Loading in 5 sec....

Computational Discovery in Evolving Complex NetworksPowerPoint Presentation

Computational Discovery in Evolving Complex Networks

- 116 Views
- Uploaded on
- Presentation posted in: General

Computational Discovery in Evolving Complex Networks

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Computational Discovery in Evolving Complex Networks

Yongqin Gao

Advisor: Greg Madey

- Background
- Methodology for Computational Discovery
- Problem Domain – OSS Research
- Process I: Data Mining
- Process II: Network Analysis
- Process III: Computer Simulation
- Process IV: Research Collaboratory
- Contributions
- Conclusion and Future Work

- Network research gains more attentions
- Internet
- Communication network
- Social network
- Software developer network
- Biological network

- Understanding the evolving complex network
- Goal I: Search
- Goal II: Prediction

- Computational scientific discovery

- Open Source Software Movement
- What is OSS
- Free to use, modify and distribute and source code available and modifiable
- Potential advantages over commercial software: Potentially high quality; Fast development; Low cost

- Why study OSS (Goal)
- Software engineering — new development and coordination methods
- Open content — model for other forms of open, shared collaboration
- Complexity — successful example of self-organization/emergence

- What is OSS

- SourceForge.net community
- The biggest OSS development communities
- 134,751 registered projects
- 1,439,773 registered users

- Our Data Set
- 25 monthly dumps since January 2003.
- Totally 460G and growing at 25G/month.
- Every dump has about 100 tables.
- Largest table has up to 30 million records.

- Experiment Environment
- Dual Xeon 3.06GHz, 4G memory, 2T storage
- Linux 2.4.21-40.ELsmp with PostgreSQL 8.1

- OSS research
- W. Scacchi, “Free/open source software development practices in the computer game community”, IEEE Software, 2004.
- C. Kevin, A. Hala and H. James, “Defining open source software project success”, 24th International Conference on Information Systems, Seattle, 2003.

- Complex networks
- L.A. Adamic and B.A. Huberman, “Scaling behavior of the world wide web”, Science, 2000.
- M.E.J. Newman, “Clustering and preferential attachment in growing networks”, Physics Review, 2001.

- Related Research:
- S. Chawla, B. Arunasalam and J. Davis, “Mining open source software (OSS) data using association rules network”, PAKDD, 2003.
- D. Kempe, J. Kleinberg and E. Tardos, “Maximizing the spread of influence through a social network”, SIGKDD, 2003.
- C. Jensen and W. Scacchi, “Data mining for software process discovery in open source software development communities”, Workshop on Mining Software Repositories, 2004.

Knowledge

Algorithm Application

Feature Selection

Relevant data

Data Purging

Database

Data Preparation

Raw data

- Data Preparation
- Data discovery
- Locating the information

- Data characterization
- Activity features: user categorization
- Network features

- Data assembly

- Data discovery
- Data Purging
- Treatment about data inconsistency
- Unifying the date presentation by loading into single depository

- Treatment about data pollution
- Removing “inactive” projects

- Treatment about data inconsistency
- Feature Selection
- This method is used to remove dependent or insignificant features.
- NMF (Non-negative Matrix Factorization)

- Result I
- Significant features
- By feature selection, we can identify the significant feature set describing the projects.
- Activity features: “file_releases”, “followup_msg”, “support_assigned”, “feature_assigned” and task related features
- Network features: “degrees”, “betweenness” and “closeness”

- Significant features

- Distribution-based clustering (Christley, 2005)
- Clustering according to the distribution of features instead of values of individual feature
- We assume every entity (project) has an underlying distribution of the feature set (activity features)
- Using statistical hypothesis test
- Non-parametric test
- Fisher’s contingency-table test is used
- Joachim Krauth, “Distribution-free statistics: an application-oriented approach”, Elsevier Science Publisher, 1988.

