Topic
Path expression
About: Path expression is a research topic. Over the lifetime, 871 publications have been published within this topic receiving 30607 citations.
Papers published on a yearly basis
Papers
TL;DR: 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.
1,314 citations
Proceedings Article•
11 Sep 2001
TL;DR: Wang et al. as mentioned in this paper proposed a new system for indexing and storing XML data based on a numbering scheme for elements, which quickly determines the ancestor-descendant relationship between elements in the hierarchy of XML data.
Abstract: With the advent of XML as a standard for data representation and exchange on the Internet, storing and querying XML data becomes more and more important. Several XML query languages have been proposed, and the common feature of the languages is the use of regular path expressions to query XML data. This poses a new challenge concerning indexing and searching XML data, because conventional approaches based on tree traversals may not meet the processing requirements under heavy access requests. In this paper, we propose a new system for indexing and storing XML data based on a numbering scheme for elements. This numbering scheme quickly determines the ancestor-descendant relationship between elements in the hierarchy of XML data. We also propose several algorithms for processing regular path expressions, namely, (1) -Join for searching paths from an element to another, (2) -Join for scanning sorted elements and attributes to find element-attribute pairs, and (3) -Join for finding Kleene-Closure on repeated paths or elements. The -Join algorithm is highly effective particularly for searching paths that are very long or whose lengths are unknown. Experimental results from our prototype system implementation show that the proposed algorithms can process XML queries with regular path expressions by up to an or
817 citations
Book•
1 Jan 2002TL;DR: In this article, a language concept for concurrent processes without common variables is introduced, where processes communicate and synchronize by means of procedure calls and guarded regions, and the concept is proposed for real-time applications controlled by microcomputer networks with distributed storage.
Abstract: A language concept for concurrent processes without common variables is introduced. These processes communicate and synchronize by means of procedure calls and guarded regions. This concept is proposed for real-time applications controlled by microcomputer networks with distributed storage. The paper gives several examples of distributed processes and shows that they include procedures, coroutines, classes, monitors, processes, semaphores, buffers, path expressions, and input/output as special cases.
463 citations
Proceedings Article•
11 Sep 2001TL;DR: The Index Fabric is described, an indexing structure that provides the efficiency and flexibility needed to optimize ad hoc queries over semistructured data, and how "refined paths" optimize specific access paths.
Abstract: Queries navigate semistructured data via path expressions, and can be accelerated using an index. Our solution encodes paths as strings, and inserts those strings into a special index that is highly optimized for long and complex keys. We describe the Index Fabric, an indexing structure that provides the efficiency and flexibility we need. We discuss how "raw paths" are used to optimize ad hoc queries over semistructured data, and how "refined paths" optimize specific access paths. Although we can use knowledge about the queries and structure of the data to create refined paths, no such knowledge is needed for raw paths. A performance study shows that our techniques, when implemented on top of a commercial relational database system, outperform the more traditional approach of using the commercial system’s indexing mechanisms to query the XML.
454 citations
25 Apr 2012
TL;DR: A brief survey of many of the graph query languages that have been proposed, focussing on the core functionality provided in these languages and issues such as expressive power and the computational complexity of query evaluation.
Abstract: Query languages for graph databases started to be investigated some 25 years ago. With much current data, such as linked data on the Web and social network data, being graph-structured, there has been a recent resurgence in interest in graph query languages. We provide a brief survey of many of the graph query languages that have been proposed, focussing on the core functionality provided in these languages. We also consider issues such as expressive power and the computational complexity of query evaluation.
426 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2024 | 1 |
| 2023 | 2 |
| 2022 | 6 |
| 2021 | 2 |
| 2020 | 4 |
| 2019 | 5 |