OKC Tools for XML Metadata Management

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OKC Tools for XML Metadata

Management

Marlon Pierce

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Overview

• We discuss systems we have built for managing XML

metadata.

• Applications include

– Newsgroups

– Bibtex-based citation managers

– Glossary term and abbreviation managers – RIB compatible browsers

• Running demos available from www.xm

lnuggets.org.

• Downlo

ads of revised newsgroup application available

soon.

• Challenge: promote scientific metadata usage

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Parts of the System

• Each application has one or more XML schemas that serve

as a data model.

• The general system contains the following components:

– Form wizards for creating valid XML instances for a particular application.

– Publishers or “feeders” that post messages into the system. – Unique URI generators for storing each message.

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<?xml version="1.0"?>

<title>Community Grids Project Reports</title> <image>

<title>ptllogo</title>

<url>http://www.communitygrids.iu.edu/img/smallLOGO.gif</url> <link>http://www.communitygrids.iu.edu</link>

<description>Pervasive Technology Labs Logo</description> </image>

<Item>

<name>CORBA</name>

<URI>glossary/C/CORBA</URI>

<description>Common Object Request Broker Architecture is an open distrubuted object-computing infrastructure being standardised

by the Object Management Group.</description> </Item>

<!—Other items deleted--> </channel>

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Sample Applications

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Newsgroup System Features

• Email and browser-based posting.

• Supports attachments.

• Multiple topic subscriptions

• Periodic topic digests

• Multiple user privileges

–

Read through browser only

–

Post through browser only

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Citation Browser

• Supports multiple schema descriptions

based on bibtex

–

Journal articles, books, book chapters,

conference proceedings, tech reports, theses

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RIB Compatible Applications

• Basic system can be used

with any schema, so we

created a version using the

Basic Interoperability

Data Model (BIDM)

– Developed by the RIB team – IEEE standard

• BIDM has two important

extensions that we do not

currently support.

– Asset certification

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Steps for a Metadata Generator

• There were common tasks that we performed for each

application:

– Design an object model and create a W3C XML Schema to represent it.

– Create a memory object model of the schema, i.e. corresponding Java classes.

– Design an interface, i.e. HTML forms, for user inputs, and bind the interface with the memory model.

– Let users input data.

– Finally, generate XML based on input, and publish it.

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Generating XML Form Wizards

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SchemaWizard and XML

• Schema Wizard maps XML Schema elements to

HTML form elements through its

schema parser

,

and creates the

framework and logic

for an XML

form wizard.

• Users use newly generated wizards to create and

publish

XML instances

, which follow a schema,

to any destinations such as publish/subscribe

messaging systems or through SMTP.

• XML form wizards are Web applications that also

serve as validating XML editors and are

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Steps for a Metadata Generator

• There were common tasks that we performed for each

application:

– Design an object model and create a W3C XML Schema to represent it.

– Create a memory object model of the schema, i.e. corresponding Java classes.

– Design an interface, i.e. HTML forms, for user inputs, and bind the interface with the memory model.

– Let users input data.

– Finally, generate XML based on input, and publish it.

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SchemaWizard and XML

• Schema Wizard maps XML Schema elements to

HTML form elements through its

schema parser

,

and creates the

framework and logic

for an XML

form wizard.

• Users use newly generated wizards to create and

publish

XML instances

, which follow a schema,

to any destinations such as publish/subscribe

messaging systems or through SMTP.

• XML form wizards are Web applications that also

serve as validating XML editors and are

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SchemaWizard Architecture

• The steps that take place in generating a XML form wizard

– The Schema Wizard unpacks and deploys the Web application package into a Web server’s application repository (i.e. webapps under Tomcat).

– User provides with a location of the Schema.

– The Schema is read in to create an in-memory representation (SOM) of the schema and also to create Java classes.

• SOM=Castor’s Schema Object Model

• SOM API provides a convenient interface to access the W3C XML Schema structures.

– Using the SOM, Castor SourceGenerator creates Java classes that correspond to the Schema structures. These classes form the memory model (i.e. Javabeans for JSP) and come with the necessary

framework to parse and regenerate (marshal and unmarshal) XML instances.

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SchemaWizard Architecture

Castor Schema Unmarshaller

Castor Sourc Generator JavaBean s Castor SOM Sche ma Parser Velocity Template s Java Compiler

Annotated XML Schema

Web Application

Template

Librarie

s Classes JSPs

XML Form Wizard created as a Web Application

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SchemaWizard Architecture

• The steps that take place in generating a XML form wizard

(cont.)

– Using the SOM once again, SchemaParser traverses the in-memory schema and collects structure information, i.e. names, types, whether element or attribute, complex or simple type.

– Based on this information, the parser chooses what type of template will be used, stores the information in a Velocity context, and invokes the template engine to generate the program logic presented in JSP. The parser also gathers the Schema annotations, i.e. page color, input sizes, at this level and place the parameters in the context.

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SchemaParse

Data Flow and Action

Traverse schema for types

Collect type information, create a context

Decide template:

Project page Index page Simple type

Enumerated simple type Unbounded simple type Complex type

Unbounded complex type

Velocity Template Engine

Castor SOM

Schema object

Individual types

Velocity context with type info

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XML Schema location is given to SchemaWizard.

XML Form Wizard is generated.

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Schema Annotations

• Users can make cosmetic changes for the final project

beforehand with annotations in the schema.

• W3C XML Schema allows developers to embed user

defined languages into the schema using <xs:annotation>

and <xs:appinfo> structures.

• Annotations for the whole schema affects the whole page,

i.e. page title, background color, default input sizes,

leading numbers on and off, XML browsing on and off.

<xs:annotation>

<xs:appinfo source="title">SchemaWizard Output for Topics Schema </xs:appinfo> <xs:appinfo source="inputsize">30</xs:appinfo>

<xs:appinfo source="bgcolor">#e0e0ff</xs:appinfo>

<xs:appinfo source="leadingnumbers">false</xs:appinfo> <xs:appinfo source="showxml">true</xs:appinfo>

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Schema Annotations

• Annotations for individual structures override the schema

annotations, i.e. input size for each element. Also, labels

for each element can be defined, and input fields can be

changed to larger text areas with a textarea parameter and

row numbers, or to password fields by a password

parameter whose value set to true.

<xs:annotation>

<xs:appinfo source=“label">User Password</xs:appinfo> <xs:appinfo source="inputsize">15</xs:appinfo>