Sedna is an open-source

database management system In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and an ...

that provides native storage for

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...

data. The distinctive design decisions employed in Sedna are (i)

schema Schema may refer to: Science and technology * SCHEMA (bioinformatics), an algorithm used in protein engineering * Schema (genetic algorithms), a set of programs or bit strings that have some genotypic similarity * Schema.org, a web markup vocab ...

-based clustering storage strategy for XML data and (ii)

memory management Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of Resource management (computing), resource management applied to computer memory. The essential requirement of memory manag ...

based on layered address space.Ilya Taranov et al. Sedna: native XML database management system (internals overview). In ACM SIGMOD '10: Proceedings of the 36th international conference on Association for Computing Machinery's Special Interest Group on Management of Data, pages 1037-1045, New York, NY, USA, 2010. ACM.

Data organization

Data Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted for ...

organization in Sedna is designed with the goal of providing a balance in

performance A performance is an act or process of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Performance has evolved glo ...

between XML queries and updates execution. The two primary design decisions in data organization in Sedna are: # ''Direct'' pointers are used to represent XML node relationships such as parent, child, and sibling ones. Unlike relational-based approaches that require performing joins for traversing an XML document, traversing in Sedna is performed by simply following a direct pointer. # A ''descriptive

-driven storage strategy'' is developed which consists of clustering nodes of an XML document according to their positions in the descriptive schema of the document. In contrast to a prescriptive schema that is known in advance and is usually specified in DTD or

XML Schema An XML schema is a description of a type of XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed by XML itself. These constrai ...

, the descriptive schema is generated from data dynamically (and is maintained incrementally) and represents a concise and an accurate

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

summary for data. Using the descriptive schema instead of the prescriptive one makes the storage strategy applicable to any XML document, even a one that comes with no prescriptive schema. The following figure illustrates the overall principles of data organization in Sedna. The descriptive schema represented as a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

of schema nodes is the central component in the data organization. Each schema node is labeled with an XML node kind M.F. Fernandez, A. Malhotra, J. Marsh, M.Nagy, and N. Walsh (editors). XQuery 1.0 and

XPath XPath (XML Path Language) is an expression language designed to support the query or transformation of XML documents. It was defined by the World Wide Web Consortium (W3C) in 1999, and can be used to compute values (e.g., strings, numbers, or ...

2.0 Data Model (XDM).

W3C Recommendation The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...

World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...

, January 2007. (e.g. ''element'', ''attribute'', ''text'', etc.) and has a pointer to data blocks that store XML nodes corresponding to the given schema node. Depending on their node kind, some schema nodes are also labeled with

names A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A person ...

(e.g., element nodes, attribute nodes). Data blocks related to a common schema node are linked via pointers into a bidirectional

list A list is a Set (mathematics), set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of t ...

. Node descriptors in a list of blocks are partly ordered according to document order.S. Boag, D. Chamberlin, M. F. Fernandez, D. Florescu, J. Robie, and J. Simeon (editors). XQuery 1.0: An XML query language.

W3C recommendation The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...

, January 2007

Citations

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External links

Sedna project homepage
Free database management systems XML databases Database-related software for Linux