1. Web Engineering & Web Information Systems Technology
Geert-Jan Houben

2. Content Web information systems evolution WIS engineering XML & XQuery
RDF & OWL
Web services
WS protocols

3. Web Information Systems

4. Web Information System
Information System based on Web technology (Web-based, Web-aware, Web-enabled etc.)
Information system
Exchanges information with Object System (= business process)
Stores and manages information: data-intensive
Requires careful engineering of information exchange

5. Web Information System
Web technology can be used as front-end, e.g. application is available on the Web (or Intranet) via a browser
Enables easy use and maintenance of (personalized) end-user access
Web metaphor is appealing for end-users
Requires different techniques for engineering the system’s interfaces

6. Web Information System
Web technology can also be used in back-end of information system
Organize (connect) the data inside the system using Web technology
Use World Wide Web as provider of data (or Intranet)
Typically highly volatile information (distributed and heterogeneous)
Requires different techniques for engineering the implementation

7. Examples Real-estate sales Employee databases Museum databases
Digital libraries
Mail order catalogs
Reservation systems
Auctions, virtual marketplaces
EPG (Electronic TV Program Guide)
Ref: Special section on Web Information Systems in Communications of the ACM, July 1998, Vol. 41, No. 7

8. Evolution in WIS Technology

9. Evolution in hypermedia
First: standalone special-purpose systems
Now: Web-based
From authoring to designing to generating
From static to dynamic (generated from database query result)
From single site to portals (integrated access service)
From read-only to interactive and often collaborative (read-write)

10. Evolution in Web Languages
HTML written by author
Easy, uniform interface
Large effort for maintenance
Not suited for changing information
Automatically generating information
First, using templates (and databases)
Later, using XML and XSLT transformations
Automatic processing of information
Explicit metadata (RDF)
Agreement on meaning (ontologies)
Semantic Web: from human-readable via machine-readable to machine-processable

11. SemWeb “Layer Cake”

12. Other Views
WebML: “A Web-enabled software system whose main purpose is to publish and maintain large amounts of data”
exploratory, browsing-oriented, personalized interfaces
(highly volatile) data stored by means of DBMS technology
OOHDM: “WWW brought new generation of IS”
hypermedia navigation through heterogeneous information space
operations querying or affecting that information
constant change, new navigation and services
“Web-based applications, first good hypermedia applications”
RMM: “History of graphics designers + programmers”
Nielsen: “On the Web, the only constant is change. A site that works perfectly as long as its stays the same will quickly die.”
“Healthy navigation structure key to success”

13. WIS Engineering

14. Device Dependency
HTML
SMIL
WML

15. WIS Engineering Methodology
Design of WIS requires careful engineering of information exchange between IS and OS
Implies engineering of front-end (interface) and back-end (storage & retrieval)
Professional applications: “from art to engineering”
well-founded (software) engineering methodologies
model-driven

16. Ref: wwwis.win.tue.nl/~hera
Hera: motivation
Methodologies exist for manual hypermedia presentation design, Hera targets automated presentation
Automated presentation is important for databased content (the ‘deep web’) as opposed to manually crafted content (the ‘surface web’): most WIS are data driven
Ref: wwwis.win.tue.nl/~hera

17. Hera Methodology Model-driven methodology, defines design phases:
Conceptual Design that results in Conceptual Model (CM, describes data content used for generation of hypermedia presentations) construction
Application Design that results in Application Model (AM, describes the navigation structure and functionality) construction
Presentation Design that results in Presentation Model (PM, describes spatial layout and rendering of hypermedia presentations) construction

18. Hera Models
Models fully specify application; hence, there is no need of additional programming
Models are used by a generic Hera engine for generation of WIS application pages (by on-demand instantiations of model subsets)

19. Hera Architecture
Defines how the models are used for automatic generation of hypermedia presentation

20. Conceptual Model
Provides a uniform semantic view over different data sources that are integrated within a given Web application.
Consists of hierarchies of concepts relevant within the given domain, their properties, and relations.

