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Designing Multi-Role, Collaborative Web Sites
with WebML The Conference Management System
Case Study
S. Ceri, P. Fraternali, M. Matera, A.
Maurino DEI - Politecnico di Milano ceri,
fraterna, matera, maurino_at_elet.polimi.it
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Presentation outline

• Overview of the WebML model
• Case study solution demo

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Requirements for Web modeling

• Expressiveness
• Real-life cases should be expressible
• Frequently used design patterns should be
  captured
• Ease of use
• Intuitive notation
• Clear semantics
• Consistency checks
• Implementability
• Efficient mapping to physical data structures
• Flexible code generation from behavioral
  specifications

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The WebML layers

• WebML a conceptual language for high-level
  design of data-intensive web sites
• WebML Layers
• Structure data organization
• Derivation redundant data definition
• Composition definition of pages as sets of
  elementary publishing units
• Navigation definition of links between units and
  between pages
• Presentation positioning of the units in the
  page and definition of graphical appearance

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Preview of WebML concepts

• Site Structure Composition Navigation
  Presentation

entities,relationships
units, pages,links
site views
styles
navigation composition
structure
presentation
user models
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Structure model

• A simplified Entity-Relationship model
• Only binary relationships
• No attributes on relationships
• IS-A hierarchies
• Typed attributes in entities

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Derivation

• Derivation queries allows designers
• To augment the content of an entity by adding
  extra attributes, either imported or calculated
  from existing information
• To define the population of entities or of
  relationships, based on some property of the
  involved objects
• Derivation queries are expressed through WebML
  OQL (Object Query Language)
• automatically transformed into SQL views
  installed in the database
• A wizard is available in WebML CC - users are not
  required to write WebML OQL queries

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Derived entities

• The population of sub-entities in ISA hierarchies
• Example All the accepted papers is expressed
  in WebML OQL as
• Paper(as SuperEntity) where SuperEntity.FinalSta
  tus 'accepted

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Derived attributes

• Extra attributes can be added to an entity, by
  defining a query that computes them
• Four types of derivation
• Constant attributes
• Imported attributes
• Aggregated attributes
• Calculated attributes
• Example The attribute AvgGrade in Paper is
  calculated as
• avg(Self.Paper2Review.FinalGrade)

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Derived relationships

• Relationships can be derived in two ways
• by subsetting and/or concatenating existing
  relationships
• by matching pairs of objects by means of a
  condition
• Example

Self.Track2Paper(as Var1) where Var1.FinalStatus
'accepted

• Variable Self denotes the instance of the source
  entity of the relationship

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Hypertext model

• Content units atomic units that specify how to
  publish information described in the structural
  schema
• Pages abstractions of the pages actually
  delivered to the user (e.g. an HTML page) -
  structured containers of units and links
• Links connects units and pages, so that to
  define the hypertext

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Content units
DATA UNIT
INDEX UNIT
MULTIDATA UNIT
FILTER UNIT
SCROLLER UNIT

• Each unit has a master object
• an entity or a relationship role

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Navigation - Links

• Semantics of a link
• Moving from one place to another
• Carrying information from one place to another
  (navigation context)
• Activating a computation (side effect)
• Contextual links
• Between units
• Context transported
• Non-contextual links
• Between pages
• No context transported

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Example of contextual link
Track
Paper
Track2Paper
Track Title XXX DescriptionYYY
Paper Title Paper1 Abstract xxxxxxxx
xxxxxyyyxxxyyxxx
Papers in YYY

• Paper1
• Paper2
• Paper3

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Site Views

• Site view Set of pages forming a global view of
  the site
• One site view per user group, access device, etc.
• A page marked as Home
• Landmark pages globally visible page within
• a site view (NC-link implicitly defined from
  every
• other page in the site view)
• Consistency checks criteria for validity of
  hypertext (e.g., topology constraints,
  computability of nodes)

PageX
H
L
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The Write Access Problem

• From read-only navigation to content management
  operations (e.g., e-commerce trolley, personal
  profile creation and updating, ecc.)
• WebML offers
• A data entry unit
• A set of operation units for
• Built-in content management operations (creation,
  update, and deletion of new entities and
  relationships)
• Generic external operations

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DataEntry Unit

• Specifies data input by user
• It contains fields to insert data (in, out,
  inout)
• It can be translated into HTML using the ltformgt
  tag and the associated submit button

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Operation Units

• Invoke built-in database operations or generic
  external operations implemented in un-modelled
  server side code
• Input from one or more incoming links (one is
  declared as operation-activating)
• Two types of output links
• OK link followed if the operation is successful
• KO link followed if the operation fails

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Built-in Operations

• A set of frequently used built-in operations to
  manage the Web site content
• Traditional database operations, predefined in
  the WebML tool suite
• create, delete, and modify entities
• create and drop relationships

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In/out flow create, modify, delete
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In/out flow connect
Identifier of first object to connect
Identifier of the first object
Identifier of second object to connect
The master object is a relationship role e.g.,
Paper2Track
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In/out flow disconnect
Identifier of first object to disconnect
Identifier of the first object
Identifier of second object to disconnect
The master object is a relationship role e.g.,
Paper2Track
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Generic Operation Login

• It is a particular case of entry unit
  operation pattern
• The entry unit typically feeds the user
  credentials to the subsequent operation
  (username, password)
• Operation failure leads automatically to the home
  page of the everyone site view
• Operation success leads to the home page of the
  unique enabled site view

