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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.0//EN" "dtd/document-v10.dtd">
<document>
<header>
<title>POI 2.0 Vision Document</title>
<authors>
<person name="Andrew C. Oliver" email="acoliver2@users.sourceforge.net"/>
<person name="Marcus W. Johnson" email="mjohnson@apache.org"/>
<person name="Glen Stampoultzis" email="gstamp@iprimus.com.au"/>
<person name="Nicola Ken Barozzi" email="barozzi@nicolaken.com"/>
</authors>
</header>
<body>
<s1 title="Preface">
<p>
This is the POI 2.0 cycle vision document. Although the vision
has not changed and this document is certainly not out of date and
the vision has not changed, the structure of the project has
changed a bit. We're not going to change the vision document to
reflect this (however proper that may be) because it would only
involve deletion. There is no purpose in providing less
information provded we give clarification.
</p>
<p>
This document was created before the POI components for
<link href="http://xml.apache.org/cocoon">Apache Cocoon</link>
were accepted into the Cocoon project itself. It was also
written before POI was accepted into Jakarta. So while the
vision hasn't changed some of the components are actually now
part of other projects. We'll still be working on them on the
same timeline roughly (minus the overhead of coordination with
other groups), but they are no longer technically part of the
POI project itself.
</p>
</s1>
<s1 title="1. Introduction">
<s2 title="1.1 Purpose of this document">
<p>
The purpose of this document is to
collect, analyze and define high-level requirements, user needs,
and features of the second release of the POI project software.
The POI project currently consists of the following components:
the HSSF Serializer, the HSSF library and the POIFS library.
</p>
<ul>
<li>
The HSSF Serializer is a set of Java classes whose main
class supports the Serializer interface from the Cocoon
2 project and outputs the serialized data in a format
compatible with the spreadsheet program Microsoft Excel
'97.
</li>
<li>
The HSSF library is a set of classes for reading and
writing Microsoft Excel 97 file format using pure Java.
</li>
<li>
The POIFS library is a set of classes for reading and
writing Microsoft's OLE 2 Compound Document format using
pure Java.
</li>
</ul>
<p>By the completion of this release cycle the POI project will also
include the HSSF Generator and the HDF library.
</p>
<ul>
<li>The HSSF Generator will be responsible for using HSSF to read
in the XLS (Excel 97) file format and create SAX events. The HSSF
Generator will support the applicable interfaces specified by the
Apache Cocoon 2 project.
</li>
<li>The HDF library will provide a set of high level interfaces
for reading and writing Microsoft Word 97 file format using pure
Java.</li>
</ul>
</s2>
<s2 title="1.2 Project Overview">
<p>
The first release of the POI project
was an astounding success. This release seeks to build on that
success by:
</p>
<ul>
<li>
Refactoring POIFS into imput and
output classes as well as an event-driven API for reading.
</li>
<li>
Refactor HSSF for greater
performance as well as an event-driven API for reading
</li>
<li>
Extend HSSF by adding the ability to read and write formulas.
</li>
<li>
Extend HSSF by adding the ability to read and write
user-defined styles.
</li>
<li>
Create a Cocoon 2 Generator for HSSF using the same tags
as the HSSF Serializer.
</li>
<li>
Create a new library (HDF) for reading and writing
Microsoft Word DOC format.
</li>
<li>
Refactor the HSSFSerializer into a separate extensible
POIFSSerializer and HSSFSerializer
</li>
<li>
Providing the create excel charts. (write only)
</li>
</ul>
</s2>
</s1>
<s1 title="2. User Description">
<s2 title="2.1 User/Market Demographics">
<p>
There are a number of enthusiastic
users of XML, UNIX and Java technology. Furthermore, the Microsoft
solution for outputting Office Document formats often involves
actually manipulating the software as an OLE Server. This method
provides extremely low performance, extremely high overhead and is
only capable of handing one document at a time.
</p>
<ol>
<li>
Our intended audience for the HSSF
Serializer portion of this project are developers writing reports or
data extracts in XML format.
