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Glossary

accessors

In OLE DB, a collection of information that describes how data is stored in the consumer's buffer. It contains the binding information for one or more columns or parameters. Consumers can use more than one accessor or a single accessor can define the mapping between a structure and multiple columns or parameters. Accessors are similar to descriptor handles in ODBC.

ActiveX Data Objects (ADO)

A high level object-oriented database API built on OLE DB. Microsoft's automation server exposes a high-level set of database programming objects to the Visual Basic, Java, or C++ programmer on top of an OLE DB data source. ADO can be used to create business applications that access OLE DB data sources.

ANSI

American National Standards Institute.

attribute pairs

Values that control various aspects of the provider's connection and interaction with the database. The values can be entered in a provider string.

autocommit mode

A transaction commit mode in which all actions taken in a transaction are committed immediately after they are performed. Contrast with manual-commit mode.

Backus-Naur Form (BNF)

A language that is used to describe another language.

Binary Large Object (BLOB)

Any binary or character data larger than a certain number of bytes. In OLE DB, BLOBs are generally sent and retrieved from the data source in parts.

binding

In OLE DB, the association of a piece of memory in the data consumer's buffer with a column of data in a Rowset. The caller supplies this information to describe a data structure with offsets for each value.

bookmark

A value that identifies a row in a rowset. Bookmarks are saved by the consumer and used later in the life of a rowset to retrieve a particular row.

Cartesian product

The Cartesian product of a set of n tables is the table consisting of all possible rows r such that r is the concatenation of a row from the first table, a row from the second table ...and a row in the nth table.

catalog

A database object that contains one or more schemas.

COM

Component Object Model (COM). Microsoft's general architecture for component-based software. An OLE object-oriented model that defines how objects interact within a single process or between processes. In COM, clients have access to an object through interfaces implemented on an object.

COM object

An object that conforms to the OLE Component Object Model (COM). A COM object is an instance of an object definition, which specifies the object's data and one or more implementations of interfaces on the object. Clients interact with a COM object only through its interfaces.

commit

To make the changes in a transaction permanent.

Component Object Type (CoType)

A way to define a group of COM objects, such as rowsets or commands, that have similar characteristics. All COM objects that belong to a particular CoType must expose the mandatory interfaces in that CoType. In addition, they can expose the optional interfaces in the CoType and any interfaces not in the CoType.

component software

An environment where users can add features to applications by buying additional components.

connection

A definition that specifies an OLE DB provider and the associated provider properties that are required to connect to a specific data store. For example, the user ID, data source name, and password might be required. These values would be specified in the connection.

connection point

An OLE DB relational provider uses connection points (notification sinks) to notify a consumer of an event with IConnectionPoint.

To receive notifications, the consumer must implement IRowsetNotify, and register it on a connection point with the data provider. When a specified event occurs, the client application must perform an action with the notification.

consumer

See data consumer.

CoType

Component Object Type. A way to define a group of COM objects, such as rowsets or commands, that have similar characteristics.

cursor

A named control stucture used by an application program to point and select to a row of data in a table or view. It holds the results of a SQL query.

ADO recordsets are sometimes called cursors.

data consumer

Application code that uses data presented through an OLE DB interface. Such code is said to consume an OLE DB interface. OLE DB components like data providers and service components can also be consumers if they consume other providers.

Data Definition Language (DDL)

One of the components of SQL. DDL is concerned with commands that create and maintain the database, for example, Create Table and Drop Table.

Data Manipulation Language (DML)

Text commands that manipulate data, as opposed to defining data. Examples include the SQL statements Insert, Update, Delete, and Select.

data provider

An OLE DB provider, such as one of the DataDirect OLE DB components, that exposes data.

data source

A collection of all the information necessary to connect to a data store. OLE DB data sources can include a provider name, a database name, or a catalog name and a schema name. The connection information required for a data source is determined by the OLE DB components used to make the connection and the data store they are connecting to.

data shaping

A new feature in ADO 2.0 that allows you to create hierarchical recordsets with data exposed by an OLE DB data provider. The MSDataShape OLE DB provider, which is part of the MDAC 2.0, acts as a service component to a Connect OLE DB relational data provider to expose data shaping functionality.

data store

The data that the user wants to access, such as the data in a database, file, or array. A data store owns data and exposes its data in a tabular form as a rowset over a native data format. Data stores can include a full SQL DBMS, an ISAM file, or a text file or data stream.

data type

The type of a piece of data. The data type of a consumer variable, a parameter, or a column is identified by a type indicator.

Database Management System (DBMS)

A layer of software between the physical database and the user. The DBMS manages all access to the database. An OLE DB data provider can be built directly on top of a DBMS or as a layer between the DBMS and the data consumer.

