Working With MediaWiki

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Semantic Drilldown
    The Semantic Drilldown extension offers a drill-down interface to browse the data in each category, available at the special page Special:BrowseData. Each filter for a category corresponds to a single Semantic MediaWiki property. Figure 19.1 shows an example of the interface created by Semantic Drilldown, for a hypothetical wiki about astronomy.
    Figure 19.1 Special:BrowseData page, from the Semantic Drilldown extension
    The “BrowseData” page lets you browse one category at a time. Note the list of categories on the right-hand side: each of those is a link, to let you browse and drill down through that category’s pages. The Semantic Drilldown interface shows, by default, the full set of top-level categories in the wiki (i.e., categories that do not have a parent category). Subcategories within each category are shown as additional filters.
    Each defined filter lists the values that exist for that filter, along with the number of pages that match that value. Already, before even clicking on anything, the user is getting a lot of information:
The number of pages in the wiki, in every main category.
An alphabetical listing of the pages in the current category. (Though this isn’t shown in the screenshots presented here.)
The list of fields (or at least, a subset of them) that each page in the category holds.
The breakdown of the data, including subcategories, in the current category.
Any discrepancies, misspellings and gaps in the current data. The “None” values, for instance, indicate the number of pages that don’t have a value for that field. There’s no opportunity to see misspellings in the screenshots shown here, because all of the filters are either numbers or a combo box that has to be clicked on, but if there were a filter that showed a set of text values on the screen, then misspellings would easily jump out.
    Figure 19.2 shows how that page from before would look, after the “5001 — 10000” value is clicked for the “Diameter, in miles” filter.
    Figure 19.2 Special:BrowseData, after a filter click
    The header has been updated; and the other filters show their new values, for only the set of pages that fit the already-selected criteria. Clicking on additional values will further reduce the set of results.
    Hopefully, this helps to demonstrate the usefulness of the Semantic Drilldown extension, and more generally, of the approach known variously as “drill-down”, “faceted browsing” and “slice-and-dice”.
    Such an approach can certainly be found elsewhere on the web, though the more common approach is field-based search, where users just fill in values for different fields and then hit a big “Search” button at the bottom. Standard search may be more popular just because that sort of search is easier to implement. But a drill-down approach offers a number of big advantages, as we’ve seen.
    If you do want a more search-like interface, there are two main options: using the alternate input types “combo box” and “date range” in Semantic Drilldown (see below), and using the “run query” option in Semantic Forms (see here ).
Setting up filters
    The interface available at Special:BrowseData is useful even if you don’t create any filters, since it lets you view all ot the wiki’s categories and their pages in one place. However, it’s even more useful if you do create filters.The easiest way to create a filter is via the filter-creation helper form, available at either the special page Special:CreateFilter or by directly going to a filter page that doesn’t exist yet and clicking on the “Create with form” tab.
    Figure 19.3 shows how the page Special:CreateFilter might appear for this astronomy wiki.
    Figure 19.3 Special:CreateFilter page from Semantic Drilldown extension
    Roughly 90% of the time, all you will need to fill out in this form is the top two fields — the name of the filter, and the property that it covers — before hitting “Save page”. (And if you’re reaching this form directly from a new filter page, you won’t even see a “Name” field, since the page’s name has already been set — you just need to set the property dropdown.)
    Why is the property value so crucial? Because every filter corresponds to a single semantic property — it lets you filter pages based on those pages’ values for that one property.
    Regardless of how this helper form gets filled out, what ends up on the filter page is a set of