to the mode of navigation, e.g., to represent navigable and non-navigable areas
with respect to the capabilities and limitations of moving persons. Moreover,
the partitioning of indoor space into smaller units may also be induced by lim-
ited propagation areas of sensor-based positioning systems, e.g., systems based
on RFID tags, which do not cover the spatial extent of an entire room. Thus, a
room can be geometrically fragmented into Cells, which again represent non-
overlapping parts of the room. This fine-grained subdivision of space and its dual
cell-to-cell representation enables more detailed escape planning routes in a fire
escape scenario. Furthermore, these single cellular partitions can be individually
addressed by sensor-based positioning and tracking systems to provide a more
accurate location of moving subjects or objects (Nagel et al. 2010 ). Similarly the
outdoor space can also be represented by the same approach where 3D discrete
spaces can be defined or a 3D solid object can be decomposed into partitions (i.e.
3D cellular spaces). The spatial hierarchy between these spaces can be built based
on containment relationships. These cellular spaces can be used to represent the
coverage volume of the sensor/device (i.e. it can be the space of signal propagation
or it can be a space that a sensor is acquiring information from). In the focus of
this research, this chapter will concentrate on the latter one.
4 The RESTful Web
Web services can be defined as components and resources that can either be
invoked over the web or reached by standard web protocols using standard mes-
sages. Two styles of Web Services exist today: SOAP and REST. REST is an
architectural style where the web service operates by calling various web-
resources. The terms REST and RESTful web services have been coined after
the Ph.D dissertation of Fielding ( 2000 ). As explained by Pautasso et al. ( 2008 ),
REST was originally introduced as an architectural style for building large-scale
distributed hypermedia systems. According to REST style, a web service can be
built upon resources (i.e. anything that is available digitally over the web), their
names (identified by uniform indicators, i.e. URIs) representations (i.e. metadata/
data on the current state of the resource) and links between the representations.
As stated by Guindard et al. ( 2011b ) at the core of a RESTful architecture lies
resources that are uniquely identified through Uniform Resource Identifiers (URIs).
The Web is an implementation of RESTful principles as it uses URLs to identify
resources and http as their service interface. Resources can have several repre-
sentation formats (e.g. HTML, JSON) negotiated at run time using HTTP content
negotiation. In a typical REST request, the client discovers the URL of a service
it wants to call by browsing or crawling its HTML representation. The client then
sends an HTTP call to this URL with a given verb (GET, POST, PUT, DELETE.),
a number of options (e.g., accepted format), and a payload in the negotiated format
(e.g., XML or JSON). In regular browsers GET is used to request a resource (e.g.
web page, picture, video from a server), POST is used to send a piece of data to the