Author: nick
Date: Tue Apr 24 09:52:03 2012
New Revision: 1329614
URL: http://svn.apache.org/viewvc?rev=1329614&view=rev
Log:
Update the Detector Documentation for DefaultDetector, which replaced the older
ContainerAwareDetection
Modified:
tika/site/publish/1.1/detection.html
tika/site/src/site/apt/1.1/detection.apt
Modified: tika/site/publish/1.1/detection.html
URL:
http://svn.apache.org/viewvc/tika/site/publish/1.1/detection.html?rev=1329614&r1=1329613&r2=1329614&view=diff
==============================================================================
--- tika/site/publish/1.1/detection.html (original)
+++ tika/site/publish/1.1/detection.html Tue Apr 24 09:52:03 2012
@@ -85,7 +85,7 @@
</div>
<div id="content">
<!-- Licensed to the Apache Software Foundation (ASF) under one or
more --><!-- contributor license agreements. See the NOTICE file distributed
with --><!-- this work for additional information regarding copyright
ownership. --><!-- The ASF licenses this file to You under the Apache License,
Version 2.0 --><!-- (the "License"); you may not use this file except in
compliance with --><!-- the License. You may obtain a copy of the License at
--><!-- --><!-- http://www.apache.org/licenses/LICENSE-2.0 --><!-- --><!--
Unless required by applicable law or agreed to in writing, software --><!--
distributed under the License is distributed on an "AS IS" BASIS, --><!--
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
--><!-- See the License for the specific language governing permissions and
--><!-- limitations under the License. --><div class="section"><h2>Content
Detection<a name="Content_Detection"></a></h2><p>This page gives you
information on h
ow content and language detection works with Apache Tika, and how to tune the
behaviour of Tika.</p><ul><li><a href="#Content_Detection">Content
Detection</a><ul><li><a href="#The_Detector_Interface">The Detector
Interface</a></li><li><a href="#Mime_Magic_Detction">Mime Magic
Detction</a></li><li><a href="#Resource_Name_Based_Detection">Resource Name
Based Detection</a></li><li><a href="#Known_Content_Type_Detection">Known
Content Type "Detection</a></li><li><a
href="#The_default_Mime_Types_Detector">The default Mime Types
Detector</a></li><li><a href="#Container_Aware_Detection">Container Aware
Detection</a></li><li><a href="#Language_Detection">Language
Detection</a></li></ul></li></ul><div class="section"><h3><a
name="The_Detector_Interface">The Detector Interface</a><a
name="The_Detector_Interface"></a></h3><p>The <a
href="./api/org/apache/tika/detect/Detector.html">org.apache.tika.detect.Detector</a>
interface is the basis for most of the content type detection in
Apache Tika. All the different ways of detecting content all implement the
same common method:</p><div><pre>MediaType detect(java.io.InputStream input,
- Metadata metadata) throws
java.io.IOException</pre></div><p>The <tt>detect</tt> method takes the stream
to inspect, and a <tt>Metadata</tt> object that holds any additional
information on the content. The detector will return a <a
href="./api/org/apache/tika/mime/MediaType.html">MediaType</a> object
describing its best guess as to the type of the file.</p><p>In general, only
two keys on the Metadata object are used by Detectors. These are
<tt>Metadata.RESOURCE_NAME_KEY</tt> which should hold the name of the file
(where known), and <tt>Metadata.CONTENT_TYPE</tt> which should hold the
advertised content type of the file (eg from a webserver or a content
repository).</p></div><div class="section"><h3><a
name="Mime_Magic_Detction">Mime Magic Detction</a><a
name="Mime_Magic_Detction"></a></h3><p>By looking for special
("magic") patterns of bytes near the start of the file, it is often
possible to detect the type of the file. For some file types, this is
a simple process. For others, typically container based formats, the magic
detection may not be enough. (More detail on detecting container formats
below)</p><p>Tika is able to make use of a a mime magic info file, in the <a
class="externalLink"
href="http://www.freedesktop.org/standards/shared-mime-info";>Freedesktop
MIME-info</a> format to peform mime magic detection.</p><p>This is provided
within Tika by <a
href="./api/org/apache/tika/detect/MagicDetector.html">org.apache.tika.detect.MagicDetector</a>.
