Schema Evolution publication categorizer

In this paper we present a formal model for the support of temporal schema versions in object-oriented databases. Its definition is partially based on a generic (ODMG compatible) object model and partially introduces new concepts. The proposed model supports all the schema changes which are usually considered in the OODB literature, for which an operational semantics and a formal analysis of their correct behaviour is provided.

Information integration is a key challenge faced by all major organizations, business and governmental ones alike. Two research facets of this challenge that have received considerable attention in recent years are data exchange and data integration. The study of data exchange and data integration has been facilitated by the systematic use of schema mappings, which are high-level specifications that describe the relationship between two database schemas.

A schema mapping is a declarative specification of the relationship between instances of a source schema and a target schema. The data exchange (or data translation) problem asks: given an instance over the source schema, materialize an instance (or solution) over the target schema that satisfies the schema mapping. In general, a given source instance may have numerous different solutions. Among all the solutions, universal solutions and core universal solutions have been singled out and extensively studied.

We develop a new algorithm for clustering search results. Differently from many other clustering systems that have been recently proposed as a post-processing step forWeb search engines, our systemis not based on phrase analysis inside snippets, but instead uses latent semantic indexing on thewhole document content.Amain contribution of the paper is a novel strategy – called dynamic SVDclustering – to discover the optimal number of singular values to be used for clustering purposes.

Research has investigated mappings among data sources under two perspectives. On one side, there are studies of practical tools for schema mapping generation; these focus on algorithms to generate mappings based on visual specifications provided by users. On the other side, we have theoretical researches about data exchange. These study how to generate a solution -- i.e., a target instance -- given a set of mappings usually specified as tuple generating dependencies.

In this paper we study the problem of schema exchange, a
natural extension of the data exchange problem to an intensional level.
To this end, we first introduce the notion of schema template, a tool for
the representation of a class of schemas sharing the same structure. We
then define the schema exchange notion as the problem of (i) taking a
schema that matches a source template, and (ii) generating a new schema
for a target template, on the basis of a set of dependencies defined over
the two templates. This framework allows the definition, once for all,

Among other issues, database evolution includes the necessity of propagating the changes inside and between abstraction levels. There exist several mechanisms in order to carry out propagations from one level to another, that are distinguished on the basis of when and how the changes are performed. The strict mechanism, which implies the immediate realization of modifications, is a time–consuming process. In this paper we propose a solution that is closer to the lazy and logical mechanisms, in which changes are delayed or not finally realized, respectively.

Schema matching is a basic operation of data integration, and several tools for automating it have been proposed and evaluated in the database community. Research in this area reveals that there is no single schema matcher that is guaranteed to succeed in finding a good mapping for all possible domains and, thus, an ensemble of schema matchers should be considered. In this paper, we introduce schema metamatching, a general framework for composing an arbitrary ensemble of schema matchers and generating a list of best ranked schema mappings.

Translating data and data access operations between applications and databases is a longstanding data management problem. We present a novel approach to this problem, in which the relationship between the application data and the persistent storage is specified using a declarative mapping, which is compiled into bidirectional views that drive the data transformation engine. Expressing the application model as a view on the database is used to answer queries, while viewing the database in terms of the application model allows us to leverage view maintenance algorithms for update translation.

Database reengineering consists of deriving a new database from a legacy database and adapting the software components accordingly. This migration process involves three main steps, namely schema conversion, data conversion and program conversion. This paper explores the feasibility of transforming the application programs through code transformation patterns that are automatically derived from the database transformations. It presents the principles of a new transformational approach coupling database and program transformations and it describes a prototype CASE tool based on this approach.

The concept of “model” is today considered as a promising technology in domains such as
data and software engineering. In the field of model engineering, models are now viewed as
firts-class entities. This new approach makes it possible to envision the integration of models
into engineering processes. Such an integration will however require a set of dedicated tools
enabling to perform standard model operations onto handled models. We strongly believe that,
in order to achieve usability for large communinities of users, model-based tools have to rely

The basic assumption in model engineering (MDE) is to consider
models as first class entities. One of the most important kinds of models in
MDE approaches are transformation models. Transformation models define
operations between different models. However, there are many operations that
are not efficiently handled by generic model transformations. For example,
models transformations are not adapted to define and to capture relationships
between models elements. Relationships between model elements are present in

Given a multirelational database scheme and a relational mapping f transforming it, an important question is whether the resulting scheme is equivalent to the original one. This question was addressed in the literature with respect to those relational schemes that satisfy the so called universal relation assumption; however, no study was ever concerned with multirelational (data base) schemes that do not necessarily satisfy this assumption.We present two general definitions of lossless transformation of the database scheme based on the so-called closed world and open world assumptions.