- Procedure:
While (still unclustered entities)

Put all unclustered entities into one cluster

While (some entities not yet pairwise compared)

A = Pick entity from cluster

For each other entity, B, in cluster not yet compared to A

Run statistical test on A and B

If significant result

Remove B from cluster

- Worst case complexity: O(n2)

- Result II
- Unsupervised learning
- Distribution-based method used to cluster the project history using the activity distribution
- We named the clusters using ID and the results are shown in the table
- High support and confidence in evaluation

- Two sample distributions from different categories
- Unbalanced feature distribution → could be “unpopular”
- Balanced feature distribution → could be “popular”

- Discoveries in Process I
- Significant feature set selection
- Network features are important
- Further inspection in next process

- Distribution based predictor
- Based on the activity feature distribution
- Prediction of the “popularity” based on the balance of the activity feature distribution

- Significant feature set selection
- Benefit of these discoveries
- For collaboration based communities, these discoveries can help in resource allocation optimization.

- Why network analysis
- Assess the importance of the network measures to the whole network and to individual entity in the network
- Inspect the developing patterns of these network measures

- Network analysis
- Structure analysis
- Centrality analysis
- Path analysis

- Related research:
- P. Erdös and A. Rényi, “On random graphs”, Publicationes Mathematicae, 1959.
- D.J. Watts and S. H. Strogatz, “Collective dynamics of small-world networks”, Nature, 1998.
- R. Albert and A.L. Barabάsi, “Emergence of scaling in random networks”, Science, 1999.
- Y. Gao, “Topology and evolution of the open source software community”, Master Thesis, 2003.

- Structure Analysis
- Understanding the influence of the network structure to individual entities in the network
- Inspected measures
- Approximate diameter
- Approximate clustering coefficient
- Component distribution

- Conversion among C-NET, P-NET and D-NET

- Result I
- Approximate Diameters
- D-NET: between (5,7) while network size ranged from 151,803 to 195,744.
- P-NET: between (6,8) while network size ranged from 123,192 to 161,798.

- Approximate Clustering Coefficient
- D-NET: between (0.85, 0.95)
- P-NET: between (0.65, 0.75)

- Approximate Diameters

- Result I

- Centrality Analysis
- Understanding the importance of individual entities to the global network structure
- Inspected measures:
- Average Degrees
- Degree Distributions
- Betweenness
- Closeness

- Result II
- Average Degrees
- Developer degree in C-NET: 1.4525
- Project degree in C-NET: 1.7572
- Developer degree in D-NET: 12.3100
- Project degree in P-NET: 3.8059

- Average Degrees

- Result II (Degree distributions in C-NET)

- Result II (Degree distributions in D-NET and P-NET)

- Result II
- Average Betweenness
- P-NET: 0.2669e-003

- Average Closeness
- P-NET: 0.4143e-005

- Normally these two measures yield very small value in large networks (N>10,000).

- Average Betweenness

- Path Analysis
- Understanding the developing patterns of the network structure and individual entities in the network
- Inspected measures:
- Active Developer Percentage
- Average Degrees
- Diameters
- Clustering coefficients
- Betweenness
- Closeness

- Result III (Active entities)

- Result III (Average degrees in C-NET)

- Result III (Average degrees in D-NET and P-NET)

- Result III (Diameters in D-NET and P-NET)

- Result III (Clustering coefficients for D-NET and P-NET)

- Result III (Average betweenness and closeness for P-NET)

- Discoveries in Process II:
- Measures of structure analysis and centrality analysis all indicate very high connectivity of the network.
- Measures of path analysis reveal the developing patterns of these measures (life cycle behavior).

- Benefits of these discoveries
- High connectivity in a network is an important feature for information propagation, failure proof. Understanding this discovery can help us improve our practices in collaboration networks and communication networks.
- Understanding the developing patterns of these network measures provides us a method to monitor network development and to improve the network if necessary.

- Related Research:
- P.J. Kiviat, “Simulation, technology, and the decision process”, ACM Transactions on Modeling and Computer Simulation,1991.
- R. Albert and A.L. Barabási, “Emergence of scaling in random networks”, Science, 1999.
- J. Epstein R. Axtell, R. Axelrod and M. Cohen, “Aligning simulation models: A case study and results”, Computational and Mathematical Organization Theory, 1996.
- Y. Gao, “Topology and evolution of the open source software community”, Master Thesis, 2003.

