Global Positioning System Reference
In-Depth Information
• difference(theGeom): returns a geometry that represents the part of
this geometry that does not intersect with theGeom;
• symDifference(theGeom): returns a geometry that represents the
portions of the geometries that do not intersect.
vii. Input/Output format:
it is important to know which data input and
output formats the NoSQL system provides, including GML, WKT,
WKB, SVG, JSON, and shapefi le. GML (Geography Markup Language)
is an Open Geospatial Consortium (OGC) standard format that uses
XML to express geographical features. GML be also used as an open
interchange format for geographic transactions on the Internet. WKT
(Well-known Text) is also developed by OGC, represents geographical
information as text. WKB (Well-Known Binary) is developed by
OGC, WKB is similar to WKT, however it represents geographical
information as binary. SVG (Scalable Vector Graphics) is an XML based
vector format for two dimensional graphics proposed by the W3C.
JSON (JavaScript Object Notation) is a lightweight data-interchange
format based on two structures: a collection of name/value pair and an
ordered list of values. Shapefi le is a proprietary geospatial vector data
format from the ESRI company. It is considered a
de facto
geospatial
standard.
NoSQL Geographic Systems
Let us now focus on different implementations of NoSQL Geographic
Systems. The following NoSQL Geographic Systems are described:
CouchDB, MongoDB, Neo4j, and BigTable. In addition, the desirable
features previously mentioned are addressed, so that a comparison among
the analysed NoSQL systems can be made ahead.
CouchDB
CouchDB is a document-oriented NoSQL system based on schema-free
documents, using a RESTful HTTP interface (Fielding 2000). CouchDB has
been an Apache project since 2008, originally implemented in C++ but later
ported to Erlang for concurrency reasons (Cattell 2010).
Main Features
In contrast to relational database systems, a database in CouchDB has
no predefi ned schema; hence, its data structure can change dynamically.
Basically, a CouchDB database is a collection of documents. A document is a
JavaScript Object Notation (JSON) object formed by an unordered collection
of name/value pairs. Each document is identifi ed by a unique identifi er.
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