Study Unit 3 - Application Architecture & Modelling

Middleware

Utility software that enables communication between different processors in a system.

Vertical partitioning vs. horizontal partitioning

Vertical partitioning assigns different columns to different servers. Horizontal partitioning assigns different rows to different servers.

Interface Architectures - Inputs, Outputs, & Middleware

- Batch inputs and outputs - Online inputs and outputs - Remote batch - Keyless data entry (and automatic identification) - Pen input - Electronic messaging and work group technology - Electronic Data Interchange (EDI) - Imaging and document interchange - Middleware

Client/Server Architecture — Servers

- Database server - a server that hosts one or more databases and executes all data manipulation commands at the server. - Transaction server - a server that hosts services which ensure that all database updates for a transaction succeed or fail as a whole. - Application server - a server that hosts application logic and services for an information system. - Messaging or groupware server - a server that hosts services for e-mail, calendaring, and other work group functionality. - Web server - a server that hosts Internet or intranet websites.

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.

Application architecture can be used as a 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

Computing Layers

1. Presentation layer—the user interface 2. Presentation logic layer—processing that must be done to generate the presentation, such as editing input data or formatting output data. 3. Application logic layer—the logic and processing to support business rules, policies, and procedures 4. Data manipulation layer—to store and retrieve data to and from the database 5. Data layer—the actual business data

Distributed data and application

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.

File server system

A LAN in which a server hosts the data of an information system.

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.

Distributed presentation

A client/server system in which the presentation and presentation logic layers are shifted from the server to reside on the client.

Distributed relational database

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

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.

Physical data flow diagram (DFDs)

A process model used to communicate the technical implementation characteristics of an information system.

Intranet

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

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.

Data partitioning vs. data replication

Data partitioning truly distributes rows and columns of tables to specific database servers with little or no duplication between servers. Data replication duplicates some or all tables on more than one database server.

Distributed system vs. centralized systems

Distributed system - a system in which components are distributed across multiple locations and computer networks. Centralized systems - a system in which all components are hosted by a central, multi-user computer.

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.

Network computing system

Presentation and presentation logic layers implemented in client-side Web browsers using content downloaded from a Web server.

Relational database

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.

Thin client vs. fat client

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.

Application architecture

a specification of the technologies to be used to implement information systems.