Download ppt - MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE ICN IGUT 3 rd Technical MedWet Codde Meeting,

MedWet information and knowledge network for the sustainable development of wetland ecosystems / MedWet CODDE

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IGUT

3rd Technical MedWet Codde Meeting,

MCU Athens, 9-11 February 2006

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

- Design considerations and functions

Panagiotis KatsarosDept. of Informatics

Aristotle University of Thessaloniki54124 Thessaloniki, GREECE



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

- Design considerations and functions




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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

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

Web-based GIS


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1. THE CONTENT

- 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

WIS design concepts I


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C u sto m ers

K ey cu sto m ers C u sto m ers b y in d u stry

C o m p u ter in d u stryC u sto m er A

C u sto m er B

G ra p h

C o m p u ter in d u stry

C u sto m ers

C u sto m ers b y in d u stry

C u sto m er A

T ree fo r 'C u sto m ers'

K ey cu sto m ers

C u sto m er 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

WIS design concepts II


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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

WIS design concepts III


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WIS design concepts IV

- 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.


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- 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

WIS design concepts V


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WIS architecture I

Input Form

1 . P ick in g u pn ew co n ten t

2 . P ro cess in gC

BA

P rocessedcontent

3 . S to r in g A

B

C

Data

S y stem fu n ctio n s fo rp ick in g u p n ew co n ten t

A

B

C

Data

1 . S to r in g

2 . P ro cess in g /a ssem b lin g

C

BA

A ssem bledcontent

Layout

3 . P resen tin g

content

W eb P age

content

S y stem fu n ctio n s fo rp resen tin g co n ten t


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WIS architecture II

R ep resen ta tio n L a y er

A p p lica tio n L a y er

D a ta S to ra g e L a y er

C o n n ectio n P o in t

S y stem la y ers

P ick in g u p /P resen tin g

P ro cessin g /A ssem b lin g

S to r in g

F u n cto n a lity o f sy stem la y ers

C

BA

L a y o u t P a g e

A

B

C

Data storage layer:- relational database scheme- mechanism for generating Web pages dynamicallyApplication layer:- functions to store, process, present and pick up contentRepresentation layer:- page-oriented user interface that handles user interaction


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Dynamic Web Pages I

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

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


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Dynamic Web Pages II

First approach to create dynamic server-side pages:to write an HTML page with placeholders for content that should be retrieved dynamically from a databaseHTML 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

Bro

wse

r

Web

Ser

ver

Ap

p E

ngi

ne

Dat

abas

e

(1 )req u est

d y n a m icp a g e

(2 )fo rw a rdreq u est

(3 )ex ecu te co d e

(4 )req u est

d a ta

retu rnd a ta(5 )

d e liv erfin a lp a g e

(7 )

resp o n sew ith f in a l

p a g e(8 )

rep la ce co d eb y d a ta

(6 )

ca ll seq u en ce o f in fra stru ctu re fo rd y n a m ic serv er s id e p a g es


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Dynamic Web Pages III

Second approach to create dynamic server-side pages:to embed the HTML code inside the execution codewhen the page is requested, the content is dynamically fetchedCommon 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 pagean XML file can be transformed with the help of XSLT into any other data format such as, HTMLadvantage: several output formats can be produced for different user interface types by using the same XML documentit is possible to generate a Web version (HTML) and a printed version of the same XML data without changing the XML document


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Security policies for Web data protection I

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.


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Security policies for Web data protection II

Issues and requirements in defining security policies for Web data:

- 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.


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Security policies for Web data protection III

- 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).

- specification levels: security policies can be specified at two different levels, either instance-level or schema-level. Instance-level policies apply to a single instance (i.e. an item) only, while schema-level policies apply to a set of instances simultaneously.


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Security policies for Web data protection IV

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.


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Security policies for Web data protection V

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.

Important to remember:The level of flexibility required in specification of complex security policies determines the accompanied development (programming) and administration costs.


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Multilanguage support I

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.


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Multilanguage support II

A multi-language database example

Part ID Att Desc ValueEX1 MULTI120 MULTI125EX2 MULTI121 10EX3 MULTI122 MULTI126EX4 MULTI120 MULTI127EX5 MULTI123 MULTI128EX6 MULTI121 9EX7 MULTI121 8

Attribute_ID Language Attribute_ValueMULTI120 English ColorMULTI121 English SizeMULTI122 English MaterialMULTI123 English TypeMULTI125 English BlackMULTI126 English LeatherMULTI127 English WhiteMULTI128 English FootballMULTI120 Italian ColoreMULTI121 Italian FormatoMULTI122 Italian MaterialeMULTI123 Italian DigitanoMULTI125 Italian NeroMULTI126 Italian CuoioMULTI127 Italian BiancoMULTI128 Italian Gioco

features table with multi-language support

master list of language attributes


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GIS I

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.


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GIS II

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.

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.


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GIS III

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.


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GIS IV

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

G eo g ra p h ic In fo rm a tio n

L o ca tio n S h a p e D escr ip tio n

M eta d a ta


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GIS V

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?


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GIS VI

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 vectorAccording 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


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GIS VII

Example of a vector representation

X co o rd in a te

Y co o rd in a te

x 2 , y 2 x 1 , y 1 N 1

x 5 , y 5

x 4 , y 4 N 2 x 7 , y 7

x 6 , y 6

x 3 , y 3

A rc 1

A rc 2 A rc 3

P o ly A

P o ly B

Polygon ArcsA 1, 2B 2, 3

Polygon topologyNode Arcs

1 1, 2, 32 1, 2, 3

Node topologyArc From Node To Node Left PolygonRight Polygon

1 N1 N2 Poly A -2 N1 N2 Poly A Poly B3 N1 N2 - Poly B

Arc topology

Arc123

x1, y1; x2, y2; x3, y3; x4, y4Coordinates

x1, y1; x5, y5; x4,y4x1, y1; x6, y6; x7,y7; x4, y4

Arc coordinates


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GIS VIII

Shape representation with rasterPhysical 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

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.

F F F F F F F F F F F F F L L L L F F F F F F L L L L L F F F F F F F L 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

Lake

Park


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GIS IX

Describing vector dataIn 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 Area (m2) Crop (2004) Crop (2003)A 180355 Wheat WheatB 174023 Barley Fallow

Describing raster dataRaster 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.


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GIS X

The components required to represent the physical features and human features in a geographic information system

C o d ed g r id

R A S T E R V E C T O R

T a b les w ithsh a p e

in fo rm a tio n

T a b les w itha ttr ib u te

d escr ip tio n s

S im p lif iedrep resen ta tio n s o f

p h y sica l fea tu res a n dh u m a n fea tu res

G eo g ra p h icIn fo rm a tio n S y stem

3 D to 2 Dp ro jectio n

ea rth sh a p em o d el


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GIS XI

Spatial relationshipsGIS 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.


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GIS XII

Functional relationships among geographic features and their attributesInformation about how features are connected and interact in real-life 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 attributesLogical 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.


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Web-based GIS

Motivation for the development of a Web-based GIS

- 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)

- To support decision making for geographically distributed organizations


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Conclusion

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

- Coverage of basic GIS functionality

- Technology perspectives


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MedWet WIS Access Control Policy





MedWet WIS Access Control Policy




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Basic principles

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).

The proposed mechanism takes into account and keeps open the prospects for the implementation of more advanced security administration functionality.