Examples of a successor-state axiom

Give two examples of a successor-state axiom that might appear in the knowledge base. One of these should in addition address the ramification problem. Explain how it does this. It means the control strategies without the motion will never lead to the solution. [7 marks] (iv) User mike gives his folder project the following access-control list: project Allow Access mike: full-access (oi,ci) Allow Access alice: read-execute (camp) Allow Access bob: read-only (oi) It contains one folder and two text files, none of which have any noninherited access-control entries: projectdoc.txt projects projects rcmain.c 15 Communicating Automata and Pi Calculus Concurrent processes are defined by the syntax – P ::= Ahb1, . . . , bni. For a transaction model based on objects and object operation time-stamps: (a) (i) Define how conflict may be specified in terms of object operation semantics. (ii) Give an example of conflicting operations. (iii) Give an example of non-conflicting operations that would be defined as conflicting under read-write semantics. [3 marks] (b) Define the necessary and sufficient condition for two transactions to be serializable. Give an example of a non-serializable execution of a pair of transactions. [3 marks] CST.2005.5.8 7 Comparative Programming Languages – Most large programs that have been written with considerable care and thoroughly checked still seem to contain bugs at a rate of over one per 3000 lines of source code. Systems involving hundreds of millions of lines of code can thus be expected to contain tens of thousands of potentially catastrophic errors. For each of these three objects, list all inherited access-control entries, showing in parentheses the inheritance-control flag bits that are set (using the same notation as above). The second requirement is that it is systematic, that is, it corresponds to the need for global motion as well as for local motion. This is a clear condition that neither would it be rational to fill a jug and empty it repeatedly, nor it would be worthwhile to move a piece round and round on the board in a cyclic way in a game. We shall initially consider two systematic approaches for searching. Define the necessary and sufficient condition for any number of transactions to be serialisable. [1 mark] (d) Discuss how the following methods of providing concurrency control in database systems enforce the properties defined above. (i) Strict two-phase locking. [4 marks] (ii) Strict timestamp ordering. [4 marks] (iii) Optimistic concurrency control. [5 marks] What is meant by spatial locality of reference? [2 marks]