Transcript IMDBPhase 2-3 Architecture

Integrated Meta
Database (IMDB)
Architecture
November 5th, 2003
Statistics Canada
1
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)
2
Implementation
•
Two different architectures:
1. 1999-2002: Phase 2 - Input of meta information for
statistical business processes
2. 2002- 2003: Phase 3 - Input of meta data for data
elements
•
Phase 2 implementation frozen because of:
1. Discontinued support for software by vendor
2. Size of system has exceeded the capabilities the
selected web deployment technology.
3
Phase 2
2-Tier (plump client) Model
Technologies
Presentation
&
Application
(Business Rules)
Middleware
Application
(Business Rules +
Data Access Logic)
&
Data Layer
Web Browser
Java Applet
JDBC
Tools
GUI
Internet Explorer
Sun Java
Plug-In
V1.1.3
Swing 1.0.3
Oracle JDBC Driver
Business Logic
Database
• Oracle 8i
RDBMS
with Stored Procs • Oracle (PL/SQL)
4
Phase 2 Bilingualism
Menu
items
Directive
Tabs
English
and
French
text fields
Labels
Coded
fields
Buttons
5
Phase 2 Bilingualism
Text for elements of the interface
English
Resource Bundle
Key
Value
menu_File
tab_ID
tab_Des
…
File
Identification
Description
...
6
Phase 2 Input Screens
Text strings related to data components
Directives Resource Bundle
IMDB
database
Key
Value
SurveySDDS
…
Statistical Data Doc…
...
Labels Resource Bundle
Key
Value
SurveySDDS
…
SDDS
...
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Phase 2 Input Screen
Administered Item
8
Phase 2 - Identification Tab
9
Phase 2 - Organization Tab
10
Phase 2 – DescriptionTab
Statistical Activity and Survey
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Factory Pattern applied to
Description
Instrument
Request
Survey
Request
Description
Factory
12
Phase 2
Model 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
13
Phase 2
Mapping 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 3
3-Tier (thin client) Model
Technologies
Presentation
Tier
Web
Browser
Standards
HTTP, HTML
JSP 2.0
Servlet 2.4
Internet Explorer 6.0
Jakarta Struts 1.2.8
Jakarta Tomcat 5.5.15
XML 1.0
XSLT 1.0
Application
Tier
Web
Server
Data Tier
Tools
RDBMS
HTTP
Apache (?)
JDBC 2.0
Oracle JDBC Driver
SQL
Oracle 9i
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Phase3
MVC - 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.
Persistence Layer
Database
• 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.
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Phase3
MVC - Model
The Database
Business Layer
• Responsible for storage and retrieval of data
according to the relational model.
• Enforces referential integrity.
Persistence Layer
• Provides vendor-specific tools for
administration and data access.
• Provides driver implementations for remote
access through JDBC, ODBC, etc…
Database
• Some non-standard aspects are unavoidable,
such as vendor-specific SQL dialects for data
definition.
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Phase3
MVC - Model
The Persistence Layer
Business Layer
• Contains low-level Java classes that model the
database tables closely.
Persistence Layer
• 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.
Database
• Protects the rest of the system from evolutionary
changes in the type, vendor or release version of
the database.
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Phase3
MVC - Model
The Business Layer
Business Layer
• Java classes in this layer model the objects
and processes in the user’s world. In our case,
these objects are instances of the metadata
items defined by the ISO 11179 specification.
Persistence Layer
• Delegates the actual saving and retrieving of
these objects to the Persistence layer.
• Defines and enforces business rules.
Database
• Contains a public API that allows any
Controller-level class to create and manipulate
metadata objects.
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Phase 3
MVC - Controller
1. User Action
Struts Controller Classes
MetaWeb
2. Process Request
4. System Response
JSP
Business Layer (Model)
3. Select View
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Phase 3
MVC - Controller
Struts Controller Classes
• A Struts servlet intercepts requests from the
user’s 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 3
MVC - View
• The View role is realized by JavaServer Pages
MetaWeb
HTML
Servlet
JSP
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.
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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.
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