Table of Contents
The functionality of this record model has been improved and replaced by the DOM XML record model, see Chapter 7, DOM XML Record Model and Filter Module. The Alvis XML record model is considered obsolete, and will eventually be removed from future releases of the Zebra software.
The record model described in this chapter applies to the fundamental,
structured XML
record type alvis, introduced in
Section 2.5.2, “ALVIS XML Record Model and Filter Module”.
This filter has been developed under the ALVIS project funded by the European Community under the "Information Society Technologies" Program (2002-2006).
The experimental, loadable Alvis XML/XSLT filter module
mod-alvis.so is packaged in the GNU/Debian package
libidzebra1.4-mod-alvis.
It is invoked by the zebra.cfg configuration statement
recordtype.xml: alvis.db/filter_alvis_conf.xml
In this example on all data files with suffix
*.xml, where the
Alvis XSLT filter configuration file is found in the
path db/filter_alvis_conf.xml.
The Alvis XSLT filter configuration file must be valid XML. It might look like this (This example is used for indexing and display of OAI harvested records):
<?xml version="1.0" encoding="UTF-8"?>
<schemaInfo>
<schema name="identity" stylesheet="xsl/identity.xsl" />
<schema name="index" identifier="http://indexdata.dk/zebra/xslt/1"
stylesheet="xsl/oai2index.xsl" />
<schema name="dc" stylesheet="xsl/oai2dc.xsl" />
<!-- use split level 2 when indexing whole OAI Record lists -->
<split level="2"/>
</schemaInfo>
All named stylesheets defined inside
schema element tags
are for presentation after search, including
the indexing stylesheet (which is a great debugging help). The
names defined in the name attributes must be
unique, these are the literal schema or
element set names used in
SRW,
SRU and
Z39.50 protocol queries.
The paths in the stylesheet attributes
are relative to zebras working directory, or absolute to file
system root.
The <split level="2"/> decides where the
XML Reader shall split the
collections of records into individual records, which then are
loaded into DOM, and have the indexing XSLT stylesheet applied.
There must be exactly one indexing XSLT stylesheet, which is
defined by the magic attribute
identifier="http://indexdata.dk/zebra/xslt/1".
When indexing, an XML Reader is invoked to split the input
files into suitable record XML pieces. Each record piece is then
transformed to an XML DOM structure, which is essentially the
record model. Only XSLT transformations can be applied during
index, search and retrieval. Consequently, output formats are
restricted to whatever XSLT can deliver from the record XML
structure, be it other XML formats, HTML, or plain text. In case
you have libxslt1 running with EXSLT support,
you can use this functionality inside the Alvis
filter configuration XSLT stylesheets.
The output of the indexing XSLT stylesheets must contain
certain elements in the magic
xmlns:z="http://indexdata.dk/zebra/xslt/1"
namespace. The output of the XSLT indexing transformation is then
parsed using DOM methods, and the contained instructions are
performed on the magic elements and their
subtrees.
For example, the output of the command
xsltproc xsl/oai2index.xsl one-record.xml
might look like this:
<?xml version="1.0" encoding="UTF-8"?>
<z:record xmlns:z="http://indexdata.dk/zebra/xslt/1"
z:id="oai:JTRS:CP-3290---Volume-I"
z:rank="47896">
<z:index name="oai_identifier" type="0">
oai:JTRS:CP-3290---Volume-I</z:index>
<z:index name="oai_datestamp" type="0">2004-07-09</z:index>
<z:index name="oai_setspec" type="0">jtrs</z:index>
<z:index name="dc_all" type="w">
<z:index name="dc_title" type="w">Proceedings of the 4th
International Conference and Exhibition:
World Congress on Superconductivity - Volume I</z:index>
<z:index name="dc_creator" type="w">Kumar Krishen and *Calvin
Burnham, Editors</z:index>
</z:index>
</z:record>
This means the following: From the original XML file
one-record.xml (or from the XML record DOM of the
same form coming from a split input file), the indexing
stylesheet produces an indexing XML record, which is defined by
the record element in the magic namespace
xmlns:z="http://indexdata.dk/zebra/xslt/1".
Zebra uses the content of
z:id="oai:JTRS:CP-3290---Volume-I" as internal
record ID, and - in case static ranking is set - the content of
z:rank="47896" as static rank. Following the
discussion in Section 9, “Relevance Ranking and Sorting of Result Sets”
we see that this records is internally ordered
lexicographically according to the value of the string
oai:JTRS:CP-3290---Volume-I47896.
In this example, the following literal indexes are constructed:
oai_identifier
oai_datestamp
oai_setspec
dc_all
dc_title
dc_creator
where the indexing type is defined in the
type attribute
(any value from the standard configuration
file default.idx will do). Finally, any
text() node content recursively contained
inside the index will be filtered through the
appropriate char map for character normalization, and will be
inserted in the index.
Specific to this example, we see that the single word
oai:JTRS:CP-3290---Volume-I will be literal,
byte for byte without any form of character normalization,
inserted into the index named oai:identifier,
the text
Kumar Krishen and *Calvin Burnham, Editors
will be inserted using the w character
normalization defined in default.idx into
the index dc:creator (that is, after character
normalization the index will keep the individual words
kumar, krishen,
and, calvin,
burnham, and editors), and
finally both the texts
Proceedings of the 4th International Conference and Exhibition:
World Congress on Superconductivity - Volume I
and
Kumar Krishen and *Calvin Burnham, Editors
will be inserted into the index dc:all using
the same character normalization map w.
Finally, this example configuration can be queried using PQF queries, either transported by Z39.50, (here using a yaz-client)
Z> open localhost:9999
Z> elem dc
Z> form xml
Z>
Z> f @attr 1=dc_creator Kumar
Z> scan @attr 1=dc_creator adam
Z>
Z> f @attr 1=dc_title @attr 4=2 "proceeding congress superconductivity"
Z> scan @attr 1=dc_title abc
or the proprietary
extensions x-pquery and
x-pScanClause to
SRU, and SRW
http://localhost:9999/?version=1.1&operation=searchRetrieve&x-pquery=%40attr+1%3Ddc_creator+%40attr+4%3D6+%22the
http://localhost:9999/?version=1.1&operation=scan&x-pScanClause=@attr+1=dc_date+@attr+4=2+a
See the section called “The SRU Server” for more information on SRU/SRW configuration, and the section called “YAZ server virtual hosts” or the YAZ CQL section for the details or the YAZ frontend server.
Notice that there are no *.abs,
*.est, *.map, or other GRS-1
filter configuration files involves in this process, and that the
literal index names are used during search and retrieval.