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Personalization

• Personalization has three facets
• Access control login/logout operations for user
  identification
• Site view assignement based on the group(s) a
  user belongs to, some site views are accessible
  (1 site view per group)
• Page personalization user or group dependent
  content

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User/Group metaphor
siteview

• Each User can belong to one or more Groups
  (predefined entities in the structural model)
• In a given time, each group can have one
  associated site-views (attribute of the Group
  entity)
• Each site view can be associated to more groups

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Site view access

• One group is predefined (everyone)
• Users belonging to this group are not required to
  login they access only one site view, including
  unprotected content (the everyone site view)
• Other site views can be accessed only after login
  (secured site views)
• These site views obviously include Login and
  Logout operations

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Page personalization

• Personalization can be achieved as a result of
  appropriate structure design

submission

• Hypertext can reflect structure, thus providing
  personalization

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Presentation Design

• An elementary unit positioning mechanism
• Gallery of default presentation styles applicable
  to site views or single pages
• each presentation style is an XSL stylesheet

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Presentation
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Preview of architecture
Legacy content
Site and Presentation Design
Conceptualize
Site Mapping
WebML schemas
Map content
content
Generateapplication
deploy
Commercial engine
Templategenerator
run
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WebML core design process
Structure Model Skeleton
Structure Model Skeleton
Refined Structure Model
Mockup and Textual Specs
Mockup and textual specs
Running Prototype
Running Prototype
Site View Skeleton
Site View Skeleton
Refined Site View
Population Presentation default
Population Presentation default
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The Conference Management System

• The project
• Structure schema
• Derivation
• Site view schema
• A demo

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Identifying users roles (1)

• PC chair
• Creates the conference
• Creates the PC members
• Assigns papers for review
• Decides the final paper evaluation
• Modifies the conference status
• PC Members
• Express their preference about subjects and
  tracks
• Express their preference about papers
• Indicate conflicts of interest
• Create new reviewers and assign papers
• Enter paper reviews
• Discuss with the PC Chair about the final
  evaluation

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Identifying users roles (2)

• Authors
• Submit papers
• Create coauthors
• Reviewers
• Enter paper reviews
• Non registered users
• Access the preliminary program, at the end of the
  conference life cycle

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The conference lifecycle
Step1 Set up

• Authors submit papers
• PC Memeber express preferences

• PC chair and PC members discuss about reviews
• PC chair assigns the final evaluation

PC chair (the only authorized user) creates the
conference and the PC members

• All users see the preliminary Program
• Authors see the review results

PC members express preferences about papers
PC chair assigns papers to PC members
PC members create reviewers and enter reviews
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Basic structure schema
User_Group
User_Preference
User_Review
User_Subject
User_Track
User_Submits_Paper
User_Reviews_Papers
Explicit_Conflict
Paper_Track
Paper_Preference
Paper_Coauthor
Paper_Subject
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Basic structure schema
NoOfSubmittedReviews MaxGrade MinGrade AvgGrade
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Hypertext

• Basic idea
• 5 users groups
• 7 conference status
• 11 site views, obtained by associating user
  groups to some conference status
• Change in the conference status ? Change in the
  association between site views and groups

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Site views
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Site views (cont.)
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Conference set-up
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PC member registration
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Review assignment (1)
To the Assign reviewer page
To the Assign paper page
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Review assignment (2)
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Paper acceptance
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Final statistics
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Access rights management
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Evolution of status

• A ralational trigger changes the access right
• It is activated when conference satus attribute
  changes
• A number of update instructions change the
  association between siteviews and groups
• When the conference status is in the bidding
  phase the trigger assigns to PC members a list of
  papers
• papers are assigned to a track, or to a set of
  subjects preferred by the PC member.
• the grade of interest for these papers is
  initally 0
• PC member can modify this grade or s/he can raise
  an explicit conflict of interest about a
  specified paper

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Derivation

• Example of derived relationship
• PcMember_NoConflicutalPaper (it shows for a given
  PC member the list of all the papers so that
• The PC member doesnt work in the same
  organization of the paper author
• The PC member doesnt work in the same
  organization of any of the paper co-authors
• The PC member does not show any explicit conflict
  with the paper
• The PC member has not been already designated as
  a reviewer for the paper.
• Self to Paper (as M2U) WHERE Self.affiliation ltgt
  M2U.User_Submits_Paper.affiliation AND
  Self.affiliation NOT IN ( M2U.Paper_Coauthor.Affil
  iation ) AND Self.Oid NOT IN (M2U.Explicit_Conflic
  t.UserOid) AND Self.Oid NOT IN (Self.M2U.User_Revi
  ewer_Papers.UserOid)

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A few data about implementation

• Number of site views 11
• Number of JSP pages 148
• Number of relational tables 16
• Dimension of the generated JSP code (Kbytes)
  950
• Number of relational views for derived data 56
• Number of JSP page templates manually retouched
  2
• Number of SQL views manually retouched 6

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A short demo

• Starting with the conference WebDB2001
• 2 PC members
• Maurino (form poli) is interested in XML
  technology DB
• Abiteboul (from INRIA) is interested in XML
• 3 papers
• 1 about XML
• 1 about DB
• 1 about XML and DB, with coauthors from INRIA
• Lets start...

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WebML Control Center

• DEMO

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Conclusions

• WebML has allowed us to complitely capture the
  requirements of the CMS applications
• Future works
• New concepts (support for set oriented operation,
  module..)
• Extensions towards Workflow Management Systems
• New tool release