摘要:
A system and method facilitating data access operations is provided. The system can facilitate an executable, instance-level interaction between a source model (e.g., schema) expressed in a first metamodel (e.g., object-oriented metamodel) and a target model expressed in a second metamodel (e.g., SQL metamodel). The system can produce instance mappings to round-trip the data between the source schema and the generated target schema. Further, an abstraction component can be employed to translate the data access operations on the object model into SQL queries and updates.
摘要:
A data access architecture may includes a mapping architecture for mapping data as may be used by an application to data as persisted in a database. Such a mapping architecture uses two types of “mapping views”—one for translating queries and the other for translating updates. A mechanism is provided that automatically generates query and update views from high-level mapping specifications. A validation may be performed to ensure that a mapping specification, when used in conjunction with a mapping architecture, allows data to “roundtrip” from the application to the database, without loss of data.
摘要:
A general-purpose reusable algebraic-based composition algorithm for composing mappings between data schemas. The algorithm handles more expressive mappings, makes a best-effort to eliminate symbols when a perfect answer cannot be obtained, includes new heuristics, and is extensible. A relational algebraic language is provided wherein each mapping is expressed as a set of constraints, and each constraint is either a containment or equality of two or more relational algebraic expressions. The composition mechanism exploits monotonicity properties of algebraic operators in operator arguments, handles NULLs and bag semantics, operates to allow composition to produce a partial result when a complete result is not possible, facilitates symbols elimination one symbol at a time using left composition, for example, as a way of isolating the symbols, supports making a best-effort to eliminate as many symbols as possible from an intermediate schema, and handles unknown or partially known operators via delayed handling.
摘要:
A data structure may exist in various representations, such as an object in an object-oriented system or a set of elements included in an extensible markup language (XML) document structured according to an XML type defined in an XML schema. While many aspects of these representations may correspond, some aspects of an XML document may not be specified by the XML schema (such as developer comments, whitespace, and preprocessor directives), and may be lost while translating an XML representation of the data structure to an object. These non-schematized aspects may be included in the object as a delta, specifying the location of an aspect with relation to an element defined by the XML schema. Preserving non-schematized aspects may promote the full representation of the data structure as an object, and may facilitate a full-fidelity regeneration of the XML document from which the object was generated.
摘要:
A general-purpose reusable algebraic-based composition algorithm for composing mappings between data schemas. The algorithm handles more expressive mappings, makes a best-effort to eliminate symbols when a perfect answer cannot be obtained, includes new heuristics, and is extensible. A relational algebraic language is provided wherein each mapping is expressed as a set of constraints, and each constraint is either a containment or equality of two or more relational algebraic expressions. The composition mechanism exploits monotonicity properties of algebraic operators in operator arguments, handles NULLs and bag semantics, operates to allow composition to produce a partial result when a complete result is not possible, facilitates symbols elimination one symbol at a time using left composition, for example, as a way of isolating the symbols, supports making a best-effort to eliminate as many symbols as possible from an intermediate schema, and handles unknown or partially known operators via delayed handling.
摘要:
A data access architecture may includes a mapping architecture for mapping data as may be used by an application to data as persisted in a database. Such a mapping architecture uses two types of “mapping views”—one for translating queries and the other for translating updates. A mechanism is provided that automatically generates query and update views from high-level mapping specifications. A validation may be performed to ensure that a mapping specification, when used in conjunction with a mapping architecture, allows data to “roundtrip” from the application to the database, without loss of data.
摘要:
Described is programmatic access to persistent XML and relational data from applications based upon explicit mappings between object classes, XML schema types, and relations. The mappings are used in data access, that is, they drive query and update processing. A query may be processed into a query for accessing the XML data and another query for second type for accessing the relational data. Mappings support strongly-typed classes and loosely-typed classes, and may be conditional upon other data, may decouple query and update translation performed at runtime from schema translation used at compile time, and/or may be compiled into transformations that produce objects from XML data and transformations that produce XML data from objects. Mappings may be generated automatically or provided by the developer.
摘要:
Described is programmatic access to persistent XML and relational data from applications based upon explicit mappings between object classes, XML schema types, and relations. The mappings are used in data access, that is, they drive query and update processing. A query may be processed into a query for accessing the XML data and another query for second type for accessing the relational data. Mappings support strongly-typed classes and loosely-typed classes, and may be conditional upon other data, may decouple query and update translation performed at runtime from schema translation used at compile time, and/or may be compiled into transformations that produce objects from XML data and transformations that produce XML data from objects. Mappings may be generated automatically or provided by the developer.
摘要:
Computers are provided with a totally ordered, durable shared log. Shared storage is used and can be directly accessed by the computers over a network. Append-log operations are made atomic in the face of failures by committing provisional append ordering information onto a log. The log may comprise multiple flash packages or non-volatile memory devices, referred to as segments, although any shared storage device(s) may be used. Each log record is a multi-page stripe, where each page of a stripe is written to a different segment. Fault-tolerant protocol variants append stripes to the log, such that stripes are totally ordered in the log and each stripe is written atomically.
摘要:
A method and system for increasing server cluster availability by requiring at a minimum only one node and a quorum replica set of replica members to form and operate a cluster. Replica members maintain cluster operational data. A cluster operates when one node possesses a majority of replica members, which ensures that any new or surviving cluster includes consistent cluster operational data via at least one replica member from the immediately prior cluster. Arbitration provides exclusive ownership by one node of the replica members, including at cluster formation, and when the owning node fails. Arbitration uses a fast mutual exclusion algorithm and a reservation mechanism to challenge for and defend the exclusive reservation of each member. A quorum replica set algorithm brings members online and offline with data consistency, including updating unreconciled replica members, and ensures consistent read and update operations.