</li>
<li>
Our intended audience for the HSSF
library portion of this project is ourselves as we are developing
the HSSF serializer and anyone who needs to read and write Excel
spreadsheets in a non-XML Java environment, or who has specific
needs not addressed by the Serializer
</li>
<li>
Our intended audience for the
POIFS library is ourselves as we are developing the HSSF and HDF
libraries and anyone wishing to provide other libraries for
reading/writing other file formats utilizing the OLE 2 Compound
Document Format in Java.
</li>
<li>
Our intended audience for the HSSF
generator are developers who need to export Excel spreadsheets to
XML in a non-proprietary environment.
</li>
<li>
Our intended audience for the HDF
library is ourselves, as we will be developing a HDF Serializer in a
later release, and anyone wishing to add .DOC file processing and
creation to their projects.
</li>
</ol>
</s2>
<s2 title="2.2. User environment">
<p>
The users of this software shall be
developers in a Java environment on any operating system, or power
users who are capable of XML document generation/deployment.
</p>
</s2>
<s2 title="2.3. Key User Needs">
<p>
The HSSF library currently requires a
full object representation to be created before reading values. This
results in very high memory utilization. We need to reduce this
substantially for reading. It would be preferable to do this for
writing, but it may not be possible due to the constraints imposed by
the file format itself. Memory utilization during read is our top
user complaint.
</p>
<p>
The POIFS library currently requires a
full object representation to be created before reading values. This
results in very high memory utilization. We need to reduce this
substantially for reading.
</p>
<p>
The HSSF library currently ignores
formula cells and identifies them as &quot;UnknownRecord&quot; at the
lower level of the API. We must provide a way to read and write
formulas. This is now the top requested feature.
</p>
<p>
The HSSF library currently does not support
charts. This is a key requirement of some users who wish to use HSSF
in a reporting engine.
</p>
<p>
The HSSF Serializer currently does not
provide serialization for cell styling. User's will want stylish
spreadsheets to result from their XML.
</p>
<p>
There is currently no way to generate
the XML from an XLS that is consistent with the format used by the
HSSF Serializer.
</p>
<p>
There should be a way to read and write
the DOC file format using pure Java.
</p>
</s2>
<s2 title="2.4. Alternatives and Competition">
<p>
Alternatives to using HSSF to manipulate Excel files include:
</p>
<ol>
<li>Buy the $10,000 Formula 1 library
(<link href="http://www.f1j.com/">www.tidestone.com</link>)
now owned by Actuate and accept its crude api and limitations.
</li>
<li>Give up XML, Java, and operating system independence, and
write Visual Basic code in a Microsoft Windows based environment
</li>
<li>Try writing output in Microsoft's poorly documented XHTML
for Office format.
</li>
</ol>
<p>
There is also a decent library for
reading Excel documents written by Andy Khan called xlReader
(<link href="http://www.sourceforge.net/projects/xlrd">http://www.sourceforge.net/projects/xlrd</link>).
It does not provide write ability.
</p>
<p>
There are a number of PERL and C alternatives.
None are consistent.
</p>
</s2>
</s1>
<s1 title="3. Project Overview">
<s2 title="3.1. Project Perspective">
<p>
The produced code shall be licensed by
the Apache License as used by the Cocoon 2 project (APL 1.1) and
maintained on at <link href="http://poi.sourceforge.net/">http://poi.sourceforge.net</link>
and <link href="http://sourcefoge.net/projects/poi">http://sourcefoge.net/projects/poi</link>.
It is our hope to at some point integrate with the various Apache
projects (xml.apache.org and jakarta.apache.org), at which point we'd
turn the copyright over to them.
</p>
</s2>
<s2 title="3.2. Project Position Statement">
<p>
For developers on a Java and/or XML
environment this project will provide all the tools necessary for
outputting XML data in the Microsoft Excel format. This project seeks
to make the use of Microsoft Windows based servers unnecessary for
file format considerations and to fully document the OLE 2 Compound
Document format. The project aims not only to provide the tools for
serializing XML to Excel and Word file formats and the tools for
writing to those file formats from Java, but also to provide the
tools for later projects to convert other OLE 2 Compound Document
formats to pure Java APIs.