It is most commonly access via <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>,
normally sourced from the <tt>tika-mimetypes.xml</tt> file.</p></div><div
class="section"><h3><a name="Resource_Name_Based_Detection">Resource Name Based
Detection</a><a name="Resource_Name_Based_Detection"></a></h3><p>Where the name
of the file is known, it is sometimes possible to guess the file type from the
name or extension. Within the <tt>tika-mimetyp
es.xml</tt> file is a list of patterns which are used to identify the type
from the filename.</p><p>However, because files may be renamed, this method of
detection is quick but not always as accurate.</p><p>This is provided within
Tika by <a
href="./api/org/apache/tika/detect/NameDetector.html">org.apache.tika.detect.NameDetector</a>.</p></div><div
class="section"><h3><a name="Known_Content_Type_Detection">Known Content Type
"Detection</a><a
name="Known_Content_Type_Detection"></a></h3><p>Sometimes, the mime type for a
file is already known, such as when downloading from a webserver, or when
retrieving from a content store. This information can be used by detectors,
such as <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>,</p></div><div
class="section"><h3><a name="The_default_Mime_Types_Detector">The default Mime
Types Detector</a><a name="The_default_Mime_Types_Detector"></a></h3><p>By
default, the mime type detection in Tika is p
rovided by <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>.
This detector makes use of <tt>tika-mimetypes.xml</tt> to power magic based
and filename based detection.</p><p>Firstly, magic based detection is used on
the start of the file. If the file is an XML file, then the start of the XML is
processed to look for root elements. Next, if available, the filename (from
<tt>Metadata.RESOURCE_NAME_KEY</tt>) is then used to improve the detail of the
detection, such as when magic detects a text file, and the filename hints it's
really a CSV. Finally, if available, the supplied content type (from
<tt>Metadata.CONTENT_TYPE</tt>) is used to further refine the
type.</p></div><div class="section"><h3><a
name="Container_Aware_Detection">Container Aware Detection</a><a
name="Container_Aware_Detection"></a></h3><p>Several common file formats are
actually held within a common container format. One example is the PowerPoint
.ppt and Word .doc formats,
which are both held within an OLE2 container. Another is Apple iWork formats,
which are actually a series of XML files within a Zip file.</p><p>Using magic
detection, it is easy to spot that a given file is an OLE2 document, or a Zip
file. Using magic detection alone, it is very difficult (and often impossible)
to tell what kind of file lives inside the container.</p><p>For some use cases,
speed is important, so having a quick way to know the container type is
sufficient. For other cases however, you don't mind spending a bit of time (and
memory!) processing the container to get a more accurate answer on its
contents. For these cases, a container aware detector should be
used.</p><p>Tika provides a wrapping detector in the parsers bundle, of <a
href="./api/org/apache/tika/detect/ContainerAwareDetector.html">org.apache.tika.detect.ContainerAwareDetector</a>.
This detector will check for certain known containers, and if found, will open
them and detect the appropriate type bas
ed on the contents. If the file isn't a known container, it will fall back to
another detector for the answer (most commonly the default <tt>MimeTypes</tt>
detector)</p><p>Because this detector needs to read the whole file to process
the container, it must be used with a <a
href="./api/org/apache/tika/io/TikaInputStream.html">org.apache.tika.io.TikaInputStream</a>.
