Different types and functions of access paths

Access paths can be referenced in OSI expressions or as data source for property handles. Since access paths can be defined in many different ways, the following sections will explain a bit more detailed, how access paths can be used to achieve certain results.

Access paths can be divided in subsequent types:

• property reference - directly refers to an extent or property in a structure instance (by name)
• property path - refers to members within a structure instance
• path properties - define iteration paths by traversing relationships or references
• operation paths - contain one or more operations in the path
• view path - includes set operations as product or join and are, hence, an extension of OQL queries.

• An access path performs mainly two essential functions:

• execute - evaluate the result from the path definition
• access - selecting and providing instances from the collection defined by the path

In an OSI expression the system decides, when to execute and when just to access the path. When using an access path as data source for a property handle, the application can decide, when to execute the path and when accessing it.

Simple access paths as property references or property paths can be called for execution but will not do anything. More complex path as operation or view path may call execution also while accessing.

An access path consists of various elements (Access Path Elements), which determine the behavior of the path.