</p>
</s2>
<s2 title="3.3. Summary of Capabilities">
<p>
HSSF Serializer for Apache Cocoon 2
</p>
<table>
<tr>
<td>
Benefit
</td>
<td>
Supporting Features
</td>
</tr>
<tr>
<td>
Ability to serialize styles from XML spreadsheets.
</td>
<td>
HSSFSerialzier will support styles.
</td>
</tr>
<tr>
<td>
Ability to read and write formulas in XLS files.
</td>
<td>
HSSF will support reading/writing formulas.
</td>
</tr>
<tr>
<td>
Ability to output in MS Word on any platform using Java.
</td>
<td>
The project will develop an API that outputs in Word format
using pure Java.
</td>
</tr>
<tr>
<td>
Enhance performance for reading and writing XLS files.
</td>
<td>
HSSF will undergo a number of performance enhancements. HSSF
will include a new event-based API for reading XLS files. POIFS
will support a new event-based API for reading OLE2 CDF files.
</td>
</tr>
<tr>
<td>
Ability to generate XML from XLS files
</td>
<td>
The project will develop an HSSF Generator.
</td>
</tr>
<tr>
<td>
The ability to generate charts
</td>
<td>
HSSF will provide low level support for chart records as well
as high level API support for generating charts. The ability
to read chart information will not initially be provided.
</td>
</tr>
</table>
</s2>
<s2 title="3.4. Assumptions and Dependencies">
<ul>
<li>
The HSSF Serializer and Generator
will support the Gnumeric 1.0 XML tag language.
</li>
<li>
The HSSF Generator and HSSF
Serializer will be mutually validating. It should be possible to
have an XLS file created by the Serializer run through the Generator
and the output back through the Serializer (via the Cocoon pipeline)
and get the same file or a reasonable facimille (no one cares if it
differs by the order of the binary records in some minor but
non-visually recognizable manner).
</li>
<li>
The HSSF Generator will run on any
Java 2 supporting platform with Apache Cocoon 2 installed along with
the HSSF and POIFS APIs.
</li>
<li>
The HSSF Serializer will run on
any Java 2 supporting platform with Apache Cocoon 2 installed along
with the HSSF and POIFS APIs.
</li>
<li>
The HDF API requires a Java 2
implementation and the POIFS API.
</li>
<li>
The HSSF API requires a Java 2
implementation and the POIFS API.
</li>
<li>
The POIFS API requires a Java 2
implementation.
</li>
</ul>
</s2>
</s1>
<s1 title="4. Project Features">
<p>
Enhancements to the POIFS API will
include:
</p>
<ul>
<li>
An event driven API for reading
POIFS Filesystems.
</li>
<li>
A low-level API for
creating/manipulating POI filesystems.
</li>
<li>
Code improvements supporting
greater separation between read and write structures.
</li>
</ul>
<p>
Enhancements to the HSSF API will
include:
</p>
<ul>
<li>
An event driven API for reading
XLS files.
</li>
<li>
Performance improvements.
</li>
<li>
Formula support (read/write)
</li>
<li>
Support for user-defined data
formats
</li>
<li>
Better documentation of the file
format and structure.
</li>
<li>
An API for creation of charts.
</li>
</ul>
<p>
The HSSF Generator will include:
</p>
<ul>
<li>
A set of classes supporting the
Cocoon 2 Generator interfaces providing a method for reading XLS
files and outputting SAX events.
</li>
<li>
The same tag format used by the
HSSFSerializer in any given release.
</li>
</ul>
<p>
The HDF API will include:
</p>
<ul>
<li>
An event driven API for reading
DOC files.
</li>
<li>
A set of high and low level APIs
for reading and writing DOC files.
</li>
<li>
Documentation of the DOC file
format or enhancements to existing documentation.
</li>
</ul>
</s1>
<s1 title="5. Other Product Requirements">
<s2 title="5.1. Applicable Standards">
<p>
All Java code will be 100% pure Java.
