Some Issues to be Concerned in our Research

There are 2 parts in the work of next month, one of them is about research, and the other is about the implementation of the Demo. Now, let's take a close look at what we should do with the research work first. (The other part will be checked soon. )

1. Query extension - XPath & XQuery: we could introduce the evaluation of complex queries in our work. We have two choices:
1. Define the intermediate representation of the query. Then, transformation from XPath or XQuery to the intermediate form should be defined. 
2. Another one is to equivalently transform the XQuery into one XPath query expression or one set of XPaths queries etc. 
2. Dealing with the branch queries: (necessary, since we want to handle more complex queries in XPath)
1. In our current work, we can process the simple path query by means of k-shortest paths algorithm in the directed graph. 
2. When the branch query is concerned, we could make use of the existing algorithm like k-shortest paths, to finish the evaluation. 
1. The assumption is that we should have a way to measure the 'agreement' of the branch, like that of the path. (More general definition of agreement. )
2. Another question is related to the way how to get the instance satisfying the branch query from the directed graph. The possible solutions include:
1. JOIN method: splitting the branch query into path queries,  evaluating each path query, and finally joining all instances from each path query. 
2. some holistic query-evaluating algorithm could be used to process the branch queries, for instance Prufer sequence gives a choice to evaluate the branch query holistically. 

       One problem is that most of holistic algorithms require tree-like data modal, not         the directed         graph. Therefore, algorithms to find spanning tree in the directed         graph may firstly be exploited in this case.

3. The last issue is about the definition of conflicts in our paper. It might need improving in the new situation where complex queries compared with the path query, are involved.

1. In sum, we (actually it's me) should do something to try solving problems above. I have a very simple plan, as follows:
1. XPath and XQuery 
1. write a report on the basic knowledge of these two concepts.
2. Path query --> Branch query
1. implement the Join algorithm to evaluate the branch query
2. implement the holistic query evaluating algorithm to evaluate the branch query.
3. Understand the current definition of conflicts in our paper, and summarize the properties of the conflicts. It should be able to handle more complex cases about conflicts, like those among path instances that have different sources or sinks.