Attribute sets define the exact meaning and semantics of queries issued. Zebra comes with some predefined attribute set definitions, others can easily be defined and added to the configuration.

The use attributes (type 1) mappings the predefined attribute sets are found in the attribute set configuration files tab/*.att.

A pair of sub query trees, or of atomic queries, is combined using the standard boolean operators into new query trees. Thus, boolean operators are always internal nodes in the query tree.

For example, we can combine the terms information and retrieval into different searches in the default index of the default attribute set as follows. Querying for the union of all documents containing the terms information OR retrieval :

       Z> find @or information retrieval
      

Querying for the intersection of all documents containing the terms information AND retrieval : The hit set is a subset of the corresponding OR query.

       Z> find @and information retrieval
      

Querying for the intersection of all documents containing the terms information AND retrieval , taking proximity into account: The hit set is a subset of the corresponding AND query (see the PQF grammar for details on the proximity operator):

       Z> find @prox 0 3 0 2 k 2 information retrieval
      

Querying for the intersection of all documents containing the terms information AND retrieval , in the same order and near each other as described in the term list. The hit set is a subset of the corresponding PROXIMITY query.

       Z> find "information retrieval"
      

Atomic queries are the query parts which work on one access point only. These consist of an attribute list followed by a single term or a quoted term list , and are often called Attributes-Plus-Terms (APT) queries.

Atomic (APT) queries are always leaf nodes in the PQF query tree. UN-supplied non-use attributes types 2-12 are either inherited from higher nodes in the query tree, or are set to Zebra's default values. See the section called “BIB-1 Attribute Set” for details.

Querying for the term information in the default index using the default attribute set, the server choice of access point/index, and the default non-use attributes.

       Z> find information
      

Equivalent query fully specified including all default values:

       Z> find @attrset bib-1 @attr 1=1017 @attr 2=3 @attr 3=3 @attr 4=1 @attr 5=100 @attr 6=1 information
      

Finding all documents which have the term debussy in the title field.

       Z> find @attr 1=4 debussy
      

The scan operation is only supported with atomic APT queries, as it is bound to one access point at a time. Boolean query trees are not allowed during scan .

For example, we might want to scan the title index, starting with the term debussy , and displaying this and the following terms in lexicographic order:

       Z> scan @attr 1=4 debussy
      

Named result sets are supported in Zebra, and result sets can be used as operands without limitations. It follows that named result sets are leaf nodes in the PQF query tree, exactly as atomic APT queries are.

After the execution of a search, the result set is available at the server, such that the client can use it for subsequent searches or retrieval requests. The Z30.50 standard actually stresses the fact that result sets are volatile. It may cease to exist at any time point after search, and the server will send a diagnostic to the effect that the requested result set does not exist any more.

Defining a named result set and re-using it in the next query, using yaz-client. Notice that the client, not the server, assigns the string '1' to the named result set.

       Z> f @attr 1=4 mozart
       ...
       Number of hits: 43, setno 1
       ...
       Z> f @and @set 1 @attr 1=4 amadeus
       ...
       Number of hits: 14, setno 2
      

The numeric use (type 1) attribute is usually referred to from a given attribute set. In addition, Zebra let you use any internal index name defined in your configuration as use attribute value. This is a great feature for debugging, and when you do not need the complexity of defined use attribute values. It is the preferred way of accessing Zebra indexes directly.

Finding all documents which have the term list "information retrieval" in an Zebra index, using its internal full string name. Scanning the same index.

       Z> find @attr 1=sometext "information retrieval"
       Z> scan @attr 1=sometext aterm
      

Searching or scanning the bib-1 use attribute 54 using its string name:

       Z> find @attr 1=Code-language eng
       Z> scan @attr 1=Code-language ""
      

It is possible to search in any silly string index - if it's defined in your indexation rules and can be parsed by the PQF parser. This is definitely not the recommended use of this facility, as it might confuse your users with some very unexpected results.

