Page 128 - JOURNAL OF LIBRARY SCIENCE IN CHINA 2018 Vol. 43

128 Journal of Library Science in China, Vol.9, 2017

of vital importance to design a data application program interface (API) that can be called by a
computer application. The data service interface technology which is based on LD is also called
LD consumption technology. There are multiple ways for LD consumption interfaces. The large
datasets including DBPedia, FreeBase and GeoNames all provide SPARQL Endpoint and Restful
API, and develop diverse customized consumption interfaces like toolkits. The following three
methods can basically meet programmers’ demands at different levels.
1) Content negotiation. When accessing a specific place or the HTTP URI of a place name,
detailed RDF data can be acquired. When using the ordinary browser, the system returns to
a human readable HTML page. When accessing the HTTP URI via a semantic browser or
application, the system will return the RDF data with corresponding serialization format, such as
RDF/XML, RDF/Turtle, JSON-LD, according to the request for content format transmitted by
requester via the HTTP Header.
2) Restful API. It is a lightweight technical framework of Web Service, providing APIs for
program call on the basis of HTTP protocol. The general manifestation of Restful API is the
URL containing various input parameters. The number of parameters, call methods as well as
data structures and formats are predefined by the developer in advance. This approach, due to
its simplicity and cross-platform feature, has gradually become the mainstream method for data
APIs and can be called by various programming languages such as C, Java, PHP, Python and so
on.
3) SPARQL endpoint. It is used for the calls by developers who are familiar with SPARQL, the
specialized query language of RDF. Compared with Restful API, SPARQL Endpoint can provide
developers with more flexibility. However, it also requires developer to understand the ontology in
detail.
Table 2 takes the Restful API of Chinese historical geography data as an example, illustrating
how to find different places and other feature information of the known place names on different
time scales. Table 3 takes the Restful API of Chinese historical chronology as an example for the
purpose of achieving the conversion between Chinese historical chronology and the year of the
Christian calendar.

4 Summary and prospect

With the development of modern historical geography, GIS technology, DH and digital library
construction, they now possess the conditions to penetrate, integrate, and provide methods and
tools with each other. The paper concludes that the combination of modern historical geography
and DH has become a hotspot and frontier in the research and application of DH based on
investigating the progress of modern historical geography, humanities and social sciences as well
as their relationships. To solve the difficulties and problems existing in the construction of DH
projects, the proposal to introduce the data, methods and tools provided by modern historical