Before launching into a discussion of XML[1] in more depth, it is important to understand some of the terminology that will be used throughout this paper.
Attribute - The characteristic of an XML element that defines the content. Example: If the elements are class, type, and color; corresponding attributes might be toy, rubber ball, and red.
Chunking - The process by which legacy content is tagged for inclusion in the content database.
Content - Content is information. It may take the form of text, graphics, audio, or video.
Database - A hierarchical distribution of data arranged in relationships that provides quick access to information of interest.
Document - Strictly speaking, when working in XML there is only one super document that contains all the content. This content fits into a common structure. We extract pieces of this super document and publish it as document instances, which may be either static or dynamic.
Dynamic Instance - When publishing a document instance, it may contain information that changes continuously. In defining the document publication instance, it may be desirable that every time a user opens the instance they see the most recently updated information. Contrast with static instance.
Element - An XML element is a definition for content. Any piece of content may be defined by one or several elements. Example: class, type, and color.
HTML - Hypertext Markup Language - developed from SGML as a means of conveying information on the web.
Learning Object - A functional component of training curriculum; a building block. Each learning object generally addresses a specific learning goal. Just how specific a goal is defined varies from system to system.
Legacy Content - Content, usually in electronic form, such as text, graphics, audio or video that has been developed outside of an XML content environment. Legacy content often resides in short-lived proprietary formats, which make reuse or conversion problematical.
Metalanguage - The language that is used to talk about (expressions of) another language, the object language. XML contains and identifies content, but the XML is not the content.
Parse - To divide into components from a larger set based upon some identifying feature or content.
SCORM - Sharable Courseware Object Reference Model - A set of specifications for developing, packaging and delivering high-quality education and training materials whenever and wherever they are needed.
Static Instance - When publishing a document instance, it may serve as a standard or reference. In defining the document publication instance, it may be desirable that users see a single, unchanging document, until any changes have been approved by a ruling/governing body. Contrast with dynamic instance.
SGML - Standard Generalized Markup Language - the international standard metalanguage for text markup systems3.
Taxonomy - a system for naming and organizing things, into groups which share similar qualities.
XML - eXtensible Markup Language - developed as a more manageable subset of SGML.
The next section introduces XML and discusses some of the features of XML that make it particularly appropriate for learning object development and learning content reuse.