21. Conceptual Model
Defines the data content in terms of RDFS (concepts, attributes, properties)

22. Application Model
Navigation structure of a hypermedia application on top of CM
Hypermedia dynamics (navigation structure updates and application functionality) of a hypermedia application

23. Slices

24. AM Example

25. Data Manipulations Defined as SeRQL queries
Used for processing forms (handle user input)
Q1 creates instances of SelectedPainting according to the SelectForm form content
CONSTRUCT
{P}<rdf:type>{acm:SelectedPainting>}
FROM
{P}<rdf:type>{cm:Painting};
<cm:aname>{Paname}
WHERE
Paname IN SELECT Faname
FROM {SF}<form:aname>{Faname},
{SF}<rdf:ID>{FormName}
WHERE FormName = “SelectForm”
creates

26. Hera Implementation
HPG 2.0 (Hera Presentation Generator, dynamic version) implemented in Java as a servlet
Uses RDF API HP Jena for RDF data transformations based on RDFS models (CM, AM)
Can use XForms processor
Uses Sesame as main content repository and application context repository; uses SeRQL/RQL as query languages
Set of graphical tools for designers for CM and AM based on Visio

27. XML & XQuery

28. HTML = Hypertext Language
The <b> X23 </b> new camera replaces the <b> X22 </b>. It comes equipped with a flash (worth by itself <i>53.99 $</i>) and provides great quality for only <i> $</i>.
Ref Name Price
X Camera
R2D2 Robot
Z PC
hard
Information System
HTML
Text + presentation
Where is the data ?

29. XML for Semistructured Data
Ref Name Price
X Camera
R2D2 Robot
Z PC
...
Information System
<product-table>
< product reference=”X23">
<designation> camera </designation>
<price unit=Dollars> </price>
<description> … </description>
</product>
< product reference=”R2D2">
<designation> Robot </designation>
<price unit=Dollars> </price>
...
</product-table>
easy
Data + Structure:
more flexible
XML

30. Complex data Structure is irregular (missing/extra data)
Schema does not exist or is unknown
Schema is rapidly evolving
Relational and ODB models are too rigid
Standard is a document/hypertext language HTML
Solution: semistructured data model XML
data model consists of a type definition language, a query/update language and more

31. XML XML: eXtensible Mark-up Language
W3C and most industrial companies [B2B]
Main idea: separate content and presentation
Use tags to represent structure and semantics
HTML: a fixed set of tags complicates the identification of information elements
XML allows to define data structures:
Tags with freely chosen names
No predefined tags enables definition, transmission, validation and interpretation of data between applications (and organizations)
Freely chosen attributes
Ref: w3c.org

32. <purchaseOrder orderDate="1999-10-20">
<shipTo country="US">
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Mill Valley</city>
<state>CA</state>
<zip>90952</zip>
</shipTo>
<billTo country="US">
<name>Robert Smith</name>
<street>8 Oak Avenue</street>
<city>Old Town</city>
<state>PA</state>
<zip>95819</zip>
</billTo>
<items>
<item partNum="872-AA">
<productName>Lawnmower</productName>
<quantity>1</quantity>
<USPrice>148.95</USPrice>
</item>
<item partNum="926-AA">
<productName>Baby Monitor</productName>
<USPrice>39.98</USPrice>
<shipDate> </shipDate>
</items>
</purchaseOrder>

33. XML Documents elements and attributes elements are ordered
attribute values are strings
well-formed documents (e.g. proper nesting)
namespaces: vocabularies for tags
valid documents: DTD, Schema

34. DTD: a grammar Catalog  Product* Product  Name Price? Cat
(Part Quantity)*
Part  BasicPart + ComposedPart
BasicPart  Name
ComposedPart  Name (Part Quantity)*

35. <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:annotation>
<xsd:documentation xml:lang="en">
Purchase order schema for Example.com.
Copyright 2000 Example.com. All rights reserved.
</xsd:documentation>
</xsd:annotation>
<xsd:element name="purchaseOrder" type="PurchaseOrderType"/>
<xsd:element name="comment" type="xsd:string"/>
<xsd:complexType name="PurchaseOrderType">
<xsd:sequence>
<xsd:element name="shipTo" type="USAddress"/>
<xsd:element name="billTo" type="USAddress"/>
<xsd:element ref="comment" minOccurs="0"/>
<xsd:element name="items" type="Items"/>
</xsd:sequence>
<xsd:attribute name="orderDate" type="xsd:date"/>
</xsd:complexType>
<xsd:complexType name="USAddress">
<xsd:element name="name" type="xsd:string"/>
<xsd:element name="street" type="xsd:string"/>
<xsd:element name="city" type="xsd:string"/>
<xsd:element name="state" type="xsd:string"/>
<xsd:element name="zip" type="xsd:decimal"/>
<xsd:attribute name="country" type="xsd:NMTOKEN" fixed="US"/>
...
</xsd:schema>

36. ...
<xsd:complexType name="Items">
<xsd:sequence>
<xsd:element name="item" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:element name="productName" type="xsd:string"/>
<xsd:element name="quantity">
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxExclusive value="100"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
<xsd:element name="USPrice" type="xsd:decimal"/>
<xsd:element ref="comment" minOccurs="0"/>
<xsd:element name="shipDate" type="xsd:date" minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="partNum" type="SKU" use="required"/>
</xsd:complexType>
<!-- Stock Keeping Unit, a code for identifying products -->
<xsd:simpleType name="SKU">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{3}-[A-Z]{2}"/>
</xsd:schema>

