In a class hierarchy, a “role set ” is t,he set of classes where an object may reside simultaneously. A “migration pattern ” is a sequence of role sets. A “migration inventory, ” which is a set, of migrat,ion patterns, is viewed as a dynamic const,raintm on ohjrct migration. A set of transact ious is “sound ” wrt a11 inventory if it. generates only pat.t.t~rns in the invrntory; “complete ” if all pat,terns in the invent,ory can be generated. An initial stucly on characterizing migration inventories of transact,ions is presented. Three update languages are considered: SL which contains five operat,ors, CSL+ which ext rn(ls SL wit.h posit.ivc conditionals, and CSL which allows hot,h positive and negative condit.ionals. Four kinds of invent.orics are studied based on ln~znrss and znj~~,rtl~ntr s/art. It is shown that inventories produced by SL t,ransactions are regular and every regular inventory can be generated by SL transactions. Soundness and complet,eness for SL t,ransactions are decidahlt3. lnvc\llt,orics gpnrrated by CSL (CSL+) t,ra.nsactions arc r.e‘. and every r.e. inventory can be generat,rd by (:SL+ (CSL) transa.ctions under nonimmediate st,art,. It is also show t,hat, every r.e. immediate-start invent,ory can be obtained by a left quotient, of t,he invent,ory of CSL+ (CSL) transactions hy a regular seb. The exact, charact#erizat.ions are open. However, cvrry contrxl-frcr srt can be generat,ed. Soundness and rmllplPt~enms for ($1, (CSL+) t,ransa.ctions are undecidahlr. 1

. Although quality issues such as accuracy, security, and performance are often crucial to the success of a software system, there has been no systematic way to achieve quality requirements during system development. We offer a framework and an implemented tool which treat quality requirements as goals to be achieved systematically during the system development process. We illustrate the process that a developer would go through, in building quality into a system. We have tested the framework on a number of studies involving a variety of quality requirements, organisational settings, and system types. Keywords: non-functional requirements, accuracy, security, performance, information systems, process, software quality, defect detection, conflicts. 1 Problem Software development is traditionally driven by functional requirements, i.e., the desired functionality of the system. For example, a credit card system should debit and credit accounts, check credit limits, charge interest, issue...

Non-functional requirements (or Quality Requirements, NFRs) such as confidentiality, performance and timeliness are often crucial to a software system. Concerns for such NFRs are often the impetus for change. To systematically support system evolution, this paper adapts the "NFR-Framework" which treats NFRs as goals to be achieved during development. Throughout the process, consideration of design alternatives, analysis of tradeoffs and rationalisation of design decisions are all carried out in relation to the stated goals, and captured in historical records. We show how such historical records of treating NFRs as goals also systematically support system evolution. This approach is illustrated by a study of changes in loan policies at Barclays Bank. The study considered changes in NFRs, and associated changes in priorities, workload and functionality. The study's historical records helped quickly determine the impact of changes. We also present guidelines for consistently managing hist...

In this paper we present the Data and Knowledge Model (DK-model) that integrates the representation of data and certain types of knowledge in a semantic data model. The ER model is used as a basis for the DK-model. The main features of the DK-model are modularity of modelling, generalization/specialization hierarchies, deductive capabilities in the form of so-called virtual attributes, and inheritance of attributes and knowledge rules. Virtual attributes do not have a static value, but an associated knowledge rule that states how to compute their value. These knowledge rules are specified declaratively in a Datalog-like way. Because virtual attributes are subject to inheritance they allow for a modular, non-redundant definition of knowledge rules. The mapping of knowledge rules, which describe virtual attributes, onto Relational Algebra is also described. This leads to an efficient, set-oriented way of solving queries. 1 Reflections on Databases and Knowledge The need for semantic dat...