Database Reference
In-Depth Information
b. The HTML Web page with information about Ash Fleet Parish
http://
c. The RDF/XML data representation of Ash Fleet Parish
http://d ata.
7.4.5 S
tep
5: G
enerate
Y
oUr
l
InkeD
D
ata
Now that Merea Maps knows where its URIs are coming from, there are several
ways of generating the actual RDF data. The choice depends both on what the input
data is like and how the RDF is to be accessed on the Web. There are four main ways
in which the data may originally be structured:
•
Plaintext
•
Structured data, such as comma-separated files, or spreadsheets
•
Data stored in RDBs
•
Data exposed via an Application Programming Interface (API)
RDF data can be published on the Web in one of the following ways:
•
As a static RDF/XML file
•
As RDFa embedded in HTML
•
As a Linked Data view on an RDB or triple store
In addition to these three main publishing mechanisms, a publisher has the option
of providing a data dump (that is, a zipped file containing all the RDF data, avail-
able for download) or a SPARQL endpoint (an interface for people or applications
to query an RDF data store directly using the SPARQL query language). However,
just providing these last two options for data access is not considered sufficient to be
classified as “Linked Data.”
We consider each of these input data structures and output publishing options in
turn in Section 7.5. These options are equally applicable for GI and non-GI data;
however, GI data may require some additional consideration and preprocessing. For
example, queries may need to be run within the GIS or spatial database system itself
to generate data about the areas of each polygon or topological relationships between
the various administrative areas. This last point requires some design decisions from
Merea Maps. Do they want to encode all possible triple relationships between every
administrative area? In both directions? (For example, if “Area a borders Area b” is
explicitly stated, should they also include the triple “Area b borders Area a”?) This
is where a carefully designed scope and competency questions can come in: Merea
Maps decides that the adjacency information (“borders”) should be included in both
directions (as it has competency questions in its list that can only be answered with
such information), but the scope precludes the need to include topological relation-
ships between entities of different classes. Similarly, containment relations are only
explicitly stated between an administrative area and the areas that it immediately
