-160. Laasch, C. and Scholl, M. 1993. Deterministic semantics of set-oriented update sequences. In Proceedings, Ninth International Conference on Data Engineering (1993), pp.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... of declarative updates to be orthogonal to the problem of using semantic knowledge in query optimization and assume that the queries we consider are safe with regard to update (which not necessarily implies that updates are not allowed ) For a discussion of problems related to updates see [11][22]. 4 to results of theoretical interest, namely a classification of the way methods appear in algebraic representations of queries, and how equivalences can be derived from specifications of the semantics of methods. Second, we propose a design that allows to realize the possibilities we have ....

C. Laasch, M. Scholl: "Deterministic Semantics of Set-Oriented Update Sequences", Proc. 9th ICDE, pp. 4--13, Vienna, Austria, April 19--23, 1993.

....in which records are processed has an influence on the resulting database state. In this paper we consider only one special type of update queries, namely the application of one update operation to a set of objects that is determined by a read only query. It has already been stated in [2] and [13] that a non deterministic evaluation of update queries is caused by conflicts between the database access operations that are executed during the evaluation. If conflicts occur between update operations that are applied to different receivers, the update query can only be evaluated ....

....are executed during the evaluation. If conflicts occur between update operations that are applied to different receivers, the update query can only be evaluated non deterministically, even if the set oriented strategy is applied. Approaches for detecting this case have been described in [2] and [13]. In this paper, we assume that the update queries can be evaluated deterministically, i.e. they give a unique result when evaluated using the set oriented strategy. In this case, conflicts may still occur between the update and the read operations in the evaluation. But these conflicts only have ....

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C. Laasch, M. Scholl: "Deterministic Semantics of Set-Oriented Update Sequences". Proc. 9th ICDE, pp. 4--13, Vienna, Austria, April 19--23, 1993.

....language, from which methods containing SQL like statements would be automatically derived. In this paper we propose a set oriented rule based method definition language. An important issue in defining the semantics of a language supporting set oriented updates is related to non determinism [3, 14]. Because of nondeterminism, set oriented updates may lead to different correct database states. Therefore, an important goal of our work is to define a language with a deterministic semantics. Then, we show how, relying on such a semantics, relevant properties of methods can be formally stated ....

....correct update sequences are semantically correct. Moreover the sharp distinction between the phase in which bindings are collected and the update phase is not convenient for our language in which updates can be method calls. Another possible approach is that of object oriented update sequences [14]. In this approach u 1 ; u n is considered as a sequence, in the real meaning of the word (one update after the other) Such sequence must be executed, in the established order, on each single object in B. In this case the order in which the objects in B are chosen to perform the updates must ....

C. Laasch and M. H. Scholl. Deterministic Semantics of Set-Oriented Update Sequences. In Proc. Ninth IEEE Int'l Conf. on Data Engineering, 1993.

....order independence, parallelization is always possible; we actually show that for key orderindependent methods the sequential and the parallel semantics coincide. Our work relates to a lot of other work reported in the literature on database query and update languages. Recently, Laasch and Scholl [14] studied order independence of updates expressed as sequences of generic operations such as insert, delete and modify, in the context of object oriented databases. They argued that the problem directly links to issues in concurrency control, and proposed to disallow the use of potentially ....

C. Laasch and M.H. Scholl. Deterministic semantics of set-oriented update sequences. In Proceedings, Ninth International Conference on Data Engineering, pages 4--13. IEEE Computer Society Press, 1993.

....language that allows certain forms of parallelism in its expressions. These forms are not at all specific for our language, and we believe that many object oriented languages that allow set expressions do indeed suffer from the problem. The problem has already been studied by a couple of authors [ChHa80,DCBM90,HuSu89, HuYo91,LaSc93]. We give two illustrations of the problem in TM syntax. First of all consider the following expression: collect m[x] for x in S iff p(x) which calculates the set of m[x] expressions for each x in S for which p(x) holds. Now consider the fact that the method m, as a side effect, updates some ....

C. Laasch & M. H. Scholl, "Deterministic semantics of set-oriented update sequences," in Proceedings Ninth International Conference on Data Engineering, Vienna, Austria, April 19--23, 1993, IEEE Computer Society Press, Washington, DC, 1993, 4--13.

