1 <chapter id="proxy-reference">
2 <title>Proxy Reference</title>
3 <section id="proxy-operation">
4 <title>Operating Environment</title>
6 The YAZ proxy is a console program. After startup it spawns
7 a child process (except on Windows or if option -X is given).
8 The child process is the core of the proxy and it handles all
9 communication with clients and servers. The parent process
10 will restart the child process if it dies unexpectedly and report
11 the reason. For options for YAZ proxy,
12 see <xref linkend="proxy-usage"/>.
15 As an option, the proxy may change user identity to a less privileged
19 <section id="proxy-target">
20 <title>Choosing the Backend Server</title>
22 When the proxy receives a Z39.50 Initialize Request from a Z39.50
23 client, it determines the backend server by the following rules:
26 <para>If the <literal>InitializeRequest</literal> PDU from the
28 <link linkend="otherinfo-encoding"><literal>otherInfo</literal></link>
30 <literal>1.2.840.10003.10.1000.81.1</literal>, then the
31 contents of that element specify the server to be used, in the
32 usual YAZ address format (typically
33 <literal>tcp:<parameter>hostname</parameter>:<parameter>port</parameter></literal>)
35 <ulink url="http://www.indexdata.dk/yaz/doc/comstack.addresses.tkl"
36 >the Addresses section of the YAZ manual</ulink>.
41 <para>Otherwise, the Proxy uses the default server, if one was
42 specified in the proxy configuration file. See
43 <xref linkend="proxy-config-target"/>.
48 <para>Otherwise, the Proxy uses the default server, if one was
49 specified on the command-line with the <literal>-t</literal>
54 <para>Otherwise, the proxy closes the connection with
61 If the proxy receives an SRW/SRU request, the following rules are used.
64 <para>If default target has Explain information with a
65 <literal>database</literal> that matches the path of the
66 HTTP request of SRW/SRU that backend server is used for
72 Otherwise the service will return HTTP 404 (Not found).
79 We know it is stupid to only check for explain in default target.
80 It means that it is only possible to offer one SRW/SRU server.
81 We expect to improve that in the next version of the YAZ proxy.
85 <section id="proxy-keepalive">
86 <title>Keep-alive Facility</title>
88 The keep-alive is a facility where the proxy keeps the connection to the
89 backend server - even if the client closes the connection to the proxy.
92 If a new or another client connects to the proxy again and requests the
93 same backend it will be reassigned to this backend. In this case, the
94 proxy sends an initialize response directly to the client and an
95 initialize handshake with the backend is omitted.
98 When a client reconnects, query and record caching works better, if the
99 proxy assigns it to the same backend as before. And the result set
100 (if any) is re-used. To achieve this, Index Data defined a session
101 cookie which identifies the backend session.
104 The cookie is defined by the client and is sent as part of the
105 Initialize Request and passed in an
106 <link linkend="otherinfo-encoding"><literal>otherInfo</literal></link>
107 element with OID <literal>1.2.840.10003.10.1000.81.2</literal>.
110 Clients that do not send a cookie as part of the initialize request
111 may still better performance, since the init handshake is saved.
114 Refer to <xref linkend="proxy-config-keepalive"/> on how to setup
115 configuration parameters for keepalive.
120 <section id="query-cache">
121 <title>Query Caching</title>
123 Simple stateless clients often send identical Z39.50 searches
124 in a relatively short period of time (e.g. in order to produce a
125 results-list page, the next page,
126 a single full-record, etc). And for many targets, it's
127 much more expensive to produce a new result set than to
128 reuse an existing one.
131 The proxy tries to solve that by remembering the last query for each
132 backend target, so that if an identical query is received next, it
133 is turned into Present Requests rather than new Search Requests.
137 In a future we release will will probably allows for
138 an arbitrary-sized cache for targets supporting named result sets.
