Building Web Information Systems using Web Services

1
Building Web Information Systems using Web
Services

• Flavius Frasincar
• frasincar_at_few.eur.nl
• Erasmus University Rotterdam
• Eindhoven University of Technology

2
Contents

• Motivation
• Solution
• I Hera Methodology
• Conceptual Model
• Application Model
• Presentation Model
• Adaptation Model
• II Hera Web Service-Oriented Architecture
• Data Service
• Presentation Service
• Profile Service
• Adaptation Service
• Conclusions

3
Motivation

• There is a large amount of data that needs to be
  presented by Web Information Systems (WIS)
• The user wants to access a WIS using different
  devices
• There is an increasing need to personalize WIS
  based on the user preferences
• There is a need to make WIS interoperable
• Information available outside the organization
• Computational power outside the organization

4
Solution

• Model-driven methodology for designing WIS
• Better understanding of the system by stakeholder
• Reuse of previously defined models
• Checking the validity/consistency of/between
  models
• Automatic presentation generation
• Systems maintainability
• Distributed architecture based on Web Services
  (WS)
• Cross-platform applications
• Cross-language applications
• Loosely coupled components robust applications
• Reuse of existing WS

5
I Hera Methodology

• Conceptual Model
• Specifies the input data
• Application Model
• Defines the navigational aspects of the
  presentation of the input data
• Presentation Model
• Describes the layout and style information of
  the presentation
• Adaptation Model
• Gives the presentation customization based on
  user/platform features
• All models are represented in RDF(S)

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RDF(S)

• The foundation language of the Semantic Web
• Flexible (schema refinement and descriptions
  enrichment)
• Extensible (allows the definition of new
  resources/properties)
• Fosters interoperability (makes model semantics
  explicit)
• Compact representations (intensional information)
• Reuse of existing vocabularies
• Domain models (museum descriptions from TOPIA
  project)
• User profiles (User Agent Profile from mobile
  phone industry)

7
Adaptation Model

• User/Platform Profile stores device capabilities
  and user preferences
• User/Platform Profile is an extended version of
  the User Agent Profile (UAProf), a Composite
  Capability/Preference Profile (CC/PP) vocabulary
• Appearance conditions presence/absence of an
  element in a model
• Hera models are overlay models presence/absence
  of an element in a model implies its
  presence/absence in all subsequent models

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User/Platform Model
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Conceptual Model (CM)

• Describes the datas schema
• Based on the notion of a concept, an entity
  specific to a particular domain
• CM is a hierarchy of concepts relevant within the
  given domain
• Concept properties are
• Attributes refer to media items that
  characterize a concept
• (media types are based on
  MPEG-7)
• Relationships refer to other concepts

10
Conceptual Model (CM)
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Adaptation in CM
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Application Model (AM)

• Captures the logical (navigational) aspects of
  the presentation
• Based on the concept of a slice, a meaningful
  presentation unit which contains attributes and
  possibly other slices
• AM is a hierarchy of slices
• A slice is associated to a concept from CM
• Slice properties are
• Aggregations a slice embeds another slice or a
  set of slices
• References link abstraction

13
Application Model (AM)
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Adaptation in AM
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Presentation Model (PM)

• Defines the look-and-feel aspects of the
  presentation
• Based on the concept of a region, an abstraction
  for a rectangular part of a display area
• PM is a hierarchy of regions
• A region is associated to a slice from AM, and
  has a layout and a style
• A layout defines the positioning of regions in
  another region
• A style defines the font characteristics (size,
  color, etc.)
• Region relationships are
• Aggregations a region embeds another region or a
  set of regions
• References link abstraction

16
Presentation Model (PM)
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Layout and Layout-related Region Attributes
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Adaptation in PM
19
Presentation in Browsers (1/2)
HTML for PC
SMIL
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Presentation in Browsers (2/2)
HTML for PDA
WML
21
II Web Services
Web Service
Shape interface
Color data types
22
Hera Web Service-Oriented Architecture
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Data Service - WSDL

• ltwsdlmessage name"getDataRequest"gt
• lt/wsdlmessagegt
• ltwsdlmessage name"getDataResponse"gt
• ltwsdlpart name"getDataReturn"
  type"xsdstring"/gt
• lt/wsdlmessagegt
• ltwsdlportType name"DataService"gt
• ltwsdloperation name"getData"gt
• ltwsdlinput messageimgetDataRequest
  name"getDataRequest"/gt
• ltwsdloutput messageimgetDataResponse
  name"getDataResponse"/gt
• lt/wsdloperationgt
• lt/wsdlportTypegt

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Presentation Service

• ltwsdlmessage name"getPresentationRequest"gt
  
• ltwsdlpart name"in0 type"xsdstring"/gt
• lt/wsdlmessagegt
• ltwsdlmessage name"getPresentationResponse"gt
  
• ltwsdlpart name"getPresentationReturn"
  type"xsdstring"/gt
• lt/wsdlmessagegt
• ltwsdlportType name"PresentationService"gt
• ltwsdloperation name"getPresentation"
  parameterOrder"in0"gt ltwsdlinput
  message"imgetPresentationRequest"
  name"getPresentationRequest"/gt
  
• ltwsdloutput message"imgetPresentationResponse
  "
  name"getPresentationResponse"/gt
  lt/wsdloperationgt
• lt/wsdlportTypegt

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SOAP Messages
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Implementation

• Data transformations
• Model adaptation (CM, AM, PM)
• Convert one model instance into another model
  instance
• (CMI-gtAMI-gtPMI)
• Presentation generation (PMI to
  HTML/SMIL/cHTML/WML)
• XSLT stylesheets specify the transformations
  between the RDF/XML serialization of RDF(S)
  models
• Java code operating on RDF models instead of
  their RDF/XML serialization

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XSLT vs. Java
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Tools

• Data transformations
• Saxon (XSLT processor)
• Jena (for RDF processing)
• Java Web Services Axis
• SOAP monitor
• Java2WSDL
• Servlets support Tomcat
• Browsers
• Internet Explorer
• Real Player
• Microsoft Pocket PC
• Deck-it

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Conclusions

• Hera methodology
• Is a model-driven methodology for designing WIS
• Facilitates adaptation at conceptual, navigation,
  and presentation level
• Uses Semantic Web technologies RDF, RDF(S)
• Has an implementation based on Web Services
• Future work
• Separation of the current Presentation Service in
  two services Application Service and
  Presentation Service
• Implementation of conceptual model adaptation
• Dynamic construction of a WIS based on existing
  WS