Journal ArticleDOI
The Lorel Query Language for Semistructured Data
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TLDR
The main novelties of the Lorel language are the extensive use of coercion to relieve the user from the strict typing of OQL, which is inappropriate for semistructured data; and powerful path expressions, which permit a flexible form of declarative navigational access and are particularly suitable when the details of the structure are not known to the user.Abstract:
language, designed for querying semistructured data. Semistructured data is becoming more and more prevalent, e.g., in structured documents such as HTML and when performing simple integration of data from multiple sources. Traditional data models and query languages are inappropriate, since semistructured data often is irregular: some data is missing, similar concepts are represented using different types, heterogeneous sets are present, or object structure is not fully known. Lorel is a user-friendly language in the SQL/OQL style for querying such data effectively. For wide applicability, the simple object model underlying Lorel can be viewed as an extension of the ODMG data model and the Lorel language as an extension of OQL. The main novelties of the Lorel language are: (i) the extensive use of coercion to relieve the user from the strict typing of OQL, which is inappropriate for semistructured data; and (ii) powerful path expressions, which permit a flexible form of declarative navigational access and are particularly suitable when the details of the structure are not known to the user. Lorel also includes a declarative update language. Lorel is implemented as the query language of the Lore prototype database management system at Stanford. Information about Lore can be found at http://www-db.stanford.edu/lore. In addition to presenting the Lorel language in full, this paper briefly describes the Lore system and query processor. We also briefly discuss a second implementation of Lorel on top of a conventional object-oriented database management system, the O2 system.read more
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Dissertation
Graph summarisation of web data: data-driven generation of structured representations
TL;DR: A formal model for graph summarisation and how to generate a summary is presented, which uses that model to compute precise summaries using the bisimulation equivalence relation and is argued for the case of approximate graph summaries as the most viable option for many applications.
Journal ArticleDOI
DVQ: Towards Visual Query Processing of XML Database Systems
TL;DR: A DTD-driven visual query interface for XML database systems that a user can easily form path-expression based queries by clicking elements in the DTD tree displayed on the screen and supplying conditions if necessary.
Book ChapterDOI
Approximate Answers in Databases of Labeled Objects
TL;DR: Some problems concerning approximate answering to queries in databases of labeled objects representing semistructured data and some novel theorems relevant to the problem are formulated are discussed.
Proceedings ArticleDOI
Mediated information gain
Joachim Biskup,David W. Embley +1 more
TL;DR: This work identifies a "mediation task" as an extended amalgamation of searching, querying and updating in traditional information systems, and introduces the notion of a "formal information state" which unifies and extends the classical notions of a schema, an instance, a query with additional specifications, and a returned answer.
Dissertation
Modelos de Base de Datos de Grafo y RDF
TL;DR: The main contribution of the thesis is to have clarified and developed the relation ship between RDF and graph database models, by formally defining a graph visualization model for RDF.
References
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Query evaluation techniques for large databases
TL;DR: This survey describes a wide array of practical query evaluation techniques for both relational and postrelational database systems, including iterative execution of complex query evaluation plans, the duality of sort- and hash-based set-matching algorithms, types of parallel query execution and their implementation, and special operators for emerging database application domains.
Book
The object database standard: ODMG 2.0
R. G. G. Cattell,Douglas K. Barry,Dirk Bartels,Mark Berler,Jeff Eastman,Sophie Gamerman,David Jordan,Adam Springer,Henry Strickland,Drew Wade +9 more
TL;DR: With this book, standards are defined for object management systems and this will be the foundational book for object-oriented database product.
Proceedings ArticleDOI
Object exchange across heterogeneous information sources
TL;DR: An object-based information exchange model and a corresponding query language are defined that are well suited for integration of diverse information sources and used to integrate heterogeneous bibliographic information sources.
Book ChapterDOI
Querying Semi-Structured Data
TL;DR: The main purpose of the paper is to isolate the essential aspects of semistructured data, and survey some proposals of models and query languages for semi-structured data.