142 You can enable/disable query caching using option -o.
146 <section id="record-cache">
147 <title>Record Caching</title>
149 As an option, the proxy may also cache result set records for the
151 The proxy takes into account the Record Syntax and CompSpec.
152 The CompSpec includes simple element set names as well.
153 By default the cache is 200000 bytes per session.
157 <section id="query-validation">
158 <title>Query Validation</title>
160 The Proxy may also be configured to trap particular attributes in
161 Type-1 queries and send Bib-1 diagnostics back to the client without
162 even consulting the backend target. This facility may be useful if
163 a target does not properly issue diagnostics when unsupported attributes
168 <section id="record-validation">
169 <title>Record Syntax Validation</title>
171 The proxy may be configured to accept, reject or convert records.
172 When accepted, the target passes search/present requests to the
173 backend target under the assumption that the target can honor the
174 request (In fact it may not do that). When a record is rejected because
175 the record syntax is "unsupported" the proxy returns a diagnostic to the
176 client. Finally, the proxy may convert records.
179 The proxy can convert from MARC to MARCXML and thereby offer an
180 XML version of any MARC record as long as it is ISO2709 encoded.
181 If the proxy is compiled with libXSLT support it can also
186 <section id="other-optimizations">
187 <title>Other Optimizations</title>
189 We've had some plans to support global caching of result set records,
190 but this has not yet been implemented.
194 <section id="proxy-config-file">
195 <title>Proxy Configuration File</title>
197 The Proxy may read a configuration file using option
198 <literal>-c</literal> followed by the filename of a config file.
201 The config file is XML based. The YAZ proxy must be compiled
202 with <ulink url="http://www.xmlsoft.org/">libxml2</ulink> and
203 <ulink url="http://xmlsoft.org/XSLT/">libXSLT</ulink> support in
204 order for the config file facility to be enabled.
207 See <xref linkend="yazproxy-schema"/> for an XML schema
208 for the configuration.
211 <para>To check for a config file to be well-formed, the yazproxy may
212 be invoked without specifying a listening port, i.e.
214 yazproxy -c myconfig.xml
216 If this does not produce errors, the file is well-formed.
219 <section id="proxy-config-header">
220 <title>Proxy Configuration Header</title>
222 The proxy config file must have a root element called
223 <literal>proxy</literal> and scoped within namespace
224 <literal> xmlns="http://indexdata.dk/yazproxy/schema/0.8/</literal>.
225 All information except an optional XML header must be stored
226 within the <literal>proxy</literal> element.
229 <?xml version="1.0"?>
230 <proxy xmlns="http://indexdata.dk/yazproxy/schema/0.8/">
231 <!-- content here .. -->
235 <section id="proxy-config-target">
236 <title>target</title>
238 The element <literal>target</literal> which may be repeated zero
239 or more times with parent element <literal>proxy</literal> contains
240 information about each backend target.
241 The <literal>target</literal> element have two attributes:
242 <literal>name</literal> which holds the logical name of the backend
243 target (required) and <literal>default</literal> (optional) which
244 (when given) specifies that the backend target is the default target -
245 equivalent to command line option <literal>-t</literal>.
249 <?xml version="1.0"?>
250 <proxy xmlns="http://indexdata.dk/yazproxy/schema/0.9/">
251 <target name="server1" default="1">
252 <!-- description of server1 .. -->
254 <target name="server2">
255 <!-- description of server2 .. -->
261 <section id="proxy-config-url">
264 The <literal>url</literal> which may be repeated one or more times
265 should be the child of the <literal>target</literal> element.
266 The CDATA of <literal>url</literal> is the Z-URL of the backend.
269 Multiple <literal>url</literal> element may be used. In that case, then
270 a client initiates a session, the proxy chooses the URL with the lowest
271 number of active sessions, thereby distributing the load. It is
272 assumed that each URL represents the same database (data).
276 <section id="proxy-config-target-timeout">
277 <title>target-timeout</title>
279 The element <literal>target-timeout</literal> is the child of element
280 <literal>target</literal> and specifies the amount in seconds before
281 a target session is shut down.