If called with a regular <tt>InputStream</tt>, then all work will be done by
the fallback detector.</p><p>For more information on container formats and
Tika, see <a class="externalLink"
href="http://wiki.apache.org/tika/MetadataDiscussion";></a></p></div><div
class="section"><h3><a name="Language_Detection">Language Detection</a><a
name="Language_Detection"></a></h3><p>Tika is able to help identify the
language of a piece of text, which is useful when extracting text from document
formats which do not include language information in their metadata.</p><p>The
language detection is provided by <a href="./api/org/apac
he/tika/language/LanguageIdentifier.html">org.apache.tika.language.LanguageIdentifier</a></p></div></div>
+ Metadata metadata) throws
java.io.IOException</pre></div><p>The <tt>detect</tt> method takes the stream
to inspect, and a <tt>Metadata</tt> object that holds any additional
information on the content. The detector will return a <a
href="./api/org/apache/tika/mime/MediaType.html">MediaType</a> object
describing its best guess as to the type of the file.</p><p>In general, only
two keys on the Metadata object are used by Detectors. These are
<tt>Metadata.RESOURCE_NAME_KEY</tt> which should hold the name of the file
(where known), and <tt>Metadata.CONTENT_TYPE</tt> which should hold the
advertised content type of the file (eg from a webserver or a content
repository).</p></div><div class="section"><h3><a
name="Mime_Magic_Detction">Mime Magic Detction</a><a
name="Mime_Magic_Detction"></a></h3><p>By looking for special
("magic") patterns of bytes near the start of the file, it is often
possible to detect the type of the file. For some file types, this is
a simple process. For others, typically container based formats, the magic
detection may not be enough. (More detail on detecting container formats
below)</p><p>Tika is able to make use of a a mime magic info file, in the <a
class="externalLink"
href="http://www.freedesktop.org/standards/shared-mime-info";>Freedesktop
MIME-info</a> format to peform mime magic detection.</p><p>This is provided
within Tika by <a
href="./api/org/apache/tika/detect/MagicDetector.html">org.apache.tika.detect.MagicDetector</a>.
It is most commonly access via <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>,
normally sourced from the <tt>tika-mimetypes.xml</tt> file.</p></div><div
class="section"><h3><a name="Resource_Name_Based_Detection">Resource Name Based
Detection</a><a name="Resource_Name_Based_Detection"></a></h3><p>Where the name
of the file is known, it is sometimes possible to guess the file type from the
name or extension. Within the <tt>tika-mimetyp
es.xml</tt> file is a list of patterns which are used to identify the type
from the filename.</p><p>However, because files may be renamed, this method of
detection is quick but not always as accurate.</p><p>This is provided within
Tika by <a
href="./api/org/apache/tika/detect/NameDetector.html">org.apache.tika.detect.NameDetector</a>.</p></div><div
class="section"><h3><a name="Known_Content_Type_Detection">Known Content Type
"Detection</a><a
name="Known_Content_Type_Detection"></a></h3><p>Sometimes, the mime type for a
file is already known, such as when downloading from a webserver, or when
retrieving from a content store. This information can be used by detectors,
such as <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>,</p></div><div
class="section"><h3><a name="The_default_Mime_Types_Detector">The default Mime
Types Detector</a><a name="The_default_Mime_Types_Detector"></a></h3><p>By
default, the mime type detection in Tika is p
rovided by <a
href="./api/org/apache/tika/mime/MimeTypes.html">org.apache.tika.mime.MimeTypes</a>.
This detector makes use of <tt>tika-mimetypes.xml</tt> to power magic based
and filename based detection.</p><p>Firstly, magic based detection is used on
the start of the file. If the file is an XML file, then the start of the XML is
processed to look for root elements. Next, if available, the filename (from
<tt>Metadata.RESOURCE_NAME_KEY</tt>) is then used to improve the detail of the
detection, such as when magic detects a text file, and the filename hints it's
really a CSV. Finally, if available, the supplied content type (from
<tt>Metadata.CONTENT_TYPE</tt>) is used to further refine the
type.</p></div><div class="section"><h3><a
name="Container_Aware_Detection">Container Aware Detection</a><a
name="Container_Aware_Detection"></a></h3><p>Several common file formats are
actually held within a common container format. One example is the PowerPoint
.ppt and Word .doc formats,
which are both held within an OLE2 container. Another is Apple iWork formats,
which are actually a series of XML files within a Zip file.</p><p>Using magic
detection, it is easy to spot that a given file is an OLE2 document, or a Zip
file. Using magic detection alone, it is very difficult (and often impossible)
to tell what kind of file lives inside the container.</p><p>For some use cases,
speed is important, so having a quick way to know the container type is
sufficient. For other cases however, you don't mind spending a bit of time (and
memory!) processing the container to get a more accurate answer on its
contents. For these cases, container aware detectors should be used.</p><p>Tika
provides a number of container aware detectors, which cover the main container
formats (OLE2, Zip etc). It is possible to call these detectors individually,
but it is more common to use <a
href="./api/org/apache/tika/detect/DefaultDetector.html">org.apache.tika.detect.DefaultDetector</a>
to h
andle this for you. DefaultDetector works like DefaultParser, and locates
available Detectors using the Services Loader, and then tries each in turn to
identify the file. If the file isn't a known container, and no specific
Detector identifies it, the default <tt>MimeTypes</tt> detector will be used to
perform Magic Based Detection.</p><p>Because the container aware detectors
needs to read the whole file in order to process the surrounding container,
they must be used with a <a
href="./api/org/apache/tika/io/TikaInputStream.html">org.apache.tika.io.TikaInputStream</a>.
