Friday, December 5, 2014

05. Technical Infrastructure of a Digital Library

इस ब्लॉग्स को सृजन करने में आप सभी से सादर सुझाव आमंत्रित हैं , कृपया अपने सुझाव और प्रविष्टियाँ प्रेषित करे , इसका संपूर्ण कार्य क्षेत्र विश्व ज्ञान समुदाय हैं , जो सभी प्रतियोगियों के कॅरिअर निर्माण महत्त्वपूर्ण योगदान देगा ,आप अपने सुझाव इस मेल पत्ते पर भेज सकते हैं -

05. Technical Infrastructure of a Digital Library

P- 01. Digital Libraries*

By :Jagdish Arora, Paper Coordinator


1 / 1 Points

Question 1: Multiple Choice

........................ is the right management software.
  • Wrong Answer Un-checked Apache
  • Correct Answer Checked Active Directory
  • Wrong Answer Un-checked Dspace
  • Wrong Answer Un-checked GNU E-Prints
1 / 1 Points

Question 2: Multiple Choice

In Cloud Computing, data and application resides on ……………………
  • Wrong Answer Un-checked Desktop Machine
  • Correct Answer Checked Public/Private Network
  • Wrong Answer Un-checked Interanet
  • Wrong Answer Un-checked Local Server
0 / 1 Points

Question 3: Multiple Choice

Which device is not required for implementing Image based digital library?
  • Wrong Answer Un-checked Scanner
  •  Un-checked Printer
  • Wrong Answer Checked Camera
  • Wrong Answer Un-checked Touch screen system
1 / 1 Points

Question 4: Multiple Choice

Which Digital Library Software is maintained by DuraSpace?
  • Wrong Answer Un-checked GreenStone
  • Correct Answer Checked FEDORA
  • Wrong Answer Un-checked CONTENTdm
  • Wrong Answer Un-checked GNU E-Prints
1 / 1 Points

Question 5: Multiple Choice

Which Digital Library Software is using MySQL as backend?
  • Wrong Answer Un-checked CONTENTdm
  • Wrong Answer Un-checked Dspace
  • Correct Answer Checked GNU E Prints
  • Wrong Answer Un-checked GreenStone
0 / 1 Points

Question 6: Multiple Choice

Which is not a Digital Library Software?
  • Wrong Answer Un-checked FEDORA
  • Wrong Answer Checked CONTENTdm
  • Wrong Answer Un-checked Dspace
  •  Un-checked SOUL
0 / 1 Points

Question 7: Multiple Choice

Which is not Open-Source Digital Library Software?
  • Wrong Answer Un-checked Dspace
  • Wrong Answer Checked FEDORA
  •  Un-checked CONTENTdm
  • Wrong Answer Un-checked GreenStone
0 / 1 Points

Question 8: Multiple Choice

Which is not required to create a DIGITAL LIBRARY?
  • Wrong Answer Un-checked Digital Library Software
  •  Un-checked RFID Tag
  • Wrong Answer Checked Database Management System
  • Wrong Answer Un-checked Web Server
0 / 1 Points

Question 9: Multiple Choice

Which is the major metadata type used for authentication in Preservation Description Information?
  • Wrong Answer Un-checked Reference Information
  • Wrong Answer Un-checked Provenance Information
  • Wrong Answer Checked Context Information
  •  Un-checked Fixity Information
1 / 1 Points

Question 10: Multiple Choice

………………………… is NoSQL Database.
  • Wrong Answer Un-checked MySQL
  • Wrong Answer Un-checked Oracle
  • Correct Answer Checked MongoDB
  • Wrong Answer Un-checked Postgres
5 / 10 PointsFinal Score:


The objectives of this module are to discuss and impart knowledge on broader aspects of technical infrastructure of a digital library i.e.computers and network infrastructure requirement including server-side hardware components, server-side software components, and client-side hardware & software components as well as role of cloud computing in digital libraries.