284 This can also be specified on the command line by using option
285 <literal>-T</literal>. Refer to OPTIONS in <xref linkend="proxy-usage"/>.
289 <section id="proxy-config-client-timeout">
290 <title>client-timeout</title>
292 The element <literal>client-timeout</literal> is the child of element
293 <literal>target</literal> and specifies the amount in seconds before
294 a client session is shut down.
297 This can also be specified on the command line by using option
298 <literal>-i</literal>. Refer to OPTIONS in <xref linkend="proxy-usage"/>.
302 <section id="proxy-config-keepalive">
303 <title>keepalive</title>
304 <para>The <literal>keepalive</literal> element holds information about
305 the keepalive Z39.50 sessions. Keepalive sessions are proxy-to-backend
306 sessions that is no longer associated with a client session.
308 <para>The <literal>keepalive</literal> element which is the child of
309 the <literal>target</literal>holds two elements:
310 <literal>bandwidth</literal> and <literal>pdu</literal>.
311 The <literal>bandwidth</literal> is the maximum total bytes
312 transferred to/from the target. If a target session exceeds this
313 limit, it is shut down (and no longer kept alive).
314 The <literal>pdu</literal> is the maximum number of requests sent
315 to the target. If a target session exceeds this limit, it is
316 shut down. The idea of these two limits is that avoid very long
317 sessions that use resources in a backend (that leaks!).
320 The following sets maximum number of bytes transferred in a
321 target session to 1 MB and maximum of requests to 400.
324 <bandwidth>1048576</bandwidth>
330 <section id="proxy-config-limit">
333 The <literal>limit</literal> section specifies bandwidth/pdu requests
334 limits for an active session.
335 The proxy records bandwidth/pdu requests during the last 60 seconds
336 (1 minute). The <literal>limit</literal> may include the
337 elements <literal>bandwidth</literal>, <literal>pdu</literal>,
338 <literal>retrieve</literal> and <literal>search</literal>.
339 The <literal>bandwidth</literal>
340 measures the number of bytes transferred within the last minute.
341 The <literal>pdu</literal> is the number of requests in the last
342 minute. The <literal>retrieve</literal> holds the maximum records to
343 which may be retrieved in one Present Request.
344 The <literal>search</literal> is the maximum number of searches
345 within the last minute.
348 If a bandwidth/pdu/search limit is reached the proxy will postpone the
349 requests to the target and wait one or more seconds. The idea of the
350 limit is to ensure that clients that downloads hundreds or thousands of
351 records do not hurt other users.
354 The following sets maximum number of bytes transferred per minute to
355 500Kbytes and maximum number of requests to 40.
358 <bandwidth>524288</bandwidth>
359 <retrieve>40</retrieve>
365 Typically the limits for keepalive are much higher than
366 those for session minute average.
371 <section id="proxy-config-attribute">
372 <title>attribute</title>
374 The <literal>attribute</literal> element specifies accept or reject
375 or a particular attribute type, value pair.
376 Well-behaving targets will reject unsupported attributes on their
377 own. This feature is useful for targets that do not gracefully
378 handle unsupported attributes.
381 Attribute elements may be repeated. The proxy inspects the attribute
382 specifications in the order as specified in the configuration file.
383 When a given attribute specification matches a given attribute list
384 in a query, the proxy takes appropriate action (reject, accept).
387 If no attribute specifications matches the attribute list in a query,
391 The <literal>attribute</literal> element has two required attributes:
392 <literal>type</literal> which is the Attribute Type-1 type, and
393 <literal>value</literal> which is the Attribute Type-1 value.
394 The special value/type <literal>*</literal> matches any attribute
395 type/value. A value may also be specified as a list with each
396 value separated by comma, a value may also be specified as a
397 list: low value - dash - high value.
400 If attribute <literal>error</literal> is given, that holds a
401 Bib-1 diagnostic which is sent to the client if the particular
402 type, value is part of a query.