If called with a regular <tt>InputStream</tt>, then all work will be done by
the <tt>MimeTypes</tt> detector.</p><p>For more information on container
formats and Tika, see <a class="externalLink"
href="http://wiki.apache.org/tika/MetadataDiscussion";></a></p></div><div
class="section"><h3><a name="Language_Detection">Language Detection</a><a
name="Language_Detection"></a></h3><p>Tika is able to help identify th
e language of a piece of text, which is useful when extracting text from
document formats which do not include language information in their
metadata.</p><p>The language detection is provided by <a
href="./api/org/apache/tika/language/LanguageIdentifier.html">org.apache.tika.language.LanguageIdentifier</a></p></div></div>
</div>
<div id="sidebar">
<div id="navigation">
Modified: tika/site/src/site/apt/1.1/detection.apt
URL:
http://svn.apache.org/viewvc/tika/site/src/site/apt/1.1/detection.apt?rev=1329614&r1=1329613&r2=1329614&view=diff
==============================================================================
--- tika/site/src/site/apt/1.1/detection.apt (original)
+++ tika/site/src/site/apt/1.1/detection.apt Tue Apr 24 09:52:03 2012
@@ -121,22 +121,24 @@ MediaType detect(java.io.InputStream inp
For some use cases, speed is important, so having a quick way to know the
container type is sufficient. For other cases however, you don't mind
spending a bit of time (and memory!) processing the container to get a
- more accurate answer on its contents. For these cases, a container
- aware detector should be used.
+ more accurate answer on its contents. For these cases, container
+ aware detectors should be used.
- Tika provides a wrapping detector in the parsers bundle, of
-
{{{./api/org/apache/tika/detect/ContainerAwareDetector.html}org.apache.tika.detect.ContainerAwareDetector}}.
- This detector will check for certain known containers, and if found,
- will open them and detect the appropriate type based on the contents.
- If the file isn't a known container, it will fall back to another
- detector for the answer (most commonly the default
- <<<MimeTypes>>> detector)
+ Tika provides a number of container aware detectors, which cover the
+ main container formats (OLE2, Zip etc). It is possible to call
+ these detectors individually, but it is more common to use
+
{{{./api/org/apache/tika/detect/DefaultDetector.html}org.apache.tika.detect.DefaultDetector}}
+ to handle this for you. DefaultDetector works like DefaultParser,
+ and locates available Detectors using the Services Loader, and then
+ tries each in turn to identify the file. If the file isn't a known
container,
+ and no specific Detector identifies it, the default
+ <<<MimeTypes>>> detector will be used to perform Magic Based Detection.
- Because this detector needs to read the whole file to process the
- container, it must be used with a
+ Because the container aware detectors needs to read the whole file in order
+ to process the surrounding container, they must be used with a
{{{./api/org/apache/tika/io/TikaInputStream.html}org.apache.tika.io.TikaInputStream}}.
If called with a regular <<<InputStream>>>, then all work will be done
- by the fallback detector.
+ by the <<<MimeTypes>>> detector.
For more information on container formats and Tika, see
{{{http://wiki.apache.org/tika/MetadataDiscussion}}}
