Structural Metadata Dictionary for LC Digital Objects


Glossary of Data Definition Related Terms    Version 1.02 Go to bottom.

Aggregate:  A group of materials such as collection items or digital objects that have similar characteristics.

Clients:  PCs using client software that enables them to transmit requests for data and receive responses to those requests.  PCs operating in this mode are analogous to a telephone receiver.

Collection:  A gathering of items, based on administrative commonality, in one or more locations having the same ordering principle.

Custodian Contact:  Identifies the individual within an LC work unit to whom matters related to digital objects under the custody of that work unit are to be referred.  Contains the the individual's initials as recorded in the list of "cataloger initials" maintained by LC Library Services.  If an LC work unit has not designated a custodian contact, this attribute is set to null.  If the custodian is not an LC work unit, this attribute is also set to null.

Custodian of Digital Object:  Identifies the institution or Library of Congress work unit that has custodial responibility for a digital object.  The default custodian or digital objects in the repository is "LC - National Digital Library Program."

Data Element:  Content within a digital object.  Within a metaobject, the information that provides the link to a digital object that is subordinate to the metaobject in a "parent-child" relationship.

Digital Compilation:  Digital objects with related intellectual content that are presented online as a group.  Analogous to a collection of physical library material or to a set of exhibit material.

Downloading:  A method of "playing" animated/motion picture or audio data received over a network.  The transmitted data file must be entirely received before it can be played.  The opposite of "downloading" is "streaming."

Entity File:  Identifies all the external links within an SGML-encoded document and maps to the related file.  The Entity File is unique to a specific SGML-encoded document and must be present if the SGML-encoded document contains external links.

Finding Aid: A document that describes the scope, contents, and provenance of a collection and lists the contents according to the physical organization of the collection (e.g., thematic, chronological, or geographical). Finding aids may be either published or unpublished.  A published finding aid often includes supplementary materials, such as essays, biographies, or chronologies that provide an intellectual context for the collection.

Graphical User Interface (GUI): GUI (pronounced "gooey") is an object-oriented display format that allows the user to select from menus and icons, using either a mouse or keystroke commands.  GUI displays are typical of the Macintosh and Windows environments and are supported by client- server technology.

Information Architecture: The clients, network, servers and repositories that form the infrastructure of the National Digital Library.

InQuery: A retrieval system that provides document indexing, query processing, query evaluation and relevance feedback.  Queries can be formulated as natural language (English sentences) and structured (Boolean).  The results of queries are returned as HTML documents. The content (and authority) of the document is determined by the format of the database under interrogation.  The interface appears to be intuitive in operation. The use of relevance feedback is a significant feature of this software.

Leaf:  One of the units into which the original sheet or half sheet of paper, parchment, etc., is folded to form part of a book.

Metadata:  Information that refers to one or more other pieces of information that can exist as separate physical forms.  In short, data about data.  Any type of description can be considered metadata.  Examples include library catalog information, encoded text file headers, and driver's license data.  In the information technology world the term is often used to indicate data which refers to digital resources available across a network.

Metaobject:  A digital object that refers to other digital objects.

Metaobject Name: The sequence of up to eight lowercase alphanumeric characters at the start of the Unique String portion of a Handle.  Corresponds to data found in MARC field 856, subfield f.

MIME:  The Multipurpose Internet Mail Extensions protocol (MIME) is used in Internet communications to transmit documents of varying formats.  It is used by World Wide Web (WWW) Servers to identify the types of files they send to WWW Clients.  The protocol provides a means of specifying the type of file being transmitted (e.g., a motion video file) and the method that should be used to return it to its original form for display.  MIME types have been defined for many types of non-text files, including:  graphic and image files (jpeg, gif, tif), sound files (au, wav), and motion video files (mpeg).

Naming Authority: An organizational unit empowered to make a decision, particularly with regard to the assigning of persistent identifiers to digital objects.  Example:  American Memory Project Unit, National Digital Library Program, Library of Congress.  For the list of currently recognized name authority values associated with LC, click here.

Network: The communications network tying the Pcs with client software together into the NDL.  The network is analogous to a telephone exchange.  On the broadest scale, the Internet serves as the network. 

[Note:  The network is the key to the National Digital Library. This is not the same as distributed processing because there is no center, or hub. The way that we communicate within LC is the same way that we communicate around the world. Pcs serve as clients communicating through a network to request data from a server which in turn retrieves the requested data from a repository and sends it to the client in a form that the client can use. The dynamic is the same whether the client, server and repository are all in the same building or thousands of miles apart.]

Nonmotion Visual Item:  Any static visual material, including still photographs, prints, drawings, posters, atlases, and raster maps.

Object: An individual item of digital information stored in a repository.  Objects that can be stored in a digital repository may take many forms, including:  Text (ASCII, SGML, HTML), Images (tif and gif), Graphics (collections of vectors such as DAD/CAM, GIS files), Audio (collections of bits structured according to sound wave theory), Video (mpeg).

Permissions:  Authorization to access and/or use intellectual property.  Includes "access permissions" (administrative access for purposes of creating, updating or deleting an object).

Plate:  A leaf containing illustrative matter, with or without explanatory text, that does not form part of either the preliminary or the main sequences of pages or leaves of a work.

Raster: A computer image that is composed of an array of pixels arranged in rows and columns.  Example:  a bitmap (BMP).

Repository: A facility for storing and maintaining digital information in accessible form.  A place where collections of digital information are stored.  Also referred to as a "digital archive." In the NDLP context, digital information objects stored in the repository include materials such as sound recordings, text, pictures, photographs and moving images that have been converted to electronic form.

Rights:  The interest that one has in a piece of intellectual property.  The property interest possessed under law or custom and agreement in an intangible thing especially of a literary or artistic nature.

Role:  Identifies a function performed by an individual or organization.  Examples: owner, copyright holder, custodian.  For the list of currently recognized roles related to digital objects, click here.

Servers:  Computers that receive and respond to requests for data from clients via the Network.  These computers contain metadata, information that enables them to locate requested data, retrieve it and send it to the requesting client in a usable form.

SGML Packet:  The set of files required to view an SGML-encoded document.  Currently (03/97) some of these files are specific to the software (Panorama) used to view the document.  Any number of SGML packets may exist with different combinations of any of the following files:

Sheet:  A single piece of paper other than a broadside with manuscript or printed matter on one or both sides.

TOCA:  The Table of Contents/Annotation file associated with a set of document images.  Note:  Current (04/97) NDLP plans are to discontinue the use of TOCA files when their function is replaced by Repository structural metadata attributes Page Information and Data Element Relationship Information.

Source Collection: The Library of Congress collection that the item from which a digital object was derived belongs.

Streaming:  A method of "playing" animated/motion picture or audio data received over a network.  The transmitted data file is played in real time AS it arrives at the recipient's end.  The opposite of "streaming" is "downloading."

Universal Resource Locator (URL): The actual address of the resource on the Net. "http://abc.edu/file.html" is a URL.

Uniform Resource Name (URN): A globally unique, location-independent, persistent name for a resource that will be less prone to the failures now encountered with URLs as resources are reorganized or moved.

Uniform Resource Characteristic (URC): Refers to any descriptive data one might store about resources.  No one even agrees what the ingredients should be, though from the library perspective, URCs can be thought of as cataloging records.

Uniform Resource Identifier (URI): Term used to collectively refer to URLs, URNs, and URCs.


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Created: 3/26/97      Revised: 4/29/99
National Digital Library Program - Digital Repository Development Project
Comments: vvit@loc.gov