The Anatomy of a Compiler by John A. N. Lee

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Example 4. Building on Example 3, Fig. 7 shows the relational data model which is created by applying the rules in Table 4 and 5 to the Σstruct -specification S in Fig. 3. Recall that arrows in Σrel -specifications are interpreted as single-valued functions. Hence, we do not need to add constraints to force single-valued functions. Table 4. Rules for the transformation of structural models to relational data models L R Rule r1 . Class to table 1:C 1:C [pk] 1:T 1:Col Rule r2 . Attribute to column 1:C 1:T [pk] 1:Col Int:DTt 1:C 1:A s s 1:DT [pk] 1:T 1:A 1:Col 1:DTt Rule r3 .

In this way, a timer is used to force an action to happen at (or before) a certain time. The value of a Timer whose on attribute is false does not change when time advances; neither can such a turned off Timer block time advance. 34 ¨ A. C. Olveczky Fig. 1. Ecore metamodel of the predefined timed constructs Clock. The value of a Clock is increased according to the elapsed time. ” Timed Value. The TimedValue construct is similar to the Clock construct. The difference is that, whereas the value of a Clock is increased by the amount of elapsed time, the value of a TimedValue object is increased by the elapsed time multiplied with the rate, which may be a negative number.

The rewrite rules are divided into ordinary, instantaneous rewrite rules that are assumed to take zero time, and tick rules of the form crl [l] : {t} => {t } in time u if cond, where u is a term (that may contain variables), denoting the duration of the rewrite, and {_} is a new operator that encloses the global state to ensure that time advances uniformly in all parts of the system. , by providing time-bounded versions of these analysis methods, and by providing a set of time-sampling strategies to execute time-nondeterministic tick rules (see [14]).