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, metadata’s 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.

2.3?function

It is obvious that resource description function is the most basic and common function of metadata. (Tony, 2000) It is a kind of ability that describes the content and Attributes of the information resource. It laid the foundation for information retrieval. The second function of metadata is information retrieval. It is the ability to support users discover resources, namely to use metadata organizing information objects and to establish the relationship between different information resources. (Muril and Jenn, 2008) In order to encourage users to easily and quickly find the information they really need from large numbers of information resources. The third one is about resource selection. According to the metadata description to the information objects, users do not have to browse the information itself can also have a basic understanding of information and determine what will be pick or abandon. Next function is resource location which means metadata can provides the original location of information resources; from it the location of information objects can be found accurately, so the acquisition of information become easier. Such as Uniform Resource Locator (URL), it is an identification method used to describe the address of a complete Web page and other resources on the Internet. (Tony, 2000) Fifthly, the resource management function is the revelation and description of the competence of information. It helps to preserve information resources and standardize the management of information resources, mainly for rights management, such as copyright, ownership, right to use and digital watermarking and electronic signatures. The last function is Resource Assessment. (Muril and Jenn, 2008)Through this function, metadata can help users identify the importance of the information resources at a certain extent in the same Category resources. Belong to the challenge of information storage; another function of metadata is being improved. That is archiving and preservation functions. Because of the Digital information can be damaged or altered, “Metadata is key to ensuring that resources will survive and continue to be accessible into the future.” (NISO, 2004:2) But, this function needs three special elements: to track the lineage of the digital information; to detail its physical features; to record its behaviour for its continuance in future technologies.

2.4?Problems

Firstly, if there is no uniform standard about what element or content should be used, the element value of metadata will become limited. Metadata cannot fully play its role unless it follows a set of specific standardization. For example, if a restaurant get two stars from food system and get three stars from service system, in which manner to compare these two systems? And what is the highest level of each level? There are different systems and have different evaluation criteria. (Jassica and Susan, 1999)Similarly, metadata value always belongs to metadata standard which is a collection of all the rules when describing a specific object of certain resources. Different types of resources may have different metadata standards. Therefore, the large number of different metadata projects and standards Probably become the biggest stumbling block in the fast development of metadata. (Jassica and Susan, 1999) Although there are some top level standardized metadata element sets highly supported by lots of parties. For instance, Dublin Core (DC) which is composed by 15 core elements is considered one of the most promising online metadata.(Sarah, 1999)

Another problem is about Metadata Interoperability. With regard to the discussion of metadata interoperability, it is a core issue of metadata study field. The aim of metadata interoperability is to provide effective organizational structure for large-scale information in an open network information environment, and to achieve a unified search across resource bases. (Muril and Jenn, 2008) However, there are still a lot of difficulties to achieve this goal. This is also the main reason that the problem of metadata interoperability has not been fully resolved so far. Due to historical reasons, previous creators build their own database without considering or rarely consider the problem of metadata interoperability. In this way, one of the most direct consequences is that there are different metadata formats in the different areas (or even the same area). At same time, different groups have their own metadata standards. However, these formats and standards are incompatible. In other words, the metadata with one certain format cannot be accepted by other formats, which lead to the information resources cannot be visited and searched between different databases Since the metadata interoperability plays an important role in the metadata study field, to solve the problem of metadata interoperability become more important for the distribution form of digital resources of the library, and the dynamic management. (Muril and Jenn, 2008) Therefore, many library workers are dedicating to the research in this area, in order to find an appropriate solution.

The last problem is the preservation of metadata. The preservation of metadata covers both the preservation of metadata itself and the information resources which are described by metadata. (Colin,1999) This problem is aware of gradually in recent years. Theoretically, metadata and the resources have the same life cycle - how long the resources are there, the metadata should be able to exist longer. In such a long period, metadata standards may change, the corresponding metadata storage format can no longer be identified under the present standard, and the physical carrier of metadata preservation has also been phased out. The early metadata faced the risk of loss. (Colin,1999) Therefore, the preservation of metadata becomes important increasingly. On the other hand, Very few people put the linker into metadata preservation and metadata intellectual copyright. In fact, there is a close relationship between the two issues. If people ignore the intellectual copyright, they would not get the real high-quality network resources. Perhaps, the problem of metadata intellectual copyright can be resolved by metadata preservation.

2.5?Solutions

This solution only focuses on the Metadata Interoperability. Because there is no suitable solutions for other two problems.