1.0 Introduction

The Internet and web technology are principle mechanism deployed in a digital library to search, navigate and deliver electronic resources across the globe. The primary objective of digital library is to meet the information need of its users. Digital libraries have to be more and more responsive by maximising the innovative impact of advancement in information and communication technology. Development in information and communication technology have greatly changed the way of information handling. To establish digital library there must be  infrastructure for managing, indexing and disseminating multimedia content. A scalable technical infrastructure needs to be carefully planned to meet the functional requirement of digital library. This module will discuss the core infrastructure elements that can handle volumonous content and other complexities of digital library.

Hardware, server allocations, databases and distribution approaches, network infrastructure and bandwidth considerations, are key in establishing the digital library as a resource that teachers, students, researchers, and the general public regard as reliable.

2. Networks and Computing Infrastructure

Establishing digital library requires a great deal of computer (both software and hardware) and network  infrastructural components that are not available off-the-shelf as packaged solution. There are no turn-key, monolithic systems available for digital libraries, instead digital libraries are collection of disparate systems and resources connected through a network, and integrated within one interface, currently the web interface. Use of open architecture, standard and protocols, however, make it possible that pieces of required infrastructure, be it hardware, software or accessories, are gathered from different vendors and integrated to construct a working environment. While some of the components required for establishing digital library would be internal to the institutions, but several others would be distributed across the Internet, owned and controlled by a large number of independent players.  The task of building a digital library, therefore, requires a great deal of integration of various components (Flecker, D., 2000).

A digital library implementation requires a enterprise-level technology solution  that is scalable both in size and functionalities with built-in reliability, availability and serviceability (RAS) features (Wright, 2002).  The storage capacity of a digital library should be scalable to accommodate its ever growing collection without requiring redesign and reengineering of system design as requirements grow. The use of open systems architecture provides robust platform, digital library management solutions and development tools. Curent servers from multiple vendors are being used by several digital library implementations for its scalability, and RAS features. These  servers also offer high-availability features  such as full hardware redundancy, fault-isolated dynamic system domains, concurrent maintenance and clustering support along with offerings for modular storage capacity that can be added incrementally.

A typical digital library in a distributed client-server environment consists of hardware and software components at server side as well as at client’s side. Clients are machines that are used for accessing digital library by users while the server hosts databases, digital objects, browse and search interfaces to facilitate its access. 

2.1 Server-side Hardware Components

Servers are the heart of a digital library. Server for digital library implementation need to be computationally powerful, have adequate main memory (RAM) to handle the expected work, have large amount of secure disc storage for the database(s) and digital objects and have adequate network bandwidth to meet communication requirements. A digital library may need a number of specialized servers for different tasks so as to distribute the workload on to different servers. It would require one or more object server(s) to store digital objects and other multimedia objects, an index server that maintains indices and support searching of data stored in a distributed system and last but not least a rights management system to take care of unauthorized usage and intellectual property right issues. However, for a smaller library, many distinct activities can be performed on a single server. It is important that the server is scalable so that additional storage, processing power or networking capabilities can be added whenever required.

2.1.1 Input Devices

Image-based digital library implementation require input devices like scanners, digital cameras, video cameras, and  touch screens systems. A large range of choices are available for these image capturing devices.  Scanners are available in all sizes and shapes. Flatbed scanners or digital cameras mounted on book cradle are more suitable for libraries. Details on such input devices are available in modules on digitization as well as in modules under the paper ICT Applications in Libraries. 

2.1.2 Storage Devices

Since digital libraries require large amounts of storage, particular attention need to be given to the storage solution. A digital library would require one or more servers to store raw data (images, text, video, etc.) indices of metadata so as to retrieve information from the digital libraries in desired fashion. Digital library collections that are too large to store entirely on a disk use hierarchical storage mechanisms (HSM). In an HSM, the most frequently used data is kept on fast disks while less frequently used data is kept in nearline such as an automated (robotic) tape library. An HSM can automatically migrate data from tape to disk and vice-versa as required.  Intelligent storage area networks (SAN) and Network Attached Storage (NAS) are now available in which the physical storage devices are intelligently controlled and made available to a number of servers.