405 If attribute <literal>error</literal> is not given, the attribute
406 type, value is accepted and passed to the backend target.
409 A target that supports use attributes 1,4, 1000 through 1003 and
410 no other use attributes, could use the following rules:
412 <attribute type="1" value="1,4,1000-1003"/>
413 <attribute type="1" value="*" error="114"/>
417 <section id="proxy-config-syntax">
418 <title>syntax</title>
420 The <literal>syntax</literal> element specifies accept or reject
421 or a particular record syntax request from the client.
424 The <literal>syntax</literal> has one required attribute:
425 <literal>type</literal> which is the Preferred Record Syntax.
428 If attribute <literal>error</literal> is given, that holds a
429 Bib-1 diagnostic which is sent to the client if the particular
430 record syntax is part of a present - or search request.
433 If attribute <literal>error</literal> is not given, the record syntax
434 is accepted and passed to the backend target.
437 If attribute <literal>marcxml</literal> is given, the proxy will
438 perform MARC21 to MARCXML conversion. In this case the
439 <literal>type</literal> should be XML. The proxy will use
440 preferred record syntax USMARC/MARC21 or <literal>backendtype</literal>
441 (if given) against the backend target.
444 If attribute <literal>backendtype</literal> is given, that holds the
445 record syntax to be transmitted to backend.
448 If attribute <literal>stylesheet</literal> is given, the proxy
449 will convert XML record from server via XSLT. It is important
450 that the content from server is XML. If used in conjunction with
451 attribute <literal>marcxml</literal> the MARC to MARCXML conversion
452 takes place before the XSLT conversion takes place.
455 If attribute <literal>identifier</literal> is given that is the
456 SRW/SRU record schema identifier for the resulting output record (after
457 MARCXML and/or XSLT conversion).
460 If sub element <literal>title</literal> is given (as child element
461 of <literal>syntax</literal>, then that is the official SRW/SRU
462 name of the resulting record schema.
465 If sub element <literal>name</literal> is given that is an alias
466 for the record schema identifier. Multiple <literal>name</literal>s
470 <title>MARCXML conversion</title>
471 <para>To accept USMARC and offer MARCXML XML plus Dublin Core (via
472 XSLT conversion) but the following configuration could be used:
475 <target name="mytarget">
477 <syntax type="usmarc"/>
478 <syntax type="xml" marcxml="1"
479 identifier="info:srw/schema/1/marcxml-v1.1"
480 <title>MARCXML<title>
481 <name>marcxml<name>
483 <syntax type="xml" marcxml="1" stylesheet="MARC21slim2SRWDC.xsl"
484 identifier="info:srw/schema/1/dc-v1.1">
485 <title>Dublin Core<title>
488 <syntax type="*" error="238"/>
498 <section id="proxy-config-explain">
499 <title>explain</title>
501 The <literal>explain</literal> element includes Explain information
502 for SRW/SRU about the server in the target section. This
503 information must have a <literal>serverInfo</literal> element
504 with a database that this target must be available as (URL path).
507 <explain xmlns="http://explain.z3950.org/dtd/2.0/">
509 <host>myhost.org</host>
511 <database>mydatabase</database>
513 <!-- remaining Explain stuff -->
517 In the above case, the SRW/SRU service is available as
518 <literal>http://myhost.org:8000/mydatabase</literal>.
523 <section id="proxy-config-cql2rpn">
524 <title>cql2rpn</title>
526 The content of the <literal>cql2rpn</literal> element specifies
527 the path from the working directory to a CQL-to-RPN conversion
528 file for the server in the target section. This element
529 is required for SRW/SRU searches to operate against Z39.50
530 servers that don't support CQL. Most Z39.50 servers only support
531 Type-1/RPN so this is usually required.
534 See YAZ documentation for more information about the
535 <ulink url="http://indexdata.dk/yaz/doc/tools.tkl#tools.cql.pqf">CQL
536 to PQF</ulink> conversion. See also the
537 <filename>pqf.properties</filename> in the <filename>etc</filename>
538 (or <replaceable>prefix/share/yazproxy</replaceable>)
539 directory of the YAZ proxy distribution.
