如何使用D2RQ合并多个MySQL数据库？

Question

I have four different MySQL databases that I need to convert into Linked Data and then run queries on the aggregated data. I have generated the D2RQ maps separately and then manually copied them together into a single file. I have read up some material on customizing the maps but am finding it hard to do so in my case because:

1. The ontology classes do not correspond to table names. In fact, most classes are column headers.
2. When I open the combined mapping in Protege, it generates only 3 classes (ClassMap, Database, and PropertyBridge) and lists all the column headers as instances of these.
3. If I import this file into my ontology, everything becomes annotation.

Please suggest an efficient way to generate a single graph that is formed by mapping these databases to my ontology.

Here is an example. I am using the EEM ontology to refine the mapping file generated by D2RQ. This is a section from the mapping file:

map:scan_event_scanDate a d2rq:PropertyBridge;
    d2rq:belongsToClassMap map:scan_event;
    d2rq:property vocab:scan_event_scanDate;
    d2rq:propertyDefinitionLabel "scan_event scanDate";
    d2rq:column "scan_event.scanDate";
    # Manually added
    d2rq:datatype xsd:int;
    .
map:scan_event_scanTime a d2rq:PropertyBridge;
    d2rq:belongsToClassMap map:scan_event;
    d2rq:property vocab:scan_event_scanTime;
    d2rq:propertyDefinitionLabel "scan_event scanTime";
    d2rq:column "scan_event.scanTime";
    # Manually added
    d2rq:datatype xsd:time;

The ontology I am interested in has the following:

Data property: eventOccurredAt
Domain: EPCISevent
Range: datetime

Now, how should I modify the mapping file so that the date and time are two different relationships?

Answer 1

I think the best way to generate a single graph of your 4 databases is to convert them one by one to a Jena Model using D2RQ, and then use the Union method to create a global model. For your D2RQ mapping file, you should read carefully The mapping language , it's not normal to have classes corresponding to columns. If you give an example of your table structure, I can give you an illustration of a mapping file. Good luck