background image
According to Warwick Cathro, Assistant Director General for IT at the National Library
of Australia, there are currently three different avenues to achieve high quality search results:
first, providing access through specialised resource discovery services that work
across sector domains,
secondly, searching and retrieving data at the collection level, and
thirdly, by granting access to collection management systems. (cf. Cathro, 2001)
The third approach offers users the possibility to directly go to an institution's web site
and search their online catalogue through an own interface, for example an OPAC (Online
Public Access Catalog). Although this model allows to achieve the best results when only
one institution is searched, it causes considerable problems when it comes to federated
searches of collection management systems across the ALM boundaries due to the signi-
ficantly different metadata standards used.
The second approach, searching and retrieving data at the collection level, builds on
EADs (Encoded Archival Description) or other standardised collection description formats
to search across sectors.Yet, at present, the search engines are not adequate enough to really
deliver good search results.
The most commonly used approach to seamless access to digital cultural artefacts across
domains today, is to establish specialised resource discovery services across sector boundaries.
Discovering information across sector boundaries: building metadata repositories
Specialised resource discovery services lower the interoperability barriers by establishing
centralised metadata repositories, where metadata is stored in a unified format for direct
search.The model adopts an interoperability solution known as metadata harvesting.
Depending on the approach, providing metadata in a unified format lies either within the
responsibility of the contributing institution or can be delegated to the resource discovery
service. In the better case, heterogeneous metadata is exported and mapped against a
uniform metadata standard. Search brokers or harvesters, i.e. client-based services that
interface with external servers through standard search protocols, are then used to launch
searches at distributed metadata repositories. If users search for resources through the portal
of the resource discovery service, they actually search the central metadata repository at the
level of the discovery service, yet do not search at the institutional level. One example for a
resource discovery service working with metadata harvesting is the Picture Australia image
Picture Australia
Picture Australia is a web service offering access to nearly 500,000 images about Australia. It
is a central resource discovery services that serves as a portal to the holdings of currently
seven Australian cultural heritage institutions, including the National Library and the
Australian War Memorial, and in the future will be further expanded to include more
libraries, museums, archives and galleries. Users can search a metadata repository held at the
National Library in Canberra which links to pictorial images that are maintained on the
web sites of participating cultural agencies around Australia.The service has a "hybrid"
architecture with a centralised search index and distributed images.
As material at the various institutions has already been digitised, Picture Australia needed a
method to collect the records, bring them into a common record format, index them and
make them available for web searching.The services uses harvesters or search brokers to
automatically collect the metadata from the participating institutions at a monthly basis and