Difference between revisions of "Help:SMWAddExtensions"

Revision as of 07:24, 14 July 2010

This section gives some guidance on, and provides examples for using other Semantic Mediawiki (Semantic MW) extensions. Basic features of the Semantic MW and the Semantic Forms extension are explained separately (see the box on help sections above). All SemanticMW extensions described here require prior installation of the basic Semantic Mediawiki components.

Semantic Drilldown extension

For more detailed descriptions of this extension see the Semantic Drilldown website. For installation notes see Semantic Drilldown.

Introduction

Semantic Drilldown is very useful for browsing and filtering the semantic data entered into a wiki. As with other SemanticMW features, Semantic Drilldown is closely linked to the category system of a wiki and Semantic Drilldown can only work through a specific category. As an example we explain here the different steps for modifying the Category:Publications to enable specific filter options.

Defining filters

1. Create the page Filter:Journal by typing this name into the search box.
2. The filter page basically needs only a statement on which property the filter is based in the form "[[Covers property::Property:Publication journal]]". However, you might want to add also some explanationary text.
3. Create another filter for the property Publication year.

Adding filter definitions to a category

We now add these 2 filters to the page Category:Publications. For this we need statements like "[[Has filter::Filter:Journal]]".

Using Semantic Drilldown

Got to the "Semantic Drilldown" section of the Special:SpecialPages and select Browse data. In the top right of this page you find a box with the different categories of this wiki, sorted alphabetically. The first category on this list has been selected. Since most categories do not contain any filters, most "browse pages" do not look differently from the normal category pages. Select the category Publications. On the top of this page you can now click on different journals and publication years. The Drilldown system then filters out the category pages according to your selections. Of course, the Drilldown system is especially useful if many data have been entered into system.

Semantic Result Formats

The Semantic Result Formats extension adds several features for displaying query results with semantic data in different formats, e.g. a graphical format. For a detailed description of this extension see the Semantic Result Formats website. For installation notes see Semantic Result Formats.

The use of these features is very simple, just use the line "format=<format type>" together with the #ask function. The following examples demonstrate some of the format types:

• Displaying data in a graph (Google bar).
• Displaying sums or averages of a data set.
• Ordering data according to semantic properties.

Semantic Internal Objects

For more detailed descriptions of this extension see the Semantic Internal Objects website. For installation notes see Semantic Internal Objects.

Why are Internal Objects needed?

In most cases we assign one value to a given property per page, e.g. the population to a page on a country, or the name of a journal to a publication page. In some cases we want to assign more than one value for a given property on the same page. E.g. the publication page Environmental Entomology (2008) 37 (2), 391-399 deals with different host plants of the whitefly Bemisia tabci (collard, cowpea, cantaloupe and watermelon). If we have the properties called Property:Publication on pest and Property:Pest host we can assign the whitefly and its host plants to these properties in order to generate on a different page a list of publications dealing with host plants of Bemisia tabaci. Thus on the above publication page we would use:

[[Publication on pest::Bemisia tabaci]], [[Pest host::collard]],
[[Pest host::cowpea]], [[Pest host::cantaloupe]] and [[Pest host::watermelon]]

However, with this method we cannot define specific relationships between different properties on the same page. E.g. the publication might deal with different pests, each having different host plants, or as in this example, the study is done in several locations and we also want to define the different pest-hosts-location relationships and display them in subsequent queries. For such a task we would use the "internal objects.

Defining internal objects

We use the #set_internal function to define the different relationships between pest, host plants and locations. For the above example we would have 4 assignments in the page Environmental Entomology (2008) 37 (2), 391-399:

{{#set_internal: Pest record|Publication on pest=Bemisia tabaci|Pest host=collard|Pest distribution=U.S.A. (SE)}}
{{#set_internal: Pest record|Publication on pest=Bemisia tabaci|Pest host=cowpea|Pest distribution=U.S.A. (SE)}}
{{#set_internal: Pest record|Publication on pest=Bemisia tabaci|Pest host=cantaloupe|Pest distribution=U.S.A. (SW)}}
{{#set_internal: Pest record|Publication on pest=Bemisia tabaci|Pest host=watermelon|Pest distribution=U.S.A. (SW)}}

corresponding to the following 4 relationships

Click on an "edit" or "view" tab in the page Environmental Entomology (2008) 37 (2), 391-399 to see the internal object assignments at the bottom of that page. In the page itself there is no display of the internal objects.

Querying internal objects

For querying internal objects, we can use the normal #ask function. The query:

{{#ask:[[Pest record::+]][[Publication on pest::Bemisia tabaci]]
|mainlabel=-
|?Pest host=Host plant
|?Pest distribution=Distribution
|?Pest record=Publication
|sort=Pest host, Pest distribution
}}

gives us the following sortable table on the host plants and locations of the whitefly Bemisia tabaci: