Are there any security issues with NJIT

A comparison of modeling languages ​​for web applications

Acomparisonof

Modeling languagesFor

Web-Applications

Literature seminar as part of the doctoral program in business informatics

Supervisor: ao. Prof. Dr. Renate Motschnig-Pitrik

February 2001

Dipl. Wi.-Inf. Harald Kühn

University of Vienna

Institute For Computer science and business informatics

Dept. of knowledge technology

BPMS group

Brno Str. 72

A - 1210 Vienna

Email: [email protected]


content

1 Amanagement ................................................. .................................................. ....................... 3

1.1 Aleadership and motivation ............................................... ......................................... 3

1.2 A overview ofModeling languagesForWeb-Applications .........................5

1.3 Ae categorization of Web-Modeling languages.............................................9

2 Acomparisonframe ForWeb-Modeling languages...........................................10

2.1 Terminology ................................................ .................................................. ..... 10

2.2 Requirements for Web-Applications....................................................................11

2.3 The criteria of the comparisonframe ................................................. ...................... 12

2.3.1 Roles and authorizations ............................................ ................................ 13

2.3.2 Navigation .............................................. .................................................. ...... 13

2.3.3 Operations and application logic ............................................ ................... 14

2.3.4 Business processes and workflows ............................................ .................... 14

2.3.5 Size of the application ............................................ ....................................... 14

2.3.6 Application architecture .............................................. ................................... 15

2.3.7 Process model .............................................. ............................................. 16

2.4 A Case study: Web-Insurance ................................................ .............................. 16

3 Modeling languagesForWeb-Applications: Description, classification and

comparison..........................................................................................................................18

3.1 Ae Hypertext-oriented modeling language: OOHDM ................................... 18

3.1.1 Description .............................................. .................................................. ..18

3.1.2 Metamodel .............................................. .................................................. .... 21

3.1.3 Classification .............................................. .................................................. .22

3.1.4 Modeling example .............................................. ...................................... 23

3.2 Ae Requirements engineering oriented modeling language: E-BPMS ........ 24

3.2.1 Description .............................................. .................................................. ..24

3.2.2 Metamodel .............................................. .................................................. .... 27

3.2.3 Classification .............................................. .................................................. .28

3.2.4 Modeling example .............................................. ...................................... 29

3.3 Ae Software engineering-oriented modeling language: WebML ................. 31

3.3.1 Description .............................................. .................................................. ..31

3.3.2 Metamodel .............................................. .................................................. .... 34

3.3.3 Classification .............................................. .................................................. .35

3.3.4 Modeling example .............................................. ...................................... 36

4 Summary ................................................ .................................................. ........ 37

Literature ................................................. .................................................. ............................... 39

2


1 Amanagement

1.1 Aleadership and motivation

The Internet and those based on Internet technologies Applications open up to users,

such as companies, organizations and individuals to create new opportunities with one another

to interact. These interaction options range from simple

Exchange of information, such as is supported by e-mail, via the

Optimizing existing business activities, such as integration

interorganizational business processes based on B2B platforms, up to A- and

Implementation of completely new interaction and business models, for example virtual

Communities and Electronic Auctions [Timm98, TSSK98].

If you look at the Aset scenarios of Internet-Applications over the last few years

away so you can make a change of the pure provision of information

(WebSites) to complex, interactive and distributed Applications (Web-

Applications) watch [BGP00, BGP01]. Figure 1 describes this change of

Web-Sites too Web-Applications with the dimensions "Information", "Navigation" and

"Operation" (after [BGP00]).

NAVIGATION

navigation

structures

Web-Sites Web-Applications

information

structures

INFORMATION

navigation

dynamics

surgery

structures

NAVIGATION

navigation

structures

OPERATIONS

information

structures

INFORMATION

information

dynamics

Figure 1: From Web-Sites too Web-Applications

according to [BGP00]

Be in [BJK00] For execution of E-businessApplications the phases "Service

Navigation "," Service Negotiation "and" Service Execution "are described in the phase

"Service Navigation" provides information to an interested party,

for example about products, services etc. Then in the "Service

Negotiation "additional information and conditions can be agreed, for example

by Web-Application interactive customized offers are created. In the

In the final "Service Execution" phase, it is then actually carried out of

Business transactions in which contracts are concluded, specific payment and product flows

etc. are involved. Ae variety of previous Web-Applicationsi.e. Web-Sites,

only supported the "Service Navigation" phase. This includes, for example

Company homepages and homepages of Public Adirections, general

Information such as product descriptions, directories, opening times, etc. are available

put. These have been and will be successively expanded to include functionalities that also include the

