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1、体系结构和流程设计体系结构和流程设计的应用的应用知识素材知识素材日日 程程第一部分 何谓信息系统的体系结构第二部分 集中式和分布式的体系结构第三部分 信息系统设计中的数据库设计第四部分 用户和数据系统界面问题第五部分 大标题5第六部分 大标题63Application Architecture&Process DesignIntroduction:The chapter will address the following questions:What is an information systems architecture in terms of DATA,PROCESSES,INTER
2、FACES,and NETWORKS the building blocks of all information systems?What are both centralized and distributed computing alternatives for information system design,including various client/server and Internet/intranet options?What are the database and data distribution alternatives for information syst
3、em design?What are the make versus buy alternatives and variations for information system design?What are the user and system interface alternatives for information system design?4Application Architecture&Process DesignIntroduction:The chapter will address the following questions:What are the variou
4、s networking topologies and their importance in information system design?What are the methods for general application architecture and design?What are the differences between logical and physical data flow diagrams,and explain how physical data flow diagrams are used to model application architectu
5、re and guide process design?How do you draw physical data flow diagrams for a system/application?5Application Architecture&Process DesignGeneral System Design:During general systems design the basic technical decisions are made.These decisions include:Will the system use centralized or distributed?W
6、ill the systems data stores be centralized or distributed?If distributed,how so?What data storage technology(s)will be used?Will software be purchased,built in-house,or both?For programs to be written,what technology(s)will be used?How will users interface with the system?How will data be input?How
7、will outputs be generated?How will the system interface to other,existing systems?6Application Architecture&Process DesignGeneral System Design:The decisions made during general systems design constitute the application architecture of the system.An application architecture defines the technologies
8、to be used by(and to build)one,more,or all information systems in terms of its data,process,interface,and network components.It serves as a framework for general design.7Application Architecture&Process Design8Application Architecture&Process DesignInformation Technology Architecture:Network Archite
9、ctures for Client/Server Computing What is client/server computing?8A client is single-user computer that provides(1)user interface services,appropriate database and processing services;and(2)connectivity services to servers(and possibly other clients).8A server is a multiple-user computer that prov
10、ides(1)shared database,processing,and interface services;and(2)connectivity to clients and other servers.8In client/server computing an information systems database,software,and interfaces are distributed across a network of clients and servers which communicate and cooperate to achieve system objec
11、tives.Despite the distribution of computing resources,each system user perceives that a single computer(their own client PC)is doing all the work.9Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server ComputingClient/server computing is an
12、 alternative to traditional centralized computing.8In centralized computing,a multi-user computer(usually a mainframe or minicomputer)hosts all of the information system components including(1)the data storage(files and databases),(2)the business logic(software and programs),(3)the user interfaces(i
13、nput and output),and(4(any system interfaces(networking to other computers and systems).The user may interact with this host computer via a terminal(or,today,a PC emulating a terminal),but all of work is actually done on the host computer.10Application Architecture&Process Design11Application Archit
14、ecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Centralized Computing:8Centralized process architectures were once dominant because the cost of placing computers closer to the end-user was prohibitive.8Many(if not most)legacy applications re
15、main centralized on large mainframe computers(such as IBMs S/370 and 3090 families of computers)or smaller minicomputers(such as IBMs AS/400).12Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Presentation:8This
16、alternative builds upon and enhances centralized computing applications.8The old character user interfaces are stripped from the centralized applications and regenerated as graphical user interfaces that will run on the PC.8The user interface(or presentation)is distributed off the server and onto th
17、e client.8All other elements of the centralized application remain on the server,but the system users get a friendlier graphical user interface to the system.13Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Pre
18、sentation:8Distributed presentation computing advantages:It can be implemented relatively quickly since most aspects of the legacy application remain unchanged.Users get a friendly and familiar interface to existing systemsThe useful lifetime of legacy applications can be extended until such a time
19、as resources warrant a wholesale redevelopment of the application.8Distributed presentation computing disadvantages:The applications functionality cannot be significantly improved,and the solution does not maximize the potential of the clients desktop computer by only dealing with the user interface
20、.14Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Data:8Sometimes called two-tiered client/server.8This architecture places the information systems stored data on a server,and the business logic and user interf
21、aces on the clients.8A local or wide area network usually connects the clients to the server.A local area network(or LAN)is a set of client computers(usually PCs)connected to one or more server computers(usually microprocessor-based,but could also include mainframes or minicomputers)through cable ov
22、er relatively short distances.A wide area network(or WAN)is an interconnected set of LANs,or the connection of PCs over a longer distance.15Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Data:8The database serv
23、er is fundamental to this architecture and its technology is different from a file server.File servers store the database,but the client computers must execute all database instructions.This means that entire databases and tables may have to be transported to and from the client across the network.D
24、atabase servers also store the database,but the database commands are also executed on those servers.The clients merely send their database commands to the server.The server only returns the result of the database command processing not entire databases or tables.Thus,database servers generate much
25、less network traffic.16Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Data:8The clients in the distributed database solution typically run the business logic of the information system application.8Distributed d
