Transcript State of the art and perspectives of Web Information Systems (WIS)

3rd Technical MedWet Codde Meeting,
ICN
MCU Athens, 9-11 February 2006
State of the art and perspectives of
Web Information Systems (WIS)
- Design considerations and functions
IGUT
Panagiotis Katsaros
Dept. of Informatics
Aristotle University of Thessaloniki
54124 Thessaloniki, GREECE
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Presentation overview
Web Information System (WIS) design concepts- 7 slides
ICN
WIS architecture
- 2 slides
Dynamic Web Pages
- 3 slides
Security policies for Web data
- 5 slides
Multilanguage support
- 2 slides
Geographic Information Systems
- 12 slides
IGUT
Web-based GIS
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS design concepts I
1. THE CONTENT
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-
integration of one or more data sources
-
use of hypertext links to redirect the user in different views of
the data provided by the WIS
-
use of search forms to request data based on specific search
criteria
2. THE STRUCTURE
-
categorization hierarchy that will allow users to classify content
into various topics.
-
use of the devised structure to provide different navigation
aids: category tree, keyword search etc
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS design concepts II
Graph
Tree for 'Customers'
Customers
Customers
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Key customers
Customers by industry
Customers by industry
Computer industry
Customer A
Computer industry
Key customers
Customer B
Customer A
Customer B
3. THE LAYOUT
-
each category with all information related to it is represented in
its own Web page
-
all children and children-children categories are shown on the
same page
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State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS design concepts III
ICN
3. THE LAYOUT (continued)
-
each category is represented by its own ID and for this reason
ID can be used to dynamically create the corresponding page
requested by a user
-
we define separate interfaces for different user roles (reader,
editor, administrator)
-
the editor interface just adds the functions of creating, editing
or deleting data records
-
the administrator interface allows the user to add, change and
remove users of the system and to edit their access rights
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS design concepts IV
3. THE LAYOUT (continued)
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-
When users log in with a password, they are identified by the
system (authenticated). Attached to each user is his/her role of
reader, editor or administrator. This information allows the
system to dynamically create the corresponding user interface.
-
The system has to check whether the authenticated user has
the necessary access rights (is authorized) to perform an action
or to access a specific piece of information. If that action is not
allowed it is not enabled or even not shown.
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS design concepts V
3. THE LAYOUT (continued)
ICN
IGUT
-
users should be supported by easy-to-use and consistent
interfaces. The addition of new data should not be difficult,
even for inexperienced users.
-
it is necessary to not allow addition of inconsistent data
-
consistency mandates that the same navigational element
should always behave in a similar way
-
navigational elements should not be put on two different places
on the page and the same navigational element should always
be represented in the same way
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS architecture I
System functions for
presenting content
1. Storing
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C
A
2. Processing/
assembling
B
C
A
3. Presenting
B
Assembled
content
Data
content
content
Web Page
Layout
1. Picking up
new content
IGUT
System functions for
picking up new content
2. Processing
C
A
B
Processed
content
3. Storing
C
A
B
Data
Input Form
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State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
WIS architecture II
System layers
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Functonality of system layers
Representation Layer
Picking up/
Presenting
Application Layer
Processing/
Assembling
Layout
Page
C
A
B
B
Data Storage Layer
Storing
A
C
Connection Point
IGUT
Data storage layer:
- relational database scheme
- mechanism for generating Web pages dynamically
Application layer:
- functions to store, process, present and pick up content
Representation layer:
- page-oriented user interface that handles user interaction
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Dynamic Web Pages I
ICN
Two kinds of dynamic web pages:
- program code executed by the web browser to control the user
interface behavior
- program code executed by the web server to create web pages
on the fly when they are requested by a client application
Technologies for web browser based dynamic code:
- scripting languages like JavaScript, ECMA Script, VBScript
- Java applets
IGUT
Technologies for web server based dynamic code:
- Server Side Includes (SSI)
- Common Gateway Interface (CGI)
- Active Server Pages (ASP) or PHP
- Perl
- Java Servlets
- JDBC and ODBC
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Dynamic Web Pages II
response
with final
page
(8)
(3)
execute code
(2)
forward
request
deliver
final
page
(7)
(4)
request
data
return
data
(5)
Database
IGUT
Browser
(1)
request
dynamic
page
Web Server
call sequence of infrastructure for
dynamic server side pages
App Engine
ICN
First approach to create dynamic server-side pages:
to write an HTML page with placeholders for content that should
be retrieved dynamically from a database
