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In General Release

The Archer@UQ group has developed three metadata related software products for the Archer project. These products are now available for download under the terms of the GNU General Public License (GPL) version 3.. Details on these products including download links can be found below.

Metadata Editor (MDE)

The Metadata Editor MDE is designed to address the tasks of creating and maintaining high quality metadata that conforms to specific, pre-defined metadata schemas. The purpose of a metadata schema is to specify what constitutes valid or meaningful metadata for a particular context. The goal is to allow metadata to be checked for completeness, consistency and (ideally) accuracy when it is saved, or at any time during the edit session as determined by the user. By taking a schema-driven approach, MDE is able to ensure that metadata records:

  • contain only elements valid for the record's schema version,
  • have all mandatory elements,
  • have syntactically valid values for all element, and
  • obey other semantic constraints specified by the schema.

The MDE has a dynamic "Web 2.0" interface that works with a number of popular web browsers (e.g. Internet Explorer 6 & 7, Firefox 2 & 3 and Safari), and a "back-end" that runs on an Apache Tomcat application server.

The MDE software is primarily designed to be used as the metadata editing component of some larger application. The MDE obtains the metadata records to be edited via an application specific implementation of a Service Provider Interface (SPI) that connects MDE to the application's metadata record store. To get you started, the MDE distribution includes a simple reference implementation of the SPI that allows you to try out the editor on some sample metadata records. Alternatively, here is an online demonstration of the current MDE release.

By default, MDE is configured to get its metadata schemas from an embedded 'flat file' repository. The MDE distribution includes an embedded repository that is prepopulated with schemas for the sample records. In the longer term, you can repopulate the embedded repository with your own schemas, or configure MDE to use an external Metadata Schema Repository (MDSR)

The latest release of MDE (version 1.1) adds support for nested elements, better support for element datatypes such as dates and indefinite precision numbers, and improved metadata record validation.

Please read the documentation and the sections below for more details, including installation instructions.

Current version: 1.1.01 [Release notes]
License: GNU General Public License (GPL) 3


Metadata Schema Facility (MSF)

The MSF is designed to address the task of defining rich and consistent metadata schemas. Previous systems have tended to conflate metadata schemas with the various mechanisms for metadata representation. For example RDF schemas provide schemas for metadata in RDF format and XSD can be used for metadata represented in XML. These approaches suffer from a variety of problems:

  • XSD and RDF have limited ability to express semantic constraints on metadata elements and values.
  • XSD in particular is a variety of issues that make it hard to understand and problematic for schema-driven software.
  • Representation oriented metadata schemas do not provide any leverage for metadata record translation.

The MSF addresses these issues by defining a schema "language" called MSS which splits schema definitions into two parts:

  • A core MetadataSchema defines the elements, their types and the applicable constraints in a representation technology independent way. The core includes a simple but powerful sublanguage for expressing semantic constraints on elements and values, as well as support for embedding multi-lingual documentation.
  • A SchemaProfile defines a mapping from the representation independent schema to some representation technology; e.g. XML.

The MSF toolset consists of the Metadata Schema Editor (MSE) and some anciliary tools. The MSE provides a graphical user interface for viewing, creating and updating schemas, and includes functions for validating them and importing exporting them in various formats. MSE can be used stand-alone, or in conjunction with the Metadata Schema Repository (MDSR). The anciliary tools allow some of MSE's schema format transformations to be performed from the command line.

The MSF code-base leverages the metamodeling and code generation capabilities of the Eclipse Modelling Framework (EMF). Most of the code is generated from an EMF model for MSS schemas. This includes the code for in-memory representations, schema serialization and the much of the MSE. The resulting code is packaged as an Eclipse "feature" and "plugins", with the MSE designed to be deployed into an instalation of the Eclipse Java IDE.

The latest release of MSF (1.1) adds MSS support for nested elements, richer data types and "models". The MSE has new and improved import and export wizards for the MSE, and improvements to the validation of MSS schemas.

Please refer to the documentation below for more details, including installation instructions.

Current version: 1.1.01 [Release notes]
License: GNU General Public License (GPL) 3


Metadata Schema Repository (MDSR)

The MDSR is a feature-rich repository, providing REST APIs and web interfaces for storing, retrieving, searching and browsing metadata schemas. Each metadata schema is uniquely identified by a 'key' and consists of a collection of alternative representations for the schema (e.g. MSS, XSD and/or RDF-S) together with some descriptive metadata for the schema. The preferred method of uploading schemas to the MDSR is to use the export wizards in the MSF schema editor. This ensures that MSS schemas are converted to the "flattened" form required by MDE. Schemas can also be uploaded via the web interface.

MDSR is implemented as servlets that run in on an Apache Tomcat server. Schemas and their metadata are stored in a back-end Fedora object store which also supports schema search based on the schema's metadata. Apart from ingestion time validation, the MDSR REST APIs treat actual schema representations as uninterpretted text streams; there are no fine-grained navigation or query interfaces.

The latest release of MDSR (1.1) adds upload-time validation for schemas with recognized formats (MSS, XSD and RDF-S), improved schema metadata entry and simple schema searching and browsing based on the schema metadata.

More details can be found in the MDSR release notes and the documentation for the MSF (see above).

Current version: 1.1.01 [Release notes]
License: GNU General Public License (GPL) 3

Note: Due to strong dependencies on the Metadata Schema Facility, the MDSR is not provided as a separate download. Instead, it is bundled with the MSF.