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diff --git a/lib/cosNotification/doc/src/ch_BNF.xml b/lib/cosNotification/doc/src/ch_BNF.xml deleted file mode 100644 index 9763c0c4ca..0000000000 --- a/lib/cosNotification/doc/src/ch_BNF.xml +++ /dev/null @@ -1,457 +0,0 @@ -<?xml version="1.0" encoding="utf-8" ?> -<!DOCTYPE chapter SYSTEM "chapter.dtd"> - -<chapter> - <header> - <copyright> - <year>2000</year><year>2016</year> - <holder>Ericsson AB. All Rights Reserved.</holder> - </copyright> - <legalnotice> - Licensed under the Apache License, Version 2.0 (the "License"); - you may not use this file except in compliance with the License. - You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - - Unless required by applicable law or agreed to in writing, software - distributed under the License is distributed on an "AS IS" BASIS, - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - See the License for the specific language governing permissions and - limitations under the License. - - </legalnotice> - - <title>Filters and the Constraint Language BNF</title> - <prepared></prepared> - <docno></docno> - <date>2000-04-13</date> - <rev></rev> - <file>ch_BNF.xml</file> - </header> - - <section> - <title>Filters and the Constraint Language BNF</title> - <p>This chapter describes, the grammar supported by - <seealso marker="CosNotifyFilter_Filter">CosNotifyFilter_Filter</seealso> and - <seealso marker="CosNotifyFilter_MappingFilter">CosNotifyFilter_MappingFilter</seealso>, - and how to create and use filter objects. - </p> - - <section> - <title>How to create filter objects</title> - <p>To be able to filter events we must create a filter and associate - it with one, or more, of the administrative or proxy objects. In the example - below, we choose to associate the filter with a ConsumerAdmin object.</p> - <code type="none"> -FilterFactory = cosNotificationApp:start_filter_factory(), -Filter = 'CosNotifyFilter_FilterFactory': - create_filter(FilterFactory,"EXTENDED_TCL"), -ConstraintInfoSeq = 'CosNotifyFilter_Filter': - add_constraints(Filter, ConstraintExpSeq), -FilterID = 'CosNotifyChannelAdmin_ConsumerAdmin': - add_filter(AdminConsumer, Filter), - </code> - <p><c>"EXTENDED_TCL"</c> is the only grammar supported by Orber Notification - Service.</p> - <p>Depending on which operation type the Admin object uses, i.e., - <c>'AND_OP'</c> or <c>'OR_OP'</c>, events will be tested using the - associated filter. The operation properties are:</p> - <p></p> - <list type="bulleted"> - <item> - <p>'AND_OP' - must be approved by the proxy's <em>and</em> its parent admin's - filters. If all filters associated with an object (Admin or Proxy) - return false the event will be discarded. In this situation it is pointless - to try and verify with the other object's associated filters since the outcome - still would be the same.</p> - </item> - <item> - <p>'OR_OP' - if one of the object's (Admin or Proxy) filters return true, the event - will not be checked against any other filter associated with a proxy or its - parent admin. If a object's associated filters all return false, - the event will be forwarded to related proxies/admins, and - tested against any associated filters.</p> - </item> - </list> - <p>Initially, filters are empty and will always return true. Hence, we must - add constraints by using <c>'CosNotifyFilter_Filter':add_constraints/2</c>. - As input, the second argument must be a sequence of:</p> - <code type="none"> -#'CosNotifyFilter_ConstraintExp'{ - event_types = [#'CosNotification_EventType'{ - domain_name = string(), - type_name = string()}], - constraint_expr = string()} - </code> - <p>The <c>event_types</c> describes which types of events that should be matched using - the associated <c>constraint_expr</c>.</p> - <p>If a constraint expression is supposed to apply for all events, then the <c>type_name</c> can - be set to the special event type <c>%ALL</c> in a constraint's event type sequence. The - <c>domain_name</c> should be <c>""</c> or <c>"*"</c>.</p> - <p>In the following sections we will take a closer look on how to write - constraint expressions.