Agift and processing of Allow information ("Service Negotiation" and "Service

Execution "). This often leads to new aspects For the creation of the Web-Application

to wear as the consideration of Products and business processes [BJK99], new

3


organizational framework such as relocations of Competencies or

IT aspects such as security [Schä99], scalability [NMMZ00],

Integration of new Applications with existing or third-party systems [WiFe98] or also

the (sometimes forced) use of new technologies and new methods [WfMC00,

iPla01, OMG01b, W3C01]. This adds complexity ofWeb-Applications and

their creation in comparison to Web-Sites or traditional uses increased.

Figure 2 shows the interplay between the core elements of Company [JKBH98]

and the Aflow of information technology, which is both supportive and inhibitory,

for example in shape of Old applications, can work. The complexity is exacerbated

ofWeb-Applications additionally due to the almost always prevailing time shortage in

Web-Application developments. In [ClEd99] an impressive case is described that

a Web-Application despite known errors due to the prevailing competitive pressure

had to be delivered.

Especially due to the fast change cycles and the complexity described ofWeb-

Applications increases the need in development ofWeb-Applications

proceed methodically, i.e. with the help of suitable procedural models, and

also to be developed on a model basis, i.e. with application of tool-based Web-

Modeling languages.

Business processes

Products

Information

technology

organization

: interdependent: implemented by means of: enabled and limited

according to [JKBH98]

Figure 2: Core elements of Companies

The present work gives an overview of current approaches For the modeling of

Web-Applications, presents you comparisonframe For the classification ofWeb-

Modeling languages ​​and represents three Web-Modeling languages opposite each other.

The structure of the thesis is as follows: Chapter 2 defines important terms and

describes requirements for Web-Applications. These requirements become a

comparisonframe ForWeb-Modeling languages derived. A Case study with which

the Asentence of the respective modeling language is clarified, closes the chapter. In

Chapter 3 will be the Modeling languages OOHDM, E-BPMS and WebML described

and based on the comparisonclassified under the frame. For any modeling language, this will be

Case study illustrated. Chapter 4 summarizes the classifications from Chapter 3 and

compare them. The final chapter 5 summarizes the results of the work

together and gives an outlook on potential further research areas and

Developments.

4


1.2 A overview ofModeling languagesForWeb-Applications

There are now a large number ofModeling languagesFor the specification and

the design ofWeb-Applications. Figure 3 shows this in the form of a

Dependency tree shows the relationships between current Web-Modeling languages 1 .

Ae Dependency describes that a downstream modeling language is based on the concepts

the upstream modeling language or the upstream modeling approach

builds up. Entity-Relationship-Modeling (ERM) plays two central roles.

[Chen76] and object-oriented modeling (OOM) [Jaco94, RBPEB91] 2. How

Figure 3 shows each one presented here is based Web-Modelling language at least

either of these two approaches. The following is For each WebModeling language

Figure 3, except for those detailed in Chapter 3 Web-Modeling languages

OOHDM, E-BPMS and WebML, given a brief description 3.

E-BPMS

MM

e 3 -value

PM

WSDM

UML

UML

Web-Extensions

OOM

WebML

EORM

XWMF

RNA

OOHDM

ERM

HDM

RMM

ARANEUS

Figure 3: Dependency tree ofWeb-Modeling languages

RDF

swirl

HDM-Lite /

automobileWeb

The Hypertext Design Model (HDM) was first introduced in 1991 of Garzotto et al. presented

[GPS91] and 1993 in [GPM93] and [GPS93] further refined to HDM2. HDM provides one

Hypertext modeling approach, which is two-tiered. The first stage is a

so-called conceptual schema, which shows the entities and relationships of the

Contains problem area. In the second stage, a navigation scheme is created using the

conceptual scheme "laid". This is based on views of the conceptual schema.

In other words: an entity schema is first defined and, based on it, the

Navigation structures to be able to navigate the contents of the entity schema. It

can also have multiple navigation schemes on a single conceptual scheme

can be defined, for example, to be able to implement different user roles

[GPM93].

In 1994 the Enhanced Object Relationship Model (EORM) of Long introduced

[Lang94]. The EORM extends the Object Modeling Technique (OMT) with the concept of

"Link Classes". This allows relationships to be typed and hierarchized in order to

1 Figure 3 does not claim to be complete, others Web-Modeling languages can

for example also in the manufacturer's product documentation of Application servers and content

Management systems can be found such as IBM WebSphere Commerce Suite [IBM00], Intershop Enfinity

[Inte00], Oracle Designer 2000 [Orac00], iPlanet Application Server [iPla01] or Coin interact! / Framework

[Coin00].

