It is crucial to take note that SPA should terminate, and not answer any queries if SPA detects an invalid source program (both syntactically and semantically).
Otherwise, queries should be answered according to the required format of results.
The format of the result returned by PQL queries is summarized below:
| Select | Should return |
|---|---|
| Statement (stmt/read/print/call/while/if/assign) | In SPA implementation, return an array of statement numbers in string format (no need to use ""). |
| Variable | In SPA implementation, return an array of variable names in string format (no need to use ""). |
| Procedure | In SPA implementation, return an array of procedure names in string format (no need to use ""). |
| Constant | In SPA implementation, return an array of constant values in string format (no need to use ""). |
Array should not be populated with any string elements if there are no answers to the query (not even none).
Results should not contain duplicates.
For syntactically invalid queries, populate the list of results with one value SyntaxError. On paper, state SyntaxError as your answer, together with the reason why.
Examples of syntactically invalid queries are as follows:
variable v;
Select v;
variable v;
select v
For semantically invalid queries, populate the list of results with one value SemanticError. On paper, state SemanticError as your answer, together with the reason why.
Examples of semantically invalid queries are as follows:
variable v;
Select v such that Uses(_, v)
stmt s;
Select s pattern s(_, _)
Note that a semantically invalid query must be syntactically valid.