Redundancy is another important storage consideration. In a system that is completely dependent on the interaction of various kinds and levels of hardware and software, failure in any one of the subsystems could mean the loss or corruption of the information object. Effective storage management thus means providing for redundant copies of the archived objects to ensure availability of documents in case of loss. A number of RAID (Redundant Array of Inexpensive Disks) models are now available for greater security and performance. The RAID technology distributes the data across a number of disks in a way that even if one or more disks fail, the system would still function while the failed component is replaced. Digital archives may also choose to make backup copies on their own or to make arrangements for other sites to serve as backup.

Although harddisc (fixed and removable) solutions are increasingly available at an affordable cost, optical storage devices including CD ROM, DVD ROM, BlueRay or opto-magnetic devices in standalone or networked mode, are attractive alternatives for long-term storage of digital information. Optical drives record information by writing data onto the disc with a laser beam. The media offer enormous storage capabilities.

2.1.3 Communication Devices

Setting-up a digital library requires network and communication equipment like communication switches, routers, hubs, repeaters, modems and other items required in a Local Area Network or to connect Internet. These hardware and software items are required for setting-up any network and are not specific to a digital library.

2.2 Server-side Software Components

A typical digital library requires a number of software packages to handle its highly diversified resources, activities and services. Different software are required to handle different components and activities of a digital library. Software required for a digital library can broadly be categories into the following two categories:

2.2.1 Software Required for Content Creation

A document capturing software is required for scanning legacy documents that are not available in computer-processible file.  Most scanners and digital camera come with a basic image capturing software. The images captured in the process may need manipulation to enhance their quality. Software like Adobe’s Photoshop or open source GIMP (GNU Image Manipulation Program) provides image enhancement features like filters, tonal reproduction, colour management, touch, crop, image sharpening, contrast, transparent background, etc. Software like  ABBYY FineReader provides multiple functionalities like image capturing, image enhancement and OCR.

Printed text, pictures and figures captured in the process of scanning are stored in a file as a bit-mapped page image, irrespective of the fact whether a scanned page contains a photograph, a line drawing or text. A bit-mapped page image is a type of computer graphic, literally an electronic picture of the page which can most easily be equated to a facsimile image of the page and as such it can be read by humans, but not by the computers. As such “text” in a page image is not searchable on a computer. The bit-mapped pages are converted into texual files using Optical Character Recognition (OCR) software. Most document imaging software have OCR package in-built. However, OCR packages, such as Scansoft, OmniPage Professional and ABBYY FineReader, are also available as separate utilities. Acrobat Capture also has an OCR built into it. Converting material already available in digital format into PDF requires Acrobat Software Suite (or other conversion software).

2.2.2 Software Required for Operations of Digital Library

Like any other server, a server for digital library requires an operating system. De facto operating system for most digital library implementation is Unix and its varient such as Linux. As digital libraries are built around Web and Internet technology, the server for a digital library requires a web server software likeApache’s httpd or Microsoft’s Internet Information Server  (IIS).

Organization of digital objects with associated metadata requires a RDBMS package such as Oracle, MySQL, MS SQL, PostgreSQLor NoSQL packages like Cassandra, MongoDB etc. The database management software provide structured storage and retrieval facilities to the contents of a digital library. Further, a digital library requires a search engine connected to a DBMS to support searching of digital objects stored in it. Dspace, for example uses Apache Lucene search engine. Moreover, contents of a  digital library may have to be offered to only authorized users. The right management software such as InterTrust Systems Developer’s Kit,Active Directory by Microsoft facilitates control and monitor of access to contents of a digital library.

Since a single integrated software package from a single vendor is not available, a digital library software may be a system with components added onto an open architecture framework. For example, the Dspace, a popular, open source digital library software consists of as number of software like: Web server, DBMS (Postgres or Oracle), Apahce Tomcat, Apache Ant, Java, Handles and Lucene Search Engine. Some of the important digital library software are described briefly below.

