1. S EQUENTIAL P ATTERNS & THE GSP A LGORITHM BY : J OE C ASABONA

2. I NTRO What are Sequential Patterns? Why don't ARs suffice? The General Sequential Pattern Algorithm o Finding Frequent Sets o Candidate Generation o Rule Generation

3. W HAT ARE S EQUENTIAL P ATTERNS ? "Finding statistically relevant patterns between data examples where the values are delivered in a sequence." [3] Very similar to Association Rules, but sequence in this case matters. There may be times when order is important.

4. S EQUENTIAL P ATTERN E XAMPLES In Transaction Processing: Do customers usually buy a new controller or a game first after buying an Xbox? In Text Mining: Order of the words important for finding linguistic or language patterns [1]

5. O BJECTIVE Given a set S of input data sequences, find all sequences that have a user-specified minimum support. This is called a 'frequent sequence' or sequential pattern. [1] We will use the Generalized Sequential Pattern Algorithm (GSP)

6. GSP Similar to Apriori Algorithm Find individual items with minSupport (1-sequences) Use them to find 2-sequences Continue using k-sequences to find (k+1)-sequences Stop when there are no more frequent sequences. Difference is in Candidate Generation

7. GSP: C ANDIDATE G ENERATION Input : Frequent Set k-1 (F[k-1]) Output: Candidate Set C[k] How it works: Join F[k-1] with F[k-1] Get rid of infrequent sequences (prune) Note: Order of items matter

8. C ANDIDATE E XAMPLE F[3] =,,,,, After Join:, After Prune: C[4]=

9. R ULE G ENERATION Objective not to generate rules, but it can be done. Sequential Rule: Apply confidence to Frequent Sequences Label Sequential Rules: Replace some elements in X with *

10. R ERERENCES [1] The Book I am using: Liu, Bing. Web Data Mining, Chapter 2: Association Rules and Sequential Patterns. Springer, December, 2006 Wikipedia: [2] "GSP Algorithm." http://en.wikipedia.org/wiki/GSP_Algorithm June 3, 2008 [3] "Sequence Mining." http://en.wikipedia.org/wiki/Sequence_mining Oct. 30, 2008