multimedia Data and Applications2.2 Data Management Issues2.3 Open Research Problems2.4 Multimedia Database Applications,Chapter 29-4,Chapter Outline(contd.),3 Geographic Information Systems3.1 GIS Applications3.2 Data Management Requirements of GIS 3.3 Specific
3、 GIS Data Operations3.4 An Example of GIS Software:ARC-INFO3.5 Problems and Future issues in GIS,Chapter 29-5,Chapter Outline(contd.),4 GENOME Data Management4.1 Biological Sciences and Genetics4.2 Characteristics of Biological Data4.3 The Human Genome Project and Existing Biological Databases,Chapt
4、er 29-6,Emerging Database Technologies and Applications,Emerging database technologiesThe major application domains,Chapter 29-7,1 Mobile Databases,Recent advances in portable and wireless technology led to mobile computing,a new dimension in data communication and processing.Portable computing devi
5、ces coupled with wireless communications allow clients to access data from virtually anywhere and at any time.,Chapter 29-8,1 Mobile Databases(2),There are a number of hardware and software problems that must be resolved before the capabilities of mobile computing can be fully utilized.Some of the s
6、oftware problems which may involve data management,transaction management,and database recovery have their origins in distributed database systems.,Chapter 29-9,1 Mobile Databases(3),In mobile computing,the problems are more difficult,mainly:The limited and intermittent connectivity afforded by wire
7、less communications.The limited life of the power supply(battery).The changing topology of the network.In addition,mobile computing introduces new architectural possibilities and challenges.,Chapter 29-10,1.1 Mobile Computing Architecture,The general architecture of a mobile platform is illustrated
8、in Fig29.1.,Chapter 29-11,Figure 27.4 A general architecture,Chapter 29-12,1.1 Mobile Computing Architecture(2),It is distributed architecture where a number of computers,generally referred to as Fixed Hosts and Base Stations are interconnected through a high-speed wired network.Fixed hosts are gene
9、ral purpose computers configured to manage mobile units.Base stations function as gateways to the fixed network for the Mobile Units.,Chapter 29-13,1.1 Mobile Computing Architecture(3),Wireless Communications The wireless medium have bandwidth significantly lower than those of a wired network.The cu
10、rrent generation of wireless technology has data rates range from the tens to hundreds of kilobits per second(2G cellular telephony)to tens of megabits per second(wireless Ethernet,popularly known as WiFi).Modern(wired)Ethernet,by comparison,provides data rates on the order of hundreds of megabits p
11、er second.,Chapter 29-14,1.1 Mobile Computing Architecture(4),Wireless Communications The other characteristics distinguish wireless connectivity options:interference,locality of access,range,support for packet switching,seamless roaming throughout a geographical region.,Chapter 29-15,1.1 Mobile Com
12、puting Architecture(5),Wireless Communications Some wireless networks,such as WiFi and Bluetooth,use unlicensed areas of the frequency spectrum,which may cause interference with other appliances,such as cordless telephones.Modern wireless networks can transfer data in units called packets,that are u
13、sed in wired networks in order to conserve bandwidth.,Chapter 29-16,1.1 Mobile Computing Architecture(6),Client/Network Relationships Mobile units can move freely in a geographic mobility domain,an area that is circumscribed by wireless network coverage.To manage entire mobility domain is divided in
14、to one or more smaller domains,called cells,each of which is supported by at least one base station.Mobile units be unrestricted throughout the cells of domain,while maintaining information access contiguity.,Chapter 29-17,1.1 Mobile Computing Architecture(7),Client/Network Relationships The communi
15、cation architecture described earlier is designed to give the mobile unit the impression that it is attached to a fixed network,emulating a traditional client-server architecture.Wireless communications,however,make other architectures possible.One alternative is a mobile ad-hoc network(MANET),illus
16、trated in 29.2.,Chapter 29-18,1.1 Mobile Computing Architecture(8),Chapter 29-19,1.1 Mobile Computing Architecture(9),Client/Network Relationships In a MANET,co-located mobile units do not need to communicate via a fixed network,but instead,form their own using cost-effective technologies such as Bl
17、uetooth.In a MANET,mobile units are responsible for routing their own data,effectively acting as base stations as well as clients.Moreover,they must be robust enough to handle changes in the network topology,such as the arrival or departure of other mobile units.,Chapter 29-20,1.1 Mobile Computing A