2 Further abbreviations used in the figure above are: MM (Metamodellierung) [KJKP99], PM

(Process modeling) [CKO92, Jung00], UML (Unified Modeling Language) [OMG01a] and RDF (Resource

Description Framework) [LaSw99].

3 Ae detailed description of all Web-Modeling languages is beyond the scope of this work, therefore

will be hereFor refer to the relevant literature.

5


subsequently For the methodological draft of Object connections and interactions

in Web-Applications to be used.

Hypertext naturally contains many relationships (links) between the individual

Information carriers. The 1995 of Isakowitz et al. published relationship

Management Methodology (RMM) (see ISB95]) extends HDM and is based on it

To design and maintain relationships in an orderly and formalized manner

manage [BBI96]. RMCase (see [DiIs95]) should provide the necessary

Provide tool support. A detailed description of the notation is given in [IKK98]

and in [IKK97b] different process models for application of RMM described.

To the draft too of complex Web-Sites to enable, Isakowitz et al. in

[IKK97a] further modeling concepts, for example the concept of M-Slices 4. M-

Slices can be compared with views of (sub) entities of a conceptual schema

that can also be nested hierarchically. Herewith stands a

Modeling concept available to be user-group specific Web-Sites from one

generate out conceptual schema.

The 1997 of Fernandez et al. featured STRUDEL Web-Site management system is

a development environment For the realization of complex Web-Sites that

Integrate information from different data sources [FFKLS97, FFKLS98]. The

Basic idea of STRUDEL is the separation of one Web-Application in three levels: the

Information provided by the Web-Application made available to the structure

the Web-Application by means of which the information is made accessible and the

Specification of the graphical user interface. Each of the three levels is in shape of

Graphs ("Data Graph", "Site Graph" and "HTML Graph") are described [FFKLS97]. These

Graphs can be queried with the declarative query language STRUQL 5 [FFLS97].

The query results of STRUQL can also be output as a graph, see above

that by querying a graph of level N, the graph of level N + 1 is generated

can be. This is used to maintain the levels consistently.

In 1998 Fraternali and Paolini published HDM-Lite [FrPa98], a procedure

for creation ofWeb-Sites. On the one hand, HDM-lite is based on concepts of ER

Modeling, on the other hand on HDM. In HDM-lite there are three logical levels

differentiated. The "Structure Schema" describes a data model with the entities and

Scope Relationships. The "Navigation Scheme" describes the actions

which are available to move between the hypertext objects of the "Navigation Scheme"

navigate ("traversal schema") and the access paths to of the hypertext objects

to access the entities and relationships of the "Structure Schema" ("access schema"). The

"Presentation Schema" describes how the information from the "Structure Schema" is transferred to the

User interface are presented. In [FrPa00] the HDM-Lite prototype becomes AutoWeb

described automatically from the schemes described above Web-Generate sites

can.

Also in 1998 of de Troyer et al. featured Web Site Design Method (WSDM) 6 is

a user-centered design method ForWeb-Applications [TrLe98, Troy98]. in the

Contrast to others Web-Modeling languages like HDM or RMM, that is

The starting point of the modeling is not an information model that describes the data,

the through the Web-Application should be made available, but the

4

The "M" in M-Slices comes from of the Russian matryoshka dolls, which are also (almost arbitrarily)

can be nested.

5

STRUQL: Site TRansformation And Query Language (see [FFLS97]).

6

WSDM is pronounced "Wisdom".

6


future users who have the Web-Application should use. As a result, de

Troyer et al. a higher quality of use of the application and an increased acceptance by

the users [GMT98]. The WSDM consists of different phases, with de Troyer et

al. leave open which specific Modeling languages in the individual phases of the

Asentence come. The individual phases are "user modeling" with the sub-phases "user"

Classification "and" User Class Description "," Conceptual Design "with the sub-phases

"Object Modeling" and "Navigational Design", "Implementation Design" and

"Implementation" (For a detailed description of the phases see [Troy98]).