37. Typing XML
Not really, the true spirit of the Web, but essential for data management: query optimization, user interfaces, applications
Differences with standard database typing
Collections are sequences instead of sets
Types may be very large (e.g., from integration)
Data is more irregular so types should be more permissive
New issues sometimes: you have the data, extract its type: an approximate type

38. <skills>
<people>
<person>
<name>Bob</name>
<know-how>XML</know-how>
</person>
<name>Peter</name>
<know-how>RDF(S)</know-how>
</people>
<seminars>
<seminar>
<topic>XML</topic>
<participant>
<name>Karin</name>
<name>Alice</name>
</participant>
</seminar>
</seminars>
</skills>

39. //person/name[../know-how=“XML"]
$union$
//seminar[topic=“XML"]/participant/name

40. XPath Path expressions in OO databases Semistructured: missing parts
/Students/Student/Status
Semistructured:
missing parts
/Students//Status
conditions
/Students/Student[Status=“U4”]
Indexing, wildcards
Selection, string manipulation, aggregation, attribute existence, union

41. XSLT XSL: XML Stylesheet Language (XSLT: XSL Transformations)
declarative language for transforming XML documents using an XSLT processor

42. XQuery http://www.w3.org/XML/Query “the” standard for XML querying
Goal: “data model for XML documents, a set of query operators on that data model, and a query language based on these query operators”
General query language (next to XPath + XSLT)
Based on XPath

43. XQuery Path Expressions
In the second chapter of the document named “zoo.xml”, find the figure(s) with caption “Tree Frogs”.
document(“zoo.xml”)/chapter[2]//
figure[caption=“Tree Frogs”]
Find captions of figures that are referenced by <figref> elements in the chapter of “zoo.xml” with title “Frogs”.
document(“zoo.xml”)/chapter[title=“Frogs”]//

44. XQuery Element Constructor
Generate an <emp> element that has an “empid” attribute. The value of the attribute and the content of the subelements are specified by variables that are bound in other parts of the query.
<emp empid={$id}>
{$name}
{$job}
</emp>

45. XQuery FLWR Expression
List each publisher and the average price of its books.
FOR $p IN distinct(document(“bib.xml”)//publisher)
LET $a := avg(document(“bib.xml”)/book[publisher=$p]/price)
RETURN
<publisher>
<name>{$p/text()}</name>
<avgprice>{$a}</avgprice>
</publisher>

46. RDF & OWL

47. Web Data Integration
WIS repository (back-end) typically assembled from different heterogeneous sources, e.g. databases, files, WWW
To manage (coordinate) data from different sources, metadata helps to structure the data

48. Metadata Describing the data and its availability
Sometimes provided by sources
Needed by IS
Engineering metadata:
Meaning
Validity
Quality
Specifying “logistics” of data

49. Resource Description Framework
W3C standard for metadata description
Describes the “meaning” of data like Web sites, parts of HTML pages, etc.
Makes data “machine - understandable” – allows automated data processing
Framework that allows you to make simple assertions about anything: distributed and extensible (as is the Web)
“meaning” expressed via “subclass of”
Ref:

50. Basic RDF Model Recognizes 3 object types:
Resources – always named by URI, e.g. web site, part of web page, others
Properties – an attribute of a Resource, its characteristics
Statements – Resource + Property + Property Value

51. Basic RDF Model Example
RDF representation of the sentence:
“Ora Lassila is the creator of the resource
Statement:
Subject (Resource)
Predicate (Property)
Creator
Object (Literal)
“Ora Lassila”

52. Basic RDF Model Example
Diagram of the statement:
Creator
Ora Lassila

53. RDF and XML RDF can be implemented using XML
The example of complete XML for the previous example is:
<?xml version=“1.0”>
<rdf:RDF
xmlns:rdf=“
xmlns:s=
<rdf:Description about=
<s:Creator>Ora Lassila</s:Creator>
</rdf:Description>
</rdf:RDF>

54. Structured Value Example
“The employee with ID 85740, Ora Lassila, with is the creator of the resource
In XML it is:
<rdf:RDF>
<rdf:Description about=“
<s:Creator>
<rdf:Description about=“
<v:Name>Ora Lassila</v:Name>
</rdf:Description>
</s:Creator>
<rdf:Description>
</rdf:RDF>
Ora Lassila
Creator
Name