Bancilhon and Spyratos [l] show how the choice of a complementary view will
select a view update translator. They claim that “User requirements impose [the
constraint that] . . . (ii) The user must have the means to cancel, if he wishes,
the effect of every update that he is allowed on the view.” (p. 562) If this
requirement is eliminated, there are other reasonable translations that become
acceptable. We present a particular view update translator that is quite reasonable,
but that does not preserve any complement, and for which the requirement
does not hold.

A temporal data warehouse can be defined as a set V of materialized views over non-temporal sources. We present a self-maintainable temporal data warehouse that, besides a set of temporal views V, has two kinds of auxiliary views: a set T of auxiliary relations containing only temporal information necessary to maintain the data warehouse and a set C of complements allowing the warehouse maintenance without consulting the source databases.

Detecting changes by comparing data snapshots is an important requirement for difference queries, active databases, and version and configuration management. In this paper we focus on detecting meaningful changes in hierarchically structured data, such as nested-object data. This problem is much more challenging than the corresponding one for relational or flat-file data.

Detecting and representing changes to data is important for active databases, data warehousing, view maintenance, and version and configuration management. Most previous work in change management has dealt with flat-file and relational data; we focus on hierarchically structured data. Since in many cases changes must be computed from old and new versions of the data, we define the hierarchical change detection problem as the problem of finding a \"minimum-cost edit script\" that transforms one data tree to another, and we present efficient algorithms for computing such an edit script.

This paper generalizes the work on the edit distance between
strings [6, 11, 13, 16, 20, 21, 25] and trees [19, 28, 29]. Various
kinds of constrained and
generalized edit distance on strings and trees have been developed
[1, 9, 10, 17, 27]. Our degree-2
distance, when applied to unordered trees, is a restricted form of
the constrained distance previously
reported in [27]. When applied to ordered trees, the degree-2
distance is a generalized
measure of the constrained distance originated from Selkow [17],
though our algorithm has the

The problems of finding a longest common subsequence of two sequences A and B and a shortest edit script
for transforming A into B have long been known to be dual problems. In this paper, they are shown to be
equivalent to finding a shortest/longest path in an edit graph. Using this perspective, a simple O(ND) time
and space algorithm is developed where N is the sum of the lengths of A and B and D is the size of the
minimum edit script for A and B. The algorithm performs well when differences are small (sequences are

We define the notion of independent views to indicate whether the range values of the two views may be achieved independently The concept of complementary views indicates when the domain element can be uniquely determined by the range values of the two complementary views We consider the relationship between independent and complementary views In unrestricted domains, a view (but not the identity or empty view) can have more than one complementary, independent view Databases, however, are more restricted domains They are finite power sets A view is monotonic if it preserves inclusion However,

Abstract. One of the most severe problems related to database evolution
is how to reflect in the data level the changes that have occurred
in the conceptual schema of a database. This is specially relevant when
evolution operations affect ISA relationships. In this paper we present
our view of the evolution of ISA relationships, focusing on the artifacts
that generate the sentences for changing the data in a consistent way.

We consider the class of path-conjunctive queries and constraints (dependencies) defined over complex values with dictionaries. This class includes the relational conjunctive queries and embedded dependencies, as well as many interesting examples of complex value and oodb queries and integrity constraints. We show that some important classical results on containment, dependency implication, and chasing extend and generalize to this class.

The problem of integrating data from multiple data sources—either on the Internet or within enterprises—has received much attention in the database and AI communities. The focus has been on building data integration systems that provide a uniform query interface to the sources. A key bottleneck in building such systems has been the laborious manual construction of semantic mappings between the query interface and the source schemas. Examples of mappings are ldquoelement location maps to addressrdquo and ldquoprice maps to listed-pricerdquo.

Learning to Map between Structured Representations of Data

The first step in finding an efficient way to solve any difficult
problem is making a complete, possibly formal, problem specification.
This paper introduces a formal specification for the problem of semantic
XML schema matching. Semantic schema matching has been extensively
researched, and many matching systems have been developed. However,
formal specifications of problems being solved by these systems do not
exist, or are partial. In this paper, we analyze the problem of seman-
tic schema matching, identify its main components and deliver a formal