2.2.3 Digital Library Software

A number of digital libraries are being constructed at present utilizing a mixture of information retrieval, media management and web server packages. All these pieces of software need to be integrated so as to present a cohesive environment and to avoid problems with growth and expansion. However, there are few software packages that attempts to provide a number functions of a digital library in an integrated fashion. Some of the important software used in setting-up a digital library are:

DSpace ( was developed in partnership between Hewlett-Packard (HP) and MIT (Massachusetts Institute of Technology) and being maintained by DuraSpace foundation. Dspace, as institutional repository software, is making its mark with an increasing number of institutions around the globe installing, evaluating and using the package. The latest stable version is 4.0 and is available for download at

DSpace captures, stores, indexes, preserves, and redistributes the intellectual output of a institution’s research faculty in digital formats. DSpace accepts all forms of digital materials including text, images, video, and audio files. Possible content includes: articles and preprints, technical reports, working papers, conference papers, e-theses, datasets (statistical, geospatial, matlab, etc.), images (visual, scientific, etc.), audio files, video files, learning objects and reformatted digital library collections.

Greenstone Digital Library (GSDL)is a suite of software which has the ability to serve digital library collections and build new collections. It provides a new way of organizing information and publishing it on the Internet or on CD-ROM. The Greenstone Digital Library Software is produced by the New Zealand Digital Library Project at the University of Waikato, and distributed in cooperation with UNESCO and the Humanities Library Project. It is open-source software, available from under the terms of the GNU General Public License. The New Zealand Digital Library Web site ( contains numerous example collections, all created with the Greenstone software. The Greenstone runs on Windows and Linux platform. The distribution includes ready-to-use binaries for all versions of Windows and for Linux. It also includes complete source code for the system, which can be compiled using appropriate compiler. Greenstone works with associated software that is also freely available: the Apache Web server and PERL.

GNU E-Prints  is an open source digital library software package designed primarily to create institutional repositories ( The default configuration creates a research papers archive. With its origins in the scholarly communication movement, E-prints default configuration is geared to research papers but it can be adapted for other purposes and content. It was developed at the Electronics and Computer Science Department of the University of Southampton. GNU E-Prints is freely distributable and subject to the GNU General Public License. The latest version is 3.3.12 and is available for download at Installing the E-prints software is relatively easy. Knowledge of MySql (used as backend database), apache WWW server and Perl programming language would be helpful. Mod_perl module for Apache significantly increases the performance of Perl scripts. Complete documentation for installation of E-prints is available on the web site (

The CONTENTdm from OCLC is a multimedia software suite that provides easy loading, management and access to media archives in a library. The software provides tools to assist with every phase of collection development. One can start small with a few items or CONTENTdm can handle databases with millions of objects. The CONTENTdm technology is based on years of university research and testing that have resulted in a proven set of programs.

FEDORA (Flexible Extensible Digital Object Repository Architecture) repository system ( is an open source, digital object repository system developed jointly by University of Virginia Library and Cornell University and now being maintained by DuraSpace Foundation. The Fedora project is devoted to the goal of providing open-source repository software that can serve as the foundation for many types of information management systems. The software demonstrates how distributed digital information management can be deployed using web-based technologies, including XML and web services. Some of the important features of FEDORA includes:

  • XML submission and storage: Digital objects are stored as XML-encoded files that conform to an extension of the Metadata Encoding and Transmission Standard (METS) schema.
  • Parameterized disseminators: Behaviors defined for an object support user-supplied options that are handled at dissemination time.
  • Access Control and Authentication: Although Advanced Access Control and Authentication are not scheduled until Phase II of the project, a simple form of access control has been added in Phase I of the project to provide access restrictions based on IP address. IP range restriction is supported in both the Management and Access APIs. In addition, the Management API is protected by HTTP Basic Authentication.
  • Default Disseminator: The Default Disseminator is a built-in internal disseminator on every object that provides a system-defined behavior mechanism for disseminating the basic contents of an object.
  • Searching: Selected system metadata fields are indexed along with the primary Dublin Core record for each object. The Fedora repository system provides a search interface for both full text and field-specific queries across these metadata fields.
  • OAI Metadata Harvesting: The OAI Protocol for Metadata Harvesting is a standard for sharing metadata across repositories. Every Fedora digital object has a primary Dublin Core record that conforms to the schema. This metadata is accessible using the OAI Protocol for Metadata Harvesting, v2.0.
  • Batch Utility: The Fedora repository system includes a Batch Utility as part of the Management client that enables the mass creation and loading of data objects.