55. RDF - more It is possible to make statements about statements
It is possible to refer a collection of resources (containers) of 3 types:
Bag – a property has multiple values, order has no significance
Sequence – a property has multiple value, order is significant
Alternative – list of literals/resources representing alternatives for single property

56. RDF Query Language Querying RDF metadata RQL, SeRQL (with Sesame)
SQL/XQL style approach, viewing RDF metadata as relational or XML database [RDF Query Specification (IBM)]
viewing Web descriptions by RDF metadata as knowledge base, applying knowledge representation and reasoning techniques [W3C related]
RQL, SeRQL (with Sesame)

57. Meaning: Ontologies
Ontology = a vocabulary with associated meaning (“shared understanding”)
Possibility to define synonyms, specializations and other relationships
Use of same ontology = contract on meaning of words (tags, attributes)
Often, industry or domain dependent

58. OWL Web Ontology Language
used to explicitly represent meaning of terms in vocabularies and relationships between terms: ontology
ontology engineering
beyond XML and RDF(S)
revision of DAML+OIL

59. Stack
XML: surface syntax for structured documents (no semantic constraints on meaning)
XML Schema: restricting structure of XML documents
RDF: datamodel for objects (resources) and relationships, provides simple semantics for this datamodel
RDF Schema: vocabulary for describing properties and classes of RDF resources, with semantics for generalization-hierarchies
OWL: adds vocabulary for describing properties and classes, e.g. relations between classes (disjoint), cardinality (exactly one), equality, richer typing of properties, characteristics of properties (symmetry), enumerated classes

60. OWL Sublanguages
OWL Lite: classification hierarchy and simple constraints
OWL DL: maximum expressiveness while retaining computational completeness and decidability (description logics)
OWL Full: maximum expressiveness and syntactic freedom of RDF with no computational guarantees

61. Web Services

62. Web Services
Distributed computing model on asynchronous messaging (XML)
Support dynamic application integration over the Web
XML message for exchanging data and accessing services
On-the-fly software creation through the use of loosely coupled, reusable software components
Software can be delivered and paid per-use as opposed to package products

63. Principles XML Message Exchange Message Transport Message Nature XML
Namespaces (URI)
HTTP
Message Nature
Request
Result of a request
Errors
Application
Client
Web Service
<B>
XML
Web Service
<C>
Web Service
<D>

64. Design Principles Wrapping services (applications) Web-based protocols
Client
XML
HTTP-SOAP
Design Principles
Wrapping services (applications)
Web-based protocols
Web-services based on HTTP
Protocols can traverse firewalls, can work in a heterogeneous environment
Interoperability
SOAP defines a common standard that allows different systems to interoperate
XML-based (XML Schema)
Machine-readable documents
Web Service
<D>

65. Design Principles Modularity Availability Machine-readable description
Repository
Application
Client
XML
HTTP-SOAP
Design Principles
Modularity
Service components are useful in themselves, reusable, composable
Availability
Services are available to systems that wish to use them
Services must be exposed outside of the particular system they are available in (wrapping)
Machine-readable description
Used to identify the interface, the location and access information
Published
Searchable service repositories of service descriptions
Web Service
Application

66. Related Technologies Comparison with Data Wrapping
Same idea (providing a transparent interface to legacy systems)
Data (data models and query languages) vs. services (procedures, functions)
Comparison with other RPC
Existing RPC (DCOM, RMI or CORBA)
Same idea (interface, dynamic discovery, protocols)
Interoperability problems
DCOM: Microsoft
RMI: Java
Technical problems
CORBA: very complex

67. Main Components/Actors
Directory
Client
Service
Provider
Description
Application
Web
Discovery
Publication
Interaction

68. Three Main Components/Protocols
Publication and Discovery: UDDI
Service Description: WSDL
Messaging: SOAP
Transport: HTTP, SMTP, FTP
Three Main Components/Protocols
UDDI (Universal Data Description Interface)
Directory for recording and searching the description of Web services
Provides a mechanism for clients to find Web services
WSDL (Web Services Description Language)
XML description of a Web service
Defines services as collections of network endpoint or ports
A port is defined by associating a network address with a binding (servers)
A collection of ports defines a service
SOAP (Simple Object Access Protocol)
Is a message layout specification that defines a uniform ways of passing XML-encoded data
Based on HTTP

69. Publication and Discovery: UDDI
Service Description: WSDL
Messaging: SOAP
Transport: HTTP, SMTP, FTP
Directory
Client
Service
Provider
Description
Application
Web
Discovery
Publication
Interaction
UDDI
WSDL
SOAP

