MARKLOGIC SERVER

A key aspect of semantic data is not just that it describes relationships (that let you
answer the question, "When was John born?"), but that these relationships can be
interlinked. You can add more triples describing John, and also triples describing Mary,
and some of these facts will intersect. This results in a connected web of information
that can be represented as a graph:
works-for
born-in
born-in
mother-of
father-of
mother-of
married-to
lives-in
lives-in
daughter-of
lives-in
born-in
born-in
works-for
Figure 17: The relationships between many semantic triples can form a web of information.
MarkLogic applications can query large collections of triples (or semantic graphs) to
tell us interesting things. By traversing the triples in a graph, an application might tell us
that John not only was born in the same year as Mary, but also lived on the same block
and went to the same school. With the help of semantic data, we can infer that John
might have known Mary.
STORING TRIPLES
Resource Description Framework (RDF) is the W3C standard that describes how
to represent facts using subject-predicate-object syntax, which is why triples in
MarkLogic are called RDF triples. In RDF, subjects and predicates are represented by
internationalized resource identifiers (IRIs). 14 Objects can be IRIs but also can be typed
literal values such as strings, numbers, and dates.
When MarkLogic ingests a raw RDF triple, it turns the triple into an XML
representation and then loads it as an XML document. So under the hood, MarkLogic
represents semantic data the same way it represents regular XML documents.
Consequently, triples can be managed with all of the features and conveniences
associated with other MarkLogic content. They can be protected with role-based
security, organized in collections and directories, and updated within ACID-compliant
transactions. Triples can also be added to traditional XML or JSON content when
14 IRIs are similar to URIs but have broader support for international characters. For details, see Wikipedia.
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