External metadata is metadata which can be applied to pages in a web collection, without actually modifying the pages in any way. For example, it is possible to make all pages in a particular website match the query genre:comedy by adding a single line to the external metadata file.
Targets of the metadata are identified by their URL as supplied by the web server when the page was originally crawled. Note: The external metadata mechanism was designed for use only with collections containing URL data (i.e. web collections).
Metadata information can be supplied for any of the allowable metadata classes, but care should be taken if reusing reserved or special classes which have special behaviour (i.e.
d is used for dates).
Activate External Metadata
To activate the external metadata for a collection, create the file
external_metadata.cfg in the collection's
conf/ subdirectory. The file can be created through the Funnelback administration interface using the file-manager.
When indexing commences
external_metadata.cfg is checked for validity and data structures are set up to enable efficient lookup. If an error is detected, an appropriate error message will be printed, scanning of the file will cease and the documents will be indexed without external metadata. (See
Step-Index.log using the "Browse Log Files" option in the administration interface.)
External metadata file format
The external metadata file must be a text file delimited into lines by linefeed (
0x0A) characters. Each line consists of a URL-prefix followed by a list of metadata elements which apply to all URLs which start with that prefix (unless overridden by a more specific URL-prefix).
URL prefixes must include a full hostname. It is permissible to commence the prefix with "http://". If no protocol is specified then "http://" is assumed.
Each metadata element consists of a metadata field specifier, followed by a colon, followed by a word or a string of text in double quotes. Metadata elements are separated by whitespace. Punctuation should only be present within quoted strings. e.g.
genre:"Historical Drama" director:Costner.
t:"example title" metadata will be used as the document title.
Here is an example of an external metadata file:
www.example.org publisher:"Movies Inc." www.example.org/comedy/ genre:Comedy www.example.org/historical-drama/ genre:"Historical Drama" www.example.org/comedy/romance/ genre:Romance year:2012
These records have the effect that:
- Any page within the
www.example.org/about.htmwill be indexed with the metadata "publisher" = "Movies Inc."
- Any page within
www.example.org/comedies/x/y/z.pdfwill be index with "genre" = "Comedy" and "publisher" = "Movies Inc."
- Any page within
www.example.org/comedy/romance/movies.htmwill be indexed with the metadata "genre" = "Romance", "year" = "2012" and "publisher" = "Movies Inc.". The "Comedy" genre will not be inherited from the second line because it was overridden in the fourth line.
Note: If multiple lines in the metadata file start with an identical prefix, only the first will be effective.
Default page handling
URL default pages (e.g. index) will be stripped from both the prefix given in the external metadata file and the URL being checked from the collection. When a URL prefix is stripped exact matching will be applied, hence example.org/index would match any default page on example.org, but would not match other pages or sub directories on example.org. Default pages are defined as any page called index, welcome, home, default or main followed by a dot and a three or four character extension (e.g. htm or html).
Metadata mapping & types
Metadata classes from external metadata don't need to be defined in
xml.cfg and will be automatically created, however these metadata classes will be of type
0 (non-indexed content). If the type needs to be changed (to have their content indexed, or for numerical metadata) then the metadata class needs to be mapped:
# external_metadata.cfg http://www.example.org/ Genre:"Comedy" # metamap.cfg Genre,1,Genre
The indexer actually ignores the last column
...,Genre when the metadata comes from external metadata. Only the first column (metadata name) and second column (type) are taken into account. Because of this, and because the mapping above may conflict with HTML tag mapping (e.g.
<meta name="Genre" content="Drama" />), it's recommended to use a dummy prefix in the metadata name, to indicate that the metadata comes from an external source:
External Metadata Date Format
Dates must be specified as 8 digit integers in the format
YYYYMMDD. The document internal date is mapped to the
d metadata, any other date field will be treated as a string (unless configured otherwise in
http://www.example.org/movies/2004/ d:20040101 maxDate:20041231
This would result in the documents under http://www.example.org/movies/2004/ to have an internal date of 20040101, and an additional metadata field "expiryDate" = "20041231"
Profile-based external metadata
It is possible to create
external_metadata.cfg files per profile, rather than in the collection
conf directory, however these files won't be processed by the indexer. To have them processed they need to be concatenated and written into
conf/external_metadata.cfg prior to indexing.
This operation can be automated using the validation tool described below.
Validation and concatenation tool
mediator.pl provides a task to validate an external metadata file, as well as concatenating per-profile files into a single collection one. This task can process per-profile external metadata files, and concatenate only valid lines into the collection's
conf/external_metadata.cfg file, discarding malformed lines.
The task name is
ValidateExternalMetadata, it takes the following parameter:
ID of the collection containing the external metadata file to validate or concatenate
check to only check an existing file for errors, or
concatenate to check and concatenate per-profile files
Percentage of errors (expressed as a floating number between 0 and 1) to tolerate before exiting with an error code. For example, using
errorThreshold=0.7 will tolerate up to 70% of errors in external metadata files before aborting. The default value is 0.The common use case is to configure this task in the update workflow using a pre_index_command:
pre_index_command=$SEARCH_HOME/linbin/ActivePerl/bin/perl $SEARCH_HOME/bin/mediator.pl ValidateExternalMetadata collection=$COLLECTION_NAME mode=concatenate
If there are more errors than the configured threshold, the task will fail with a non-zero exit code, causing the update to fail before indexing.
A log of the validation is produced under the collection log folder: