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<html><head><meta charset="ISO-8859-1"><title>7.Sorting</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"><link rel="home" href="index.html" title="YAZ User's Guide and Reference"><link rel="up" href="tools.html" title="Chapter7.Supporting Tools"><link rel="prev" href="tools.retrieval.html" title="6.Retrieval Facility"><link rel="next" href="facets.html" title="8.Facets"></head><body><link rel="stylesheet" type="text/css" href="common/style1.css"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">7.Sorting</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="tools.retrieval.html">Prev</a></td><th width="60%" align="center">Chapter7.Supporting Tools</th><td width="20%" align="right"><a accesskey="n" href="facets.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sorting"></a>7.Sorting</h2></div></div></div><p>
This chapter describes sorting and how it is supported in YAZ.
Sorting applies to a result-set.
The
<a class="ulink" href="http://www.loc.gov/z3950/agency/markup/05.html#3.2.7" target="_top">
Z39.50 sorting facility
</a>
takes one or more input result-sets
and one result-set as output. The most simple case is that
the input-set is the same as the output-set.
</p><p>
Z39.50 sorting has a separate APDU (service) that is, thus, performed
following a search (two phases).
</p><p>
In SRU/Solr, however, the model is different. Here, sorting is specified
during the search operation. Note, however, that SRU might
perform sort as separate search, by referring to an existing result-set
in the query (result-set reference).
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="id1339"></a>7.1.Using the Z39.50 sort service</h3></div></div></div><p>
yaz-client and the ZOOM API support the Z39.50 sort facility. In any
case the sort sequence or sort criteria is using a string notation.
This notation is a one-line notation suitable for being manually
entered or generated, and allows for easy logging (one liner).
For the ZOOM API, the sort is specified in the call to ZOOM_query_sortby
function. For yaz-client the sort is performed and specified using
the sort and sort+ commands. For description of the sort criteria notation
refer to the <a class="link" href="yaz-client.html#sortspec">sort command</a> in the
yaz-client manual.
</p><p>
The ZOOM API might choose one of several sort strategies for
sorting. Refer to <a class="xref" href="zoom.query.html#zoom-sort-strategy" title="Table3.2.ZOOM sort strategy">Table3.2, “ZOOM sort strategy”</a>.
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="id1340"></a>7.2.Type-7 sort</h3></div></div></div><p>
Type-7 sort is an extension to the Bib-1 based RPN query where the
sort specification is embedded as an Attribute-Plus-Term.
</p><p>
The objectives for introducing Type-7 sorting is that it allows
a client to perform sorting even if it does not implement/support
Z39.50 sort. Virtually all Z39.50 client software supports
RPN queries. It also may improve performance because the sort
criteria is specified along with the search query.
</p><p>
The sort is triggered by the presence of type 7, and the value of type 7
specifies the
<a class="ulink" href="http://www.loc.gov/z3950/agency/asn1.html#SortKeySpec" target="_top">
sortRelation
</a>.
The value for type 7 is 1 for ascending and 2 for descending.
For the
<a class="ulink" href="http://www.loc.gov/z3950/agency/asn1.html#SortElement" target="_top">
sortElement
</a>
only the generic part is handled. If generic sortKey is of type
sortField, then attribute type 1 is present and the value is
sortField (InternationalString). If generic sortKey is of type
sortAttributes, then the attributes in the list are used. Generic sortKey
of type elementSpec is not supported.
</p><p>
The term in the sorting Attribute-Plus-Term combo should hold
an integer. The value is 0 for primary sorting criteria, 1 for second
criteria, etc.
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tools.retrieval.html">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="tools.html">Up</a></td><td width="40%" align="right"><a accesskey="n" href="facets.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">6.Retrieval Facility</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">8.Facets</td></tr></table></div></body></html>
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