Integrated Meta Database IMDB Architecture

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Integrated Meta Database (IMDB) Architecture

• November 5th, 2003

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Design Goals

• Web deployable (Project/Architectural)
• Acceptable Performance (Project/Architectural)
• Thin-client (Architectural)
• Alleviates burden on client machine
• Faster run and load time, ease of deployment
• n-tier (Architectural)
• Development of corporate components
• Services/products available from multiple vendors
  (Architectural)
• Bilingual (Architectural)

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Implementation

• Two different architectures
• 1999-2002 Phase 2 - Input of meta information
  for statistical business processes
• 2002- 2003 Phase 3 - Input of meta data for data
  elements
• Phase 2 implementation frozen because of
• Discontinued support for software by vendor
• Size of system has exceeded the capabilities the
  selected web deployment technology.

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Phase 22-Tier (plump client) Model
Technologies
Presentation Application (Business Rules)

Tools

GUI Internet Explorer Sun Java Plug-In
V1.1.3 Swing 1.0.3
Web Browser Java Applet


JDBC
Oracle JDBC Driver
Middleware

• Business Logic Database
• Oracle 8i
• Oracle (PL/SQL)

Application (Business Rules Data Access
Logic) Data Layer
RDBMSwith Stored Procs
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Phase 2 Bilingualism
Menu items
Directive
Tabs
English and French text fields
Labels
Coded fields
Buttons
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Phase 2 Bilingualism
Text for elements of the interface
English
Resource Bundle Key Value menu_File File tab_
ID Identification tab_Des Description ...
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Phase 2 Input Screens
Text strings related to data components
Directives Resource Bundle Key
Value SurveySDDS Statistical Data Doc ...
IMDB database
Labels Resource Bundle Key Value SurveySDDS
SDDS ...
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Phase 2 Input ScreenAdministered Item
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Phase 2 - Identification Tab
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Phase 2 - Organization Tab
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Phase 2 DescriptionTab Statistical Activity
and Survey
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Factory Pattern applied to Description
Instrument Request
Survey Request
Description Factory
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Phase 2Model View Controller Pattern

• Model maintains the data
• View displays the data
• Controller event handlers for the Model and
  View
• Phase 2 combines the View and Controller

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Phase 2Mapping of Relational Model to OO
Visual Age DATA ACCESS BUILDER
IMDB Relational Database
JDBC Class
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Phase 2 2001 Achievement of design goals

• Web deployable? via Applet however plug-in
  technology was not stable and removed from
  deployment.
• Acceptable Performance? Applet very slow for
  load time. Performance is improved by deployment
  as an application on the client. Support provided
  for both Applet and Application versions.
• Thin-client? Plump client
• n-tier? 2-tier
• Services/products available from multiple
  vendors? No vendor support for Visual Age 3.0
  DAB. Code is not compliant with JDK 1.3
• Bilingual ? English and French

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Phase 2 Data Migration

• Microsoft Access form to collect business meta
  data from various sources.
• Load from existing meta data systems.
• PL/SQL procedure for conversion and load into the
  phase 2 database

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Phase 3 Considerations

• Design Goals
• Conformance with standards.
• Minimize use of auto generation tools/wizards,
  therefore reducing risk of vendor lock-in.

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Phase 33-Tier (thin client) Model
Technologies
Standards
Tools
Presentation Tier
Web Browser



Internet Explorer 6.0
HTTP, HTML
JSP 2.0
Jakarta Struts 1.2.8
Servlet 2.4
Jakarta Tomcat 5.5.15
Application Tier
XML 1.0
XSLT 1.0
Web Server
Apache (?)
HTTP


JDBC 2.0
Oracle JDBC Driver
Data Tier

Oracle 9i
RDBMS
SQL
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Phase3MVC - Model
Model Layers
Business Layer

• The Model role is realized by two software
  layers from the Application tier, plus the Data
  tier.
• Layering reflects division of responsibilities.
• Each layer knows nothing about the layers above,
  and can delegate work only to the layer directly
  below.
• This reduces the scope of change for example,
  if a database table definition is altered, the
  Persistence layer can usually absorb the change,
  leaving the Business classes totally unaffected.

Persistence Layer
Database
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Phase3MVC - Model
The Database
Business Layer

• Responsible for storage and retrieval of data
  according to the relational model.
• Enforces referential integrity.
• Provides vendor-specific tools for
  administration and data access.
• Provides driver implementations for remote
  access through JDBC, ODBC, etc
• Some non-standard aspects are unavoidable, such
  as vendor-specific SQL dialects for data
  definition.

Persistence Layer
Database
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Phase3MVC - Model
The Persistence Layer
Business Layer

• Contains low-level Java classes that model the
  database tables closely.
• Knows how to store and retrieve data directly
  from the database using JDBC methods.
• Also contains higher-level Java classes that
  provide data access services to any kind of
  Business layer, through a public API.
• Protects the rest of the system from
  evolutionary changes in the type, vendor or
  release version of the database.

Persistence Layer
Database
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Phase3MVC - Model
The Business Layer
Business Layer

• Java classes in this layer model the objects and
  processes in the users world. In our case,
  these objects are instances of the metadata items
  defined by the ISO 11179 specification.
• Delegates the actual saving and retrieving of
  these objects to the Persistence layer.
• Defines and enforces business rules.
• Contains a public API that allows any
  Controller-level class to create and manipulate
  metadata objects.

Persistence Layer
Database
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Phase 3 MVC - Controller
1. User Action
Struts Controller Classes
MetaWeb
2. Process Request
4. System Response
Business Layer (Model)
JSP
3. Select View
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Phase 3 MVC - Controller
Struts Controller Classes

• A Struts servlet intercepts requests from the
  users browser, and dispatches each request (by
  URL) to an Action class for processing.
• Depending on the outcome of processing, the most
  suitable view is selected to display the result.
• View selection can be controlled in an XML
  configuration file as well as in code.
• The Struts framework enables a clean and
  flexible separation of MVC responsibilities in a
  web application.

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Phase 3MVC - View

• The View role is realized by JavaServer Pages in
  the Application tier, and by the browser in the
  Presentation tier.
• JavaServer Pages are similar to HTML pages, but
  combine HTML markup with special JSP tags that
  enable the insertion of dynamic content.
• Struts provides a rich and powerful assortment
  of tags that integrate well with the rest of the
  framework.
• Every JSP is transformed into a servlet when
  first requested, and the generated servlet
  returns the view as pure HTML to the browser.

MetaWeb
HTML
Servlet
JSP
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Phase 3 Bilingualism

• The user interface language can be changed by the
  user at any time, to any language for which a
  resource bundle has been created. (So far, the
  only demand is for English and French)
• Data in any two languages can be simultaneously
  displayed and edited.
• Data in multiple languages can be stored in the
  database, and new languages can be supported
  without changes to the data model.
• Java and the Struts framework both provide rich
  support for localized content, including
  variations by country, and formatting of dates,
  times, and currencies.

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Phase 3 2003 Achievement of design goals

• Web deployable? Application resides entirely on
  the server and is available to any browser.
• Acceptable Performance? Servlets are designed
  for high efficiency and scalability. Database
  I/O can be optimized in the Persistence layer.
• Thin-client? Ultra-thin (no client-side code
  required).
• n-tier? 3-tier
• Services/products available from multiple
  vendors? Open solution using open software.
• Bilingual? Multi-lingual.