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Although Metadata has great power and the superiority in digital resources organization and retrieval, it inevitably has a number of issues within this relatively new domain.

Standard
Currently there isn't a universe Metadata standard in the digital world. Most of Metadata schemas were created for specific project or purpose, and named as standards for local usage or within that domain. It's very understandable because each project has specific requirements and data structure. It may not be feasible and economic to accept another metadata schema. In lots of circumstances,"(the project) may start up its own metadata definition effort, and creators are free to use whatever tags happen to come to mind", "any group that is developing metadata sets is free to limit its work to its narrow interests; it need not take a broader view unless it voluntarily chooses to do so"(Metadata: Cataloging by Any Other Name).

Currently a variety of Metadata standards and Metadata schemas exist that create a huge barrier for user accessing different systems simultaneously, and sharing the their resources. At the same time, the number of players in this field is continuing increasing. To solve this problem and improve the inter-operability of Metadata, setting guidelines for new comers becomes very important and urgent. There are too many factors involved, including technology and policy.

However, the advanced information technologies and Internet are making the dream of sharing digital resources worldwide become true. Some solutions could be:

• Set up several international standards and guidelines for general usage of Metadata. Dublin Core could be a good sample. After six years development, DC has been used as the module in a variety of disciplines, and different types of elements and qualifiers are added to its fifteen core elements accordingly. The guidelines should be standardized to keep the creation of new schema consistent to the module, but be flexible to ensure the extensions to represent the specific requirements.

• Develop technology and tools to make it easy to map different metadata schema. Implement the registry and harvest system for the application profile. Resource Discovery Framework (RDF) and XML namespace can be suitable for this purpose. RDF provides a way to encode Metadata, and XML provides a machine-readable and executable syntax for RDF. Further investigations and studies are needed to apply these technology and rules together.