2.3 Client-side Hardware & Software Components

Clients are the machines that reside on the user’s desks.  Planners of the digital library, therefore, need to prescribe minimum level of hardware and software that a user would require so as to achieve efficient and effective interaction with the digital library. Most digital library require an Internet-enabled multimedia PC (or Machintosh) or a tabletequipped with an Internet Browser like Internet Explorer,Mozilla FireFox or Google Chrome  as their clients. The client-side PCs may also require the following software packages (plug-ins) to download format-specific deliverables from a digital library:

Internet Browser
Google Chrome
Internet Explorer
Mozilla Firefox
Reading PDF Files
Acrobat Reader(Adobe)
For Playing Audio and Video Files
Real Player
VLC Player
File Transfer Client
Display and printing of Word, Powerpoint , Access Documents
Microsoft Office
Open Office
TIFF Images
TIFF Viewer

Image Manipulation and Editing
GIMP (The GNU Image Manipulation Program)
Video Editing
Adobe Premier

3.0 Digital Libraries and Cloud Computing

Cloud computing can be understood as a way to use off-site computer processing power to replace content creation and servers that were traditionally hosted onsite. In layman’s terms this means “using Web services for our computing needs” (Kroski, 2009). Cloud computer allows content creation to be made “when data and software applications reside on and are drawn from the network rather than locally on any one workstation”. By utilizing online applications, users can create and save their files online, share content, work collaboratively with others or create entire services that can all be accessed online without need of having the programs on their own computer.  These online services can reduce the need for expensive software, hardware, and even advanced technical knowledge from library staff since cloud computing services are often streamlined to be very user-friendly.

The cloud computing can be advantageous and it will increase the ability of a library to try out new software without having to buy the hardware as well as being able to scale the computing power to meet the demand of users. A library can increase quantum of cloud computing they require by contacting their vendor instead of physically acquiring new hardware to meet increased demands. This approach will be quite cost effective in terms of money and manpower. Followings are the general advantages of having digital library on cloud:

  • Compliant facilities and processes
  • Cost effective
  • Enterprise grade services and management
  • Faster provisioning of systems and applications
  • Flexible and innovative
  • Flexible and resilient in disaster recovery
  • Highly secured infrastructure
  • Reduces hardware and maintenance cost
  • Round the clock access
  • Simplicity of integration
  • Simplified cost and consumption model

4.0 Summary

Digital libraries are built around Internet and web technologies. A typical digital library implementation follow client-server architecture as does the Internet and web technology. Client-server architecture as applied to the digital library is discussed broadly, however utmost care needs to be taken to create sustainable digital library with proper balancing between economy and technicalities ensuring long term preservation.

References and Reading List

Davis, J.R. and Lagoze, C. NCSTRL: Design and development of a globally distributed digital library. Journal of the American Society for Information Science, 51(3), 273-280, 2000.

Ferrer, Robert. University of Illinois: the federation of digital libraries: Amongst heterogeneous information systems. Science and Technology Libraries, 17(3&4), 81-119, 1999.

Fox, E.A. and Powell, J. Multilingual federated searching across heterogeneous collections.  D-Lib Magazine, September, 1998.

Fox, E.A. et al. Networked Digital Library of Theses and Dissertations: bridging the gaps for global access. Part. 1: Mission and progress. D-Lib Magazine, 7(9), 2001.

Fox, E.A. et al. Networked Digital Library of Theses and Dissertations: bridging the gaps for global access. Part. 2: Services and research, D-Lib Magazine, 7(9), 2001.

