Fabio Arciniegas A. Rubby Casallas G.

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Fabio Arciniegas A.Rubby Casallas G.
Samxa

• An XML Based Academic
• Test Manager

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Agenda

• The Problem
• The Solution
• Evolution of Samxa
• Contributions
• Future Works

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The Problem

• Maximize the portability of questions and tests

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Agenda

• The Problem
• The Solution
• Typical user steps
• Basic Architecture
• Kernel
• CGIHelper

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The Solution Typical Steps user
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The Solution Typical Steps user (2)
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The Solution BasicArchitecture
SamxaServer
SamxaCGIHelper

• Produces and storages
• questions and tests.
• This is the component
• capable of reading /
• writing objects to XML

• This component takes
• the responsibility of
• converting CGI answers
• to XML

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The Solution Server Architecture
GUI

• SamXa Server follows a layered architecture.
• The XMLPersisters, the components capable of
  reading/writing objects from/to XML files are
  embbeded, in the Kernel.

Kernel
XMLPersisters
Database
XML
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The Solution Kernel

• Two reasons inspire this organization
• Abundant, objects should not bear the
  responsiblity of saving themselves as XML.
  Consequences
• Flyweight pattern GoF95 can be applied leading
  to a much smaller memory consumption.
• Coupling between the rest of the solution and the
  XML processor is greatly diminished

• The need of a domain specific object hierarchy
  imposes the need of an object model
  representation of the XML other than DOM.

• The kernel is composed of several units that
  replicate an Object-Object Server-Object
  Persister architecture.
• The generalization of this structure is what we
  call the XMLable design pattern.

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The Solution Kernel (2)

• Samxas XML to DBMS is based on an intermediate
  object representation for both.
• This is similar to the XML to DBMS proposal for
  java by David Megginson

• Samxas XMLPersisters (in classes
  XMLQuestionPersister, XMLTestPersister)
• Follow the Builder Pattern GoF95.
• Currently XMLPersisters use a modified version of
  Andy Dents C Expat wrapper.
• XML4C2 Dom implementation is used for Object to
  XML document persistance

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The Solution Kernel (3)

• Transformations in Samxa are performed using
  external tools.
• A Transformation Manager class takes care of the
  calls to these tools.

When a stylesheet is registered it can specify
its type (DSSSL or XSL) and a recomnended
external tool to use.

• Currently, Samxa users have a set of 10
  stylesheets.
• 7 of them are written in DSSSL (use James Clarks
  Jade)
• 2 more of them use XSLT
• 1 is a special template that inserts the XML in a
  page that uses the XML/XSL capabilities of IE5.0

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The Solution CGIHelper
This helper follows a pipe-filter architecture in
order to convert CGI-POST based information
(the answers) into XML answer documents which
conform to an Answers DTD.
The CGI Helper is written in Perl. It uses
XMLDOM for the actual translation of the posted
data to XML. It also uses XMLXSLT in order to
produce the HTML statistic pages that students
look at.
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Agenda

• The Problem
• The Solution
• Evolution of Samxa
• XML Relevant changes over Time
• Comparisions

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Evolution XML Relevant changes

• Samxa, now in its version 2.0, has undergone
• several changes that compomise its relation with
• The XML libraries/tools that it uses.
• These changes took place mainly in two
  components
• XMLPersister classes in the kernel and
• the CGIHelper.
• We believe this experimentation... Better yet,
• wandering through parsers and tools is
  representative
• of what many developers are going thru.

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Evolution XMLPersister changes
Ad Hoc Home made perl script
Expat. Using intermediate structures in userData
XML4C2 SAXParser
XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Evolution XMLPersister changes
Pros
Ad Hoc Home made perl script

• Solution can be highly optimized for the problem
• at hand

Expat. Using intermediate structures in userData
XML4C2 SAXParser
Cons
XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Evolution XMLPersister changes
Pros
Ad Hoc Home made perl script

• Really Fast
• Easy to learn
• Clear, concise code
• Totally portable

Expat. Using intermediate structures in userData
XML4C2 SAXParser
Cons
XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Evolution XMLPersister changes
Pros
Ad Hoc Home made perl script

• Highly readable code
• Fast development
• Originally developed for C

Expat. Using intermediate structures in userData
XML4C2 SAXParser
Cons
XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Evolution XMLPersister changes
Pros
Ad Hoc Home made perl script

• Highly readable code
• Fast development
• Originally developed for C

Expat. Using intermediate structures in userData
XML4C2 SAXParser
Cons
XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Evolution XMLPersister changes
Pros (The best of both worlds)
Ad Hoc Home made perl script

• Highly readable code
• Fast development
• Presents only a C façade

Expat. Using intermediate structures in userData
XML4C2 SAXParser

XML4C2 DomParser
Enhanced Expatpp using Run-time linking of
xmlparse.dll
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Agenda

• The Problem
• The Solution
• Evolution of Samxa
• Contributions
• The Software development process and XML related
  contributions

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Contributions
During the development of SamXa several other
tools were developed. XML Tools for various
stages of the development process are now
an integral part of our work.
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Contributions
The tools developed have been useful on
several stages of the development process.
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Contributions Samples
ltREQUIREMENT ID1.1 CRITICFALSEgt ltNAMEgtText
context Creationlt/NAMEgt... lt/REQUIREMENTgt
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Contributions Samples

• Multiple objects whose data is to be gathered
  from XML documents need to be manipulated.
• Design and program quality imposes the need to
  represent the data as something more meaningful
  in your domain than the DOM tree.

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Contributions Samples
... ltTEST IDt29gt ltPROGRAM NAME/usr/local/bin
/h.plgt ltINPUT VIAstdingtHellolt/INPUTgt ltEXPE
CTEDgtHi there!lt/EXPECTEDgt lt/PROGRAMgt ltVALUEgt5lt/V
ALUEgt lt/TESTgt ...
Munin
HTML with the results
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Future Works
Create tools for the automatic generation of
classes that follow the Samxa approach for the
event oriented construction of domain specific
objects
Create simple to use components in order to
popularize parsers among developers
Complete a full set of XML based tools
that support the whole development cycle e.g dtds
visual tools for the definition of
architectures.
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Conclusions
Samxa history shows a common struggle
between tools. We hope that others can make use
of our experience when facing similar problems
Samxa shows useful, reusable techniques for
the creation of domain specific objects from XML
Samxa is an example of how an XML based
solution, using XML based assistant tools can be
applied to real life problems.
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Questions
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Fabio Arciniegas A.Rubby Casallas G.
Samxa

• An XML Based Academic
• Test Manager

www.uniandes.edu.co/l-arcini/TheFAActoryl-arcini
_at_uniandes.edu.co