HTML code is mixed with program code of another programming
language (e.g. ASP, JSP)
the program code is then replaced by actual data when the page
is requested
replace code
by data
(6)
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Dynamic Web Pages III
ICN
IGUT
Second approach to create dynamic server-side pages:
to embed the HTML code inside the execution code
when the page is requested, the content is dynamically fetched
Common Gateway Interface (CGI): the user interface designer
has to split the HTML code into many portions and incorporate
these into the complex execution code
Third approach to create dynamic server-side pages:
use of XML instead of HTML for the definition of the structure of
a page
an XML file can be transformed with the help of XSLT into any
other data format such as, HTML
advantage: several output formats can be produced for different
user interface types by using the same XML document
it is possible to generate a Web version (HTML) and a printed
version of the same XML data without changing the XML
document
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Security policies for Web data protection I
ICN
IGUT
The simpler access control mechanism:
- use a “log in” page that picks up the user name and password
and checks it against the users that are known by the WIS
- when the user is authenticated the “logged in” state is saved for
the session
- every page can check that state in its dynamic code and
depending on the state, show or hide its content
- role-dependent behavior of the WIS: every page and form can
check the role of the user in its dynamic code and, according to
that role, offer users a choice of actions they can perform e.g. a
data provider should only be able to edit his own documents but
not the documents of others
Basic principle:
Complex security policies impose high administration costs.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Security policies for Web data protection II
Issues and requirements in defining security policies for Web data:
ICN
IGUT
- subject qualification: the subjects are the users entitled to
access data.
Subjects are referred to on the basis of an “ID” based
mechanism, exploiting some information for their identification in
the system. Examples of identity information could be a user
name, an IP address or a combination of user name and IP
address.
Web user population is highly dynamic in that the number and
type of users is not known a priori and can change very
frequently over time.
We employ the notion of subject credentials. Subject credentials
assert arbitrary properties of a subject such as characteristics
and properties deriving from relationships the subject has with
other subjects (e.g. qualifications within an organization).
User roles can be specified as sets of subject credentials.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Security policies for Web data protection III
ICN
- protection granularity levels: the access control policies must be
flexible enough to support spectrum of protection granularity
levels, such as all the data regarding an item, a portion of this
data, or the data regarding a set of items.
Having the possibility of specifying fine-grained protection
objects, different policies can be formulated.
- access privileges: specification of access control policies requires
also the identification of the privileges that subjects can exercise
on protection objects. Privileges correspond to the different
modes with which data to be protected can be accessed (e.g.
browsing, editing etc).
IGUT
- specification levels: security policies can be specified at two
different levels, either instance-level or schema-level. Instancelevel policies apply to a single instance (i.e. an item) only, while
schema-level policies apply to a set of instances simultaneously.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Security policies for Web data protection IV
ICN
IGUT
A policy type for access control
<Who, What, How, KindOfAccess, KindOfGrant>
- Who{UserID, Credential} denotes the way subjects are
qualified in the policy, either identity-based or credential-based
- What{Item, typeOfitem, setOfItems, setOfTypesOfItems}
denotes the target protection objects to which the policy applies.
In this way, it is possible to specify policies either at the instance
or schema level.
- How{whole, portion, content} denotes the kind of policy
protection granularity for the target protection object specified in
the What field.
- KindOfAccess{browsing, authoring} denotes the kind of access
to be allowed/denied on the protection object(s) of the policy.
- KindOfGrant{Grant, Deny} denotes the kind of authorization to
be granted.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Security policies for Web data protection V
ICN
An example policy type
<Credential, Item (wetland), portion, browsing, grant>
corresponds to a permission grant policy for credential-based
browsing of a selected portion of an item
The shown policy type specification is a design tool, allowing the
Security Administrator to select the most appropriate type of
policy for a target source.
IGUT
Important to remember:
The level of flexibility required in specification of complex
security policies determines the accompanied development
(programming) and administration costs.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Multilanguage support I
ICN
Proper multi-language support requires a certain structure in the
underlying relational database.
We need to have a master table of all of the different words in all
of the different languages.
When a new language is to be added, no new tables or columns
are added (this may be done only when developing the WIS).
Only new rows to existing tables and columns are added and this
allows to support an unlimited number of languages.
