Each standard expression consists of a simple expression. The tables below show the grammar that you can use for creating standard expressions:
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<expression> ::= |
<simple-expression> [ ( "=" | "<>" | "<" | "<=" | ">" | ">=" ) <simple-expression> ] |
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<simple-expression> ::= |
[ "+" | "-" ] <term> [ ( "+" | "-" | OR ) <term> ] |
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<term> ::= |
<factor> [ ( "*" | "/" | MOD | AND | XOR ) <factor> ] |
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<factor> ::= |
[ NOT | "+" | "-" ] ( <function> | "(" <expression> ")" | <boolean> | <integer> | <real> | <date-time> | <string> | <tag> | <cell> | <cell-block> | <field> | <field-block> |) |
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<function> ::= |
<function-name> "(" [ <expression> { "," <expression> } ] ")" |
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<boolean> ::= |
TRUE | FALSE |
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<integer> ::= |
<digit> { <digit> } |
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<digit> ::= |
"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" |
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<real> ::= |
[ <integer> ] "." <integer> [ <exponent> ] | <integer> <exponent> |
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<exponent> ::= |
( "E" | "e" ) [ "+" | "-" ] <integer> |
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<date-time> ::= |
"#" ( <date> | <time> | <date> " " <time> ) "#" |
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<date> ::= |
<short-date> | <long-date> |
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<short-date> ::= |
<day> "/" <month-number> "/" <year> |
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<long-date> ::= |
<day> " " <month-name> " " <year> |
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<year> ::= |
<digit> <digit> [ <digit> <digit> ] |
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<time> ::= |
<hours> ":" <minutes> [ ":" <seconds> [ <fraction> ] ] |
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<fraction> ::= |
"." <digit> [ <digit> [ <digit> ] ] |
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<string> ::= |
"'" <text> "'" |
In addition to the grammar shown above, you can use the following grammar in expressions other than Template expressions:
NOTE: Tags do not apply to Template expressions, instead you use Template Parameters.
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<tag> ::= |
""" ( <relative-tag> | [ <system-name> ":" ] |
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<relative-tag> ::= |
"." { "." } ( <data-tag> | <historic-tag> | |
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<absolute-tag> ::= |
<data-tag> | <historic-tag> | <historic-calc-tag> | <server-status-tag> | <register-tag> |
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<data-tag> ::= |
( <item> | <search-key> ) [ "." ( <property-name> | <method-name> "(" [ <expression> { "," <expression> } ] ")" ) ] |
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<historic-tag> ::= |
( <item> | <search-key> ) [ "." |
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<historic-calc-tag> ::= |
( <item> | <search-key> ) [ "." |
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<item> ::= |
( <group> | [ <group> "." ] <item-name> ) [ "." |
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<group> ::= |
<group-name> [ "." <group> ] |
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<server-status-tag> ::= |
"#" <status-tab-name> "." <status-key> "." |
Where:
<aggregate-name>is the name of an aggregate of an item in the database- <cell> is a cell in a Data Grid. This only applies to expressions that are associated with Data Grids (see Data Grid Expressions).
- <cell-block> is a block of cells in a Data Grid. This only applies to expressions that are associated with Data Grids (see Data Grid Expressions).
<day>is the day of the month, from 1 to 31<field>is the name of a field in a Data Set. This only applies to expressions that are associated with Data Sets (see Data Set Expressions).- <field-block> is a block of fields in a Data Set. This only applies to expressions that are associated with Data Sets (see Data Set Expressions).
<function-name>is the name of any built in function (see Functions)<group-name>is the name of a group in the database<month-name>is either the full month name (for example, October) or short month name (for example, Oct)<month-number>is the month number, from 1 to 12<historic-algorithm-name>is the name of a historic algorithm of an item in the database (this can only be omitted when the item has exactly one historic algorithm)<hours>is a number from 0 to 23<interval>is an OPC time (see Using OPC Time Formats in the ClearSCADA Guide to Core Configuration)<item-name>is the name of an item in the database<method-name>is the name a method of an item or aggregate in the database<minutes>is a number from 0 to 59<parameter-name>is the full name (including group(s)) of a Mimic parameter. This is only applicable to expressions on Mimics (see the ClearSCADA Guide to Mimics)<property-name>is the name of a property of an item or aggregate in the database<opc-aggregate>is the name of an OPC HDA aggregate (see OPC Historic Tags)<relative-time>is an OPC relative time (see Using OPC Time Formats in the ClearSCADA Guide to Core Configuration)<search-key>is the value of a database search key (see Search Key Tags)<seconds>is a number from 0 to 59<status-key>is the key value of a row in a server status tab (see Server Status Property Tags)<status-property-name>is the name of a property of a server status tab (see Server Status Property Tags)<status-tab-name>is the name of a server status tab (see Server Status Property Tags)<system-name>is the name of a system available to ViewX (this only applies to in expressions that are evaluated by ViewX clients). A system is a ClearSCADA database<text>is any literal text (if the text includes the single quotation character ', the character has to be replaced by two ' characters).
You can also include comments in your expressions. Usually, comments are used to provide a brief description of the code so that other users can quickly determine its purpose. You can add comments to any part of the expression code (see Comments in Expressions).