張娟

Today it is an information age. It is important to find the information you need, and understand what you want in such vast information resources. The emergence of metadata improved the efficiency in the use of information, especially the electronic resources. As information technology develops continual, as well as people need to share information urgently, metadata technology is applied in more fields, such as library and information, Data warehousing, Software Construction and other information fields. Whether authors or seekers, Metadata leaves a pathway for them to follow to search the information they need in a small place. (Jessica and Susan, 1999) Metadata has become an essential element in the electronic resources. As the data about data, “metadata is expected to improve matching by standardizing the structure and content of indexing or cataloguing information”(Jessica and Susan, 1999:2). Therefore, this report will analyse the current conditions from views, types, functions and feature aspects. After that, the focus will be put on the problems and solution and the likely future according to the development of different Characteristics of metadata.

1?Definition

Metadata is a description of data resources; is used to provide a resource for information about the structured data; is often defined as “data about data”(Muriel and Jenn, 2008:3). Metadata describes a group of typical characteristics about the data，such as the content, quality, representation, spatial reference, management methods and other features of data sets, but usually does not contain the data itself.

Metadata contains the contents of the description of original information resources, in order to enable users to retrieve the relevant original information resources for selection, positioning and collection. It also includes a number digital documents which generated internally by the library, such as the page file released to the community, internal documents and other documents.(Jassica and Susan, 1999) It is the supporting conditions of location and retrieval for original information resources. In other words, metadatas aim is to identify resources, evaluate resources and track the change of resources in the process of using.

2?Current situation

2.1?views

In contemporary information society, People have different understandings of metadata. Some of them considered that there is no difference between metadata and the traditional library cataloguing system. This is mainly from the library community who think that metadata is data about data; it provides such as the author of writings, creation date and basic information relate to the literature (Jassica and Susan, 1999). However, another point of view emphasizes that metadata is a kind of machine-understandable information of network resources or other resources, and the machine-understandable is the key. These two kinds of different cognitions of metadata come from their different focus.

Metadata as a tool of information resources description is often constituted by a number of elements which describe characteristics according to the prescriptive encoding language and encoding mode. These elements which formed specific metadata formats with the prescriptive relationships and structures apply to a specific subject or expertise area. For instance, Dublin Core metadata is primarily used to describe the World Wide Web pages and other Internet resources, so it can be used for general areas ( Chris, 2003) .It can be seen that the value of metadata elements is limited if there is no uniform agreement on what elements to use or what content should be included. (Jessica and Susan, 1999)

2.2?Type

Usually in the digital library system, metadata can be divided into three distinct types: Descriptive metadata, Structural metadata and Administrative metadata. (NISO, 2004)Firstly, Descriptive metadata is used to describe, discovery and identify the digital information objects. It includes elements such as title, abstract, author, topics Index, connection and keywords. For example: Machine-Readable?Cataloguing and Dublin Core both are the descriptive metadata. Compare with descriptive metadata, structural metadata put more focus on the features of intrinsic form of digital information resources, such as content, sections, paragraphs, and other characteristics of resources. (NISO, 2004) It puts the focus on the structure and indicates how compound objects are put together. the third type, Administrative metadata, is used to describe the basic conditions and deadlines of the digital information resources and indicate the characteristics of intellectual property rights and using permission of these resources. In other worlds, Administrative metadata provides information or data to assist in the management of a resource, “such as when and how it was created, file type and other technical information, and who can access it.” (NISO, 2004:1) The division of above three types of metadata received the consensus of the digital library community. For example, the digital library program of Library of Congress and the digital library projects of University of Michigan have employed this classification method already. (NISO, 2004) In fact, there are also some subsets under administrative data. Two of them are treated as separate metadata types. They are management metadata and Preservation metadata. Management metadata which deals with intellectual property rights controls the copyright and republication. Preservation metadata is used to save the information resources, such as resource entities condition literature, data update and transplantation literature.