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The following page has been changed by RahulAkolkar: http://wiki.apache.org/jakarta-commons/SCXML/FrequentlyAskedQuestions The comment on the change is: New entry about contexts and evaluators (from Tim O'Brien's FAQ suggestions) ------------------------------------------------------------------------------ [[TableOfContents]] ---- + + ==== What is a Context? And what is an Evaluator? ==== + + The SCXML specification allows an implementation to support multiple expressions languages. These expressions become part of attribute values for executable content, such as: + + {{{ + <var name="foo" expr="1 + 2 + bar" /> + }}} + + or are used to evaluate the boolean guard conditions that decide whether or not a particular transition is followed once its associated trigger event is received, such as: + + {{{ + <transition event="day.close" cond="day eq 'Friday'" target="weekend" /> + }}} + + In order to support multiple expression languages, Commons SCXML uses two interfaces which serve as adapters to the APIs for the particular expression language used for a particular SCXML document. + + * The ''Context'' is a collection of variables that defines a variable "scope". Each <state> element within an SCXML document gets its own ''Context'' or variable scope. + + * The ''Evaluator'' is a component with the capability of parsing and evaluating expressions. It is the "expression language engine". + + Commons SCXML currently provide implementations for [http://jakarta.apache.org/commons/sandbox/scxml/apidocs/org/apache/commons/scxml/env/jexl/package-summary.html JEXL] and [http://jakarta.apache.org/commons/sandbox/scxml/apidocs/org/apache/commons/scxml/env/jsp/package-summary.html JSP 2.0 EL]. ==== How do I try out the sample SCXML documents? ==== --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