Furthermore, in 1998 of Atzeni et al. those in the context of the ARANEUS project

developed ARANEUS Web Design Methodology (short: ARANEUS Methodology)

published [AMM98, MMAC99]. This is based on RMM, i.e. the starting point For the

Design a WebApplication is also a conceptual data model from which the

structural elements of the For the navigation necessary hypertext level derived

become. The ARANEUS Methodology distinguishes between the following six phases: In phase (1),

carried out the conceptual database design. On the one hand, this is based on this

logical database design (2) and on the other hand the conceptual hypertext design (3)

carried out. The two main aspects of hypertext conceptual design are choice

of the entities from the conteptional database design that are part of the hypertext

should be, and the definition of Navigation paths between these entities. The

The result is the Navigation Conceptual Model (NCM). Based on the NCM, the

logical hypertext design (4) describes how the individual pages of a Web-Application

are built up and connected. This is done in the ARANEUS Data Model (ADM)

pictured 7. In phase (5) - Presentation Design -, based on the ADM, the layout

the respective side of the WebApplication defined. Finally, in phase (6)

the presentation design defines views on the logical database design that

"filter" those information which of the respective WebPage are needed.

Finally, the pages of the

Web-Application can be generated [MAMMS98a]. In [MMAC99] there are tools

that offer support in this regard.

The Unified Modeling Language (UML) has been standardized since 1997

Modeling language For the object-oriented specification of Software systems. The

UML is made up of nine model types that represent different aspects of a software system

describe [OMG01a]. So that the UML For different Aset scenarios adapted and

can be adapted to specific objectives of a modeling, the

Mechanisms "Stereotypes" 8, "Tagged Values" and "Object Constraint Language" for

Disposal 9. These are also used to create the UML For the modeling ofWeb-

Applications to adapt. In 1999 Conallen published his UML Web Application

Extensions [Cona99]. He introduces new stereotypes and symbols For Concepts like "Web

Page "," Hyperlink "," Forms "," Frames "," Client component "and" Server component "

a 10. The focus of the WAE is on implementation-related modeling, especially the

interaction ofWebClient and Web-Server to get out of it with help of Generators one Web-

7

In [MMA99] the relationships between ADM and XML-based data descriptions

explained.

8

Since the stereotype mechanism is a change and expansion of existing UML modeling concepts,

however, a definition of new modeling concepts is not allowed in […] stereotypes too

as "metamodeling concepts For Arms ".

9

A [ErPe00] and [ErPe00] give a more detailed description of the UML extension mechanisms

[OMG01a].

10

Ae detailed description of the Web Application extensions For UML (WAE) can be found in [Cona00].

Ae A brief description of the WAE can be found in [Koch01], for example.

7


To be able to generate application. AAnother approach For the modeling ofWeb-

Applications based on the UML, Baresi at al. in [BGP01]. The presented

W2000 Framework links HDM and UML in the following points [BGP01, p. 2]:

• "Defining several stereotypes and customizations of diagrams to render HDM with UML;

• Specifying guidelines to use UML as a way to specify some of the dynamic and

operational aspects of web applications;

• Refining use case diagrams to describe high level user requirements, related to both

functional and navigational aspects. "

In [VSSdS00] of Vilain et al. In addition, an approach is described that supports the Use Case

UML diagrams extended to User Interaction Diagrams (UIDs). As a result, the

Requirements definition For interactive Applications, particularly Web-Applications,

be improved, since the UIDs (partly) the navigation structure of a hypertext

Application can be derived.

The of Klapsing and Neumann published eXtensible in 1999 Web Modeling

Framework (XWMF) provides a modeling language for formal description ofWeb-

Applications available [KlNe99, KlNe00]. XWMF is based on RDF [LaSw99], i.e.

XWMF is made up of a crowd of RDF schemes and RDF descriptions [KlNe00],

through which the properties of a Web-Application, separated by structure and content,

can be described. The starting point in XWMF are so-called "Generic Web

Engineering schemes "which are from the"Web Object Composition Model "(WOCM) and

other schemes such as "Content Management Scheme", "Access Control Scheme" or

"Navigation scheme" exist [KlNe00]. More schemes can be For new Asentence areas

To be defined. Based on the generic schemes, specific types ofWeb-

Applications can be described by expressions of the schemes. These will "Web

Application Schemas ". Ae concrete Web-Application ("Web Application

Description ") is made with the help of the generic schemes and the"Web Application schemes "

modeled. The GRAMTOR tools are available for processing the RDF models

(graphical RDF editor), WebObjectComposer and WebObjectBrowser available

[KlNe00].

The 1999 of Gordjin et al. presented e 3 -VALUE framework focused on the

Requirements definition For EcommerceApplications 11 [GAvV99]. It is in [GAvV99]

argues that requirements under of EcommerceApplications Not of the

future users can be derived, since these are (mostly) not known.

