Difference between revisions of "COSMOS Design 237921"

Revision as of 15:53, 24 June 2008

Support PSVI in SML Validation

Change History

Workload Estimation

Terminologies/Acronyms

The terminologies/acronyms below are commonly used throughout this document. The list below defines each term regarding how it is used in this document:

Purpose

This enhancement is associated with bugzilla 237921.

The purpose of the feature is to add support for PSVI to data builders used in constructing structures required for validation of SML constraints. Currently the validator parses through each definition document to determine element types, their derivation and any associated SML constraints. Manual parsing of definition documents negatively impacts performance and memory consumption required by the validator. Another disadvantage of manual parsing is the inability to cover all possible cases. There are unpredictable methods of how schema can be used. It's preferred to rely on an established interface as opposed to manually parse through each schema document.

What is PSVI?

Post Schema Validation Infoset (PSVI) is the ability to access schema-level information when parsing an XML document. The interface set is available via DOM or SAX. The snippet below describes how the PSVI provider can be retrieved when SAX parsing a document:

SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
saxParserFactory.setFeature("http://apache.org/xml/features/generate-synthetic-annotations", true);
saxParserFactory.setFeature("http://xml.org/sax/features/validation", true);

SAXParser newSaxParser = saxParserFactory.newSAXParser();
newSaxParser.setProperty("http://java.sun.com/xml/jaxp/properties/schemaLanguage", "http://www.w3.org/2001/XMLSchema"); 
newSaxParser.setProperty("http://java.sun.com/xml/jaxp/properties/schemaSource", <LIST OF SCHEMA INPUT>);					
			
PSVIProvider psviProvider = (PSVIProvider)newSaxParser.getXMLReader();

Assuming the presence of psviProvider, an element or an attribute declaration can be retrieved using psviProvider.getElementPSVI() or getAttributePSVI(...). The following snippet of code determines the base type for the current element:

ElementPSVI elementDeclaration = psviProvider.getElementPSVI();
XSTypeDefinition typeDefinition = elementDeclaration.getTypeDefinition();
System.out.println("The base type of the current element is: " + typeDefinition.getBaseType().getName());

The following code is used to determine if sml:acyclic is set on the current element. The code retrieves the annotation of the type associated with the current element to determine if the attribute sml:acyclic is set:

ElementPSVI elementDeclaration = psviProvider.getElementPSVI();
XSTypeDefinition typeDefinition = elementDeclaration.getTypeDefinition();
		
XSObjectList annotationList = ((XSComplexTypeDefinition)typeDefinition).getAnnotations();
	
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();            
Document domDocument = factory.newDocumentBuilder().newDocument();
		
for (int i = 0, annotationCount = annotationList.getLength(); i < annotationCount; i++)
{
   XSObject annotation = annotationList.item(i);			
   ((XSAnnotation)annotation).writeAnnotation(domDocument, XSAnnotation.W3C_DOM_DOCUMENT);
   Node acyclicAttribute = domDocument.getFirstChild().getAttributes().getNamedItemNS(ISMLConstants.SML_URI, ISMLConstants.ACYCLIC_ATTRIBUTE);
   if (acyclicAttribute != null)
   {
      System.out.println(acyclicAttribute.getNodeValue());
   }
}			

Implementation Detail

All data builders used to construct structures based on definition documents are expected to be replaced with PSVI. There are currently three phases to the validation process:

1. Constructing the data structures required by each validator
2. Executing validators to verify SML constraints
3. Checking schematron constraints

A validator is currently used to register a set of data structures it requires for validating a constraint. The data builder associated with a validator are content handlers that are invoked when parsing through an SML-IF document.

The first and second phase will be affected by this enhancement. The SMLMainValidator will be modified to parse through an SML-IF document using three different content handlers:

1. HeaderContentHandler
2. DefinitionContentHandler
3. InstanceContentHandler

HeaderContentHandler is used to determine the identity, rule binding, and the schema binding of the SML-IF document. The structures build by this content handler is used later during the parsing process to bind definition documents with instance documents. DefinitionContentHandler is used to gather all schemas that are to be used when validating instance documents. InstanceContentHandler schema parses each instance document to build the data structures required for validating the SML constraints. Once the document content is parsed, SMLMainValidator invokes each validator to check the state of each constraint.

Figure 1.1 depicts the validator's flow when processing an SML-IF document:

Figure 1.1 - SML Validator's flow

Data Builders

The following data builders will need to be modified/removed:

• AbstractDeclarationBuilder.java - Abstract class for classes such as GroupDeclarationBuilder
• AcyclicDataTypesList.java - Extract complex types that have sml:acyclic set to true
• ComplexTypeElementBuilder.java - Stores complex type declaration
• ElementDeclarationBuilder.java - Stores global element declaration
• ElementSchematronCacheBuilder.java - Stores schematron associated with an element/type declaration
• ElementTypeMapDataBuilder.java - Stores the relationship between the element names and their associated type.
• GroupDeclarationBuilder.java - Stores group declarations
• IdentityConstraintDataBuilder.java - Stores the identity constraints associated with elements
• SchemaBindingDataBuilder.java - Used for schema binding
• ElementSourceBuilder.java - Stores the source for definition/instance documents
• SMLValidatingBuilder.java - Stores elements
• SubstitutionBuilder - Used for substitution groups
• TargetSchemaBuilder.java - Element declarations with target* constraints
• TargetSchemaBuilder.java - Stores type declarations
• TargetSchemaBuilder.java - Keeps track of type inheritance

Task Breakdown

The following section includes the tasks required to complete this enhancement

1. Modify SMLMainValidator to invoke the three content handlers
2. Create HeaderContentHandler
3. Build the structures for HeaderContentHandler
4. Create DefinitionContentHandler
5. Build the structures for DefinitionContentHandler
6. Create InstanceContentHandler
7. Build the structures required for sml:acyclic
8. Complete the validator for acyclic
9. Build the structures required for target* constraints
10. Complete the validator for target* constraints
11. Build the structures required for identity constraints
12. Complete the validator for identity constraints
13. Test to make sure all existing test cases pass

Open Issues/Questions

All reviewer feedback should go in the Talk page for 224166.