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Multilanguage support II
A multi-language database example
ICN
Part ID
EX1
EX2
EX3
EX4
EX5
EX6
EX7
Att Desc
MULTI120
MULTI121
MULTI122
MULTI120
MULTI123
MULTI121
MULTI121
Value
MULTI125
10
MULTI126
MULTI127
MULTI128
9
8
features table with multi-language support
IGUT
Attribute_ID
MULTI120
MULTI121
MULTI122
MULTI123
MULTI125
MULTI126
MULTI127
MULTI128
MULTI120
MULTI121
MULTI122
MULTI123
MULTI125
MULTI126
MULTI127
MULTI128
Language
English
English
English
English
English
English
English
English
Italian
Italian
Italian
Italian
Italian
Italian
Italian
Italian
Attribute_Value
Color
Size
Material
Type
Black
Leather
White
Football
Colore
Formato
Materiale
Digitano
Nero
Cuoio
Bianco
Gioco
master list of language attributes
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS I
ICN
What is a GIS? (more than one definition)
GIS have been developed in recent years for the purpose of
using and studying geographic information.
Geographic information is information that expresses and
describes the locations of objects and features (what is where on
the earth) like for example:
- physical features or phenomena like rivers, roads, forests etc
- human features or phenomena like population, migration etc
With GIS it is possible to map, model, query, and analyze large
quantities of data all held together within a single database.
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS II
ICN
What is the value of combining geographic information?
A single set of geographic information is limited in its analysis
potential. It can be used to provide information about the
location of the features to which it relates and this can be used
as the basis for recording and investigating distributions.
However, the great appeal of GIS stems from their ability to
integrate different geographical information themes and to
provide a powerful repertoire of analytical tools to explore them.
The geography, or location, is used as the common denominator
– the link.
IGUT
In this way, the GIS has the potential to generate new
information on patterns and relationships between multiple sets
of geographic information that would otherwise be missed, and
to aid in answering more complex questions or decision making.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS III
ICN
An example of a GIS based analysis: map overlay analysis
GIS allows us to arrange information about a given region or city
as a set of maps with each map displaying information about one
characteristic of the region. Each of these separate thematic
maps is referred to as a layer, coverage, or level.
Each layer is carefully overlaid on the others so that every
location is precisely matched to its corresponding locations on all
the other maps. The bottom layer represents the grid of a
common coordinate system.
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS IV
ICN
What are the essential elements of geographic information?
- Location of the geographic information – maps use a coordinate
system to allow locations to be read
- The shape (geometry) of the geographic information – the shape
of the features and themes are drawn onto the map
- The description of the geographic information – a legend
provides descriptions of the shapes drawn on the map
Geographic Information
Metadata
IGUT
Location
Shape
Description
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State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS V
ICN
IGUT
What are the essential elements of geographic information?
- Metadata are also called “data about data”.
They are used to determine if the data meets the user’s needs.
They play a critical role in GIS system interoperability. Metadata
describe different aspects of data, including:
Identification – What is the name of the data set? Who
developed the data set? What geographic area does it cover?
What themes of information does it include? Restrictions on
accessing or using the data.
Data Quality – Information that allows a user to decide if the
data are suitable for his or her purpose. What is the positional
and attribute accuracy? Are the data complete?
Entity and Attribute Information – What geographic information
(roads, houses etc) is included? How is the information encoded
and what do the codes mean?
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS VI
ICN
IGUT
How do we represent shapes?
Two methods:
1. Physical features and human features are reduced to points,
lines and polygons which are linked to information that
describes them (attributes). This method of representing the
world around us is called vector.
2. Physical features and human features are divided into a regular
grid with each cell in the grid holding descriptive information
about its contents. This method of representing the world
around us is called raster.
