The Philosophy of Portfolio
Portfolios versus electronic portfolios
According to National Learning Infrastructure Initiative (NLII), portfolios are collections of work designed for a specific objective—that is, to provide a record of accomplishments (See my search )
According to NLII, an electronic portfolio is a collection of authentic and diverse evidence, drawn from a larger archive representing what a person or organization has learned over time on which the person or organization has reflected, and designed for presentation to one or more audiences for a particular rhetorical purpose(Barrett & Carney, 2005).
To my mind, electronic portfolios (e-portfolios) are the digital versions of portfolios, which perform the service function and which content depend on target audience to permit informed judgments and decisions.
Repositories versus electronic portfolios
According to JISC (2008) Figure 1 page 7, repositories are spaces (local or remote) to store resources and an archive of evidence.
To my mind, repositories are places where large quantities of (digital or non-digital) original items are stored safe and e-portfolios are collections of digital reproduced items using modern technology.
Personalised Learning Environment (PLE) versus electronic portfolios
See my searches:
Lars Glimbert presentation (slide 4: LMS versus PLE and e-portfolio and slide 5: personal space versus community space) 
History of personal learning environments (PLE)
e-portfolio presentation 
Electronic Portfolios in Education 
Constructivist versus Positivist educational portfolios
Upon a constructivist model portfolios are considered work in process or assessment for learning. Work in process is a product that is partway trough the learning process but not yet complete. Upon a positivist model portfolios are considered products or assessment of learning. The following Table 1 summarizes the differences between Constructivist and positivist educational portfolios.
Table 1 Portfolios for learning versus portfolios for accountability, adapted from Horngren Exhibit 19-2 Management Accounting versus Financial Accounting (2005)
To my mind during the module My Learning we should focus on the concept of digital portfolio as assessment for learning as a means of presenting learning outcomes for summative assessment.
How I can use e-portfolio in my own learning and teaching
I have designed pedagogical activity using Elgg software to test the educational development in practice. 
Barrett, H. (2004). Conflicting Paradigms in Electronic Portfolio Approaches.  (Retrieved Dec. 28, 2008).
Barrett, H. and Carney, J. (2005). Conflicting Paradigms and Competing Purposes in Electronic Portfolio Development.  (Retrieved Dec. 29, 2008).
Horngren, C.T., Harrison, W.T., Bamber,L.S. (2005). Accounting. 6th ed. New Jersey: Pearson Education, Inc.
JISC (2008). Effective Practice with e-Portfolios – Supporting 21st century learning, (Retrieved Dec. 29, 2008).