</p> - </section> - - <section> - <title>The CosNotification Constraint Language</title> - <p>The constraint language supported by the Notification Service is:</p> - <code type="none"><![CDATA[ -<constraint> := /* empty */ - | <bool> - -<bool> := <bool_or> - -<bool_or> := <bool_or> or <bool_and> - | <bool_and> - -<bool_and> := <bool_and> and <bool_compare> - | <bool_compare> - -<bool_compare> := <expr_in> == <expr_in> - | <expr_in> != <expr_in> - | <expr_in> < <expr_in> - | <expr_in> <= <expr_in> - | <expr_in> > <expr_in> - | <expr_in> >= <expr_in> - | <expr_in> - -<expr_in> := <expr_twiddle> in <Ident> /* sequence only */ - | <expr_twiddle> - | <expr_twiddle> in $ <Component> /* sequence only */ - -<expr_twiddle> := <expr> ~ <expr> /* string data types only */ - | <expr> - -<expr> := <expr> + <term> - | <expr> - <term> - | <term> - -<term> := <term> * <factor_not> - | <term> / <factor_not> - | <factor_not> - -<factor_not> := not <factor> - | <factor> - -<factor> := ( <bool_or> ) - | exist <Ident> - | <Ident> - | <Number> - | - <Number> - | <String> - | TRUE - | FALSE - | + <Number> - | exist $ <Component> - | $ <Component> - | default $ <Component> /* discriminated unions only */ - -<Component> := /* empty */ - | . <CompDot> - | <CompArray> - | <CompAssoc> - | <Ident> <CompExt> /* run-time variable */ - -<CompExt> := /* empty */ - | . <CompDot> - | <CompArray> - | <CompAssoc> - -<CompDot> := <Ident> <CompExt> - | <CompPos> - | <UnionPos> - | _length /* only valid for arrays or sequences */ - | _d /* discriminated unions only */ - | _type_id /* only valid if possible to obtain */ - | _repos_id /* only valid if possible to obtain */ - -<CompArray> := [ <Digits> ] <CompExt> - -<CompAssoc> := ( <Ident> ) <CompExt> - -<CompPos> := <Digits> <CompExt> - -<UnionPos> := ( <UnionVal> ) <CompExt> - -<UnionVal> := /* empty */ - | <Digits> - | - <Digits> - | + <Digits> - | <String> - -/* Character set issues */ -<Ident> :=<Leader> <FollowSeq> - | \ < Leader> <FollowSeq> - -<FollowSeq> := /* <empty> */ - | <FollowSeq> <Follow> - -<Number> := <Mantissa> - | <Mantissa> <Exponent> - -<Mantissa> := <Digits> - | <Digits> . - | . <Digits> - | <Digits> . <Digits> - -<Exponent> := <Exp> <Sign> <Digits> - -<Sign> := + - | - - -<Exp> := E - | e - -<Digits> := <Digits> <Digit> - | <Digit> - -<String> := ' <TextChars> ' - -<TextChars> := /* <empty> */ - | <TextChars> <TextChar> - -<TextChar> := <Alpha> - | <Digit> - | <Other> - | <Special> - -<Special> := \\ - | \' - -<Leader> := <Alpha> - -<Follow> := <Alpha> - | <Digit> - | _ - -<Alpha> is the set of alphabetic characters [A-Za-z] -<Digit> is the set of digits [0-9] -<Other> is the set of ASCII characters that are not <Alpha>, <Digit>, or <Special> - ]]></code> - <p>In the absence of parentheses, the following precedence relations hold :</p> - <list type="ordered"> - <item><c>()</c>, <c>exist</c>, <c>default</c>, <c>unary-sign</c></item> - <item><c>not</c></item> - <item><c>*</c>, <c>/</c></item> - <item><c>+</c>, <c>-</c></item> - <item><c>~</c></item> - <item><c>in</c></item> - <item><c>==</c>, <c>!=</c>, <c><![CDATA[<]]></c>, <c><![CDATA[<=]]></c>, <c>></c>, <c>>=</c></item> - <item><c>and</c></item> - <item><c>or</c></item> - </list> - </section> - - <section> - <title>The Constraint Language Data Types</title> - <p>The Notification Service Constraint Language, defines how to write - constraint expressions, which can be used to filter events. The - representation does, however, differ slightly from ordinary Erlang terms.</p> - <p>When creating a <c>ConstraintExp</c>, the field <c>constraint_expr</c> must be - set to contain a string, e.g., <c><![CDATA["1 < 2"]]></c>. The Notification Service Constraint - Language, is designed to be able to filter structured and unstructured events - using the same constraint expression. The Constraint Language Types and Operations - can be divided into two sub-groups:</p> - <list type="bulleted"> - <item> - <p>Basic - arithmetics, strings, constants, numbers etc.</p> - </item> - <item> - <p>Complex - accessing members of complex data types, such as unions.</p> - </item> - </list> - <p>Some of the basic types, e.g., integer, are self explanatory. Hence, they are not described further.</p> - <table> - <row> - <cell align="center" valign="middle"><em>Type/Operation</em></cell> - <cell align="center" valign="middle"><em>Examples</em></cell> - <cell align="center" valign="middle"><em>Description</em></cell> - </row> - <row> - <cell align="left" valign="middle"><c>string</c></cell> - <cell align="left" valign="middle"><c>"'MyString'"</c></cell> - <cell align="left" valign="middle">Strings are represented as a sequence of zero or more <c><![CDATA[<TextChar>]]></c>s enclosed in single quotes, e.g., <c>'string'</c>.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>~</c></cell> - <cell align="left" valign="middle"><c>"'Sring1' ~ 'String2'"</c></cell> - <cell align="left" valign="middle">The operator <c>~</c>is called the substring operator and mean "String1 is contained within String2".</cell> - </row> - <row> - <cell align="left" valign="middle"><c>boolean</c></cell> - <cell align="left" valign="middle"><c>"TRUE == (('lang' ~ 'Erlang' + 'fun' ~ 'functional') >= 2)"</c></cell> - <cell align="left" valign="middle">Booleans may only be TRUE or FALSE, i.e., only capital letters. Expressions which evaluate to TRUE or FALSE can be summed up and matched, where TRUE equals 1 and FALSE 0.