EXAM 2 - CH 13

File server system

a LAN in which a server hosts the data of an information system. -All other layers are implemented on the client computers. -Frequently excessive network traffic to transport data between servers and clients. -Client must be fairly robust ("fat") because it does most of the work. -Database integrity can be compromised.

Distributed data

a client/server system in which the data and data manipulation layers are placed on the server(s), and other layers are placed on the clients. -Sometimes called two-tiered client/server computing. -Difference to file server systems is where the data manipulation commands are executed. -Much less network traffic than file server systems because only the database requests and the results of those requests are transported across the network. -Database integrity is easier to maintain.

Data replication

duplicates some or all tables on more than one database server. -Propagates updates on one database server to any other database server where the data is duplicated.

Physical process

either a processor, such as a computer or person, or a technical implementation of specific work to be performed, such as a computer program or manual process.

The Tactical Application Architecture Strategy

-Defines architecture for each new system on an application-by-application basis as needed. -Requires feasibility analysis for each application.

Why the Trend Toward Distributed Systems?

-Modern businesses are already decentralized (distributed). -Distributed computing moves information and services closer to the customers and users who need them. -Distributed computing consolidates the power of personal computers across the enterprise. -Distributed computing solutions are in general more user-friendly because they use the PC as the user interface processor. -Personal computers and network servers are less expensive than mainframe computers

Data Distribution Options

-Store all data on a single server. -Store specific tables on different servers. -Store subsets of specific tables on different servers. -Replicate (duplicate) specific tables or subsets on different servers.

Process Distribution and Technology Assignments

1. For two-tiered client/server systems, all logical even diagrams are assigned to the client. 2. For three-tiered client/server and network computing systems, must closely examine each event's primitive (detailed) DFD. -Determine which primitive processes should be assigned to the client and which should be assigned to an application server. -Generally data capture and editing are assigned to servers -If different aspects of a single DFD are partitioned to different clients and servers, draw separate physical DFD for each.

Distributed relational database

A database system that duplicates tables to multiple database servers located in geographically important locations.

The Enterprise Application Architecture Strategy

Enterprise-wide information technology architecture to be followed in all development projects. -Approved network, data, interface, and processing technologies and development tools. -Strategy for integrating legacy systems and technologies. -On-going process for continuously reviewing application architecture. -On-going process for researching emerging technologies -Process for analyzing requests for variances from the above.

Distributed presentation

a client/server system in which the presentation and presentation logic layers are shifted from the server to reside on the client. -The application logic, data manipulation, and data layers remain on the server (frequently a mainframe). -Character user interface (CUI) -Graphical user interface (GUI)

Clean layering

a design strategy that requires that presentation, application, and data layers of an application be physically separated. -Allows components of each layer to be revised or enhanced without affecting the other layers

Client/server system

a distributed computing solution in which the presentation, presentation logic, application logic, data manipulation, and data layers are distributed between client PCs and one or more servers.

Software development environment (SDE)

a language and tool kit for developing applications.

Thin client

a personal computer that does not have to be very powerful because it only presents the user interface to the user.

Fat client

a personal computer, notebook computer, or workstation that is typically powerful.

Network architecture

a physical DFD that allocates processors (clients and servers) and devices (machines and robots) to a network and establishes: -the connectivity between clients and servers -where users will interface with the processors

Physical data flow diagram (DFDs)

a process model used to communicate the technical implementation characteristics of an information system. Communicate technical choices and other design decisions to those who will actually construct and implement the system.

Intranet

a secure network that uses Internet technology to integrate desktop, work group, and enterprise computing into a cohesive framework.

Design unit

a self-contained collection of processes, data stores, and data flows that share similar design characteristics. -A __________ serves as a subset of the total system whose inputs, outputs, files and databases, and programs can be designed, constructed, and tested as a self-contained unit. -Ultimately, __________ must be integrated into a whole system.

Web server

a server that hosts Internet or intranet websites.

Application server

a server that hosts application logic and services for an information system.

Database server

a server that hosts one or more databases and executes all data manipulation commands at the server.

Messaging or groupware server

a server that hosts services for e-mail, calendaring, and other work group functionality.

Transaction server

a server that hosts services which ensure that all database updates for a transaction succeed or fail as a whole.

Local area network (LAN)

a set of client computers (PCs) connected over a relatively short distance to one or more servers.

Distributed relational database management system

a software program that controls access to and maintenance of stored data in the relational format.

Application architecture

a specification of the technologies to be used to implement information systems. The blueprint to communicate the following design decisions: -The degree to which the information system will be centralized or distributed. -The distribution of stored data. -The implementation technology for software developed in-house. -The integration of commercial off-the-shelf software. -The technology to be used to implement the user interface. -The technology to be used to interface with other systems

Centralized systems

a system in which all components are hosted by a central, multi-user computer. -Users interact with the system via terminals (or a PC emulating a terminal). -Virtually all the actual processing and work is done on the host computer.

Distributed system

a system in which components are distributed across multiple locations and computer networks. -Accordingly, the processing workload is distributed across multiple computers on the network.

Distributed data and application

client/server system: 1. The data and data manipulation layers are placed on their own server(s), 2. The application logic is placed on its own server, 3. The presentation logic and presentation layers are placed on the clients. -Also called three-tiered or n-tiered client/server computing. -Requires design partitioning.

Network computing system

presentation and presentation logic layers implemented in client-side Web browsers using content downloaded from a Web server. -Presentation logic layer connects to application logic layer running on application server, which connects to database servers on the backside of the system. -The greatest potential of this approach is its applicability to redesign of traditional information systems to run on an intranet.

Presentation logic layer

processing that must be done to generate the presentation, such as editing input data or formatting output data.

Relational database

stores data in tabular form. Each file is implemented as a table. Each field is a column in the table. Related records between two tables are implemented by intentionally duplicated columns in the two tables.

Data layer

the actual business data

Partitioning

the art of determining how to best distribute (duplicate) application components across the network.

Application logic layer

the logic and processing to support business rules, policies, and procedures

Electronic Data Interchange (EDI)

the standardized electronic flow of business transactions or data between businesses. Typically, many businesses must agree to a common data format to make EDI feasible.

Presentation layer

the user interface

Data manipulation layer

to store and retrieve data to and from the database

Data partitioning

truly distributes rows and columns of tables to specific database servers with little or no duplication between servers. -Vertical partitioning assigns different columns to different servers. -Horizontal partitioning assigns different rows to different servers.

Middleware

utility software that enables communication between different processors in a system. -It may be built into the respective operating systems or added through purchased middleware products. -Presentation middleware -Application middleware -Database middleware