Characteristics of sequence rules, sequences, and item sets

A >>> B1, B2 ==> C1, C2

One graph represents one sequence. The item sets of a sequence rule are represented as nodes. Sequence steps are represented as highlighted arrows. Rule steps are indicated by thin arrows.

In the tabular form of the Sequence Rules View, you can include the graphical representation of the sequence rules. In the graphical representation of the sequence rules, item sets are represented as nodes, and the steps are represented as arrows. One graph represents one sequence rule. The graphs are static, you cannot move the item sets or the arrows.

Item sets

The nodes that represent the item sets are colored depending on the item set color that you have specified in the Properties notebook.

You can specify the characteristics that are used as item set labels. The item set labels are displayed in the graphical representation of the sequence rules.

Steps

You can differentiate between the following steps:

Sequence step

The sequence step is indicated by the thin arrow. It represents the steps from one item set to the next item set within the sequence. Sequence steps occur in the rule body.

Rules step

The rule step is indicated by the highlighted arrow. It represents the step from the sequence to the item set. Sequence steps lead from the rule body to the rule head.

By default, the steps are labeled with the measure Time Mean. In the Properties notebook, you can replace this measure with the following measures:

• Time Mean+-Standard Dev.
• Time Min.
• Time Max.

You can show or hide the steps labels in the Sequence Rules View by clicking View => Labels for Steps on the menu bar of the Sequence Visualizer. If Labels for Steps is selected in the View menu, the steps labels are displayed in the Sequence Rules View.

If you include the graphical representation of the sequence rules in the Sequence Rules Visualizer, the legend additionally shows the following information:

• The item set color that you selected in the Properties notebook
• The measure that you selected for the step

The following figure shows the Sequence Rules View with the graphical representation of the sequence rules and the extended legend information.

Rule groups help you to distinguish sets of sequence rules that do not have a direct or indirect relationship.

If two sequence rules, for example, R₁ and R₂, share at least one item set (regardless whether the item set appears in the rule head or in the rule body), these sequence rules are directly related (R₁ ~ R₂). Therefore they belong to the same rule group.

The rule group of a given sequence rule R₁ consists of all sequence rules in the model that are directly or indirectly related to R₁. This means that a rule group contains all sequence rules that are connected via a chain of directly related sequence rules in the model.

The figure below illustrates the direct and the indirect relationship of sequence rules. Each of the sequence rules has a direct relationship to another sequence rule because they contain the same item set. For example, sequence rule number 1 and sequence rule number 2 contain the item set L.

Sequence rule number 2 and sequence rule number 4 are not directly related because they do not contain the same item set. However, they are indirectly related based on the direct relation ship of sequence rule number 2 and sequence rule number 3 (both contain the item set D) and the direct relationship of sequence rule number 3 and sequence rule number 4 (both contain the item set S).

The sequence rules 4 and 5 belong to a different rule group because they are not linked to any item set of sequence rule number 1, sequence rule number 2, or sequence rule number 3.

Item sets that belong to sequence rules in different rule groups are not typically contained in the same transaction group. For example, if you are looking at repair histories, you can interpret this as not having dependencies in breaking down. However, if you sort the sequence rules of by sequence rule group, you can easily detect item sets (product parts) that are typically broken down in a sequence.

A >>> B1, B2 ==> C1, C2

For sequences, the lift value shows the difference between the sequence and the sum of the different parts of a sequence. This means, if the lift value of a sequence is greater than 1, previous item sets in a sequence are related with consecutive item sets. The occurrence of the previous item sets enforces the occurrence of the consecutive item sets.

For item sets, the lift value shows the difference between the item set and the sum of the different parts of the item set. This means, if the lift value of an item set is greater than 1, the items in the item set are related.

The sequence of item sets in the rule body influences the item set in the rule head.

A >>> B1, B2 ==> C1, C2. 

[ignition distributor] >>> 
[air bag fron right] + [fuse_15] ==> [air condition]
Support=24% Confidence=60% Lift=2.0

These item sets might contain additional items, and the transaction group might contain additional item sets.

For sequences, a transaction group supports a sequence if the transaction group contains all item sets of the sequence in the same order as in the sequence. The support value is the ratio of transaction groups supporting the sequence and the total number of transaction groups within your database of transaction groups.

For item sets, a transaction group supports an item set if the item set is a subset of at least one transaction within the transaction group. The support value is the ratio of transaction groups supporting the item set and the total number of transaction groups within your database of transaction groups.

For sequences, this value reflects the minimum time between the successive item sets of a sequence.

For sequences, this value reflects the maximum time between the successive item sets of a sequence.

For sequences, this value reflects the minimum time between the successive item sets of a sequence.