Modeling XML

XML Schema Languages

DTD, XML Schema, Relax NG Specification of structure of XML

documentsWhat elements and attributes can be

used Problems

ComplexityToo technical for non-technical peopleAbsence of semantics

XML Schema Languages

Real applicationsDifferent groups of users viewing

problem domain from different viewpoints various types of XML documents ("XML views") in system

XML Schema Languages

Data

Data

<<XML schema>>

PurchaseRequest

<<XML schema>>

PurchaseResponse

<<XML schema>>

Catalogue

<<XML schema>>

SalesReport

XML Schema Languages

One real-world concept (e.g. customer or product) represented in various types of XML documents in different waysDescription distributed across various

XML schemasredundancy & incompleteness

Lack of complete & non-redundant description

XML Schema Languages

HL7exchanging medical records

UBLexchanging business data

ISO20022exchanging financial data

common charasteristics:Hundreds of XML schemas

XML Schema Visualization

XML Spy, Stylus Studio, Oxygen XML Editor, …

Visualization of each construct of particular XML schema languageUsually XML Schema

XML Schema Visualization

XML Schema Visualization

XML Schema Visualization

Easier to understand XML schemas Just visualization – does not provide

complete & non-redundant description

Model-Driven Architecture

IDEA: describe data at various levels of abstractionPIM (Platform-Independent Model)

• Description of data independent of any data model and particular user view

PSM (Platform-Specific Model)• Description of data from particular user view• Description of implementation in particular data

model (relational, xml)

PIM Diagram

PSM Diagram – Relational Schema

Model-Driven Architecture

Can be naturally applied on designing XML as well

PSM = UML class model extended with set of stereotypes for modeling constructs of particular XML schema language

Enterprise ArchitectPSM for XML Schema

PSM Diagram

PSM Diagram – Relational DB

Model-Driven Architecture

Allows describing problem domain independently of XMLComplete and non-redundant description

No or weak binding between PIM and PSM level in recent tools

A Tool for XML Data Modeling

XCase Software Project

‘XSEM - Proof of concept’ project at MFF UK• March – December 2008

Supervisor: Martin Nečaský, PhD Team members:

• Jakub Klímek, Lukáš Kopenec, Lucie Kučerová, Jakub Malý, Kateřina Opočenská

Official website: http://www.ksi.mff.cuni.cz/~necasky/xcase/

Download & sources: http://www.codeplex.com/xcase

• Almost 4000 downloads so far! Presented at ITAT 2008

XCase Overview

XCase implements XSEM, a conceptual model for XML data

XSEM is based on MDA (Model-Driven Architecture) Platform Independent Model (PIM):

• UML class diagram• XML-independent conceptual description of

problem domain Platform-Specific Model (PSM):

• Extended UML class diagram• Introduced new constructs for modeling XML

hierarchy

XCase Design Process

XCase PIM Level

Support of all well-known UML class diagram constructs:

Classes• Class attributes• Class operations

Associations• Binary associations, n-ary associations• Aggregations, compositions

Association classes Generalizations

XCase PSM Level

New constructs to UML class diagram:

Attribute container Models attributes that should be expressed as XML

elements instead of XML attributes Content choice

Models variants in the content of PSM class Content container

Models XML element that has no semantic equivalent at the PIM level (i.e. no equivalent PIM class)

Class union Models a mixture (union) of instances of two or more PSM

classes.

Ensuring PIM – PSM ConsistencyDynamic propagation of changes:1] from PIM diagrams to corresponding PSM diagrams

New PIM association added → new child available in PSM Association cannot be removed from PIM if corresponding

association is still present in PSM New attribute added in PIM → available in PSM Attribute removed from PIM → warning about removing

from PSM Attribute changes in PIM propagated to corresponding

attribute in PSM• Automatic propagation: name, data type, default value• User asked for confirmation: multiplicity

2] from PSM diagrams to corresponding PIM diagrams User can propagate free PSM attribute to PIM

XML Schema Derivation

1 XML Schema document derived from 1 PSM diagram Automatic derivation

Starts in root PSM classes and proceeds recursively

to their descendants Each PSM construct is translated to appropriate XML

Schema construct Derived schemas are not saved within XCase project

• Can be derived, edited and saved anytime again

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