       Z> find @attr 1=silly/xpath/alike[@index]/name "information retrieval"
      

See also the section called “Mapping from PQF atomic APT queries to Zebra internal register indexes” for details, and the section called “The SRU Server” for the SRU PQF query extension using string names as a fast debugging facility.

As we have seen above, it is possible (albeit seldom a great idea) to emulate XPath 1.0 based search by defining use (type 1) string attributes which in appearance resemble XPath queries . There are two problems with this approach: first, the XPath-look-alike has to be defined at indexation time, no new undefined XPath queries can entered at search time, and second, it might confuse users very much that an XPath-alike index name in fact gets populated from a possible entirely different XML element than it pretends to access.

When using the GRS-1 Record Model (see Chapter 9, GRS-1 Record Model and Filter Modules ), we have the possibility to embed life XPath expressions in the PQF queries, which are here called use (type 1) xpath attributes. You must enable the xpath enable directive in your .abs configuration files.

Finding all documents which have the term "content" inside a text node found in a specific XML DOM subtree , whose starting element is addressed by XPath.

       Z> find @attr 1=/root content 
       Z> find @attr 1=/root/first content
      

Notice that the XPath must be absolute, i.e., must start with '/', and that the XPath descendant-or-self axis followed by a text node selection text() is implicitly appended to the stated XPath. It follows that the above searches are interpreted as:

       Z> find @attr 1=/root//text() content 
       Z> find @attr 1=/root/first//text() content
      

Searching inside attribute strings is possible:

       Z> find @attr 1=/link/@creator morten 
      

Filter the addressing XPath by a predicate working on exact string values in attributes (in the XML sense) can be done: return all those docs which have the term "english" contained in one of all text sub nodes of the subtree defined by the XPath /record/title[@lang='en']. And similar predicate filtering.

       Z> find @attr 1=/record/title[@lang='en'] english
       Z> find @attr 1=/link[@creator='sisse'] sibelius
       Z> find @attr 1=/link[@creator='sisse']/description[@xml:lang='da'] sibelius 
      

Combining numeric indexes, boolean expressions, and xpath based searches is possible:

       Z> find @attr 1=/record/title @and foo bar
       Z> find @and @attr 1=/record/title foo @attr 1=4 bar
      

Escaping PQF keywords and other non-parseable XPath constructs with '{ }' to prevent client-side PQF parsing syntax errors:

       Z> find @attr {1=/root/first[@attr='danish']} content
       Z> find @attr {1=/record/@set} oai
      

The following Explain search attributes are supported: ExplainCategory (@attr 1=1), DatabaseName (@attr 1=3), DateAdded (@attr 1=9), DateChanged(@attr 1=10).

A search in the use attribute ExplainCategory supports only these predefined values: CategoryList, TargetInfo, DatabaseInfo, AttributeDetails.

See tab/explain.att and the Z39.50 standard for more information.

Classic Explain only defines retrieval of Explain information via ASN.1. Practically no Z39.50 clients supports this. Fortunately they don't have to - Zebra allows retrieval of this information in other formats: SUTRS , XML , GRS-1 and ASN.1 Explain.

List supported categories to find out which explain commands are supported:

       Z> base IR-Explain-1
       Z> find @attr exp1 1=1 categorylist
       Z> form sutrs
       Z> show 1+2
      

Get target info, that is, investigate which databases exist at this server endpoint:

       Z> base IR-Explain-1
       Z> find @attr exp1 1=1 targetinfo
       Z> form xml
       Z> show 1+1
       Z> form grs-1
       Z> show 1+1
       Z> form sutrs
       Z> show 1+1
      

List all supported databases, the number of hits is the number of databases found, which most commonly are the following two: the Default and the IR-Explain-1 databases.

       Z> base IR-Explain-1
       Z> find @attr exp1 1=1 databaseinfo
       Z> form sutrs
       Z> show 1+2
      

Get database info record for database Default.

       Z> base IR-Explain-1
       Z> find @and @attr exp1 1=1 databaseinfo @attr exp1 1=3 Default
      

Identical query with explicitly specified attribute set:

       Z> base IR-Explain-1
       Z> find @attrset exp1 @and @attr 1=1 databaseinfo @attr 1=3 Default
      

Get attribute details record for database Default. This query is very useful to study the internal Zebra indexes. If records have been indexed using the alvis XSLT filter, the string representation names of the known indexes can be found.

