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The "gsoc_xs_override_proposal" page has been changed by uswick. http://wiki.apache.org/xerces/gsoc_xs_override_proposal?action=diff&rev1=14&rev2=15 -------------------------------------------------- </override> }}} - . .Here “schemaLocation” indicates the location of the overriding schema document while “Content” corresponds to the types/groups/attributes/elements this schema will be overriding on the schemas available at corresponding “schemaLocation” . xs:override semantics are very much similar to class/prototypical inheritance where after successful application , corresponding overridden schemas replaces their old schemas by the new overriding schemas contained within a <xs:override> element. Following describes the criteria of xs:override on a general overview that should be considered in the implementation of xml schema composition on xs:override . + . .Here “schemaLocation” indicates the location of the overriding schema document while “Content” corresponds to the types/groups/attributes/elements this schema will be overriding on the schemas available at corresponding “schemaLocation” . xs:override semantics are very much similar to class/prototypical inheritance where after successful application , corresponding overridden schemas replaces their old schemas by the new overriding schemas contained within a <xs:override> element. Following describes the criteria of xs:override on a general overview. Implementing thsese sematics on XML schema composition framework ,can be be considered the main objective of the project. + . {{{ - . . - {{{ 1.override only applies if the schema component within <xs:override> exists in the overridden schema (corresponding to the respective schema Location defined). If this condition is not true, there’s no effect on the overriden schema location and overriding grammer won’t exist in the final schema representation. }}} - . {{{ + {{{ 2. - a)Each and every <override> schema information element would be subjected to “override transformation”[5] . However when target namespaces of overriding and overridden schemas don’t match “chameleon inclusion transformation”[6] is also performed prior to the override transform. Override transformation itself is pervasive and therefore would be applied to <include> information items on the overridden schema.(ie:- if schema A overrides B and B includes C then C will also be overridden accordingly ).Further more override transformation applies to <override> information items present on the overridden schema by merging. . . + a)Each and every <override> schema information element would be subjected to “override transformation”[5] . However when target namespaces of overriding and overridden schemas don’t match “chameleon inclusion transformation”[6] is also performed prior to the override transform. Override transformation itself is pervasive and therefore would be applied to <include> information items on the overridden schema.(ie:- if schema A overrides B and B includes C then C will also be overridden accordingly ).Further more override transformation also applies to <override> information items present on the overridden schema by merging. . . }}} - . . Although the idea behind xs:override seems to be rather simple , several scenarios need to be considered where some complications would inevitably arise.Following are several such considerations. + . Although the idea behind xs:override seems to be rather simple , several scenarios need to be considered where some complications would inevitably arise.Following are several such considerations. . {{{ Circular includes and overrides would end up creating duplicate components that should be flagged as errors . (ie:- if Schema A include B , B override C and C intern include B then we could endup with different versions of B included in both A and C . Versions of B included in A and C will only be considered same if C->B override transformation does not apply ) . . }}} @@ -44, +43 @@ This scenario could occur in circular overrides as well (ie:- if schema A overrides B and B overrides A , then if B->A override transformation affects schema A then duplicate errors will occur) . . }}} . {{{ - In general if overriding schemas produce same override transformation schema result for inclusion, then they would be considered the same other wise duplicates will occur .(ie:- If schema A includes B,C and B,C both inturn override D ,then B,C would include same version of D if B->D and C->D override transform doesn’t affect D OR if B,C both got same override schema components ) + In general if overriding schemas produce same override transformation schema result for inclusion, then they would be considered the same , other wise if the transformation results differ , duplicates will occur .(ie:- If schema A includes B,C and B,C both inturn override D ,then B,C would include same version of D if B->D and C->D override transform doesn’t affect D OR if B,C both got same override schema components ) }}} . Implementation of xs:override should take into account the aforementioned factors so that dependencies are correctly evaluated and necessary schema preprocessing is performed. @@ -67, +66 @@ . xs:override implementation intends to extend this functionality to implement <override> structure semantics. Also several supporting structures will be needed so that <override> schema components will be identified during schema processing. For example extending of following class structures. - . • org.apache.xerces.impl.xs.SchemaSymbols – keeps track of collection of symbols used in parsing Schema Grammer. Need to introduce new <override> grammer symbols to this. + . • org.apache.xerces.impl.xs.SchemaSymbols – keeps track of collection of symbols used in parsing Schema Grammer. Need to introduce new <override> grammer symbols to this. - . • org.apache.xerces.impl.xs.XSDDescription - keeps track of all information specific to XML Schema grammars. This can be used to indicate the Schema processor that the current schema document is overridden by another scheama document. + . • org.apache.xerces.impl.xs.XSDDescription - keeps track of all information specific to XML Schema grammars. This can be used to indicate the Schema processor that the current schema document is overridden by another scheama document. - . Additionally Xs:override implementation may require many new components/data structures to be added to org.apache.xerces.impl.xs package inorder to handle different scenarios regarding <override> semantics as was described in the beginning. + Additionally Xs:override implementation may require quite a few new components/data structures to be added to org.apache.xerces.impl.xs package inorder to handle different scenarios regarding <override> semantics as was described in the beginning. - - == Things I have Done So far == - . Since this project is about implementing a XMLSchema 1.1 specification construct , I had to go through this specification docs several times to understand the exact structure and semantics of the component I’m going to implement which I think is of vital importance when it comes to the design n implementation. Previous discussions (that has happened in Xerces-j-dev mail archives) about this xs:override support , online articles and tutorials also helped a lot in this cause. I also interacted with Xerces mailing list (especially with my mentor) to clarify critical points and implementation details. Since knowing Xerces and it’s internal framework(XNI) is obviously essential for the implementation I had to dig into various documentation, API information ,samples regarding Xerces Design,architecture and especially XML schema processing. I did download source code of Xerces2-j from trunk and build the code inorder to try and test out some samples to get a hang on the flow of things related to schema loading and processing. + . Since this project is about implementing a XMLSchema 1.1 specification construct , I had to go through this specification docs several times to understand the exact structure and semantics of the component I’m going to implement which I think is of vital importance when it comes to the design and implementation. Previous discussions (that has happened in Xerces-j-dev mail archives) about this xs:override support , online articles and tutorials also helped a lot in this cause. I also interacted with Xerces mailing list (especially with my mentor) to clarify critical points and implementation details. Since knowing Xerces and it’s internal framework(XNI) is obviously essential for the implementation I had to dig into various documentation, API information ,samples , regarding Xerces Design,architecture and especially XML schema processing. I did download the source code of Xerces2-j from trunk and build the code inorder to try and test out some samples to get a hang on the flow of things related to schema loading and processing.Running through several samples (xs.QuerryXS , jaxp.SourceValidator, xni samples,etc) and debugging them , really gave me a good inisght into to Xerces framework... == Development Schedule == ||<tablewidth="854px" tableheight="291px"width="200px" style="font-weight: bold; font-style: italic;">Time Schedule/Duration ||<style="font-weight: bold; font-style: italic;">Activity || --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
