Global Positioning System Reference
In-Depth Information
Non-relational data models
: data models vary, but generally, they are
not relational. Usually, they allow for more complex structures and are
not as rigid as the relational model.
NoSQL Categories
Although NoSQL systems have several common characteristics, they also
present some particularities (Leavitt 2010). As a result, there have been
various approaches to classify and subsume NoSQL databases, each with
different categories and subcategories (Hoff 2009; North 2009). Although
there is no universally accepted taxonomy for NoSQL systems, often
suggested taxonomies divide these systems, at least partly, based on their
data models. For instance, the data model-based taxonomy proposed by
(Cattell 2010) is composed of four families:
Key-value NoSQL systems: store values indexed for retrieval by keys.
They are highly scalable and offer a good performance, but are diffi cult
to query and to implement real-world problems. Example: Amazon
Dynamo;
Document-oriented NoSQL systems: store and organize data as
collections of documents, rather than as structured tables with uniform-
sized fi elds for each record. Any number of fi elds of any length can be
added to a document. The documents are indexed and a simple query
mechanism is provided. Examples: CouchDB and MongoDB;
Column-based NoSQL systems: store extensible records that can
be partitioned vertically and horizontally across nodes. They are
also known as “wide column systems”. Examples: Cassandra and
BigTable;
Graph-oriented NoSQL systems: store objects and relationships in
nodes and edges of a graph. For situations that fi t this model, like
hierarchical data, this solution could be faster than the other ones.
Example: Neo4j.
NoSQL Geographic Data: Desirable Features
We highlight some desirable features of spatial database systems, aiming
to enable a comparison between NoSQL geographic systems. We choose
these features based on the ISO SQL/MM (Stolze 2003). The features
analyzed are:
i. Basic concepts
: we are interested whether the NoSQL system provides
any support for using different spatial reference systems (SRID);
whether reprojection can be performed. It is important to have different
systems to choose from, according to application requirements.
Another important issue concerns the multi-dimensionality of data
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