The first example presented here is concerned with updating a processing dialog meter for a tool that manages a database schema. The updating of the progress meter represents a crosscutting concern because the code to increment the meter is spread across the methods that perform much of the functionality (e.g., deleting database triggers, compiling new stored procedures, and other evolution tasks). Lines 2-8 in the listing below contain a redundant code fragment that appears in 62 different places of the Schema Manager. This code is necessary to update the processing dialog after each database evolution task is completed. Technically, this happens after every call to the predefined Inc procedure.

Crosscutting in Progress Meter Updating

Aspect to capture Progress Meter Updating

Aspect Model (Internal Representation of Progress Meter aspect)

The ATL transformation (a call join point) required to transform this Aspect Model to RSL Model is available below:

Complete ATL Specification for Translating Primitive Call Expression

Often, a commercial application must support databases from several different vendors (e.g., Oracle, Interbase, and SQL Server). In such a situation, exception handling of database errors is a major difficulty because each database has its own way of raising exceptions. The same conceptual error (e.g., a null value in a required field) may be raised in completely different ways with dissimilar error codes. Moreover, the exception handling code must be thread-safe because numerous clients may access the database at the same time. The addition of this concurrency concern resulted in a manual invasive change to over 20 classes in the Schema Manager utility. An example error handler is shown below.

Crosscutting in Database Error Handler Synchronization

• Aspect Source for DB Error Handler
• Aspect Model for DB Error Handler
• Complete ATL specification for Translating Exec Expr
• Generated RSL model
• Extracted RSL code from RSL model

According to our definition, the join point for a loop has the following signature: (init::[val], exit::[val], stride::[val]). Init specifies the loop initialization value, exit specifies the loop termination value and stride specifies the loop increment counter. An aspect for adding timing information within the body of an ObjectPascal function named SortByResourceIDClick and execution of for loops with an initialization value of 1 and exit condition any (*) is shown below. The aspect will match all for loops with the given signature and within the body of the named function.

Aspect to monitor Loops

Aspect Model (Internal Representation of Loop aspect)

• Complete ATL specification for Translating For Loop Execution
• Generated RSL model
• Extracted RSL code from RSL model