Rather, requirements must be systematically designed. Within of e 3 -VALUE

an e-commerce application is described on three levels of abstraction: the

Business model, business processes and the underlying software architecture

[GAvV00a]. The business model describes how business partners interact with each other,

in order to conduct their business successfully [GAvV00b]. A

Business process model describes which activities in which order of whom under

With the help of which resources are carried out. The software architecture describes

the individual components of the underlying information system. With help of

Scenarios 12 are individual business alternatives starting with the business model up to

the software architecture level played through [GdBA01].

11

In the present work, e-commerceApplications as a special category ofWeb-

Applications seen.

12 3

A In e -VALUE, the scenario is one or more paths through the models described that lead to a specific

Represent business case. Ae tool support For this scenario analysis is described in [GAvV99,

GAvV00a, GAvV00b, GdBA01] not described and does not seem to be available.

8


The Relationship Navigation Analysis (RNA) was made of Yoo and Bieber 2000

published and is independent of the application area and modeling language

Process model for description and analysis of Relationships [YoBi00a], [YoBi00b].

The RNA can For Areas such as system analysis, system design, specification of

HypermediaApplications etc. can be used. Within the RNA there are five steps

distinguished, with the help of which an area of ​​application, for example a Web-Application,

is described and examined. In the "Stakeholder Analysis" roles are identified

which have different perspectives on the area of ​​application to be examined. The

"Element Analysis" focuses on the respective interests of the roles and describes them

Aspects such as components, entities of an application area, their attributes, etc. For

every element identified in the "Element Analysis" becomes a "Relation Analysis"

carried out. This will identify the important relationships and potentially new ones

Elements that are connected to the original elements through these relationships,

found. The "Relation Analysis" can be carried out on three levels of abstraction:

"Generic", "Application area-dependent" and "Application area-independent". The

"Navigational Analysis" describes For any role, like this role between the elements

can navigate from and access the "Element Analysis". For one

Assessment of the relationships is made in the concluding "Implementation Feasibility"

Analysis "performed a cost-benefit analysis to decide which

Relationships For the application to be created is relevant or justifiable

Effort can be realized.

1.3 Ae categorization of Web-Modeling languages

Modeling languagesForWeb-Applications are from different research disciplines

emerged and also have different objectives that correspond to the

models created in each case can be tracked. Looking at the ones presented in Figure 3

Approaches, three main categories can be identified in which the

Modeling languages can be divided (see also Figure 4). Chapter 3 will

For a representative presented in detail for each category.

• The first category is requirements engineering [Jark99, MCN92, SMMM98].

Web-Modeling languages like E-BPMS, e3-value and WSDM focus on the

Modeling of the user and business requirements of a Web-Application.

Aspects of generation of executable Web-Applications or of Components,

which in a Web-Application can be integrated, thereby playing a

subordinate role.

• The second category is software engineering [Booc94, PoBl96, Somm00].

This includes approaches such as UML Web Extensions, WebML and XWMF. The

The focus is on formal or semi-formal modeling and

Specification of the Web-Application. Executable Web-

Applications can be generated.

• The third category is hypertext engineering [BBI96, HaSc94, YoBi00b]. approaches

Examples of this category are ARANEUS, OOHDM and RMM. The contemplation

the navigation structures within a WebApplication and at the

User interfaces are the central element. Form the origin

Work like HDM that is based on the modeling of Hypertext and complex hypertext

Focus documents, and Web-Applications as a next generation of

View hypertext documents.

9


E-BPMS

MM

e 3 -value

PM

WSDM

Category: Requirements

Engineering

UML

UML

Web-Extensions

OOM

WebML

EORM

RDF

XWMF

RNA

OOHDM

ERM

HDM

RMM

ARANEUS

swirl

HDM-Lite /

automobileWeb

Category: Software engineering Category: Hypertext engineering

Figure 4: Categorization of the Web-Modeling languages

2 Acomparisonframe ForWeb-Modeling languages

2.1 Terminology

Some important terms that are used in the For this work central

Areas of Web-Engineerings and modeling often - but often too

different - be used.

Under one Web-Site is understood in the following to be an information structure that uses

of Internet technology, mostly anonymous users, For Read access provided

turns 13.

Ae Web-Application is a (mostly) interactive and distributed information system,

which is based on internet technology. In addition to read access to the Web-Site offers the

Web-Application also the possibility of the underlying information structure through the

Change user 14.

