content/framework/binfilter.html - openoffice-org - Git at Google

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 <h1>binfilter project<br>
 </h1>
 (short form of binary filters)<br>
 <h2>Summary:</h2>
 Before implementing the OpenOffice XML formats the main file
 format was the binary format for all applications. In OOo 1.0 and OOo
 1.1 we have both file formats included and did change the default
 format to XML. The binary formats exist as long as the applications
 exist. They were developed straightforward and run through various bug
 fixing/extension cycles. When starting implementing that filters it was
 straightforward to directly stream in and out the object model data.
 This was done mostly in implementing streaming operators at/for that
 classes defining the object model.<br>
 <p>
 Today, after that fixing/extension cycles, that format has several
 problems:<br>
 Due to extensions/changes (which is possible in small amounts in the
 binary files but always needs to stay readable for older versions,
 including previously made errors) the format is no longer
 straightforward. In many parts huge transitions to older object model
 data are done at saving and transition to newer data structures at
 loading.<br>
 The biggest problem is the streaming approach itself. This prevents us
 from doing necessary bigger changes at the application cores. It is
 possible to add new data to the binary format in a compatible manner,
 but at least at writing the corresponding older document model data
 needs to be created and written compatible for older versions. This
 also leads to having much data twice in the files. It is not possible
 to change the structure between the data chunks (which are the core
 classes normally) at all.<br>
 To get rid of that not well structured approach, the XML formats were
 developed and introduced as a first step. Now, in a second step, we
 want to break that document model core blockage by removing the old
 binary formats from the cores. Thus, a OOo 1.1 should be the last
 version containing XML and the binary filters. This will allow us to do
 a lot of more than necessary changes in the application cores for
 future versions.<br>
 This opens the problem that for later versions we still want to offer
 the user the possibility to read/write our 'old' binary file formats.
 There are different possibilities to do that which will now be shown.</p>
 <p>Thus, the targets of this project are:</p>
 <ul>
   <li>Remove the binary filters from the document model cores</li>
 </ul>
 <ul>
   <li>
     <p> Find and supply a possibility for the users of OOo after 1.1
 to work with the 'old' binary file formats. This is called Filter
 Migration</p>
   </li>
 </ul>
 The first point is obvoiusly not a big problem, but the 2nd one is.
 This new project thus deals with solvong the second point.<br>
 After the evaluation of different possibilities of Filter Migration it
 seems to be the safest and simplest to take a copy of the modules
 containing the binary filters and 'strip' everything that is not
 needed. Thus, the remaining modules will still contain the old data
 model cores, parts of the API implementations and the XML
 implementations. It is simplest to use XML as exchange format since we
 have a way to read/write XML with the current application cores and XML
 is well defined and will stay compatible to later OOo versions.<br>
 <br>
 <h2>Project Description:</h2>
 This OOo project covers the Filter Stripping approach to enable us
 to remove the outdated binary filters contained in OOo. Main reason is
 that the old filters are blocking future development. Since in later
 OOo versions there needs to be a possibiulity offered to still work
 with file formats from OOo 1.0 and OOo 1.1, this project will develop a
 solution for that. The solution will provide 'stripped' (reduced)
 versions of the core modules which keep the binary filter functionality
 and will be able to import/export from there to XML. Thus we will
 derive isolated, reduced filter modules for the old binary file formats.<br>
 </body>
 </html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
	<html>
	<head>
	<meta http-equiv="content-type"
	content="text/html; charset=ISO-8859-1">
	<title>binfilter</title>
	</head>
	<body>
	<h1>binfilter project<br>
	</h1>
	(short form of binary filters)<br>
	<h2>Summary:</h2>
	Before implementing the OpenOffice XML formats the main file
	format was the binary format for all applications. In OOo 1.0 and OOo
	1.1 we have both file formats included and did change the default
	format to XML. The binary formats exist as long as the applications
	exist. They were developed straightforward and run through various bug
	fixing/extension cycles. When starting implementing that filters it was
	straightforward to directly stream in and out the object model data.
	This was done mostly in implementing streaming operators at/for that
	classes defining the object model.<br>
	<p>
	Today, after that fixing/extension cycles, that format has several
	problems:<br>
	Due to extensions/changes (which is possible in small amounts in the
	binary files but always needs to stay readable for older versions,
	including previously made errors) the format is no longer
	straightforward. In many parts huge transitions to older object model
	data are done at saving and transition to newer data structures at
	loading.<br>
	The biggest problem is the streaming approach itself. This prevents us
	from doing necessary bigger changes at the application cores. It is
	possible to add new data to the binary format in a compatible manner,
	but at least at writing the corresponding older document model data
	needs to be created and written compatible for older versions. This
	also leads to having much data twice in the files. It is not possible
	to change the structure between the data chunks (which are the core
	classes normally) at all.<br>
	To get rid of that not well structured approach, the XML formats were
	developed and introduced as a first step. Now, in a second step, we
	want to break that document model core blockage by removing the old
	binary formats from the cores. Thus, a OOo 1.1 should be the last
	version containing XML and the binary filters. This will allow us to do
	a lot of more than necessary changes in the application cores for
	future versions.<br>
	This opens the problem that for later versions we still want to offer
	the user the possibility to read/write our 'old' binary file formats.
	There are different possibilities to do that which will now be shown.</p>
	<p>Thus, the targets of this project are:</p>
	<ul>
	<li>Remove the binary filters from the document model cores</li>
	</ul>
	<ul>
	<li>
	<p> Find and supply a possibility for the users of OOo after 1.1
	to work with the 'old' binary file formats. This is called Filter
	Migration</p>
	</li>
	</ul>
	The first point is obvoiusly not a big problem, but the 2nd one is.
	This new project thus deals with solvong the second point.<br>
	After the evaluation of different possibilities of Filter Migration it
	seems to be the safest and simplest to take a copy of the modules
	containing the binary filters and 'strip' everything that is not
	needed. Thus, the remaining modules will still contain the old data
	model cores, parts of the API implementations and the XML
	implementations. It is simplest to use XML as exchange format since we
	have a way to read/write XML with the current application cores and XML
	is well defined and will stay compatible to later OOo versions.<br>
	<br>
	<h2>Project Description:</h2>
	This OOo project covers the Filter Stripping approach to enable us
	to remove the outdated binary filters contained in OOo. Main reason is
	that the old filters are blocking future development. Since in later
	OOo versions there needs to be a possibiulity offered to still work
	with file formats from OOo 1.0 and OOo 1.1, this project will develop a
	solution for that. The solution will provide 'stripped' (reduced)
	versions of the core modules which keep the binary filter functionality
	and will be able to import/export from there to XML. Thus we will
	derive isolated, reduced filter modules for the old binary file formats.<br>
	</body>
	</html>