- Iterative simulation method
- Empirical dataset
- Model
- Simulation

- Verification and validation
- More measures
- More methods

- Previous iterated models (master thesis):
- Adapted ER Model
- BA Model
- BA Model with fitness
- BA Model with dynamic fitness

- Iterated models in this study
- Improved Model Four (Model I)
- Constant user energy (Model II)
- Dynamic user energy (Model III)

- Model I
- Realistic stochastic procedures.
- New developer every time step based on Poisson distribution
- Initial fitness based on log-normal distribution

- Updated procedure for the weighted project pool (for preferential selection of projects).

- Realistic stochastic procedures.

- Average degrees

- Diameter and CC

- Betweenness and Closeness

- Degree Distributions

- Deficit in the measures

- Model II
- New addition: user energy.
- User energy
- the “fitness” parameter for the user
- Every time a new user is created, a energy level is randomly generated for the user
- Energy level will be used to decide whether a user will take a action or not during every time step.

- Degree distributions for Model II

- Deficit in the measures

- Model III
- New addition: dynamic user energy.
- Dynamic user energy
- Decaying with respect to time
- Self-adjustable according to the roles the user is taking in various projects.

- Degree distributions (Model III)

- Discoveries in Process III
- Expanding the network models for modeling evolving complex networks (more parameters)
- Providing a validated model to simulate the community network at SourceForge.net

- Benefits of these discoveries
- Expanded network models can benefit other researchers in complex networks.
- Validated model for SourceForge.net can be used to study other OSS communities or similar collaboration networks.

- Related Research:
- G. Chin Jr. and C. Lansing, “The biological sciences collaboratory”, Mathematics and Engineering Techniques in Medicine and Biological Sciences, 2004.
- L. Koukianakis, “A system for hybrid learning and hybrid psychology”, Cybernetics and Information Technologies, Systems and Applications, 2003.
- NCBI, FlyBase, Ensembl, VectorBase

- What is Collaboratory?
- An elaborate collection of data, information, analytical toolkits and communication technologies
- A new networked organizational form that also includes social processes, collaboration techniques and agreements on norms, principles, value, and rules

- Data tier - schema design

- Data tier - connection pool

- Presentation Tier
- Various access methods
- Documentation and references
- Community support
- Wiki interface

- Logic Tier
- Interactive web query system
- Authorized user can submit query to the back end repository through the web query
- Results are provided by files with various formats

- Dynamic web schema browser
- Authorized user can access the dynamic schema of the repository through the schema browser

- Interactive web query system

- Utilization reports
- Monthly statistics (June 2006)
- Total queries submitted: 16,947
- Total data files retrieved: 13,343
- Total bytes of query data downloaded: 26,684,556,278

- Monthly statistics (June 2006)
- Programmable access method
- Programmable access method should be provided for complicated access
- Web services planned

- Results in Process IV
- Designing, implementing and maintaining a research collaboratory for OSS related research.

- Benefits of these results
- OSS researchers can access one of the most complete data sets for a OSS community development.
- By providing the community service to OSS researchers, the collaboratory can help in sparkling, improving and promoting research ideas about OSS.

- Designed and demonstrated a computational discovery methodology to study evolving complex networks using research on OSS as a representative problem domain
- Understanding the OSS movement by applying the methods.
- Process I: data mining
- Identifying significant features to describe a project
- Using distribution based clustering to generate a distribution based predictor to predict the “popularity” of a project

- Process II: network analysis
- Introducing more complete analysis to inspect more complete data set from SourceForge.net.
- Discovering high connectivity and possible life cycle behaviors in both the network structure and individuals in the network

- Process III: computer simulation
- Introducing more parameters in modeling evolving complex networks
- Generating a “fit” model to replicate the evolution of the SourceForge.net community.

- Process IV: research collaboratory
- Designing, implementing and maintaining a research collaboratory to host the SourceForge.net data set and provide community support for OSS related researches.

