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2.3.4.8.4 Operation Data
Overview
Any particular operation within an Object is generally Imperative in nature. This means that the Operations are composed of a set of statements. As the program steps through the Operation and executes each statement (i.e., instruction) the state of the Object is changed. Some statements change the values of the Field Data while others change the flow of execution through Control Flow operations (i.e., IF / ELSE IF / ELSE / ENDIF, or FOR LOOPS | WHILE LOOPS /, etc.).
As the statements are executed, the Program Counter for the Operation is also modified. Note: Rarely all the statements contained within a single operation, but relies on calling and executing other Operations. Therefore, most Operations are also considered a Procedural Language. Figure 1 provides a graphic of the difference between Imperative and Procedural Programs.
To confuse the situation even more, there is a differentiation between the Imperative or Procedural: function, procedure, and method.
| function | a named set of instructions that perform a task and return a single value to the caller of the function. Generally, all the parameters passed to the function are considered IN (i.e., Read-Only). |
| procedure | a named set of instructions that perform a task and do not return any values to the caller. The results of the procedure call are changes made to the parameters which can be declared, IN, OUT (i.e., Write-Only), or INOUT (i.e., Read-Write). Procedures often behave like functions in that they return a single value to the caller. The value can be a success flag or a return code. The caller can examine the results to help control the flow through the program. Most modern languages would rather use Exceptions instead. |
| method | a function or a procedure that is associated with an Object in OOP. |
- Note: Regardless of the classification of the set of instructions, there should be no unintended side effects from calling the function. For example, calling a function should not affect anything else in the system. For example, calling a square Root function should not start a printer.
- Note: The use of Exceptions requires that the caller has an Exception Handler. Therefore, most modern Object-Oriented (OO) languages require the declaration of known Exceptions in the specification of a function, procedure or method.
Exceptions
An important aspect of executing any set of instructions is What happens if there is an error?.
The error condition could arise from system errors such as:
- Access denied Segmentation Fault (SEGFAULT) occurs when the user does not have privileges to a resource, such as a file, or when the resources are locked by some program or user. Other examples would be trying to access memory that is outside the current program space or trying to execute a null instruction.
- Device not ready occurs when an external device is not ready or available. For example, a disk drive that has not been mounted, accessing a monitor that has been disconnected. The resource may have been powered down, disconnected, damaged, moved, deleted, or a had a fault. Alternatively, the resource as specified may simply might not exist (i.e., typographical errors in its name).
- Low Disk Space occurs when the disk system is full or nearly full.
- Out of memory occurs when the system runs out of Heap and/or Stack memory. The system can not load new programs or functions (i.e., Stack) or execute the existing ones (i.e., Heap limit)
The error conditions could arise from runtime errors such as:
- Dividing an integer by zero.
- Accessing an element that is out of range of the array
- Trying to store a value into an array that is not compatible type
- Passing an argument that is not in a valid range or valid value for a method
- Striving to use a negative size for an array
- Attempting to convert an invalid string into a number
The error conditions could arise from syntax or semantic errors. Note: strongly typed systems avoid these errors) such as
Value must be an Unsigned IntegerToo Few Parametersoccurs when the code tries to call a procedure, function or memberClass Not Foundoccurs when the code is trying to instantiate a class whose definition is not included in the current program or any of the other Shared Library.Interruptedoccurs when one thread or process interrupts another thread or process.
DIDO Specifics
An interesting phenomenon about many of the DIDO Platforms, is the way they treat Operation Data. Many of the Platforms not only distribute Field Data using Distributed Ledger or Journal, they also distribute the Operation Data in the same way (in essence, treating the software just as any other data). When changes are made to the Operation Data, a Transaction is created to be pushed to the Node Network.
General Methods
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