Kahn, Robert and Wilensky, Robert. A framework for distributed digital object services. cnri.dlib/tn95-01, May 13, 1995. (

Kardorf, B. SGML and PDF: Why we need both. Journal of Electronic Publishing, 3(4), 1998. 14p. (

Lagoze, C.  and Fielding, D. Defining collections in distributed digital libraries. D-Lib Magazine, November, 1998

Paepcke, A.,  Chang, C-C.K., Garcia-Molina, H. and Winograd, T. Interoperability for digital libraries worldwide. Communications of the ACM, 41(4), 33-43, 1998.

Payette, S., Blanchi, C., Lagoze, C. and Overly, E.A. Interoperability for digital objects and repositories.  D-Lib Magazine, 5(3), May1999.

Sayer, Donald, et al (2001). The Open Archival Information System (OAIS) Reference Model and its usage.

Sheth, A.P. and Larson, J.A. federated database systems for managing distributed, heterogeneous and autonomous databases. ACM Computing Surveys, 22, 183-236, 1990.



BMP file format - The BMP file format, also known as bitmap image file or device independent bitmap (DIB) file format or simply a bitmap, is a raster graphics image file format used to store bitmap digital images, independently of the display device (such as a graphics adapter), especially on Microsoft Windows and OS/2 operating systems.

Blu-ray Disc (BD) - A type of high-definition optical disc introduced by Sony in 2006, BD quickly outdistanced HD-DVD (abandoned by Toshiba in 2008) in the emerging market for this new high-capacity storage medium. Named for the blue-violet laser used to read data in BD players, Blu-ray provides the highest resolution HDTV is capable of reproducing. Because the blue laser has a shorter wavelength than the red beam used to read standard DVDs, Blu-ray discs have a storage capacity five times greater (50 gigabytes) than standard DVDs. On discs that have become scratched, the greater data compression increases the likelihood of playback problems.

CD ROM- Compact Disc-Read Only Memory (pronounced "see dee rahm"), a small plastic optical disk similar to an audio compact disc, measuring 4.72 inches (12 centimeters) in diameter, used as a publishing medium and for storing information in digital format. Stamped by the producer on the metallic surface, the data encoded on a CD-ROM can be searched and displayed on a computer screen but not changed or erased. The disc is read by a small laser beam inside a device called a CD-ROM drive.

Cloud Computing - A marketing term for the delivery of computing technologies as a service rather than a product, allowing capital expenditure to be converted into operating expenditure. In this model, software, data access, and storage are provided to computers and other devices over a network as a shared IT service. The end-user sees only interface software and has no need to know the physical location or configuration of the delivery system.

DVD ROM- A new type of read-only compact disc that can hold a minimum of 4.7GB (gigabytes), enough for a full-length movie.

Communication Switches - In computer networking and telecommunications, switched communication network is a communication network which uses switching for connection of two non-adjacent nodes. Switched Communication Networks are divided into circuit switched networks, message switched networks, and packet switched networks.

Client-server Environment - The client–server model of computing is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate over a computer network on separate hardware, but both client and server may reside in the same system. A server host runs one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server's content or service function. Clients therefore initiate communication sessions with servers which await incoming requests.

Distributed System - Distributed computing is a field of computer science that studies distributed systems. A distributed system is a software system in which components located on networked computers communicate and coordinate their actions by passing messages. The components interact with each other in order to achieve a common goal.

Document Capturing Software - Document Capture Software refers to applications that provide the ability and feature set to automate the process of scanning paper documents. Most scanning hardware, both scanners and copiers, provides the basic ability to scan to any number of image file formats, including: PDF, TIFF, JPG, BMP, etc. This basic functionality is augmented by document capture software, which can add efficiency and standardization to the process.

Hierarchical Storage Mechanisms (HSM) - Hierarchical storage Mechanisms (HSM) is a data storage technique, which automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as hard disk drive arrays, are more expensive (per byte stored) than slower devices, such as optical discs and magnetic tape drives. While it would be ideal to have all data available on high-speed devices all the time, this is prohibitively expensive for many organizations. 