- Process I: data mining

- Y. Gao; G. Madey and V. Freeh. “Modeling and simulation of the open source software community”, ADSC, San Diego, 2005.
- Y. Gao and G. Madey. “Project development analysis of the oss community using st mining”, NAACSOS, Notre Dame, 2005.
- S. Christley; Y. Gao; J: Xu and G. Madey. “Public goods theory of the open source software development community”, Agent, Chicago, 2004.
- Y. Gao, Y. Huang and G. Madey, “Data Mining Project History in Open Source Software Communities”, NAACSOS, Pittsburgh, 2004.
- J. Xu, Y. Gao, J. Goett and G. Madey, “A Multi-model Docking Experiment of Dynamic Social Network Simulations”, Agent, Chicago, 2003.
- Y. Gao, V. Freeh, and G. Madey, “Analysis and Modeling of the Open Source Software Community”, NAACSOS, Pittsburgh, 2003.
- Y. Gao, V. Freeh, and G. Madey, “Conceptual Framework for Agent-based Modeling and Simulation”, NAACSOS, Pittsburgh, 2003.
- G. Madey; V. Freeh; R: Tynan and Y. Gao. “Agent-based modeling and simulation of collaborative social networks”, AMCIS, Tampa, 2003.
- Y. Gao; V. Freeh and G. Madey. “Topology and evolution of the open source software community”, SwarmFest, Notre Dame, 2003.

- Chapter III (data mining)
- Journal of Machine Learning Research
- Journal of Systems and Software

- Chapter IV (network analysis)
- Journal of Network and Systems Management
- Journal of Social Structure

- Chapter V (computer simulation)
- Spring Simulation Conference 2007 (under review)
- IEEE Computing in Science and Engineering

- Chapter VI (research collaboratory)
- CITSA 2007
- Journal of Computer Science and Applications

- Cyclic computational discovery method for studying evolving complex networks
- Study of Open Source Software by applying this method
- Future works:
- Maintaining and expanding the collaboratory
- Verifying the discoveries in the SourceForge.net against further accumulated database dump from SourceForge.net
- Applying our simulation model on other software development communities
- Extending our methodology to other evolving complex networks like Internet, communication network and various social networks

- My advisor: Dr. Madey
- My committee members:
- Dr. Flynn
- Dr. Striegel
- Dr. Wood

- My Colleagues:
- Scott Christley, Yingping Huang, Tim Schoenharl, Matt Van Antwerp, Ryan Kennedy, Alec Pawling and Jin Xu

- SourceForge.net managers:
- Jeff Bates, VP of OSTG Inc.
- Jay Seirmarco, GM of SourceForge.net.

- US NSF CISE/IIS-Digital Society & Technology, under Grant No. 0222829.

Questions

dev[72]

dev[67]

dev[52]

dev[65]

dev[70]

dev[57]

7597 dev[46]

6882 dev[47]

dev[45]

dev[64]

dev[99]

7597 dev[46]

7597 dev[46]

dev[52]

dev[72]

dev[67]

7597 dev[46]

dev[47]

6882 dev[47]

dev[55]

dev[55]

dev[55]

7597 dev[46]

7028 dev[46]

dev[70]

7597 dev[46]

7028 dev[46]

dev[57]

dev[45]

dev[51]

dev[99]

7597 dev[46]

7028 dev[46]

6882 dev[47]

6882 dev[58]

dev[61]

dev[51]

dev[79]

dev[47]

dev[58]

7597 dev[46]

dev[58]

dev[46]

9859 dev[46]

dev[54]

15850 dev[46]

dev[58]

9859 dev[46]

dev[79]

dev[58]

9859 dev[46]

dev[49]

dev[53]

9859 dev[46]

15850 dev[46]

dev[59]

dev[56]

15850 dev[46]

dev[83]

15850 dev[46]

dev[48]

dev[53]

dev[56]

dev[83]

dev[48]

OSS Developer Network (Part)

Project 7597

Developers are nodes / Projects are links

24 Developers

dev[64]

5 Projects

2 hub Developers

Project 6882

1 Cluster

Project 7028

dev[61]

dev[54]

dev[49]

dev[59]

Project 9859

Project 15850

- Characteristics of data set
- Massive
- Incomplete, noisy, redundant
- Complex structures, unstructured

- Classic analysis tools are often inadequate and inefficient for analyzing these data, especially in exploratory research
- What is DM (Data mining)
- Nontrivial extraction of implicit, previously unknown and potentially useful information from data.