18、rchitecture(10),Client/Network Relationships MANET applications can be considered as peer-to-peer,meaning that a mobile unit is simultaneously a client and a server.Transaction processing and data consistency control become more difficult since there is no central control in this architecture.Resour
19、ce discovery and data routing by mobile units make computing in a MANET even more complicated.Sample MANET applications are multi-user games,shared whiteboard,distributed calendars,and battle information sharing.,Chapter 29-21,1.2 Characteristics of Mobile Environments,The characteristics of mobile
20、computing include:Communication latency.Intermittent connectivity.Limited battery life.Changing client location.,Chapter 29-22,1.2 Characteristics of Mobile Environments(2),The server may not be able to reach a client.A client may be unreachable because it is dozing in an energy-conserving state in
21、which many subsystems are shut down or because it is out of range of a base station.In either case,neither client nor server can reach the other,and modifications must be made to the architecture in order to compensate for this case.Proxies for unreachable components are added to the architecture.Fo
22、r a client(and symmetrically for a server),the proxy can cache updates intended for the server.,Chapter 29-23,1.2 Characteristics of Mobile Environments(3),Mobile computing poses challenges for servers as well as clients.The latency involved in wireless communication makes scalability a problem.Beca
23、use latency due to wireless communications increases the time to service each client request,the server can handle fewer clients.One way servers relieve this problem is by broadcasting data whenever possible.A server can simply broadcast data periodically.Broadcast also reduces the load on the serve
24、r,as clients do not have to maintain active connections to it.,Chapter 29-24,1.2 Characteristics of Mobile Environments(4),Client mobility also poses many data management challenges.Servers must keep track of client locations in order to efficiently route messages to them.Client data should be store
25、d in the network location that minimizes the traffic necessary to access it.The act of moving between cells must be transparent to the client.The server must be able to gracefully divert the shipment of data from one base to another,without the client noticing.Client mobility also allows new applica
26、tions that are location-based.,Chapter 29-25,1.3 Data Management Issues,From a data management standpoint,mobile computing may be considered a variation of distributed computing.Mobile databases can be distributed under two possible scenarios:The entire database is distributed mainly among the wired
27、 components,possibly with full or partial replication.A base station or fixed host manages its own database with a DBMS-like functionality,with additional functionality for locating mobile units and additional query and transaction management features to meet the requirements of mobile environments.
28、The database is distributed among wired and wireless components.Data management responsibility is shared among base stations or fixed hosts and mobile units.,Chapter 29-26,1.3 Data Management Issues(2),Data management issues as it is applied to mobile databases:Data distribution and replicationTrans
29、actions modelsQuery processingRecovery and fault toleranceMobile database designLocation-based serviceDivision of laborSecurity,Chapter 29-27,1.4 Application:Intermittently Synchronized Databases,Whenever clients connect through a process known in industry as synchronization of a client with a serve
30、r they receive a batch of updates to be installed on their local database.The primary characteristic of this scenario is that the clients are mostly disconnected;the server is not necessarily able reach them.This environment has problems similar to those in distributed and client-server databases,an
31、d some from mobile databases.This environment is referred to as Intermittently Synchronized Database Environment(ISDBE).,Chapter 29-28,1.4 Application:Intermittently Synchronized Databases(2),The characteristics of Intermittently Synchronized Databases(ISDBs)make them distinct from the mobile databa
32、ses are:A client connects to the server when it wants to exchange updates.The communication can be unicast one-on-one communication between the server and the client or multicast one sender or server may periodically communicate to a set of receivers or update a group of clients.A server cannot conn
33、ect to a client at will.,Chapter 29-29,1.4 Application:Intermittently Synchronized Databases(3),Issues of wireless versus wired client connections and power conservation are generally immaterial.A client is free to manage its own data and transactions while it is disconnected.It can also perform its
34、 own recovery to some extent.A client has multiple ways connecting to a server and,in case of many servers,may choose a particular server to connect to based on proximity,communication nodes available,resources available,etc.,Chapter 29-30,2 Multimedia Databases,In the years ahead multimedia informa
