Mapping Hacks

Map Health Code Violations with RDFMapper #21

Chapter 2, Mapping Your Neighborhood

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HACK

Most of the remaining parameters denote functions defined in the Fabl pro-

gramming language, an open source language designed specifically for

manipulating RDF. (Fabl is implemented within RDF as well; see http://fabl.

net for more details.) Parameters naming Fabl functions may take the form:

<function_name>

or

<URL-of-Fabl-code-file>#<function_name>

In the former case, the function is taken from a library of utility functions for

RDFMapper, available at http://www.mapbureau.com/libsrc/rdfmapper_utils-

2.0.fbl. In the latter case, the function is taken from the specified Fabl code

file. See the rdfmapper_utils-2.0.fbl file for documentation of the utilities

used in the previous example, such as

itemGen1, extractTopicLocation, and

so on. If, as is often the case, the functions appearing in the library suit the

purposes of an application, there is no need to develop new versions.

The

extractor parameter denotes a Fabl function that, when given an RDF

resource, returns a

geom2d:Point representing its location, or nil. RDFMap-

per maps everything (that is, all resources) in the content file for which

extractor returns a non-nil value. Here’s a sample extractor:

geom2d:Point function extractGeoLatLong(Resource x) {

var geom2d:Point rs;

if ((count(x,geo:lat)>0) && (count(x,geo:long)>0))

{

rs = new(geom2d:Point);