Arc Syntax

1. Two Syntax Forms

Arc syntax is common for all methods that take arc= arguments. There are two distinct syntax forms, one for arc insertion and one for arc filters.

2. Arc Insertion

Methods that create relationships between vertices accept a tuple of zero, one, two, or three elements in the arc= parameter.

Inserting or modifying a relationship will always create an outbound arc from the initial to the terminal vertex.

2.1. Arc Insertion Syntax

<arc> ::= ( [ <relationship> [, <modifier> [, <value> ] ] ] )

2.2. Arc Elements

Parameter	Type	Default Value	Comment
<relationship>	<str>	"__related__"	Relationship type names are enumerated as integers internally in the graph, using a limited enumeration space. The maximum number of unique relationship types allowed per graph instance is 15616. An insertion attempt that exhausts the enumeration space will raise pyvgx.EnumerationError
<modifier>	Arc Modifier	pyvgx.M_STAT	Arc modifier constants are integer values. Although a method will perform the correct operation if the correct plain integer is used for the arc modifier, the method behavior is generally undefined if an invalid integer is passed.
<value>	<int> <float>	<modifier> dependent	The value type and range depend on the modifier.

Parameter

Type

Default Value

Comment

<str>

"__related__"

Relationship type names are enumerated as integers internally in the graph, using a limited enumeration space. The maximum number of unique relationship types allowed per graph instance is 15616. An insertion attempt that exhausts the enumeration space will raise pyvgx.EnumerationError

Arc Modifier

pyvgx.M_STAT

Arc modifier constants are integer values. Although a method will perform the correct operation if the correct plain integer is used for the arc modifier, the method behavior is generally undefined if an invalid integer is passed.

<value>

<int>

<float>

<modifier> dependent

The value type and range depend on the modifier.

2.3. Shortcut Notation

Insert a fully unspecified arc pass None or the empty tuple ()

arc = None
arc = ()

Insert an arc with unspecified relationship type, pass None for <relationship>

arc = ( None, <modifier>, <value> )

2.4. Automatic Value Assignment

Create arc and set creation time to now (set once, cannot be changed)

arc = ( <relationship>, pyvgx.M_TMC )

Create/modify arc and update modification time to current time

arc = ( <relationship>, pyvgx.M_TMM )

Counter (integer value)

# Increment arc value, or set it to <assign_value>
arc = ( <relationship>, pyvgx.M_CNT[, <assign_value>] )

Accumulator (float value)

# Accumulate arc value, or set it to <assign_value>
arc = ( <relationship>, pyvgx.M_ACC[, <assign_value>] )

3. Arc Filter

Query methods that support the arc= parameter accept a filter tuple of zero, one, two, three or five elements. (Four-element tuples are not valid since <condition> also requires <value>.)

The filter logic is inverted when wrapping the filter tuple within another tuple (False, filter).

3.1. Arc Filter Syntax

positive (default) logic

arcfilter ::= ( [ <relationship> [, <direction> [, <modifier> [, <condition>, <value> ] ] ] ] )

inverse logic

arcfilter ::= ( False, ( [ <relationship> [, <direction> [, <modifier> [, <condition>, <value> ] ] ] ] ) )

3.2. Arc Filter Elements

Parameter Type Default Value Comment

Parameter	Type	Default Value	Comment
<relationship>	<str>	None	To match any relationship type use `None` or `"*"`. Wildcard syntax for partial string match is not supported.
<direction>	Arc Direction	Query method dependent
<modifier>	Arc Modifier	pyvgx.M_ANY
<condition>	Value Condition	-	Specifying a <condition> also requires <modifier> and <value> to be specified. The specified <modifier> cannot be pyvgx.M_ANY.
<value>	<numeric> or ( <numeric>, <numeric> )	-	Depending on the <condition> code this may either be a single numeric value n or a 2-tuple (a, b).