....rematerialise the whole table. Hau95] gives a more detailed BOT(1) T1.1 T1.2 T1.3 T1.4 T1.5 EOT(1) Figure 4: The dependency graph for the transaction hierarchy description of the implementation of the COOL update operations, while [Stu96] implements the update sequence iterator apply to all [LS93] 4.3 Logging and Recovery Strategy If a COOL transaction has to be aborted, not yet committed subtransactions will be aborted by the RDBMS. However, since subtransactions are committed on the RDBMS before the COOL transaction is committed, it is necessary to compensate the committed ....

Christian Laasch and Marc H. Scholl. Deterministic Semantics of Set-oriented Update Sequences. In Proceedings of the IEEE Conference on Data Engineering, pages 4--13, Vienna, April 1993.

....can be performed by methods as combinations of the above operations. Again, we do not propose a full method language here, but only employ the two most basic constructs: besides sequencing, the iterator apply to all provides set oriented application of update sequences with deterministic semantics [13]: u = u ; u = composition of updates = j apply to all [u] e) set oriented application of updates = 3 Semantics of BCOOL In the denotational approach, the semantics of a language is defined by (higher order) functions [24] A semantic domain represents interpreted constructs used as the ....

.... (see the notion of O isomorphisms in [2] Therefore, we take the freedom to allow the nondeterministic invention of object identities: This is certainly desirable on the implementation level, furthermore it allows new operations to be executed in parallel within an apply to all statement [13]. new ( fi Object E[ new ( oe = o with o 2 [ o 62 oe( Active domains of object types are returned by the operation adom: f1 ; fn ] fi Object adom ( f1 ; fn ] f[f1 ; fn ]g E[ adom ( f1 ; fn ] oe = oe( f1 ; fn ] Lambda abstractions ....

[Article contains additional citation context not shown here]

C. Laasch and M.H. Scholl. Deterministic semantics of set-oriented update sequences. In Proc. of the IEEE Conf. on Data Engineering, pages 4--13, Vienna, Austria, April 1993.

....identities. Therefore, we can not fix the relationship between an object and its type as of the time of object creation. All of the basic updates are single object operators. They can be applied to a whole set of objects (e.g. a set obtained by a query) by using the set iterator apply to all [LS92a] As is known for long in the relational context, it is nontrivial to combine set orientation and updates, since non deterministic effects arise very easily. We have developed a formal model for set oriented updates which essentially restricts updates to non conflicting ones in order to be ....

C. Laasch and M.H. Scholl. Deterministic semantics of set-oriented update sequences. Submitted for Publication, 1992.

.... (see the notion of O isomorphisms in [AK89b] Therefore, we take the freedom to allow the non deterministic invention of object identities: This is certainly desirable on the implementation level, furthermore it allows new operations to be executed in parallel within an apply to all statement [LS93] new ( Object E[ new ( oe = o with o 2 [ o 62 oe( Active domains of object types are returned by the operation adom: f 1 ; f n ] Object adom ( f 1 ; f n ] f[f 1 ; f n ]g E[ adom ( f 1 ; f n ] oe = oe( f 1 ; f n ] Sets ....

....of conflicts: Conflicts can be avoided if the applicability of instructions is restricted. Therefore, we also state the restrictions. For a detailed discussion of this trade off and a discussion of the strong similarities between the apply to all instruction and semantic concurrency control see [LS93] The sign means that two operations do not conflict, and the variable self is the iterator variable: i.e. self denotes the object that is associated to the thread. Since the conflict relation is symmetric, the values of the conflict relation for empty cells are specified by changing row and ....

C. Laasch and M.H. Scholl. Deterministic semantics of set-oriented update sequences. In Proc. of the IEEE Conf. on Data Engineering, pages 4--13, Vienna, Austria, April 1993.

....and by means of gain lose operations throughout their lifetime) Both features are not included in the ODMG proposal, but they are mentioned as planned for the final release. In order to provide more flexible (object preserving) query functionality, we added this from the beginning (see also (Laasch and Scholl 1993a, Schek and Scholl 1990)) Furthermore, we adopt the BCOOL approach to arrange object types into a lattice (as opposed to just an arbitrary (multiple) hierarchy) such that (object preserving) projections ( casts in the OQL terminology) need not be restricted to named supertypes present in the ODB schema. ODL types are ....

Laasch, C. and Scholl, M. H.: 1993b, Deterministic Semantics of Set-Oriented Update Sequences, Proc. of the IEEE Intl. Conf. on Data Engineering, pp. 4--13.

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-160. Laasch, C. and Scholl, M. 1993. Deterministic semantics of set-oriented update sequences. In Proceedings, Ninth International Conference on Data Engineering (1993), pp.

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