35、tion systems are expected to dominate our daily lives.Our houses will be wired for bandwidth to handle interactive multimedia applications.Our high-definition TV/computer workstations will have access to a large number of databases,including digital libraries,image and video databases that will dist
36、ribute vast amounts of multisource multimedia content.,Chapter 29-31,2.1 Multimedia Databases,DBMSs have been constantly adding to the types of data they support.Today the following types of multimedia data are available in current systems.Text:May be formatted or unformatted.For ease of parsing str
37、uctured documents,standards like SGML and variations such as HTML are being used.Graphics:Examples include drawings and illustrations that are encoded using some descriptive standards(e.g.CGM,PICT,postscript).,Chapter 29-32,2.1 Multimedia Databases(2),Images:Includes drawings,photographs,and so fort
38、h,encoded in standard formats such as bitmap,JPEG,and MPEG.Compression is built into JPEG and MPEG.These images are not subdivided into components.Hence querying them by content(e.g.,find all images containing circles)is nontrivial.Animations:Temporal sequences of image or graphic data.,Chapter 29-3
39、3,2.1 Multimedia Databases(3),Video:A set of temporally sequenced photographic data for presentation at specified rates for example,30 frames per second.Structured audio:A sequence of audio components comprising note,tone,duration,and so forth.Audio:Sample data generated from aural recordings in a s
40、tring of bits in digitized form.Analog recordings are typically converted into digital form before storage.,Chapter 29-34,2.1 Multimedia Databases(4),Composite or mixed multimedia data:A combination of multimedia data types such as audio and video which may be physically mixed to yield a new storage
41、 format or logically mixed while retaining original types and formats.Composite data also contains additional control information describing how the information should be rendered.,Chapter 29-35,2.1 Multimedia Databases(5),Nature of Multimedia Applications:Multimedia data may be stored,delivered,and
42、 utilized in many different ways.Applications may be categorized based on their data management characteristics as follows:Repository applications:A large amount of multimedia data as well as metadata is stored for retrieval purposes.Examples include repositories of satellite images,engineering draw
43、ings and designs,space photographs,and radiology scanned pictures.,Chapter 29-36,2.1 Multimedia Databases(6),Presentation applications:A large amount of applications involve delivery of multimedia data subject to temporal constraints;simple multimedia viewing of video data,for example,requires a sys
44、tem to simulate VCR-like functionality.Complex and interactive multimedia presentations involve orchestration directions to control the retrieval order of components in a series or in parallel.Interactive environments must support capabilities such as real-time editing analysis or annotating of vide
45、o and audio data.,Chapter 29-37,2.1 Multimedia Databases(7),Collaborative work using multimedia information:This is a new category of applications in which engineers may execute a complex design task by merging drawings,fitting subjects to design constraints,and generating new documentation,change n
46、otifications,and so forth.Intelligent healthcare networks as well as telemedicine will involve doctors collaborating among themselves,analyzing multimedia patient data and information in real time as it is generated.,Chapter 29-38,2.2 Data Management Issues,Multimedia applications dealing with thous
47、ands of images,documents,audio and video segments,and free text data depend critically on appropriate modeling of the structure and content of data and then designing appropriate database schemas for storing and retrieving multimedia information.Multimedia information systems are very complex and em
48、brace a large set of issues:Modeling complex objects,Chapter 29-39,2.2 Data Management Issues(2),Designconceptual,logical,and physical design of multimedia has not been addressed fully.Storagemultimedia data on standard disklike devices presents problems of representation,compression,mapping to devi
49、ce hierarchies,archiving,and buffering during the input/output operation.Queries and retrieval“database”way of retrieving information is based on query languages and internal index structures.,Chapter 29-40,2.2 Data Management Issues(3),Performancemultimedia applications involving only documents and
50、 text,performance constraints are subjectively determined by the user.applications involving video playback or audio-video synchronization,physical limitations dominate.,Chapter 29-41,2.3 Multimedia Database Applications,Large-scale applications of multimedia databases can be expected encompasses a
