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Scalable and Interoperable Tourism
Information System based on the WebGIS
Wencai Du, Yair Gabay
*The Center for Geographic Information Sciences
Technion-Israel Institute of Technology
Haifa, 32000, Israel
Phone: +972-4-8293134
Fax: +972-4-8234757
Email : wencai@tx.technion.ac.il,
cvryair@tx.technion.ac.il
1. Introduction
Tourism is an information-intensive and
information-sensitive industry in which electronic commerce, WebGIS, and
Internet technologies are expected to play a significant role. It is evident
that both the way the information is presented and the approach to tourist
searching for information has a great impact on the tourist’s decision and satisfaction.
vWith the tremendous growth of the Web, today, all types of Tourism
Information (TI) providers already have homepages on the Web for storing the
comprehensive description of the tourist destination and for presenting
tourism products. Almost all homepages support static HTML-page. However, the
problem is that HTML was designed specifically to describe the presentation,
not the content. There is nothing in the HTML text to make it easy for other
programs to understand the structure and content of such data. Existing TISs
built on HTML are a lack of dynamic, scalable, extensible and interactive
functionalities. They are also unable to integrate geographic data and
tourism information. They fail in accessing and exchanging the data available
in heterogeneous TISs. These limitations have pushed for the need for more
sophisticated information system and web standards, such as WebGIS, XML and
SVG technologies.
The challenges are how to
present information related to tourism on the Web and to access to multiple,
distributed, heterogeneous and autonomous information sources. One of the
solutions is through establishing a WebGIS-based TIS and creating flexible
data interchange facilities in the system, thus allowing dynamic and
interactive presentation of tourism information and interchange of data with
other TISs. Information technologies, for example, web-based GIS and
XML-based technology, can be expected to meet these challenges.
vIn this paper, we investigate the design of WebGIS-based TIS using XML and
SVG technologies. We present an architecture for such a tourism information
system, and describe such prototype Tel Aviv WebGIS tourism Information
System (TATIS). The prototype does not currently implement all the features
and components that we present in this paper, but the most important elements
are already designed.
2. Design of WebGIS-Based Tourism
Information System
2.1 Design objectives
The tourists play the main role in tourism.
Thus, the purpose in designing this WebGIS-based TIS is to improve the
contact with the tourist through better, more attractive, multimedia and
up-to-date information, in particular digitized information in the form of
text, image, videos, sound, etc. as well as instantaneous information such as
availability of rooms and seats. Thus, to design TATIS has to focus on the
content aspects by providing detailed, accurate and actual tourism
information and by offering vividly presenting the information on the system
as well as providing appropriate search mechanisms. Using the system, users
may obtain a comprehensive, accurate and up-to-date tourism information on Tel
Aviv and all destination facilities, places worth seeing, and certain tourism
products can get attracting view of the destination, and can buy products either
offline or online. By providing better information the tourists might be more
satisfied and willing to spend their holidays in Tel Aviv.
2.2 Prototype Development
This system is based on a three-tier
architecture, from top to down, consisting of graphical presentation layer, a
structure management layer and database management layer (Figure 1). TATIS
web site construction involves three tasks: managing the tourism information
presented at the site, managing the structure of the web site, and creating
the graphical presentation of the SVG pages in SVG or HTML formats.
Figure 1 Architecture of integration of
WebGIS and tourism information system
The function of data
management layer is to integrate tourism data from multiple, heterogeneous
sources into a single semi structured data repository called the data graph.
The data graph is stored in a text file in a syntax layer. The data integration
part of TATIS is standard: there is a wrapper for each source and specific
mediator. Each wrapper translates the tourism data from the source’s logical
model to TATIS’s logical model. The structure makes it easy to add a new
source only by making the one-time effort of writing a wrapper for that
source. The mediator integrates logically the data from several sources and
is defined by a query.
The function of structure management layer is to manage the structure. Here
we construct a site graph that encodes the TATIS web site’s structure using
XML and SVG technologies; nodes correspond to SVG pages, or components
thereof, and edges to hyperlinks or to component inclusion. The site graph is
constructed declaratively by XML query language from the data graph.
The function of graphical presentation layer is to describe the graphical
layout in SVG templates for end users via the public Internet, which are
input together with the site graph into the SVG generator to create SVG
files. This layer allows searching for topic-oriented information and route
planning information by hierarchical navigation and complex structured
searches.
The layer represents dynamic and
interactive vector graphics using SVG. In contrast to exiting most
conventional TISs on the world, this new design poses fundamentally new
challenges: The geographic search for tourist objects and dynamically
generated tourist maps.
TATIS uses SVG DOM standards to interface with Web tools and editor in order
to specify mechanisms for querying, processing, and retrieving of data. SVG
DOM is an API for SVG documents. The advantages of this approach is that SVG
DOM is a platform- and language-neutral interface that will allow programs
and scripts to dynamically access and update the content, structure and style
of documents. The document can be further processed and the results of that
processing can be incorporated back into the presented page.
3. XML-based Data Integration
The integration of geospatial data from
heterogeneous data sources is a challenging problem when trying to utilize
existing TIS on the web, because of heterogeneity of sources and lack of
source metadata. Another new challenge occurs in the integration of GIS and
TIS. The reason is that GISs were originally developed independently by
software vendors, who tailored their applications for their specific user
needs, using locally created terminologies and approaches (Goodchild
1999).
