I discussed with Dr.Candan about my research on Null Value last afternoon. In the meeting, we decided to put focus on the understanding what our tasks are first of all, based on which we could introduce an indexing structure for the graph representing all assertions in the XML document. 

First of all, the definition and property of the compatibility should be brought up in order to develop a  deep discussion. Basically, the compatibility is kind of property among two objects. In our case, we can say (a) one path instance is compatible with the other path instance, or (b) one path instance is compatible with a set composed of many path instances, or (c) a set of path instances is compatible with the other set. It's easy to understand the relationship of compatibility between two path instances based on the definition we introduced in the paper.  When a set is concerned, such as (b) and (c), each elements in the set should be considered. To satisfy compatibility defined in (b) one path instance should be compatible with every element in the set, and so is (c).  In addition, we call a universe here to be a set of compatible path instances for one path query. 

An operator is defined to represent the compatibility relation among objects, which is ~. 

1. Given a path query q, we have path instances p_1 and p_2. Then, 

• p_1 ~ p_2 iff. both of them satisfy constraints defined by 1-4.

2.  Given a path query q, we have a path instance p' and a set of path instances P = {p_1, p_2, ..., p_N}. Then,

• p_1 ~ P iff. for each p_i in P, p ~ p_i.

3.  Given a path query q, we have two sets of path instances P = {p_1, p_2, ..., p_N} and Q = {q_1, q_2, ..., q_M}. Then, 

• P ~ Q iff for each p_i in P, p_i ~ Q. 

There are three categories of tasks we have to deal with:

Given a path query q, we can get a set of instances of q as P = {p_1, p_2, ..., p_N}. 

1. Compatibility Checking

• Check whether P is a universe, i.e., is there any pair of elements in P which are not compatible.
• Given an instance p' of the query q, decide whether p' ~ P.
• Given an instance p' of the query q, decide whether p' !~ p_i. ('!~' means the 'not compatible') 

Given all instances U = {p_1, p_2, ..., p_N} for a path query q, we can build a set of subsets of U, U = {V_1, V_2, ..., V_M}.  Each subset V_i includes some elements in U, all of which are compatible to each other. 

2. Ranking all instances for a path query based on the compatibility

3. Set operations based on the compatibility

"The Daffodils"

by: William Wordsworth

 I wandered lonely as a cloud

That floats on high o'er vales and hills, 

When all at once I saw a crowd, 

A host, of golden daffodils; 

Beside the lake, beneath the trees, 

Fluttering and dancing in the breeze. 

Continuous as the stars that shine

And twinkle on the milky way, 

They stretched in never-ending line

Along the margin of a bay: 

Ten thousand saw I at a glance, 

Tossing their heads in sprightly dance. 

The waves beside them danced; but they

Out-did the sparkling waves in glee: 

A poet could not but be gay, 

In such a jocund company: 

I gazed -- and gazed -- but little thought

What wealth the show to me had brought: 

For oft, when on my couch I lie

In vacant or in pensive mood, 

They flash upon that inward eye

Which is the bliss of solitude; 

And then my heart with pleasure fills, 

And dances with the daffodils.

Progression of Null Values

1. Assertions: definition and semantics
2. Graph
3. Data structure (indexing)
4. Path query processing
5. Validation and Compatibility Checking
6. Different worlds composing

Firefox, and GoSurf

Some days ago, I happened to use the browser firefox, and found that there are so many good extensions for it. With these extensions, the armed firefox could almost finish any kind of task you can image, such as dragging links, undoing closed tabs, managing tabs etc. The extensions I think much of include:

• Tab Mix Plus - More tweaks added to tabs. Ability to select and open muliple links in tabs, open link in a duplicated tab, merge tabs and close tabs from similar domain…

• Undoclosetab - Allows accidently closed recent tabs to be reopened

• Restart Firefox - Adds “Restart Firefox” menuitem to “File”, and a toolbar button for easy restarting. Great for when you install themes or extensions and need to restart Firefox.

• IE Tab - can open the current page or a selected link embedding Internet Explorer in tabs of Mozilla/Firefox. Very useful for those IE only pages.

• SuperDrag&Go - Drag a link or picture and throw it anywehere on your webpage (content area) and open it on a new tab.

• FlashGot - handles single and massive downloads with several external Download Managers.

All of descriptions above are extracted from the webpage: 50 Best Firefox Extensions for Power Surfing.

Just when I started to get used to the new browser, I get the newer version of GOSURF, which is an IE-based explorer. There are some new features with the latest GOSURF, and the most important is that it improves the memory management. While using the new GOSURF, the management of memory used becomes much more flexible. For example, the process for GOSURF could reallocate the memory each time you switch to other program, so that the memory used by GOSURF can be kept in the low level. The memory hold by the process but not used for the moment can be released, although maybe more workload is added to the CPU. In summary, the first glance on the feature makes it interesting enough. Additionally, GOSURF seems to some other new features including new search bar (just like what it is in the firefox!!). And then I decided to go back to GOSURF that I have been used to for a long while. The firefox is good, but it might not be good enough for me to switch to it.

"You have to dream, you have to have a vision, and you have to set a goal for yourself that might even scare you a little because sometimes that seems far beyond your reach. Then I think you have to develop a kind of resistance to rejection, and to the disappointments that are sure to come your way. " – Gregory Peck