26、ata computing advantages:Separates data and business logic to(1)isolate each from changes to the other,(2)make the data more available to users,and(3)retain the data integrity of centralized computing through centrally managed servers.8Distributed data computing disadvantages:The application logic m
27、ust be maintained on all of the clients.17Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Data and Logic:8Referred to as three-tiered or n-tiered client/server computing.8This approach distributes databases and
28、business logic to separate servers.8Uses the same database server(s)as in the two-tiered approach.8Uses an application server.The application server provides a transaction monitor such as to manage transactions.Some or all of the business logic of the application can be moved from the client to the
29、application server.8Only the user interface and some relatively stable or personal business logic need be executed on the clients.18Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing Distributed Data and Logic:8Distributed dat
30、a and logic computing disadvantages:Very complex to design and development.The most difficult aspect of three-tier client/server application design is partitioning.Partitioning is the act of determining how to best distribute or duplicate application components(data,process,and interfaces)across the
31、 network.19Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Internet and Intranets:8The Internet is an(but not necessarily the)information superhighway that permits computers of all types and sizes,all over the world to
32、exchange data and information using standard languages and protocols.8An intranet is a secure network,usually corporate,that uses Internet technology to integrate desktop,workgroup,and enterprise computing into a single cohesive framework.The intranet provides management and users with a common inte
33、rface to applications and information20Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Internet and Intranets:8Java is a cross-platform programming language designed specifically to exploit the Internet standards.Java a
34、pplets(modular software components)are stored on an Internet or intranet server and downloaded to the client when they access the application.Java applets can execute on any client computing platform.8A network computer(or NC)is designed to only run Internet-based applications(such as web browsers a
35、nd Java applets).The NC(also called a thin client)is simpler,and much cheaper than personal computers(increasingly called a fat client).21Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Role of Network Technologies:8The
36、 well designed network provides connectivity and interoperability.Connectivity defines how computers are connected to“talk”to one another.Interoperability is an ideal state in which connected computers cooperate with one another in a manner that is transparent to their users(the clients).Network top
37、ology describes how a network provides connectivity between the computers on that network.22Application Architecture&Process Design23Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Role of Network Technologies:8The Bus
38、network topology:A direct point-to-point link between any two computer systems.The simplest network topology.The network can contain mainframes,minicomputers(or mid-range computers),personal computers,and dumb and intelligent terminals.To completely connect all points between n computers,you would n
39、eed n times(n-1)/2 direct paths.Only one computer can send data through the bus at any given time.24Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Role of Network Technologies:8The Ring network topology:Connects multip
40、le computers and some peripherals into a ring-like structure.Each computer can transmit messages,instructions,and data(called packets)to only one other computer(or node on the network).Every transmission includes an address.When a computer receives a packet,it checks the address and if the packets a
41、ddress is different than the computers address,it passes it on to the next computer or node.Ring networks generally transmit packets in one direction;therefore,many computers can transmit at the same time to increase network throughput.25Application Architecture&Process DesignInformation Technology
42、Architecture:Network Architectures for Client/Server Computing The Role of Network Technologies:8The Star network topology:Links multiple computer systems through a central computer.The central computer does not have to be a mainframe or minicomputer.Central computer could be an application server t
43、hat manages the transmission of data and messages between the other clients and servers(as in the n-tier model).26Application Architecture&Process DesignInformation Technology Architecture:Network Architectures for Client/Server Computing The Role of Network Technologies:8The Hierarchical network to
44、pology:Can be thought of as a multiple star network,where the communications processors are arranged in a hierarchy.The top computer system(usually a mainframe)controls the entire network.8All network topologies operate according to established network protocols that permit different types of comput
45、ers to communicate and interoperate.27Application Architecture&Process DesignInformation Technology Architecture:Data Architectures for Distributed Relational DatabasesThe underlying technology of client/server computing has made it possible to distribute data without loss of centralized control.8Th
46、is control is being accomplished through distributed relational databases.A relational database stores data in a tabular form.Each file is implemented as a table.Each field is a column in the table.Each records in the file is a row in the table.Related records between two tables are implemented by i
47、ntentionally duplicating columns in the two tables.A distributed relational database distributes or duplicates tables to multiple database servers(and in rare cases,clients).28Application Architecture&Process DesignInformation Technology Architecture:Data Architectures for Distributed Relational Dat
48、abasesThe software required to implement distributed relational databases is called a distributed relational database management system.8A distributed relational database management system(or distributed RDBMS)is a software program that controls access to,and maintenance of the stored data.It also p
49、rovides for backup,recovery and security.It is sometimes called a client/server database management system.29Application Architecture&Process DesignInformation Technology Architecture:Data Architectures for Distributed Relational DatabasesWhat sets a distributed RDBMS apart from a PC RDBMS is the da
50、tabase engine.8The database engine is that part of the DBMS that executes database commands to create,read,update,and delete records(rows)in the tables.In a PC RDBMS,the database engine that processes all database commands must execute on the client PC,even if the data is actually stored on the serv