543 <section id="proxy-config-preinit">
544 <title>preinit</title>
546 The element <literal>preinit</literal> is the child of element
547 <literal>target</literal> and specifies the number of spare
548 connection to a target. By default no spare connection are
549 created by the proxy. If the proxy uses a target exclusive or
550 a lot, the preinit session will ensure that target sessions
551 have been made before the client makes a connection and will therefore
552 reduce the connect-init handshake dramatically. Never set this to
557 <section id="proxy-config-max-clients">
558 <title>max-clients</title>
560 The element <literal>max-clients</literal> is the child of element
561 <literal>proxy</literal> and specifies the total number of
562 allowed connections to targets (all targets). If this limit
563 is reached the proxy will close the least recently used connection.
566 Note, that many Unix systems impose a system on the number of
567 open files allowed in a single process, typically in the
568 range 256 (Solaris) to 1024 (Linux).
569 The proxy uses 2 sockets per session + a few files
570 for logging. As a rule of thumb, ensure that 2*max-clients + 5
571 can be opened by the proxy process.
575 Using the <ulink url="http://www.gnu.org/software/bash/bash.html">
576 bash</ulink> shell, you can set the limit with
577 <literal>ulimit -n</literal><replaceable>no</replaceable>.
578 Use <literal>ulimit -a</literal> to display limits.
583 <section id="proxy-config-target-authentication">
584 <title>target-authentication</title>
586 The element <literal>target-authentication</literal> specifies
587 fixed authentication information to be sent to the backend target.
590 This element takes a an attribute <literal>type</literal> which is
591 the authenticatin type to be used..
594 <varlistentry><term><literal>none</literal></term>
597 No authentication. There is no CDATA associated with this.
602 <varlistentry><term><literal>anonymous</literal></term>
605 Anonymous authentication. There is no CDATA associated with this.
610 <varlistentry><term><literal>open</literal></term>
613 Open authentication. The CDATA consists of the
614 open authentication string.
619 <varlistentry><term><literal>idPass</literal></term>
622 IdPass authentication. The CDATA consists of
623 three terms: user, group and password.
630 <section id="proxy-config-log">
633 The element <literal>log</literal> is the child of element
634 <literal>proxy</literal> and specifies what to be logged by the
638 Specify the log file with command-line option <literal>-l</literal>.
641 The text of the <literal>log</literal> element is a sequence of
642 options separated by white space. See the table below:
643 <table frame="top"><title>Logging options</title>
645 <colspec colwidth="1*"/>
646 <colspec colwidth="2*"/><thead>
648 <entry>Option</entry>
649 <entry>Description</entry>
654 <entry><literal>client-apdu</literal></entry>
656 Log APDUs as reported by YAZ for the
657 communication between the client and the proxy.
658 This facility is equivalent to the APDU logging that
659 happens when using option <literal>-a</literal>, however
660 this tells the proxy to log in the same file as given
661 by <literal>-l</literal>.
665 <entry><literal>server-apdu</literal></entry>
667 Log APDUs as reported by YAZ for the
668 communication between the proxy and the server (backend).
672 <entry><literal>clients-requests</literal></entry>
674 Log a brief description about requests transferred between
675 the client and the proxy. The name of the request and the size
676 of the APDU is logged.
680 <entry><literal>server-requests</literal></entry>
682 Log a brief description about requests transferred between
683 the proxy and the server (backend). The name of the request
684 and the size of the APDU is logged.
692 To log communication in details between the proxy and the backend, th
693 following configuration could be used:
695 <target name="mytarget">
696 <log>server-apdu server-requests</log>
703 <section id="proxy-max-connect">
704 <title>max-connect</title>
706 The element <literal>max-connect</literal> is a child of element
707 <literal>proxy</literal> and specifies the maximum number
708 of connections to be initiated within the last minute.
