An Extensible Constraint Markup Language Specification, Modeling, and Processing

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An Extensible Constraint Markup
LanguageSpecification, Modeling, and Processing

Dr. Jingkun Hu, Philips Medical Systems Dr. Lixin
Tao, Pace University 18 November 2004
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Outline

• XML constraints
• Problem statement
• Previous work
• eXtensible Constraint Markup Language (XCML)
• Visual modeling of XML constraints
• XCML constraint processing
• Conclusions and future work

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What are XML constraints

• Syntactic constraints and semantic constraints
• Syntactic constraints those restrictions on the
  structures, data types, and data formats.
• Semantic constraints those restrictions on the
  content of XML documents.
• A semantic constraint can be expressed in the
  form of an assertion (true/false statement) or a
  rule (if-then-else) with embedded assertions. The
  content of a constraint can be static or dynamic.

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Semantic XML Constraints
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Sample XML constraints- Assertion-based

• The value of element taxRate must be 0.06.
• The value of element taxRate must be greater than
  0.02 and less than 0.10.
• The value constraint of element taxRate varies
  from state to state.
• The amount of tax must equal to the product of
  net income and tax rate.
• (Schema diagram of sample XML document)

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Sample XML constraints - Rule-based

• If the value of an employees role does not equal
  to manager, then department element must not be
  present. Otherwise, it must be present at least
  once.
• If the value of netIncome is less than or equal
  to a given value of parameter level, then the
  value of taxRate should be 0.05 .

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Problem statement

• Validating XML documents against Schemas
  (syntactic validation) is not sufficient in
  practice.
• Syntactic validity cant guarantee if XML
  documents meaningful.
• Semantic validation is necessary.
• How to express semantic constraints.

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Problem statement (Contd)

• Manually creating XML constraint documents is a
  painful task.
• Can XML constraints be visually modeled so that
  constraint documents are automatically generated?

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Previous work

• W3C XML Schemas (WXS)
• Schematron, Jelliffe
• XML Constraint Specification Language (XCSL),
  Ramalho
• eXtensible Inter-Nodes Constraint Markup Language
  (XincaML), IBM
• Xlinkit, Nentwich

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eXtensible Constraint Markup Language (XCML)-
Specification
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Syntax
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Sample XCML definitions
ltConstraint contextpayrollgt ltAssertion
testtaxRate0.06/gt lt/Constraintgt
ltConstraint contextpayrollgt ltAssertion
testtaxRate gt 0.02
and taxRate lt 0.10/gt lt/Constraintgt
ltConstraint contextpayrollgt ltAssertion
testtax netIncome taxRate/gt lt/Constraintgt
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Sample XCML definitions (Contd)
ltConstraint contextpayrollgt ltParametergt
ltnamegtratelt/namegt
lttypegtfloatlt/typegt ltdefaultValuegt0.07lt/de
faultValuegt lt/Parametergt ltAssertion
testtaxRaterate/gt lt/Constraintgt
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Sample XCML definitions (Contd)
ltConstraint context"employee"gt ltRulegt ltIf
testyearsOfWork gt 5/gt ltThen
testpayroll/hasSavingFund true/gt ltElse
testpayroll/hasSavingFund false/gt lt/Rulegt
lt/Constraintgt
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Comparison of XCML with existing XML constraint
languages
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XCML constraints - Visual modeling
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XML data modeling

• UML and XML Schemas
• Carson, Provost, and Routledge et al.
• Three-level-design approach without constraints
• Conceptual, logical, and physical
• Three-level-design approach with constraints
• Conceptual, logical, and physical

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Three-level-design approach
(a)
(b)
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UML profile for XCML schema
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Sample physical models

• XML Schema document
• XCML instance document

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XML schema document of employee profile

• ltxsschema xmlnsxs"http//www.w3.org/2001/XMLSch
  ema"gt
• ltxselement name"employee" typeEmployee"/gt
• ltxscomplexType nameEmployee"gt
• ltxssequencegt
• 
  
• ltxselement name"role" typeRoleType"/gt
• ltxselement name"department"
  typeDepartmentType" minOccurs"0"/gt
• ltxselement name"yearsOfWork"
  type"xsinteger"/gt
• ltxselement name"payroll" typePayrollType"/gt
  
• lt/xssequencegt
• ltxsattribute name"employeeID"
  type"xsstring" use"required"/gt
• lt/xscomplexTypegt
• ltxscomplexType namePayrollType"gt
• ltxssequencegt
• ltxselement name"salary" type"xsfloat"/gt
• ltxselement name"bonus" type"xsfloat"/gt
• ltxselement name"taxRate" type"xsfloat"/gt
• ltxselement name"tax" type"xsfloat"/gt

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XCML instance document for employee profile
ltxcmlConstraints name"Employee Profile
Constraints" xmlnsxcml"http//www.csis.pace.edu
/dps/xcml" xmlnsxsi"http//www.w3.org/2001/XMLS
chema-instance" xsischemaLocation"http//www.csi
s.pace.edu/dps/xcml ..\..\schema\xcml\Constraints.
xsd"gt ltConstraint context"employee"gt ltRulegt
ltIf testyearsOfWork gt 5/gt ltThen
test"payroll/hasSavingFund 'true'"/gt ltElse
test"payroll/hasSavingFund 'false'"/gt lt/Rulegt
lt/Constraintgt ltConstraint context"employee/pay
roll"gt ltAssertion test"salary bonus - tax
netIncome"/gt lt/Constraintgt ltConstraint
context"employee"gt ltRulegt ltIf test"role
manage/gt ltThen test"count(department) gt
1"/gt ltElse test"count(department)
0"/gt lt/Rulegt lt/Constraintgt lt/xcmlConstraintsgt
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XCML constraints - Processing
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Design and implementation

• Generation of XML Schemas and XCML instance
  documents
• XML document validation
• Technologies UML 1.4, XMI 1.1, and XSLT 1.0

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Workflow of generating XML Schemas and XCML
instance documents
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Workflow of XML document validation
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Conclusions

• Proposed XCML is much more powerful than the
  existing XML constraint languages in expressing
  various constraints specifically dynamic and
  composite rule-based ones.
• Using OCL and the proposed UML profile for XCML
  schema together with a UML profile for W3C XML
  Schema can model XML constraints over XML data
  models.

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Conclusions (Contd)

• UML modeling of XCML makes the design of XCML
  instance documents model-driven.
• The automation of XCML instance documents
  generation can be done using XMI and XSLT
  technologies.

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Future work

• OCL 2.0 vs XML Constraint Languages
• Xlink use in XCML
• Reference implementation

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Sample Schema document
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Conceptual mode of Employee profile(w/o
constraints)
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Logical model of Employee profile(w/o
constraints)
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Sample conceptual model
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Sample logical model