       Z> base IR-Explain-1
       Z> find @and @attr exp1 1=1 attributedetails @attr exp1 1=3 Default
      

Identical query with explicitly specified attribute set:

       Z> base IR-Explain-1
       Z> find @attrset exp1 @and @attr 1=1 attributedetails @attr 1=3 Default
      

A use attribute specifies an access point for any atomic query. These access points are highly dependent on the attribute set used in the query, and are user configurable using the following default configuration files: tab/bib1.att, tab/dan1.att, tab/explain.att, and tab/gils.att.

For example, some few BIB-1 use attributes from the tab/bib1.att are:

       att 1               Personal-name
       att 2               Corporate-name
       att 3               Conference-name
       att 4               Title
       ...
       att 1009            Subject-name-personal
       att 1010            Body-of-text
       att 1011            Date/time-added-to-db
       ...
       att 1016            Any
       att 1017            Server-choice
       att 1018            Publisher
       ...
       att 1035            Anywhere
       att 1036            Author-Title-Subject
      

New attribute sets can be added by adding new tab/*.att configuration files, which need to be sourced in the main configuration zebra.cfg.

In addition, Zebra allows the access of internal index names and dynamic XPath as use attributes; see the section called “Zebra's special access point of type 'string'” and the section called “Zebra's special access point of type 'XPath' for GRS-1 filters”.

Phrase search for information retrieval in the title-register, scanning the same register afterwards:

      Z> find @attr 1=4 "information retrieval"
      Z> scan @attr 1=4 information
     

Relation attributes describe the relationship of the access point (left side of the relation) to the search term as qualified by the attributes (right side of the relation), e.g., Date-publication <= 1975.

The relation attributes 1-5 are supported and work exactly as expected. All ordering operations are based on a lexicographical ordering, except when the structure attribute numeric (109) is used. In this case, ordering is numerical. See the section called “Structure Attributes (type 4)”.

       Z> find @attr 1=Title @attr 2=1 music
       ...
       Number of hits: 11745, setno 1
       ...
       Z> find @attr 1=Title @attr 2=2 music
       ...
       Number of hits: 11771, setno 2
       ...
       Z> find @attr 1=Title @attr 2=3 music
       ...
       Number of hits: 532, setno 3
       ...
       Z> find @attr 1=Title @attr 2=4 music
       ...
       Number of hits: 11463, setno 4
       ...
       Z> find @attr 1=Title @attr 2=5 music
       ...
       Number of hits: 11419, setno 5
      

The relation attribute Relevance (102) is supported, see the section called “Relevance Ranking and Sorting of Result Sets” for full information.

Ranked search for information retrieval in the title-register:

       Z> find @attr 1=4 @attr 2=102 "information retrieval"
      

The relation attribute AlwaysMatches (103) is in the default configuration supported in conjecture with structure attribute Phrase (1) (which may be omitted by default). It can be configured to work with other structure attributes, see the configuration file tab/default.idx and the section called “Mapping from PQF atomic APT queries to Zebra internal register indexes”.

AlwaysMatches (103) is a great way to discover how many documents have been indexed in a given field. The search term is ignored, but needed for correct PQF syntax. An empty search term may be supplied.

       Z> find @attr 1=Title  @attr 2=103  ""
       Z> find @attr 1=Title  @attr 2=103  @attr 4=1 ""
      

The position attribute specifies the location of the search term within the field or subfield in which it appears.

The structure attribute specifies the type of search term. This causes the search to be mapped on different Zebra internal indexes, which must have been defined at index time.

The possible values of the structure attribute (type 4) can be defined using the configuration file tab/default.idx. The default configuration is summarized in this table.

