1.0 Introduction

Metadata is usually defined as "data about data". It is the supporting information that provides context to a resource, i.e. tool, task graph etc. Metadata in Triana includes information at various levels e.g. at the Unit, task graph, network level etc.

Triana needs metadata for several reasons:

• It will be difficult to reuse other people's tools and task graphs without metadata to provide the context for these objects. A scientist considering reusing someone else's tool or task graph will need to know things such as: what the tool does, the allowed input types, output types, parameters, the author, help files and so on.
• As the number of models and components grows, metadata will provide the only scalable method for locating particular models and components. Experience in many fields shows that as a field grows, powerful search techniques are needed to enable researchers to find relevant resources. These search techniques require structured metadata.
• Metadata will also be essential for monitoring the flow and extracting QoS parameters.

Metadata in Triana can be used in many different ways, such as:

• To support searches of a unit repository.
• To enable automatic discovery of tools published on remote websites.
• To enable the user to reconstruct a network
• To enable the user to ascertain the status of a network

The metadata structure should be flexible and extensible because it is almost certain that we have not thought of all possible uses of Triana Metadata.

The living document concept illustrates the use of metadata within Triana.A living document is a web page that contains an example of a data-flow network (simulated within Triana) that comes alive when a user clicks on it and instantiates Triana and shows the complete reconstruction of the experimental results. To do this, we need to be able to save units state in a standardized way, standardize the Triana data types into a common representation and record data flow information (within a task graph).