711 If the maximum number is reached the proxy will terminate the
712 just initiated session (connection terminated).
716 <section id="proxy-limit-connect">
717 <title>limit-connect</title>
719 The element <literal>max-connect</literal> is a child of element
720 <literal>proxy</literal> and specifies the limit of number
721 of connections to be initiated within the last minute.
724 If the maximum number is reached the proxy delay the first operatation
725 in the session (Thus delaying the connection).
729 <section id="proxy-docpath">
730 <title>docpath</title>
732 The element <literal>docpath</literal> is a child of element
733 <literal>proxy</literal> and specifies an allowed HTTP path
734 for local file access. Using <literal>docpath</literal> the
735 proxy may return static file content.
738 The value of docpath both serves as a HTTP path prefix
739 <emphasis>and</emphasis> as a local file prefix.
740 If a value of <literal>etc</literal> is used only URLs with the
741 prefix <literal>/etc/</literal> results in a local file access to the
742 directory <literal>etc</literal> within the working directory
747 Care has been taken to ensure that hostile URLs are rejected - including
748 strings such as <literal>..</literal> and <literal>/</literal> (absolute
755 <section id="proxy-usage">
756 <title>Proxy Manual Pages</title>
757 <refentry id="yazproxy-man">
762 <section id="otherinfo-encoding">
763 <title>OtherInformation Encoding</title>
765 The proxy uses the OtherInformation definition to carry
766 information about the target address and cookie.
769 OtherInformation ::= [201] IMPLICIT SEQUENCE OF SEQUENCE{
770 category [1] IMPLICIT InfoCategory OPTIONAL,
772 characterInfo [2] IMPLICIT InternationalString,
773 binaryInfo [3] IMPLICIT OCTET STRING,
774 externallyDefinedInfo [4] IMPLICIT EXTERNAL,
775 oid [5] IMPLICIT OBJECT IDENTIFIER}}
777 InfoCategory ::= SEQUENCE{
778 categoryTypeId [1] IMPLICIT OBJECT IDENTIFIER OPTIONAL,
779 categoryValue [2] IMPLICIT INTEGER}
782 The <literal>categoryTypeId</literal> is either
783 OID 1.2.840.10003.10.1000.81.1, 1.2.840.10003.10.1000.81.2
784 for proxy target and proxy cookie respectively. The
785 integer element <literal>category</literal> is set to 0.
786 The value proxy and cookie is stored in element
787 <literal>characterInfo</literal> of the <literal>information</literal>
791 <section id="yazproxy-schema">
792 <title>YAZ Proxy Configuration Schema</title>
794 Here an XML Schema for the YAZ proxy configuration file.
795 The schema, <filename>yazproxy.xsd</filename> is located in sub
796 directory <filename>etc</filename> of the distribution.
799 <?xml version="1.0"?>
800 <!-- XML Schema for YAZ proxy config file.
