Note on the expansion and filtering of searches
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Authors : Jean Christophe Desconnets (jcd@teledetection.fr) ; Stéphane Clerc (clerc@teledetection.fr ) Date de création : 16/11/2006 17:04:00 Date de modification : 20/02/2008 16:17:00 Comments on modifications : re-writing of document based on the prévious one of version 1.4 and updating document style for version 1.5 Translation : Kim Agrawal (kim@auromail.net) Modified at : 16/01/2008 12:40:00 Comments on English version : english screen shot entry |
Concept of expansion and filtering
Expansion and filtering in MDweb
Search over a geographical zone
Two classic situations can arise when we conduct a search for documents: the search engine finds none or very few results or, on the other hand, it finds so many that it becomes difficult to find the relevant ones.
Expansion is the mechanism for dealing with the first situation: it allows us to extend the scope of a search to obtain more results than the original search gave. Filtering, on the other hand, is a mechanism for dealing with the second situation: it allows us to refine a search to obtain fewer results but which better represent our area of interest.
MDweb includes two features to help the user in obtaining better search results. These are the expansion and filtering features available during multi-criteria searching. They make use of the thesaurus attached to the cataloging service and the geographical database.
When the user conducts a search with keywords that are present in the thesaurus, two different situations can arise: if he gets none or very few results, the search engine offers him the option of extending the scope of his search, or, on the other hand, if gets too many results, he is offered the option to refine his search.
a) Thematic expansion with keywords
The user has conducted a search by choosing keywords1 in the thesaurus but he gets no results or an insufficient number of results. The search engine automatically extends the scope of his search by including terms linked to his original keywords in the search request2 and then displays the search results of this broadened request3. It then offers the user the option of further extending the scope of the search with a list of additional linked terms4.
The user can then select one or more of these proposed terms and launch the search again by clicking the Submit5 button.
b) Thematic filtering with keywords
The user has conducted a search by choosing keywords1 in the thesaurus but he gets numerous results. All the responses are displayed2, but so is a list of terms from the thesaurus that are more specialised3 than the ones chosen by the user. He has the option of using these terms should he want to refine his search.
Should he choose to do so, he can select one or more proposed terms and re-launch the refined search request by clicking the Submit5 button.
In the same way as for a search using keywords, it is possible to get too many results when we search using a geographical criteria (‘Where’ criteria of the multi-criteria search). During a search with geographical coordinates, the search engine returns results that are within the search zone but also those that only overlap or touch it.
All results returned from a geographical search are displayed. At the same time, the user is offered the possibility of refining the search to include only those results that are strictly included in the search zone.
For example, in the screenshot above, we see in black the rectangle drawn by the user on the cartographic interface to specify the search zone. The blue and red rectangles represent the locations of the documents found in this search zone. But the red rectangles are the only ones strictly included in the search zone and thus are the only ones retained when the search is refined.
On the results page, the ‘Filter responses’ button allows the user to refine the search to strictly included entities.
Some thesaurus keywords are special: they are called spatial, i.e., they correspond to a geographical layer of the geographical database (for example, the ‘lagoon’ keyword corresponds to the geographical layers containing lagoons).
A user conducting a search using a spatial keyword can obtain an excessive number of results. In such a case, MDweb gives him an option to display the cartographic interface with the geographical layer corresponding to the spatial keyword for him to select an object therein and thus refine his search.
For example, here the user has conducted a search with the keywords ‘lagoon’ and ‘fishing’1. The ‘lagoon’ keyword is spatial because it corresponds to the geographical layer containing the lagoon. MDweb offers the user the option of viewing this layer on the cartographic interface (by clicking the globe icon)2.
He can then choose a particular lagoon on the cartographic interface as the new scope of his search (for example, here the ‘lagoon of Thau’3) and Validate4 to display the corresponding results.
Contacts
IRD / ESPACE unit (US 140)
500, rue Jean François Breton, 34093 Montpellier Cedex 05, France
TEL : +33 (0)4 67 54 87 02
J.C Desconnets jcd@teledetection.fr
MDweb project site: www.mdweb-project.org
Online demo: demo15.mdweb-project.org