Web-Applications are, as described in Chapter 1.1, mostly complex Applications. Around

Models are often used to make this complexity manageable ForWeb-Applications

created. In the computer science and business informatics literature, different

Model terms described and used. In the present work the

constructivist model term used, under which one a model as "the result

a construction of a modeler who For Model user a representation of a

Originals declared at a time as relevant with the help of a language "understands [Schü98,

P. 59]. 15th

13

Ae Web-Site is, for example, the person register of a public administration, which is on the Internet

is published.

14

Ae WebApplication is for example a of Customer service offered on the Internet by a bank through the

Account postings can be carried out. This is the basis for the information system

Information structure, i.e. the account data, changed.

15

In contrast to the image-oriented model term [Stac73], in which a model is an "image" of the

Represents the real world, in the constructivist concept of the model, the model is a "role model" For the real world, i.e.

an (ideal) specification For the real world that is then to be implemented (cf. also [Jung00]).

10


model

is construction

of

described

by

Web-Application

Web-

Modeling language

makes concepts

explicit of

described

by

meta-

model

Figure 5: Relationships between the terms

A modeling language is used to create a model. Ae

Modeling language consists of modeling elements and rules like the

Modeling elements can be used for modeling. Ae Web-

Modeling language thus consists of modeling elements and rules, using

those Web-Applications can be described.

Following the language-based metamodel term (cf. [Stra96]), a

Metamodel understood the model of a modeling language. The metamodel describes

accordingly the modeling elements and rules of the modeling language 16.

2.2 Requirements for Web-Applications

Web-Applications are subject to a multitude of Conditions. These are enough of

Requirements that relate to manageability up to system-technical requirements.

This chapter gives an overview of such requirements 17. There one Web-

Modeling language a WebApplication describes (see chapter 2.1), a Web-

Modeling language take these requirements into account. The featured

Requirements therefore serve as a starting point in Section 2.3 For the identification of

Criteria one comparisonframe, based on that Web-Modeling languages compared

can be.

1. Scalability

The internet is available worldwide. This stands ForWeb-Applications potentially one

large, almost unlimited, number of User available 18. The design ofWeb-

Applications should therefore include aspects of both performance and scalability

consider.

2. Integrability

The existing IT infrastructures and the software landscapes of today

Companies and organizations have mostly grown over time. Web-

Applications can therefore often not be completely redesigned, but

must be integrated with existing or third-party systems [BJK00]. also

are in the environment of the Web-Application development a variety of different

- partially complementary, partially competing - technologies are available. This

has an inherent complexity ofWeb-Applications. Web-Applications should

16

The metamodels presented in Chapter 3 describe the AFor the sake of simplicity, only the modeling elements

the modeling language. The rules are not listed.

17

Similar requirements from the point of view of network computing or e-business can be found in [NMMZ00]

or [KJB00].

18

If so, this and the third requirement are put into perspective Web-Applications can be used in an intranet

and this limits the number of users and accessibility.

11


therefore be easy to integrate, for example via open or standardized

Interfaces.

3. Security

Due to the open accessibility of the Internet and the associated

Security issues must be in Web-Applications Security mechanisms

implemented or used (see also [RKN00]). Security mechanisms should

should be offered on (at least) two levels: (a) on the system level

For example, unauthorized access can be avoided through encryption processes

and (b) at the application level, the application data should be transacted

"logically" protected (transaction security).

4. Operability

Web-Applications are often interactive, hypertext-oriented Applications. The

Users are mostly anonymous and sporadic users. Therefore should the

The user interface is intuitive and the functionalities accessible with it are minimal

Aworkload to be found and applicable.

5. Distribution

A Business model describes how a company acts in the market for products

or to provide or use services. Internet technologies and

based on it Web-Applications offer the option of existing

Expand business models or introduce new business models (cf. [Timm98]).

Often, cross-company business processes result from

cross-organizational and distributed Web-Applications realized and integrated

become.

6. Maintainability

As a result of the requirements described in points 1-5 Web-

Applications mostly complex Applications. Added to this is a special one

Expression ofWeb-Applications, the e-businessApplications, the short and yourself

rapidly changing development cycles (see also [KJB00]). Maintainability will

including through prototyping approaches and changes to already operational ones

Applications difficult 19.

2.3 The criteria of the comparisonframe

The comparisonThe framework of the present work consists of seven criteria. The criteria

cover both the "what" of a Web-Modelling language, i.e. which aspects

should be modeled, as well as the "how", i.e. in which way modeled

shall be. The following subsections describe these criteria. To meet the criteria on the

to be compared Web-