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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 by zero occurs when, during execution, an attempt is made to divide a number by zero. Because these types of errors can not be c=found at compile time, they occur at runtime.
- Out of Bound occurs when a program tries to access an element in an array that is out of range of the array. Many languages dimension arrays from 0 to +number), some allow negative indexing and others do not.
- Type Mismatch occurs when an attempt is made to store a value into an array that is not compatible (i.e., trying to store an integer in an array of strings).
- Range Error occurs when a value does not meet the allowable range of values specified by the code. For example, trying to set a value of 200 into a value described by a percent type that ranges from 0 to 100.
- Number Format Error occurs when an attemot is made to convert a string to a number but the string does not match the rescibed format. For Example, trying to convert the String
“one”to 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 Integeroccurs when the basic types of parameters do not match. Usually this occurs when the code has change or the correct Shared Library can not be found.Too Few Parametersoccurs when the code tries to call a procedure, function or method that requires more parameters than can be found in the existing libraries. This can occur due to changes in the calling signature or when a Shared Library is not found.Class 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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