The XData system, currently being developed at IIT Bombay, provides an automated and interactive platform for grading student SQL queries, as well as for learning SQL. Prior work on the XData system focused on generating query specific test cases to catch common errors in queries. These test cases are used to check whether the student queries are correct or not. For grading student assignments, it is usually not sufficient to just check if a query is correct: if the query is incorrect, partial marks may need to be given, depending on how close the query is to being correct. In this paper, we extend the XData system by adding features that enable awarding of partial marks to incorrect student queries. Our system is able to go beyond numerous syntactic features when comparing a student query with a correct query. These features of our grading system allow the grading of SQL queries to be fully automated, and scalable to even large class sizes such as those of MOOCs.

Grading of student SQL queries is usually done by executing the query on sample datasets (which may be unable to catch many errors) and/or by manually comparing/checking a student query with the correct query (which can be tedious and error prone). In this demonstration we present the XDa-TA system which can be used by instructors and TAs for grading SQL query assignments automatically. Given one or more correct queries for an SQL assignment, the tool uses the XData system to automatically generate datasets that are designed specifically to catch common errors. The grading is then done by comparing the results of student queries with those of the correct queries against these generated datasets; instructors can optionally provide additional datasets for testing. The tool can also be used in a learning mode by students, where it can provide immediate feedback with hints explaining possible reasons for erroneous output. This tool could be of great value to instructors particularly, to instructors of MOOCs.

This paper presents a resource-constrained scheduling scheme that minimizes power consumption for the case when the resources operate at multiple voltages and varied clock frequency. The resource constrained scheduling is achieved by performing a constructive, force-directed scheduling. The proposed algorithm consists of two phases, the voltage assignment phase and the clock frequency variation phase. It also includes a pre processing phase of node minimization, where redundant nodes are eliminated. In the first phase the assignment of voltages to each functional unit is performed based on its occurrence on the critical path. In the next stage, the clock frequency for each control step is varied by using the clock frequency of the maximum number of operation type in that control step. It is taken care that, the total execution delay does not exceed the timing constraint given by CP /spl les/ /spl alpha/ < 2CP, where '/spl alpha/' is a certain factor of the critical path time delay (CP). The power consumed in the level shifters is also taken into consideration. The power consumed is compared with the power consumed by operating all functional units at the maximum available voltage and maximum clock frequency. A power reduction of about 40-65% has been achieved.