ASDD implementation overview

Here is a brief overview of how the ASDD operates and the status of its implementation (as at 2003-02-20).

Please first read the ASDD Z39.50 search and retrieve overview for background understanding.

• The ASDD is being gradually built and is an ongoing process.
• ASDD nodes can use various Z39.50 server software.
• Not all ASDD nodes are yet fully capable, and some are either poorly configured or have invalid xml metadata (which causes apparent configuration issues). See the ASDD Quarterly Reports.
• Each node is to be an independent Z39.50 server which can stand alone to respond to various clients and gateways.
• The first stage is to get all nodes able to respond to a request for XML, HTML or SUTRS (plain text) record syntaxes:
  • Isite servers based on document collections will simply send the relevant pre-prepared document. Alternatively they can generate the requested document on-the-fly from the XML document.
  • Isite servers with RDBMS connection will generate a document on-the-fly from the database;
  • MetaStar servers would generate a document from their metadata repository.
• Each node can format and present the HTML document however they choose. Style and layout is entirely up to the custodian - either very plain or with bells and whistles like header and footer images (Geoscience Australia, QLD, IndexGeo), navigation bars and table of contents (WALIS, IndexGeo, SA, QLD), locality map images (SA, IndexGeo, QLD, ERIN, WALIS). The HTML documents can also have links to further information, and even direct download or online purchasing. Additional information can be presented that is not necessarily present in the geospatial metadata. There is no standard HTML presentation layout.
• The ASDD HTTP-Z39.50 gateways at Geoscience Australia will always request the Z39.50 servers to deliver full results using a record syntax of HTML.
• In this initial stage all nodes must also be able to respond to a request for SUTRS record syntax (Simple Unstructured Text Record Syntax - plain text).
• When all nodes have established a fully-fledged document collection based on XML metadata (i.e. ANZMETA DTD v1.3+) then the ASDD gateway can have a user option to request XML record syntax. The user would need an XML capable WWW browser, or come through an HTTP-Z39.50 gateway that translates the XML for them.
• The Quarterly Reports show which XML document type each node is based on.
• If the Isite nodes receive a request to present the metadata in a record syntax that they cannot deal with (e.g. GRS) then they will simply present the document that was indexed (soon always XML, but currently some nodes still have metadata in SGML with with the old draft ANZMETA DTD v1.0).
• The ASDD gateway will not be doing any translation of structured documents. It will simply pass the request on to each node and will present whatever the server supplies.
• However, other gateways to the ASDD can be built which request structured metadata (XML) and translate and present the metadata in a consistent layout. WWW-based applications (like Australian Atlas) can also take advantage of this.
• This approach leaves it up to each node to deal with the request, and so enables various gateways to ASDD.