The structure attribute values Word list (6) is supported, and maps to the boolean AND combination of words supplied. The word list is useful when google-like bag-of-word queries need to be translated from a GUI query language to PQF. For example, the following queries are equivalent:

      Z> find @attr 1=Title @attr 4=6 "mozart amadeus"
      Z> find @attr 1=Title  @and mozart amadeus
     

The structure attribute value Free-form-text (105) and Document-text (106) are supported, and map both to the boolean OR combination of words supplied. The following queries are equivalent:

      Z> find @attr 1=Body-of-text @attr 4=105 "bach salieri teleman"
      Z> find @attr 1=Body-of-text @attr 4=106 "bach salieri teleman"
      Z> find @attr 1=Body-of-text @or bach @or salieri teleman 
     

This OR list of terms is very useful in combination with relevance ranking:

      Z> find @attr 1=Body-of-text @attr 2=102 @attr 4=105 "bach salieri teleman"
     

The structure attribute value Local number (107) is supported, and maps always to the Zebra internal document ID, irrespectively which use attribute is specified. The following queries have exactly the same unique record in the hit set:

      Z> find @attr 4=107 10
      Z> find @attr 1=4 @attr 4=107 10
      Z> find @attr 1=1010 @attr 4=107 10
     

In the GILS schema (gils.abs), the west-bounding-coordinate is indexed as type n, and is therefore searched by specifying structure = Numeric String . To match all those records with west-bounding-coordinate greater than -114 we use the following query:

      Z> find @attr 4=109 @attr 2=5 @attr gils 1=2038 -114
     

The truncation attribute specifies whether variations of one or more characters are allowed between search term and hit terms, or not. Using non-default truncation attributes will broaden the document hit set of a search query.

The truncation attribute values 1-3 perform the obvious way:

       Z> scan @attr 1=Body-of-text  schnittke
       ...
       * schnittke (81)
       schnittkes (31)
       schnittstelle (1)
       ...
       Z> find @attr 1=Body-of-text  @attr 5=1 schnittke
       ...
       Number of hits: 95, setno 7
       ...
       Z> find @attr 1=Body-of-text  @attr 5=2 schnittke
       ...
       Number of hits: 81, setno 6
       ...
       Z> find @attr 1=Body-of-text  @attr 5=3 schnittke
       ...
       Number of hits: 95, setno 8
      

The truncation attribute value Process # in search term (101) is a poor-man's regular expression search. It maps each # to .*, and performs then a Regexp-1 (102) regular expression search. The following two queries are equivalent:

       Z> find @attr 1=Body-of-text  @attr 5=101 schnit#ke
       Z> find @attr 1=Body-of-text  @attr 5=102 schnit.*ke
       ...
       Number of hits: 89, setno 10
      

The truncation attribute value Regexp-1 (102) is a normal regular search, see the section called “Zebra Regular Expressions in Truncation Attribute (type = 5)” for details.

       Z> find @attr 1=Body-of-text  @attr 5=102 schnit+ke
       Z> find @attr 1=Body-of-text  @attr 5=102 schni[a-t]+ke
      

The truncation attribute value Regexp-2 (103) is a Zebra specific extension which allows fuzzy matches. One single error in spelling of search terms is allowed, i.e., a document is hit if it includes a term which can be mapped to the used search term by one character substitution, addition, deletion or change of position.

       Z> find @attr 1=Body-of-text  @attr 5=100 schnittke
       ...
       Number of hits: 81, setno 14
       ...
       Z> find @attr 1=Body-of-text  @attr 5=103 schnittke
       ...
       Number of hits: 103, setno 15
       ...
      

The Completeness Attributes (type = 6) is used to specify that a given search term or term list is either part of the terms of a given index/field (Incomplete subfield (1)), or is what literally is found in the entire field's index (Complete field (3)).

The Completeness Attributes (type = 6) is only partially and conditionally supported in the sense that it is ignored if the hit index is not of structure type="w" or type="p".

Incomplete subfield (1) is the default, and makes Zebra use register type="w", whereas Complete field (3) triggers search and scan in index type="p".

The Complete subfield (2) is a reminiscens from the happy MARC binary format days. Zebra does not support it, but maps silently to Complete field (3).