1 CIS607, Fall 2005 Semantic Information Integration Presentation by Dong Hwi Kwak Week 5 (Oct. 26)

2 Questions from Homework 3 Some concepts: – Could you explain skolem functions in more detail (perhaps with an easy to understand example)? – Shiwoong – Could you explain the deep-union in more detail? – Shiwoong – In figure 4, I take quantifiers apply for all variables. Are skolem functions arbitrary? -- Enrico

3 Questions from Homework 3 About the algorithms in Clio – Does the mapping generator find anything more than 1-1 correspondences? -- Amanda – Is the grouping algorithm used based entirely on the syntax of the schema? -- Enrico – Since the mappings connect very large data systems, efficiency would be a very important factor. What’s the efficiency about Clio? -- Jiawei – In the mapping generation component of Clio, how to decide which group of correspondences to use in a logical mapping? What’s the current solution, and how important it is? – Jiawei – What are the criteria to decide whether the end-points in schemas are related? Name, data attributes, taxonomy? How about those elements and attributes which do not present in both source and target? Just ignore them? -- Dayi

4 Questions from Homework 3 (cont ’ d) Other questions about this paper: – Does this work between two semi-related schemas? -- Amanda – Can you explain the description in page 807: “The use of collection-bound variables (rather than that of arbitrarily bound variables) has the advantages that the resulting notation maps easily to efficient iteration patterns (e.g., the from clause of SQL, or the for loops of XQuery/XSLT).” Can you give an example for this? -- Zebin – Can you clarify the theoretic limitation/difference of relational database (or the model they use) and the output language, e.g. XSLT, XQuery, etc. The paper did mention that they are not equally expressive,but I can’t find the exact definition. Their sample case explains one constrain that can be expressed in the hierarchical XML. Any other constraint? -- Zebin – Want to see the comparison with other systems and how much user input are needed for the best performance? -- Dayi