In the TATIS, the information integration
of geospatial data which are stored in GIS database and tourism data in TIS
are achieved by using a two-part middleware between the information sources
and the tourists’ application (Figure 2).
The first part is called a mediator. Its
function is to accept tourist request, breaks up the request into small
fragments according to the capabilities of the sources and delegates the
request-fragments to the appropriate sources. When the sources process the
requests and return the results, the mediator integrates the results and
sends the combined information back to the user.
In the process, the spatial mediator
browses the schema information exported by GIS wrapper as an XML DTD, and
dynamically evaluates the minimal combination of sources that satisfy the
query attributes and predicates.
The aspatial mediator integrates and
transforms data from several sources using a declarative specification. For
example, it is used to convert aspatal data between different models by
translating data from a relational database into XML format and integrating
data from different sources into a common view. The key technology in the
mediator consists in query rewriting.
Figure 2 The spatial mediator and
XML-wrapped sources of geospatial data and GIS and TIS services
The second part of the
middleware is called a wrapper. The task of the wrapper is to translate a
request from the mediator’s language to that of the information source and
transform the results provided by the information source back to the
mediator’s language. Acting as a proxy of an information source, the wrapper
communicates with an information source in SVG DOM, and communicates with the
mediator in XML and SVG. In this way, “wrapping” each information source into
the translation software makes the protocol diversity of particular sources
manageable.
4.
Strategies for transferring data between XML documents and relational
databases and middleware
As design examples of our work, we discuss
the strategies for transferring data between XML documents and relational
databases according to two mapping rules of a table-based mapping and an
object-based mapping. The table-based mapping views an XML document as a
serialized table or set of tables. The following code is the example of
structure of the document.
<Tables> <Table> <row> <column_1>......</columN-1> <column_2>......</columN-2> .......................................... <column_n-1>......</columN-n-1> <column_n>......</columN-n> </row> <row> ......... </row> </table> ......... </tables>
From the above text we can see
the table-based mapping has the advantage of simplicity. Simplicity makes it
useful as a model for writing data transfer tools, especial using XML to
transfer data from the relational databases. Furthermore, the code to transfer
data between an XML document and a relational database is independent of
whether SAX or DOM is used. The reason is that the table-based mapping allows
the document to be processed in single pass in document order. The
table-based mapping is commonly used by middleware to transfer data between
XML documents and relational databases.
In TATIS we store some data in
object-relational model. For this case, we adopt an object-relational mapping
to transferring the data. Contract to the table-based mapping, the
object-relational mapping views an XML document a tree of data-specific
object and then uses an object mapping to map these objects to the database.
In this model, elements types with attributes, element content, or mixed
content are generally modeled as classes. Element types are modeled as scalar
properties. The model is then mapped to relational databases using
traditional object-relational mapping technology or SQL objective view. That
is, classes are mapped to table, scalar properties are mapped to columns, and
object-valued properties are mapped to primary key/foreign key pairs. For
example, the following figure shows the structure of the XML document (Figure
3).
Figure 3
Structure of XML document using object-relational model
5. XML-Based Virtual Map
Interfaces
In TATIS, query results are returned as map and tabular data from the
mediator to the user interface on a Web client based on SVG rendering
capabilities of Internet Explorer 5. The results of the integration of GIS
data and tourism data will be touristic maps including the information where
touristic objects are, how they can be reached, and which objects are located
nearby. SVG allows to interact, analyze, and use screen-related functions,
such as zooming and panning. It will lead to change in maps from static
raster graphics to interactive graphical representations that allow the
presentation of the most extensive information possible thus satisfying the
demands of the users.
6. Conclusion and Future Work
As discussed in the previous section, TATIS framework based WebGIS and
XML-based technologies, for integrating distributed and heterogeneous data
elements of TISs have been proposed. In contrast to exiting most conventional
TISs in the world, this new design poses fundamentally new challenges: the
geographic searching for tourist objects and dynamically generating scalable
and interoperable tourist maps. The architecture of this system is logical
integration for geographic information stored in a GIS system and tourism
information stored in database management system. This approach to present
integrated GIS and tourism information is based on the following concepts: a
powerful geographic search which is the base to create dynamically generated
vector maps in SVG which are enriched with additional tourism layers, to
offer the users fast, flexible and meaningful access to the data to fulfill
their requirements. The value of this study and its implications lie in
providing us with an initial set of relevant technologies, requirements and
issues to consider the in development of WebGIS-based TIS using XML and SVG.
We also create some API using XML and SVG programming. We will develop a
prototype for implementing and testing, and this prototype will be
implemented fro the tourism information system in Tel Aviv City of Israel.
References
- Goodchild, Michael. Preface.
Interoperating Geographic Information Systems. Edited by Goodchild, M.
& Egenhofer, M. & Fegeas, R. & Kottman, C. Kluwer Academic
Publishers 1999.
- W3C 2001 XML Query
Requirements, http://www.w3.org/TR/2001/WD-xmlquery-req-20010215
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