Shape representation with vector
According to the vector method, all shapes, no matter how
complicated, can be simplified to a number of very simple
tables containing information about the shapes that are linked
together. The linked tables together use a database to draw the
shapes. Possible to represent: points, lines, polygons
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS VII
Example of a vector representation
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x2, y2
x1, y1
N1
x6, y6
Arc 1
Arc 2
Arc 3
x5, y5
X coordinate
Poly B
Poly A
x3, y3
x4, y4
N2
x7, y7
Y coordinate
IGUT
Polygon topology
Polygon Arcs
A
1, 2
B
2, 3
Arc
Node topology
Node
Arcs
1 1, 2, 3
2 1, 2, 3
Arc
Arc topology
From Node To Node Left PolygonRight Polygon
1 N1
N2
Poly A
2 N1
N2
Poly A
Poly B
3 N1
N2
Poly B
Arc coordinates
Coordinates
1 x1, y1; x2, y2; x3, y3; x4, y4
2 x1, y1; x5, y5; x4,y4
3 x1, y1; x6, y6; x7,y7; x4, y4
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS VIII
ICN
Shape representation with raster
Physical features and human features can usually be divided into a
grid and this is a much more simple way of representing the world
around us than using points, lines and polygons.
An example of a lake in a park
Lake
Park
Lake
Park
IGUT
F
F
F
F
F
F
F
F
L
F
F
F
F
L
L
L
F
F
F
L
L
L
F
F
F
L
L
L
F
F
F
L
L
L
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
Raster is limited in the reality with
which it can represent geographic
information and the detail that the
raster data is able to provide is
limited by the size of the grid that
is used.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS IX
ICN
Describing vector data
In the same way that the information needed to draw points, lines
and polygons using the vector method can be held in one or more
tables, so the attribute information can also be held in tables.
The following table holds information about two polygons that
form boundaries of two agricultural fields. The crop planting
history of the last two years is recorded in the table.
Polygon
A
B
IGUT
Area (m2) Crop (2004) Crop (2003)
180355 Wheat
Wheat
174023 Barley
Fallow
Describing raster data
Raster data does not use tables of information linked to the grid
shapes to describe the information. Instead, each grid cell
contains a single code that represents the geographic information
held within the cell.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS X
ICN
The components required to represent the physical features and
human features in a geographic information system
3D to 2D
projection
earth shape
model
Geographic
Information System
Simplified
representations of
physical features and
human features
IGUT
RASTER
Coded grid
VECTOR
Tables with
shape
information
Tables with
attribute
descriptions
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS XI
ICN
IGUT
Spatial relationships
GIS have the power to record more than location and simple
attribute information. In some situations, we will want to examine
spatial relationships based upon location:
- Absolute and relative location
- Distance between features
- Proximity of features
- Features in the “neighborhood” of other features
- Direction and movement from place to place
- Boolean relationships of “and”, “or”, “inside”, “outside”,
“intersecting”, “non-intersecting” etc.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
GIS XII
ICN
IGUT
Functional relationships among geographic features and their
attributes
Information about how features are connected and interact in reallife terms.
As an example, consider the case of assessing habitats, where
various environmental conditions function together to define the
optimal living environments for certain species.
Logical relationships among geographic features and their
attributes
Logical relationships involve “if-then” and “and-or” conditions that
must exist among features stored in the dataset.
As an example, development may disallowed in the habitat of
some endangered species.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Web-based GIS
Motivation for the development of a Web-based GIS
ICN
- To provide a widely accessible on-line tool that will offer a
powerful repertoire of analytical tools to explore the data
- To make geographic information available for use within a large
spatial data infrastructure (interoperability support)
- To utilize the geographic information available in a large spatial
data infrastructure (geographical information e.g. for population
density, road network etc)
IGUT
- To support decision making for geographically distributed
organizations
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Conclusion
ICN
We provided an overview of the technologies and design
concerns we (would like to) take into account in the development
of the MedWet WIS
- WIS basic design concepts
- WIS architecture
- Security policies for the protection of Web data
- Multilanguage support
IGUT
- Coverage of basic GIS functionality
- Technology perspectives
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
3rd Technical MedWet Codde Meeting,
ICN
MCU Athens, 9-11 February 2006
MedWet WIS Access Control Policy
Panagiotis Katsaros
Dept. of Informatics
Aristotle University of Thessaloniki
54124 Thessaloniki, GREECE
IGUT
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE
State of the art and perspectives of WIS
Panagiotis Katsaros / Aristotle University of Thessaloniki, Greece
Basic principles
ICN
The level of flexibility required in specification of complex
security policies determines the accompanied development
(programming) and administration costs.
Complex security policies impose high administration costs.
We propose an access control mechanism that will balance the
need for a functional and at the same time cost-effective solution
(limited development and administration costs).
IGUT
The proposed mechanism takes into account and keeps open the
prospects for the implementation of more advanced security
administration functionality.
MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE