Theory

Schema Evolution and the Relational Algebra

Authors: 
McKenzie, L.E.; Snodgrass, R.T.
Year: 
1990
Venue: 
Inf. Syst. 15(2): 207-232 (1990)

The authors discuss extensions to the conventional relational algebra to support both aspects of transaction time, evolution of a database's contents and evolution of a database's schema. They define a relation's schema to be the relation's temporal signature, a function mapping the relation's attribute names onto their value domains, and class, indicating the extent of support for time. They also introduce commands to change a relation, now defined as a triple consisting of a sequence of classes, a sequence of signatures, and a sequence of states.

Inheritance of Workflows An approach to tackling problems related to change

Authors: 
van der Aalst, Wil M.P.; Basten, T.
Year: 
2002
Venue: 
Journal of Theoretical Computer Science, 2002

Inheritance is one of the key issues of object-orientation. The inheritance mechanism allows for the definition of a subclass which inherits the features of a specific superclass. When adapting a workflow process definition to specific needs (ad-hoc change) or changing the structure of the workflow process as a result of reengineering efforts (evolutionary change), inheritance concepts are useful to check whether the new workflow process inherits some desirable properties of the old workflow process.

Schema Evolution for XML: A Consistency-preserving Approach

Authors: 
Bouchou, B.; Duarte, D.; Halfeld, M.; Alves, M. H. F.; Laurent, D.; Musicante, M.
Year: 
2004
Venue: 
29th International Symposium, Mathematical Foundations of Computer Science MFCS 2004

This paper deals with updates of XML documents that satisfy
a given schema, e.g., a DTD. In this context, when a given update
violates the schema, it might be the case that this update is accepted,
thus implying to change the schema. Our method is intended to be used
by a data administrator who is an expert in the domain of application of
the database, but who is not required to be a computer science expert.
Our approach consists in proposing different schema options that are
derived from the original one. The method is consistency-preserving:

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