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>sequence</c></cell> - <cell align="left" valign="middle"><c>"myIntegerSequence[2]"</c></cell> - <cell align="left" valign="middle">The BNF use C/C++ notation, i.e., the example will return the <em>third</em>element.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>_length</c></cell> - <cell align="left" valign="middle"><c>"myIntegerSequence._length"</c></cell> - <cell align="left" valign="middle">Returns the length of an sequence or array.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>in</c></cell> - <cell align="left" valign="middle"><c>"'Erlang' in $.FunctionalLanguagesStringSeq"</c></cell> - <cell align="left" valign="middle">Returns <c>TRUE</c>if a given element is found in the given sequence. The element must be of a simple type and the same as the sequence is defined to contain.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>$</c></cell> - <cell align="left" valign="middle"><c>"$ == 40"</c></cell> - <cell align="left" valign="middle">Denote the current event as well as any run-time variables. If the event is unstructured and its contained value 40, the example will return <c>TRUE</c>.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>.</c></cell> - <cell align="left" valign="middle"><c>"$.MyStructMember == 40"</c></cell> - <cell align="left" valign="middle">The structure member operator <c>.</c>may be used to reference its members when the data refers to a named structure, discriminated union, or CORBA::Any data structure.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>_type_id</c></cell> - <cell align="left" valign="middle"><c>"$._type_id == 'MyStruct'"</c></cell> - <cell align="left" valign="middle">Returns the unscoped IDL type name of the component. This operation is only valid if said information can be obtained.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>_repos_id</c></cell> - <cell align="left" valign="middle"><c>"$._repos_id == 'IDL:MyModule/MyStruct:1.0'"</c></cell> - <cell align="left" valign="middle">Returns the RepositoryId of the component. This operation is only valid if said information can be obtained.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>_d</c></cell> - <cell align="left" valign="middle"><c>"$.eventUnion._d"</c></cell> - <cell align="left" valign="middle">May only be used when accessing discriminated unions and refers to the discriminator.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>exist</c></cell> - <cell align="left" valign="middle"><c>"exist $.eventUnion._d and $.eventUnion._d == 10"</c></cell> - <cell align="left" valign="middle">To avoid that a filtering of an event fails due to that, for example, we try to compare a union discriminator which does not exist, we can use this operator.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>default</c></cell> - <cell align="left" valign="middle"><c>"default $.eventUnion._d"</c></cell> - <cell align="left" valign="middle">If the <c>_d</c>operation is in conjunction with the <c>default</c>operation, TRUE will be returned if the union has a default member that is active.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>union</c></cell> - <cell align="left" valign="middle"><c>"$.(0) == 5"</c>eq. <c>"$.('zero') == 5"</c></cell> - <cell align="left" valign="middle">When the component refers to a union, with one of the cases defined as <c>case 0: short zero;</c>, we use <c>0</c>or <c>'zero'</c>. The result of the example is <c>TRUE</c>if the union has a discriminator set to <c>0</c>and the value <c>5</c>. If more than one case is defined to be<c>'zero'</c>, <c>$.('zero')</c>accepts both; <c>$.(0)</c>only returns <c>TRUE</c>if the discriminator is set to <c>0</c>. Leaving out the identifier, i.e., <c>$.()</c>, refers to the default value.</cell> - </row> - <row> - <cell align="left" valign="middle"><c>name-value pairs</c></cell> - <cell align="left" valign="middle"><c>"$.NameValueSeq('myID') == 5"</c>eq.<c>"$.NameValueSeq[1].name == 'myID' and $.NameValueSeq[1].value == 5"</c></cell> - <cell align="left" valign="middle">The Notification service makes extensive use of <c>name-value pairs</c>sequences within structured events, which allow us to via the identifier <c>name</c>access its <c>value</c>, as shown in the example.</cell> - </row> - <tcaption>Table 1: Type and Operator Examples</tcaption> - </table> - <p>In the next section we will take a closer look at how it is possible to write constraints using - different types of notation etc.