Syntactic methods
Often, syntactic methods are used when formal methods are not an option. In non-mission-critical systems, formal methods may prove to be too expensive for the benefit they provide. The costs of modelling, personnel, execution, and development may often outweight the benefits gained by preventing possible failures.
Syntactic methods are often a simpler, and more importantly, cheaper alternative to formal methods. This approach revolves around the use of a abstract dependency graph which is created from the system in question. A abstract dependency graph is a directed graph, a graph of vertices connected by one-way edges. Most often, the vertices and edges of the graph represent the inputs and outputs of functions in, or components of, the system.
By looking at the created abstract dependency graph, the developer can detect syntactic anomalies in the system. While anomalies are not always defects, they often provide clues to finding defects in a system. Therefore, the anomalies in a system help point the developer in the right direction in finding defects.
There are four main types of anomalies:
- Redundancies - A chunk of the graph is redundant if its terminals can be reached if the chunk is removed from the graph
- Conflicts - A system contains conflicts if the same inputs can infer differenct outputs
- Circularities - A loop in the graph indicates a circularity in the system
- Deficiencies - A chunk is deficient if a subset of inputs leads to no terminals
While anomalies often point to defects, they can just as easily, reflect normal intended functionality in the system. It is up to the developer to look into anomalies in order to determine whether they are clues to problems or simply false alarms.
Ending: Say something about why it is called syntactic: because the source code is analyzed at a syntactic level to make a graph.