70. Basic Usage Scenario 2 http get 1 register WSDL file (manually)
(manual) Web
service lookup
Client
Write client
application
Run client
Directory (UDDI)
Publish Web
service
1 register WSDL file (manually)
Web Service
Provider
2 http get
3 WSDL file
4 SOAP request
5 SOAP response
Run Server

71. Web Service Implementation
HTTP
Server
Web Service Provider
SOAP
Application
Requestor
(SOAP client)
SOAP Message
(HTTP transport)
Application server (Web service-enabled)
Provides implementation of services and exposes it through WSDL/SOAP (Wrapping)
Implementation in Java, as EJB, as .NET(C#), etc.
SOAP server
Implements the SOAP protocol
HTTP server
Standard Web server
SOAP client
Implements the SOAP protocol on the client site

72. Web Service Classification
ebXML
Rosetta
Net
Biztalk
Communication and transport services
W3C Recommendations
SOAP, XML, Namespace
Technical services
Services for message
publication and exchange
Examples: WSDL, UDDI
Business services
Specific for an activity area
Defined and used by a group of companies working on the same activity area
Examples: ebXML, RosettaNet, BizTalk
Enterprise
Web Service
Business Service
SOAP
TCP-IP-HTTP
Technical Service
WSDL
UDDI
BPML

73. Web Service Examples Google http://www.google.com/apis/
Free but limited access

74. Web Service Examples Amazon Free but limited access
Free but limited access
Search and management of Amazon products
Access products
Add products
Customize presentations

75. Web Service Examples SellerEngine (http://www.sellerengine.com/)
Uses Amazon Web Services
Brings Amazon data to a desktop in real time (create new listings and upload them to Amazon in seconds using a easy to use interface)

77. WS Protocols

78. Protocol: SOAP Simple Object Access Protocol
Communication protocol via Internet between applications: data exchange and data structures
Format for sending messages
Platform and language independent
Based on XML
Messages with two types of elements
Pre-defined tags
Application-specific tags
Directory
Client
Service
Provider
Description
Application
Web
Discovery
Publication
Interaction
UDDI
WSDL
SOAP

79. Protocol: SOAP SOAP: Communication and Transport Services
SOAP document
Envelop: message type and destination
Data type: representation of data types
Conventions for the RPC and for the result or error sending
Rules for the SOAP transport on HTTP
Transport
SOAP
HTTP
TCP/IP
POST: …
Host: …
Content-type: …
Content-length: …
<Envelope>
<Body>
</Body>
</Envelope>
Message depends
on Web services

80. Protocol: WSDL Web Services Description Language
XML-based language for describing Web services and how to access them
Specification of the location of the service
Specification of the operations (or methods) the service exposes
Directory
Client
Service
Provider
Description
Application
Web
Discovery
Publication
Interaction
UDDI
WSDL
SOAP

81. Protocol: WSDL Description of Web Services in XML format
Abstract description of operations and their parameters (messages)
Concrete description
Binding to a concrete network protocol (SOAP)
Specification of endpoints for accessing the service
Types: structure of messages
Abstract
Messages: used by operations
Binding: concrete protocol
Concrete
Service: collection of related ports
Ports: Binding and a network address

82. Protocol: UDDI Universal Description, Discovery and Integration
Directory service where businesses can register and search for Web services (described in WSDL)
Communication via SOAP
Directory
Client
Service
Provider
Description
Application
Web
Discovery
Publication
Interaction
UDDI
WSDL
SOAP

83. Protocol: UDDI UDDI Support
UDDI is a cross-industry effort driven by all major platform and software providers like Dell, Fujitsu, HP, Hitachi, IBM, Intel, Microsoft, Oracle, SAP, and Sun, as well as a large community of marketplace operators, and e-business leaders
Over 220 companies are members of the UDDI community
Microsoft (uddi.microsoft.com)
IBM (ibm.com/services/uddi)
HP (uddi.hp.com)
SAP (udditest.sap.com)

84. Example: Flight Reservation
If the industry published an UDDI standard for flight rate checking and reservation, airlines could register their services into an UDDI directory
Travel agencies could then search the UDDI directory to find the airline's reservation interface
When the interface is found, the travel agency can communicate with the service immediately because it uses a well-defined reservation interface

85. Microsoft’s UDDI uddi.microsoft.com Search Results Search of a
Web Service: Xmethods
Search Results

86. Microsoft’s UDDI Description of the selected service
Returns book price from
Barnes and Noble
online store, given ISBN

87. Microsoft’s UDDI
WSDL Description
of the Web service

88. Service Development
Two main technologies
Java (EJB server)
.NET