1. Characteristic Identifier Scoring and Clustering for Email Classification By Mahesh Kumar Chhaparia

2. Email Clustering Given a set of unclassified emails, the objective is to produce high purity clusters keeping the training requirements low. Outline: –Characteristic Identifier Scoring and Clustering (CISC), Identifier Set Scoring Clustering Directed Training –Comparison of CISC with some of the traditional ideas in email clustering –Comparison of CISC with POPFile (Naïve-Bayes classifier), –Caveats –Conclusion

3. Evaluation Evaluation on Enron Email Dataset for the following users (purity measured w.r.t the grouping already available): UserNumber of folders Number of Messages Messages in smallest folder Messages in largest folder Lokay-M11248961159 Beck-S10119713166 Sanders-R3011884420 Williams-w318276931398 Farmer-D25367251192 Kitchen-L4740155715 Kaminski-V4144773547

4. CISC: Identifier Set Sender and Recipients Words from the subject starting with uppercase Tokens from the message body –Word sequences with each word starting in uppercase (length [2,5] only) split about stopwords (excluding them) –Acronyms (length [2,5] only) –Words followed by an apostrophe and ‘s’ e.g. TW’s extracted to TW –Words or phrases in quotes e.g. “Trans Western” –Words where any character (excluding first is in uppercase) e.g. eSpeak, ThinkBank etc.

5. CISC: Scoring Sender: –Initial idea: generate clusters of email addresses with frequency of communication above some threshold, (+) Identifies “good” clusters of communication (-) Difficult to score when an email has addresses spread across more than one cluster (-) Fixed partitioning and difficult to update

6. CISC: Scoring (Contd…) Sender: –Need a notion of soft clustering with both recipients and content –Generate a measure of its non-variability with respect to the addresses it co-occurs with or the content it discusses in emails –Example: 1  {2,3} {3,4} {2,3,4} in Folder 1 2  {1} {3} {4} {1} {3} {1,3} in Folder 2 Emphasizes social clusters {1,2,3} {1,3,4} Classify 2  {1,3,4} –Traditionally: Folder 2 (address frequency based) –CISC: Folder 1 (social cluster based) –Difficult to say upfront which is better ! –Efficacy discussed later

7. CISC: Scoring (Contd…) Words or Phrases: –Generate a measure of its importance –Using context captured through the co-occurring text –Sample scenarios for score generation: Different functional groups in a company mentioning “Conference Room”  Low score A single shipment discussion for company “CERN”  High score Several different topic discussions (financial, operational etc.) for company “TW”  Low score Clustering: Pair with highest similarity message and merge clusters sharing atleast one message to produce disjoint clusters Directed Training: –For each cluster, identify a message likely to belong to majority class –Suggest the user to classify this message

8. Efficacy of TF-IDF Cosine Similarity Clustering using the traditional TF-IDF cosine similarity measure for emails not very effective ! Note: Both TF-IDF and CISC figures with only word and phrase tokens Number of clusters is different in both cases, but the purity figures indicate the discriminative capability of the respective algorithms UserTF-IDF (% Purity before merging) TF-IDF (% Purity) CISC (% Purity) Lokay-M57.6946.6877.54 Beck-S51.449.6359.66 Sanders-R61.5337.4570.03 Williams-w358.9261.7190.61

9. Efficacy of Social Cluster Based Scoring Results UserCISC (with social clusters) (% Purity) CISC (without social clusters) (% Purity) Lokay-M84.2177.54 Beck-S60.5259.66 Sanders-R78.2870.03 Williams-w393.3190.61

10. CISC vs. POPFile Results Purity may sometimes (marginally) decrease with increasing training set in POPFile ! # Training Messages Lokay-MBeck-SSanders-RWilliams-w3 10062.6315.6015.396.75 20066.6219.7031.7935.50 30069.5320.0150.6835.72 100072.6824.6336.5118.40 CISC80.47 (265)52.81 (218)75.67 (146)91.40 (153) 85.22 (614)71.47 (587)84.79 (332)93.38 (365)

11. Conclusion Given a set of unclassified emails, the proposed strategy obtains higher clustering purity with lower training requirements than POPFile and TF-IDF based method. Key differentiators: –Incorporates a combination of communication cluster and content variability based scoring for senders instead of the usual tf-idf scoring or naïve-bayes word model (POPFile), –Picks a set of high-selectivity features for final message similarity model than retaining most content of messages (i.e. all non-stopwords), –Observes and uses the fact that any email in a class may be “close” to only a small number of emails than to all in that class, –Finally, helps lower training requirements through “directed training” than indiscriminate training over as many emails as possible.

12. Future Work Design and evaluation for non-corporate datasets Tuning of message similarity scoring –Different weights for the score components –Different range normalization for different components to boost proportionally –Test feature score proportional to its length Richer feature set –Phrases following ‘the’ –Test with substring-free collection e.g. “TW Capacity Release Report” and “TW” are replaced with “Capacity Release Report” and “TW” Hierarchical word scoring to change granularity of clustering Online classification using training directed feature extraction Merging high purity clusters effectively to further reduce training requirements

13. Q &A