This is a DRAFT
Glossary -- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

NDLP Glossary - R

RAID - Redundant Array of Independent (or Inexpensive) Disks
A technique by which data is written to an array of physically separate disk drives with enough redundancy that the data can be rebuilt automatically if any single drive has bad sectors or fails. The computer science department at UC Berkeley first developed the RAID concept in the 1980s. They used the word "Inexpensive" rather than "Independent." Within the RAID approach, several levels have been defined; the Library is standardizing on RAID 5 for its Enterprise Storage Network, which involves "striping" data and parity (that's the redundant part) across all drives (typically 5 or more) in the array. Other levels use a dedicated parity drive or incorporate full mirroring of data. RAID 5 is a cost-effective approach for applications and systems that involve more read operations than write operations.

For more on RAID, see:

resolution
This term has three distinct meanings in the NDLP context. The first two relate to characteristics of a digital image or of a display device that govern the amount of detail visible. The third meaning is from the computing field.

  1. Spatial resolution relates to the size of a digital image or display device (such as a computer screen).

    The term may refer to absolute size in rows and columns of pixels ("dots"), particularly when comparing different versions of the same image or specifying a computer display. In the NDLP collection of photos from the Detroit Publishing Company, thumbnail versions have a resolution of roughly 150x150 pixels, while the reference versions are about 560x420. Some common resolutions for computer displays are 640x480, 800x600, and 1024x728.

    The term is also used to describe the quality of a printer or scanner, usually using dots-per-inch (dpi) as a unit. In the mid-1990s, regular laser printers have resolution of 300-600 dpi, while camera-ready copy for printing is usually produced at 1200 dpi or better. Most scanners can scan at 300-400 dpi.

  2. Tonal resolution (also depth or color depth) relates to the number of colors or levels of grey captured by a scanner, represented in a digital image format, or displayable on a particular computer screen (or other display device). 8 bits-per-pixel (bpp) allows for 256 colors or levels of grey. Today, color images are often captured at 24 bpp, which allows for 16 million different colors, which appears close to the discriminant capacity of the human eye.

  3. Name resolution is the process by which a logical name is "resolved" into the physical address for a resource on a computer or network. It is most commonly used in relation to the Domain Name Service used on the Internet as a universal lookup service that takes domain names (such as lcweb.loc.gov, the address of LC's home page) and resolves it into the current corresponding numeric IP address (in this case, as of 2/7/96, 140.147.248.7). A similar process will be used to resolve the logical name for an item in LC's digital archive into the physical address of the corresponding file(s).

restrictions
Limitations on use. In the NDL context, restrictions on access or further use of some objects in the digital archive will be necessary. Reasons for restrictions include: terms of gift, purchase, or license; copyright law; privacy and publicity rights of individuals; protection of trademarks.

See:

RFC
Request For Comments. The Internet Engineering Task Force issues a series of papers as RFCs. Although it is not immediately obvious from the phrase used, RFCs often represent the current consensus on an Internet standard and are widely used as the basis for implementation of network services and systems. Proposals are submitted by groups or individuals for consideration by one of the IETF working groups and are automatically declared obsolete after six months unless they are re-issued as RFCs. Eventually, some RFCs are upgraded to STD (standard) status. RFCs are available at http://ds.internic.net/ds/dspg1intdoc.html.

RFI
Request For Information. Posted by government agencies in the Commerce Business Daily, inviting companies to submit information relating to potential contracts for products or services. Responses can be more informal than responses to RFPs.

RFP
Request For Proposal. Posted by government agencies in the Commerce Business Daily, inviting companies to bid for contracts for products or services.

RLG
Research Libraries Group. According to a description from the RLG web-site, the organization "is a not-for-profit membership corporation of universities, archives, historical societies, museums, and other institutions devoted to improving access to information that supports research and learning."

Some RLG services are similar to those offered by OCLC (the largest library consortium and bibliographic utility), but with an emphasis on support for scholarship and for the archival functions of libraries. One interesting technical development from RLG is Ariel, a system for transmitting high-quality scanned images over the Internet to support document delivery. They sponsor many activities relating to preservation and are building an archive of finding aids (or "collection guides") marked up using the Encoded Archival Description (EAD) DTD.

LC is a member of the Research Libraries Group and finding aids produced at LC are included in the RLG archive of finding aids.

RLIN
Research Libraries Information Network. An information management and retrieval system offered by the Research Libraries Group (RLG) to support research libraries.

Glossary -- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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NDLP Glossary - R - This is a DRAFT
(7/30/98)