1)semantic interoperability

a.Metadata mapping. Metadata format conversion is one of methods to solve the problem of metadata interoperability, named Metadata Mapping or Metadata Crosswalking. Theoretically, as a descriptive system, metadata should allow the Descriptive mapping between systems. If different systems could allow the creation of mappings between different metadata, then each system could find the metadata in other systems; if all systems create universal mapping, the extensive search which across the system can be realized. (Muril and Jenn, 2008)Nowadays, there are some kinds of mapping that have been created, such as one to one mapping mode, XYZ mapping mode and X mapping mode.

b.Using Core Metadata Element Set: Dublin Core (DC). DC has 15 core elements which not only can be chosen but also can be repeated. (Sarah, 1999) It is used for the description of the simple or complex metadata, in order to create the metadata that can be used in any search engine and database structure. The aim is to provide a kind of description that can be used for any application software, data format or subject areas. This metadata is suitable for any web resource and any standard. DC provides semantic interoperability crossover different disciplines and formats and compatible with existing metadata. (Sarah, 1999) It as the modular basic structure becomes a solid tool that can be used to describe and label electronic resources by any libraries and publishers.

2)Resource Description Framework ( RDF)

Another way to solve the problem of metadata interoperability is to establish a standardized?Resource Description Framework and then to use this framework to describe all metadata formats. (Tony, 2000)RDF is a kind of system framework that encodes, exchanges and reuses structured metadata. It provides a workable carrier for metadata. This system structure proves metadata interoperability between a variety of systems, according to the support of usual semantics, syntax and structure. (Murtha, 2008) In the description system of RDF, creator could choose different metadata schemes with different description request of different types of resources objects. These metadata schemes can be combined together closely. At the same time, the same resource type can also use different metadata standard, so that creator could describe the content of resource more deeply and effectively under the opened standard?situation. RDF could provide better ability of resources retrieval and access for future.

3?future developments

The future metadata development must establish a standardized metadata framework. In this framework, metadata can easily achieve the mapping, interoperability and preservation. It is a development trend for metadata to achieve interoperability in the future. Therefore, the development of metadata must solve the problem of metadata interoperability. (Muril and Jenn, 2008) For the existing metadata, it is necessary to establish a conversion and mapping mechanism, and then convert into a uniform metadata format finally.

On the other hand, the usability?and flexibility of the standard of metadata is very important. It is an evolving dynamic and complex system. Furthermore, the simplifying of metadata standards could improve the flexible and scalability. Whether a system is flexible, the most essential feature is the ability to adapt to the changing. The flexibility of metadata standards mostly belong to the technical factors of long-term preservation of metadata. Of course, the flexibility must be limited by the standard. How to deal with the relationship between flexibility and the limited flexibility will also become the important problem in the future development of metadata.

The future digital library will be a virtual group, in where the producers, providers and users of resource will deal with information in it. These people may are not all the library professionals. (Charlotte and et al.,1999)In particular, the users of resource are more likely to have different culture level. Therefore, the future of metadata development will face the popularization problem. It should include three aspects of meaning. They are semantic popularization, processing platform standardization and interface friendliness. Metadata semantics easy to understand in order to ensure that non-library professionals could understand and accept the metadata. The standardization processing platform use to provide a set of simple description format of electronic resources for the creator of information resources. Finally, the interface friendliness uses to help the users to grasp the resources easier and to promote the adaptability for different cultural levels of users, the professionals and the general public.

As a result, it is obviously that popularization, interoperability, flexibility and effective long-term preservation of metadata will be treated as the trend of development in the future.

Reference:

[1]Baca, M. (2008). Introduction to Metadata. The getty research institute.

[2]Foulonneau, M., Riley, J. (2008). Metadata for digital resources. Great Britain

[3]Gill, T. (2000). Metadata and World Wide Web.

[4]Jenkins, C., Jackson, M., Burden, P., Wallis, J. (1999). Automatic RDF metadata generation for resource discovery.

[5]John, J., Helly, T., Elvins, D., Sutton, D. (1999). A method for interoperable digital libraries and data repositories.

[6]Milstead, J., Feldman, S. (1999). Metadata: cataloguing by any other name. Information Today Inc.

[7]NISO (2004). Understanding metadata. NISO press.

[8]Taylor, C. (2003). An introduction to metadata. University of Queensland Library.

[9]Webb, C. (1999). Presevation metadata for digital collection. Astralia: National library of Astralia.

[10]Whittaker, S. (1999). Dublin core metadata and the Non-specialist user.

相关文档：
小议房地产甲方代表在工程施工阶段的质量管理
浅谈人事档案管理存在的问题及对策思考
变电一次设备的检修和安全运行
电子商务环境下第三方物流企业发展对策
浅谈我国保险市场营销的现状及发展
夯实高校基础党组织建设 努力实现中国梦