801 $Id: reference.xml,v 1.15 2006-04-06 01:16:54 adam Exp $
804 xmlns:xs="http://www.w3.org/2001/XMLSchema"
805 xmlns:exp="http://explain.z3950.org/dtd/2.0/"
806 xmlns="http://indexdata.dk/yazproxy/schema/0.9/"
807 targetNamespace="http://indexdata.dk/yazproxy/schema/0.9/"
809 <xs:import namespace="http://explain.z3950.org/dtd/2.0/"
810 schemaLocation="zeerex-2.0.xsd"/>
811 <xs:element name="proxy">
814 <xs:element ref="target" minOccurs="0" maxOccurs="unbounded"/>
815 <xs:element ref="max-clients" minOccurs="0"/>
816 <xs:element ref="log" minOccurs="0"/>
817 <xs:element ref="module" minOccurs="0"/>
822 <xs:element name="target">
825 <xs:element ref="url" minOccurs="0" maxOccurs="unbounded"/>
826 <xs:element ref="target-timeout" minOccurs="0"/>
827 <xs:element ref="client-timeout" minOccurs="0"/>
828 <xs:element ref="keepalive" minOccurs="0"/>
829 <xs:element ref="limit" minOccurs="0"/>
830 <xs:element ref="attribute" minOccurs="0" maxOccurs="unbounded"/>
831 <xs:element ref="syntax" minOccurs="0" maxOccurs="unbounded"/>
832 <xs:element ref="preinit" minOccurs="0"/>
833 <xs:element ref="exp:explain" minOccurs="0"/>
834 <xs:element ref="cql2rpn" minOccurs="0"/>
835 <xs:element ref="target-authentication" minOccurs="0"/>
836 <xs:element ref="client-authentication" minOccurs="0"/>
837 <xs:element ref="negotiation-charset" minOccurs="0"/>
838 <xs:element ref="negotiation-lang" minOccurs="0"/>
840 <xs:attribute name="default" type="xs:string" use="optional"/>
841 <xs:attribute name="name" type="xs:string"/>
842 <xs:attribute name="database" type="xs:string"/>
846 <xs:element name="url" type="xs:string"/>
847 <xs:element name="target-timeout" type="xs:integer"/>
848 <xs:element name="client-timeout" type="xs:integer"/>
849 <xs:element name="bandwidth" type="xs:integer"/>
850 <xs:element name="pdu" type="xs:integer"/>
851 <xs:element name="retrieve" type="xs:integer"/>
852 <xs:element name="preinit" type="xs:integer"/>
853 <xs:element name="cql2rpn" type="xs:string"/>
854 <xs:element name="target-authentication">
857 <xs:extension base="xs:string">
858 <xs:attribute name="type" type="xs:string"/>
864 <xs:element name="client-authentication">
867 <xs:extension base="xs:string">
868 <xs:attribute name="module" type="xs:string"/>
869 <xs:attribute name="args" type="xs:string"/>
875 <xs:element name="negotiation-charset" type="xs:string"/>
876 <xs:element name="negotiation-lang" type="xs:string"/>
878 <xs:element name="keepalive">
881 <xs:element ref="bandwidth" minOccurs="0"/>
882 <xs:element ref="pdu" minOccurs="0"/>
886 <xs:element name="limit">
889 <xs:element ref="bandwidth" minOccurs="0"/>
890 <xs:element ref="pdu" minOccurs="0"/>
891 <xs:element ref="retrieve" minOccurs="0"/>
896 <xs:element name="attribute">
898 <xs:attribute name="type" type="xs:string"/>
899 <xs:attribute name="value" type="xs:string"/>
900 <xs:attribute name="error" type="xs:integer"/>
904 <xs:element name="syntax">
907 <xs:element ref="title" minOccurs="0"/>
908 <xs:element ref="name" minOccurs="0" maxOccurs="unbounded"/>
910 <xs:attribute name="error" type="xs:string" />
911 <xs:attribute name="type" type="xs:string" />
912 <xs:attribute name="marcxml" type="xs:string" />
913 <xs:attribute name="identifier" type="xs:string" />
914 <xs:attribute name="stylesheet" type="xs:string" />
915 <xs:attribute name="backendtype" type="xs:string" />
916 <xs:attribute name="backendcharset" type="xs:string" />
917 <xs:attribute name="usemarconstage1" type="xs:string" />
918 <xs:attribute name="usemarconstage2" type="xs:string" />
922 <xs:element name="title" type="xs:string"/>
923 <xs:element name="name" type="xs:string"/>
925 <xs:element name="max-clients" type="xs:integer"/>
926 <xs:element name="log" type="xs:string"/>
927 <xs:element name="module" type="xs:string"/>
935 <!-- Keep this comment at the end of the file
940 sgml-minimize-attributes:nil
941 sgml-always-quote-attributes:t
944 sgml-parent-document: "yazproxy.xml"
945 sgml-local-catalogs: nil
946 sgml-namecase-general:t