</p>
</s2>
<s2 title="5.2. System Requirements">
<p>
The minimum system requirements for the POIFS API are:
</p>
<ul>
<li>64 Mbytes memory</li>
<li>Java 2 environment</li>
<li>Pentium or better processor (or equivalent on other platforms)</li>
</ul>
<p>
The minimum system requirements for the the HSSF API are:
</p>
<ul>
<li>64 Mbytes memory</li>
<li>Java 2 environment</li>
<li>Pentium or better processor (or equivalent on other platforms)</li>
<li>POIFS API</li>
</ul>
<p>
The minimum system requirements for the the HDF API are:
</p>
<ul>
<li>64 Mbytes memory</li>
<li>Java 2 environment</li>
<li>Pentium or better processor (or equivalent on other platforms)</li>
<li>POIFS API</li>
</ul>
<p>
The minimum system requirements for the HSSF Serializer are:
</p>
<ul>
<li>64 Mbytes memory</li>
<li>Java 2 environment</li>
<li>Pentium or better processor (or equivalent on other platforms)</li>
<li>Cocoon 2</li>
<li>HSSF API</li>
<li>POI API</li>
</ul>
</s2>
<s2 title="5.3. Performance Requirements">
<p>
All components must perform well enough
to be practical for use in a webserver environment (especially
the "killer trio": Cocoon2/Tomcat/Apache combo)
</p>
</s2>
<s2 title="5.4. Environmental Requirements">
<p>
The software will run primarily in
developer environments. We should make some allowances for
not-highly-technical users to write XML documents for the HSSF
Serializer. All other components will assume intermediate Java 2
knowledge. No XML knowledge will be required except for using the
HSSF Serializer. As much documentation as is practical shall be
required for all components as XML is relatively new, and the
concepts introduced for writing spreadsheets and to POI filesystems
will be brand new to Java and many Java developers.
</p>
</s2>
</s1>
<s1 title="6. Documentation Requirements">
<s2 title="6.1 POI Filesystem">
<p>
The filesystem as read and written by
POI shall be fully documented and explained so that the average Java
developer can understand it.
</p>
</s2>
<s2 title="6.2. POI API">
<p>
The POI API will be fully documented
through Javadoc. A walkthrough of using the high level POI API shall
be provided. No documentation outside of the Javadoc shall be
provided for the low-level POI APIs.
</p>
</s2>
<s2 title="6.3. HSSF File Format">
<p>
The HSSF File Format as implemented by
the HSSF API will be fully documented. No documentation will be
provided for features that are not supported by HSSF API that are
supported by the Excel 97 File Format. Care will be taken not to
infringe on any &quot;legal stuff&quot;. Additionally, we are
collaborating with the fine folks at OpenOffice.org on
*free* documentation of the format.
</p>
</s2>
<s2 title="6.4. HSSF API">
<p>
The HSSF API will be documented by
javadoc. A walkthrough of using the high level HSSF API shall be
provided. No documentation outside of the Javadoc shall be provided
for the low level HSSF APIs.
</p>
</s2>
<s2 title="6.5 HDF API">
<p>
The HDF API will be documented by
javadoc. A walkthrough of using the high level HDF API shall be
provided. No documentation outside of the Javadoc shall be provided
for the low level HDF APIs.
</p>
</s2>
<s2 title="6.6 HSSF Serializer">
<p>
The HSSF Serializer will be documented
by javadoc.
</p>
</s2>
<s2 title="6.7 HSSF Generator">
<p>
The HSSF Generator will be documented
by javadoc.
</p>
</s2>
<s2 title="6.8 HSSF Serializer Tag language">
<p>
The XML tag language along with
function and usage shall be fully documented. Examples will be
provided as well.
</p>
</s2>
</s1>
<s1 title="7. Terminology">
<s2 title="7.1 Filesystem">
<p>
filesystem shall refer only to the POI formatted archive.
</p>
</s2>
<s2 title="7.2 File">
<p>
file shall refer to the embedded data stream within a
POI filesystem. This will be the actual embedded document.
</p>
</s2>
</s1>
</body>
</document>