Online Help - Searching the ASDD

ASDD searching overview

This interface to the Australian Spatial Data Directory (ASDD) is a gateway between the World Wide Web and sophisticated distributed library information systems. This enables you to use your familiar WWW browser to conduct powerful searches simultaneously at various spatial data directories (nodes).

Each node is a certain custodian's collection of consistent geospatial dataset descriptions. The uniformly structured documents enable powerful and precise searches.

A search query is composed using the WWW gateway interface and then broadcast to each of the specified nodes. Each individual server will process the query and return their set of results. The nodes will respond at different times. The order of the list of results will be in the order in which the nodes respond. That is, the first nodes to respond will have their results listed first.

The technical page ASDD Z39.50 search and retrieve overview discusses the ASDD architecture and operation in some detail.

Search timeout

Searches are conducted simultaneously at each node. The gateway interface will wait for 60 seconds to allow a node to respond. If a node does not respond within this time or an error occurs then the node name and a relevant message will be shown in pink.

You specified an empty query. Please go back and try again

If you receive this message when you conduct a search, then it means that you did not specify your query properly. If you are using the advanced search interface, then most likely you have left all the search criteria empty. You must specify at least one search criteria.

Phrase searching

More than one word in a "text input" box of the advanced search interface constitutes a phrase. This will search for the words occurring adjacently. It does not perform an "OR" search like many search systems. There is no need for double-quotes.

Truncation and wild card

A limited wild card facility is supported with right-truncation. Append an asterisk "*" to the end of a search term to match any word that begins with the given prefix. Use the wild card to search for all plural and singular forms of a word. So "region*" will match "region, regions, regional". This is also useful if you are not sure how to spell the end of a word. Use as many known characters in the term as possible to get a more accurate and faster search. The use of wild cards does cause a slower search.

Case insensitive

Searching is completely case-insensitive ...

• "solar", "Solar", and "SOLAR" are equivalent

Common words excluded from query

Certain very common words are discarded from the query. These "stop words" such as: it, these, and, or, a, also, two will have no effect. Here is the complete current list of 400 stop words.

Sometimes slow to search

The response time is largely dependent on the size of the result set. So if the search is for a single very common word like "land" then there will be plenty of results to compile. If you search for a rare word like "bird" then there should be less document titles to extract.

Always try to conduct a precise search using phrases and multiple search terms (however, complex searches may also be slow). Spatial searches will always be slow. Wild card searches will be slow if you do not provide as much information as possible (e.g. region* is better than regio*).

No servers selected

Be sure to select at least one server from the list of nodes at which to conduct the query. If none are selected, then all the nodes will be selected for the basic search interface or you will get a javascript "alert" message telling you to select at least one node in the advanced search interface.

Order of servers

The order of the servers is shown in order of response. That is, those that repond the quickest are closer to the top of the list.

Ranking of results

The search results are always returned by the servers in a "relevance ranking" and not as an alphabetical list. So the order of the list depends on the search query that was conducted. The relevance is determined by a complex method which considers the size of the document, how many times the search terms occur in the document, and whether any search terms occur in the title. So this tries to put the most relevant records at the top.

The search results are scored and then ranked according to their relevance within the set of results from any one node.

A document that contains more instances of high-scoring search terms will get ranked higher. What makes a search term "high-scoring"? Basically, the fewer documents the term occurs in, the more important it must be. If many instances of the term occur in a particular document, then that document will be ranked higher, especially if it is a short document.

Navigation within results

The results of a search are presented in a list, in batches of the number that you specified. Select a link to present a full dataset description. Use your browser's "back" to return to the list.

Status of servers

Sometimes a particular node may be having difficulties and is not available for searching. This may be due to the server being off line or perhaps that area of the network is slow to respond. The name of that node and a relevant message will be should in pink. Regular automatic checks are conducted to produce the "Status of ASDD nodes" page where you can check their condition.

Advanced search

To conduct an advanced search, you select one or more groups of search terms (text, theme keywords, spatial). Then add relevant input to those groups. The map is a tool for defining a geographic rectangle of interest. When you have completed the process of defining the rectangle of interest, then the radio button is automatically set to "include spatial search".

JavaScript

The interfaces make extensive use of JavaScript to compose complex search expressions for sending to the servers. Please ensure that your browser has Javascript enabled (via the preferences option).

See also Brief Help.