- Feature Selection
- Given a non-negative n x m matrix V, find factors W (n, r) and H (r, m) , such that
V ≈ W *H

- This is called the non-negative matrix factorization (NMF) of the matrix V
- NMF can be used on multivariate data to reduce the dimension of the data set
- By using NMF, we can reduce dimension from m features to r features

- Given a non-negative n x m matrix V, find factors W (n, r) and H (r, m) , such that

- Feature extraction methods
- linear methods are simpler and more completely understood.
- nonlinear methods are more general and more difficult to analyze.

- Linear methods:
- ICA: Independent Component Analysis
- Matrix decomposition: PCA, SVD, NMF

- In practice, NMF is most popular and simple.
- Dimensionality reduction is effective if the loss of information due to mapping to a lower-dimensional space is less than the gain due simplifying the problem.

- Feature-based Clustering
- Grouping data into K number of clusters based on features.
- The distance metrics used is Euclidean distance like
- Hierarchical K-Means is used.
- The result is a binary tree.
- The root is the whole data set and the leaf clusters are the fine-grained clusters, which are the resulting K clusters.

- Case Study Result II
- Unsupervised learning
- K-Means method used to cluster the project history using the features we selected
- We named the clusters using ID and the results are shown in the table
- The result is not acceptable by evaluation

- Evaluation test set generation
- Popular/unpopular projects
- Stratified sampling to make 500 projects

- Feature sets used
- Popular feature set
- Activity Feature set (Page 34, Table 3.2)
- Network Feature set (Page35, Table 3.3)

- Generating rules for the test sets
- Calculating the support and confidence value

- The algorithm has remained extremely popular because it converges extremely quickly in practice. In fact, many have observed that the number of iterations is typically much less than the number of points.
- K-Means is most successful algorithm in large data set (size>1000, dimension > 2) than GA and Evolution
- CLIQUE is sensitive to noise
- CURE is not scalable O(n2logn)
- CLARANS & BIRCH are not good for high dimension data
- D. Arthur, S. Vassilvitskii (2006): "How Slow is the k-means Method?," Proceedings of the 2006 Symposium on Computational Geometry (SoCG).

- It maximizes inter-cluster (or minimizes intra-cluster) variance, but does not ensure that the result has a global minimum of variance. Multiple run is needed.
- Elbow criterion

Simulation model procedure

- Poisson Process:
- It expresses the probability of a number of events occurring in a fixed period of time if these events occur with a known average rate, and are independent of the time since the last event.
- PDF:

- Log-normal distribution:

- Kolmogorov-Smirnov test
- Used to determine whether two underlying one-dimensional distributions differ.
- Two one-sided K-S test statistics are given by

- Chapter III (data mining)
- JMLR: G. Hamerly, E. Perelman..Using machine learning to guide simulation (Feb. 2006)
- JSS: S. Kim, J. Yoon..Shape-based retrieval in time-series database (Feb. 2006)

- Chapter IV (network analysis)
- JNSM: Special Issue Self-Managing Systems and Networks
- JoSS: The Journal of Social Structure (JoSS) is an electronic journal of the International Network for Social Network Analysis (INSNA)

- Chapter V (computer simulation)
- SSC 2007: simulation co
- IEEE/CSE: E. Luijten..Fluid simulation with monte carlo algorithm (2006 Vol. 8, Issue 2)

- Chapter VI (research collaboratory)
- CITSA 2007: L. Koukianakis..A system for hybrid learning and hybrid psychology (2005)
- JCSA: S. Chen, K. Wen..An Integrated System for Cancer-Related Genes Mining from Biomedical Literatures (2006)