PathExpression (Hydra Java API)

java.lang.Object
- com.gdblab.pathAlgebra.expressions.PathExpression

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<PathExpression>

Direct Known Subclasses:

PathExpression.Base, PathExpression.GroupBy, PathExpression.Join, PathExpression.OrderBy, PathExpression.Projection, PathExpression.Recursive, PathExpression.Selection, PathExpression.Union
```
public abstract class PathExpression
extends java.lang.Object
implements java.io.Serializable, java.lang.Comparable<PathExpression>
```
A path algebra expression that evaluates to a set of paths

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`PathExpression.Base`	Base case: extract paths from graph
`static class`	`PathExpression.GroupBy`	Group-by operator (γ): organize paths into solution space
`static class`	`PathExpression.Join`	Join operator (⊲⊳): concatenate compatible paths
`static class`	`PathExpression.OrderBy`	Order-by operator (τ): sort solution space
`static interface`	`PathExpression.PartialVisitor<R>`	Partial visitor over `PathExpression` with a default `PathExpression.PartialVisitor.otherwise(com.gdblab.pathAlgebra.expressions.PathExpression)` branch.
`static class`	`PathExpression.Projection`	Projection operator (π): extract paths from solution space
`static class`	`PathExpression.Recursive`	Recursive operator (φ): compute transitive closure with semantics
`static class`	`PathExpression.Selection`	Selection operator (σ): filter paths by condition
`static class`	`PathExpression.Union`	Union operator (∪): combine path sets
`static interface`	`PathExpression.Visitor<R>`	Visitor over `PathExpression`.

Field Summary

Fields
Modifier and Type	Field	Description
`static Name`	`BASE`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.base` field.
`static Name`	`GROUP_BY`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.groupBy` field.
`static Name`	`JOIN`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.join` field.
`static Name`	`ORDER_BY`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.orderBy` field.
`static Name`	`PROJECTION`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.projection` field.
`static Name`	`RECURSIVE`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.recursive` field.
`static Name`	`SELECTION`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.selection` field.
`static Name`	`TYPE_`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression` type.
`static Name`	`UNION`	Name of the `com.gdblab.pathAlgebra.expressions.PathExpression.union` field.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type Method Description

abstract <R> R accept(PathExpression.Visitor<R> visitor)
Dispatch to visitor.
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
- Methods inherited from interface java.lang.Comparable
  compareTo

- Field Detail
  - TYPE_
```
public static final Name TYPE_
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression type.
  - BASE
```
public static final Name BASE
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.base field.
  - SELECTION
```
public static final Name SELECTION
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.selection field.
  - JOIN
```
public static final Name JOIN
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.join field.
  - UNION
```
public static final Name UNION
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.union field.
  - RECURSIVE
```
public static final Name RECURSIVE
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.recursive field.
  - GROUP_BY
```
public static final Name GROUP_BY
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.groupBy field.
  - ORDER_BY
```
public static final Name ORDER_BY
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.orderBy field.
  - PROJECTION
```
public static final Name PROJECTION
```
    Name of the com.gdblab.pathAlgebra.expressions.PathExpression.projection field.
- Method Detail
  - accept
```
public abstract <R> R accept(PathExpression.Visitor<R> visitor)
```
    Dispatch to visitor.