</p> - </section> - - <section> - <title>Accessing Data In Events</title> - <p>To filter events, the supplied constraints must describe the contents of - the events and desired values. We can, for example, state that we are only - interested in receiving events which are of type <em>CommunicationsAlarm</em>. - To be able to achieve this, the constraint must contain information - that points out which fields to compare with. Figure one illustrates a conceptual overview of a - structured event. The exact definition is found in the <c>CosNotification.idl</c> file.</p> - <marker id="eventstructure"></marker> - <image file="eventstructure.gif"> - <icaption> -Figure 1: The structure of a structured event.</icaption> - </image> - <p>The Notification Service supports different constraint expressions - notation:</p> - <list type="bulleted"> - <item> - <p>Fully scoped, e.g., "$.header.fixed_header.event_type.type_name == 'CommunicationsAlarm'"</p> - </item> - <item> - <p>Short hand, e.g., "$type_name == 'CommunicationsAlarm'"</p> - </item> - <item> - <p>Positional Notation, e.g., "$.0.0.0.1 == 'CommunicationsAlarm'"</p> - </item> - </list> - <note> - <p>Which notation to use is up to the user, however, the fully scoped may - be easier to understand, but in some cases, if received from an ORB that do not populate ID:s of - named parts, the positional notation is the only option.</p> - </note> - <note> - <p>If a constraint, which access fields in a structured event structure, - is supposed to handle unstructured events as well, the CORBA::Any must contain - the same type of members.</p> - </note> - <p>How to filter against the fixed header fields, is described in the - table below.</p> - <table> - <row> - <cell align="center" valign="middle">Field</cell> - <cell align="center" valign="middle">Fully Scoped Constraint</cell> - <cell align="center" valign="middle">Short Hand Constraint</cell> - </row> - <row> - <cell align="left" valign="middle">type_name</cell> - <cell align="left" valign="middle">"$.header.fixed_header.event_type.type_name == 'Type'"</cell> - <cell align="left" valign="middle">"$type_name == 'Type'"</cell> - </row> - <row> - <cell align="left" valign="middle">domain_name</cell> - <cell align="left" valign="middle">"$.header.fixed_header.event_type.domain_name == 'Domain'"</cell> - <cell align="left" valign="middle">"$domain_name == 'Domain'"</cell> - </row> - <row> - <cell align="left" valign="middle">event_name</cell> - <cell align="left" valign="middle">"$.header.fixed_header.event_name == 'Event'"</cell> - <cell align="left" valign="middle">"$event_name == 'Event'"</cell> - </row> - <tcaption>Table 2: Fixed Header Constraint Examples</tcaption> - </table> - <p>If we are only interested in receiving events regarding 'Domain', 'Event' - and 'Type', the constraint can look like - <c>"$domain_name == 'Domain' and $event_name == 'Event' and $type_name == 'Type'"</c>.</p> - <p>The variable event header consists of a sequence of <em>name-value pairs</em>. One way to filter on these are to use a constraint that looks - like <c>"($.header.variable_header[1].name == 'priority' and $.header.variable_header[1].value > 0)"</c>. An easier way to - accomplish the same result is to use a constraint that treats the name-value - pair as an associative array, i.e., when given a name the corresponding - value is returned. Hence, instead we can use - <c>"$.header.variable_header(priority) > 0"</c>.</p> - <p>Accessing the event body is done in the same way as for the event header - fields. The user must, however, be aware of, that if a run-time variable - (<c>$variable</c>) is used data in the event header may take precedence. - The order of precedence is:</p> - <list type="ordered"> - <item>Reserved, e.g., <c>$curtime</c></item> - <item>A simple-typed member of <c>$.header.fixed_header</c>.</item> - <item>Properties in <c>$.header.variable_header</c>.</item> - <item>Properties in <c>$.filterable_data</c>.</item> - <item>If no match is found it is translated to <c>$.variable</c>.</item> - </list> - </section> - - <section> - <title>Mapping Filters</title> - <p>Mapping Filters may only be associated with Consumer Administrators or Proxy - Suppliers. The purpose of a Mapping Filter is to override Quality of Service - settings.</p> - <p>Initially, Mapping Filters are empty and will always return true. Hence, we must - add constraints by using <c>'CosNotifyFilter_MappingFilter':add_mapping_constraints/2</c>. - If a constraint matches, the associated value will be used instead of the - related Quality of Service system settings.</p> - <p>As input, the second argument must be a sequence of:</p> - <code type="none"> -#'CosNotifyFilter_MappingConstraintPair'{ - constraint_expression = #'CosNotifyFilter_ConstraintExp'{ - event_types = [#'CosNotification_EventType'{ - domain_name = string(), - type_name = string()}], - constraint_expr = string()}, - result_to_set = any()} - </code> - </section> - </section> -</chapter> - |