Hubs - An Ethernet hub, active hub, network hub, repeater hub, multiport repeater or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming.

Index Server - Index Server is based on catalogs (Index Server's term for the index and related files) and directories. A catalog in Index Server is like a search root, where you make queries. It can contain one or more directories on separate locations.

Intellectual Property Rights - Intellectual property (IP) refers to creations of the mind, such as inventions; literary and artistic works; designs; and symbols, names and images used in commerce. IP is protected in law by, for example, patents, copyright and trademarks, which enable people to earn recognition or financial benefit from what they invent or create. By striking the right balance between the interests of innovators and the wider public interest, the IP system aims to foster an environment in which creativity and innovation can flourish.

Main memory see RAM - Computer data storage, often called storage or memory, is a technology consisting of computer components and recording media used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but larger and cheaper options farther away. Often the fast, volatile technologies (which lose data when powered off) are referred to as "memory", while slower permanent technologies are referred to as "storage", but these terms can also be used interchangeably.

Modems - A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information and demodulates the signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data.

Monolithic Systems- A software system is called "monolithic" if it has a monolithic architecture, in which functionally distinguishable aspects (for example data input and output, data processing, error handling, and the user interface), are not architecturally separate components but are all interwoven.

Nearline - Nearline storage (where the word "nearline" is a contraction of near-online) is a term used in computer science to describe an intermediate type of data storage that represents a compromise between online storage (supporting frequent, very rapid access to data) and offline storage/archiving (used for backups or long-term storage, with infrequent access to data).

Network Attached Storage (NAS) - Network-attached storage (NAS) is file-level computer data storage connected to a computer network providing data access to a heterogeneous group of clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements. NAS is often manufactured as a computer appliance – a specialized computer built from the ground up for storing and serving files – rather than simply a general purpose computer being used for the role.

Object server - An object server is the component of an OnDemand system that holds the reports that are accessed by your users. An object server belongs to an OnDemand instance. An instance is a logical server environment consisting of a library server, , one or more object servers, a database, and cache storage.

Open Architecture - Open architecture is a type of computer architecture or software architecture that is designed to make adding, upgrading and swapping components easy. For example, the IBM PC and Apple IIe have an open architecture supporting plug-in cards, whereas the Apple IIc and Amiga 500 computers have a closed architecture.

Open Protocols - An open protocol is a protocol that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed (e.g. open process).

Open Standards - An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed (e.g. open process).

Open Systems Architecture - Open systems architecture, in telecommunication, is a standard that describes the layered hierarchical structure, configuration, or model of a communications or distributed data processing system
Optical Character Recognition (OCR) - Optical Character Recognition, usually abbreviated to OCR, is the mechanical or electronic conversion of scanned or photoed images of typewritten or printed text into machine-encoded/computer-readable text. It is widely used as a form of data entry from some sort of original paper data source, whether passport documents, invoices, bank statement, receipts, business card, mail, or any number of printed records.

Reliability, Availability and Serviceability (RAS) - Reliability, availability, and serviceability (RAS) is a computer hardware engineering term. The phrase was originally used by IBM as a term to describe the robustness of their mainframe computers.  The concept is often known by the acronym RAS.

Random Access Memory (RAM) - Random-access memory (RAM /ræm/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations.

Digital Rights Management System - Digital Rights Management (DRM) is a class of technologies that are used by hardware manufacturers, publishers, copyright holders, and individuals with the intent to control the use of digital content and devices after sale.

Redundancy - In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the form of a backup or fail-safe.

Redundant Array of Inexpensive Disks (RAID) - RAID is a data storage technology that combines multiple disk drive components into a logical unit for the purposes of data redundancy and performance improvement.[1] Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the specific level of redundancy and performance required.

Routers - A router is a device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.

Repeaters - In telecommunications, a repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.

Storage Area Networks (SAN) - A storage area network (SAN) is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to enhance storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices to the operating system.

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