DCOM

Distributed Component Object Model (DCOM). An extension to Microsoft's general architecture for component-based software. DCOM supports communication between COM components, such as ActiveX controls and Java applets, that are distributed over a network.

DDL

Data definition language.

direct connection

A connection that does not use a catalog. A direct connection is faster than a data source connection that uses a catalog, because it does not have to wait for the system to look up information. However, a direct connection cannot access views.

DML

Data manipulation language.

enumerator

An OLE DB object that searches for data sources and other enumerators.

error object

An object that contains detailed information about an error.

event

An action taken by a provider, of which the provider notifies the consumer. For example, the provider notifies the consumer when a row is added or a column is deleted.

fetch

To retrieve one or more rows from the data store and instantiate them in a rowset.

file moniker

A persistent file name that contains information that can be used to identify objects that are saved as files. It is based on a path in the file system.

foreign key

One or more columns that match the primary key in another table.

Globally Unique Identifier (GUID)

A 16-byte value that uniquely identifies something, usually the software that implements one or more COM objects or an interface on one of those objects.

GUID

Globally Unique Identifier.

index rowset

A rowset built over an index in a data source. It is usually used with a rowset built over a base table in the same data source.

infix operator

An operator that appears between two operands.

initialize

To change the state of an enumerator or data source object so that it can be used to access data. For example, initializing a data source object might require the data provider to open a data file or connect to a database.

instantiate

To create an instance of a COM object. For example, to change the state of a data source object so that it can be used to access data. Initializing a data source object might require the data provider to open a data file or connect to a database.

interface

A group of semantically related functions that provide access to a COM object. Each OLE DB interface defines a contract that allows objects to interact according to the Component Object Model (COM). While OLE DB provides many interface implementations, most interfaces can also be implemented by developers designing OLE DB applications.

key

One or more columns whose values uniquely identify a row.

manual-commit mode

A transaction commit mode in which transactions must be committed or terminated by calling ITransaction::Commit or ITransaction::Abort.

manufactured schema

A schema generated by the Reflector OLE DB component that consists of the Connection Name, the pound sign (#), and the local schema that contains the table.

metadata

Data that describes a parameter in a text command or a column in a rowset. For example, the data type, length, and updatability of a column.

method

In object-oriented programming, a function in an interface.

middleware

Software that mediates the communication between an application and a data store. The middleware provides an interface that manages the differences in the application's and the data store's data formats.

moniker

A COM object that contains information that can be used to create and initialize an instance of a specific COM object. A client can use a moniker to locate that object, activate it when necessary, and get a pointer to one of the object's interfaces.

Clients of COM objects can create and initialize the objects without using a moniker. However, using a moniker can simplify complex initialization operations for the client.

nonrelational data

Data that is not stored with logical relationships attached to it. For example, email data and word processing files are nonrelational data. Contrast with relational data.

nonrelational database

A database that stores nonrelational data. Examples include Lotus Notes and hierarchical data in ISAM files, IMS, and DL/I.

notification

A call, using OLE notification sinks (IConnectionPoint), from a data provider to notify a consumer that an event is occurring. When the event occurs, the client application must perform an action with the notification. The consumer must implement IRowsetNotify and register it on a connection point with the data provider.

The provider performs the notification, but does not expect or wait for a response.

notification sink

An object that implements the notification interface.

object

Compiled code that provides a service to the rest of the system. Within an OLE DB context, an object is the same as a component.

Object Linking and Embedding (OLE)

Microsoft's object-based technology for sharing information and services across machine and process boundaries.

ODBC

Microsoft's Open Database Connectivity (ODBC) specification. The ODBC specification for an Application Programming Interface (API) allows applications to access multiple database systems using Structured Query Language (SQL). For detailed information on ODBC, refer to the Microsoft programming documentation on ODBC.

OLE DB

A set of interfaces that exposes data from a variety of data sources using COM. OLE DB enables standards-based access to both relational and nonrelational data stores through reusable components. For detailed information on OLE DB, refer to the Microsoft programming documentation on OLE DB.

OLE DB Automation error object

An error object that conforms to the standards specified for such objects by OLE Automation.

OLE DB error object

An error object used by OLE DB to return an error. OLE DB error objects are an extension of OLE DB Automation error objects.

persist

To save the current state of a COM object, such as to a file. In OLE DB, only data source objects can be persisted. Objects can be restored from their persisted state, saving initialization steps.

phase

A step in a sequence of notifications caused by a single event. The sequence of notifications is similar to the phases in a two-phase commit protocol.

postfix operator

An operator that is preceded by its operands.

primary key

One or more columns that uniquely identify a row in a table.

property

Attributes of an OLE DB object. For example, the maximum number of rows in a rowset that can be active at one time.

property group

The set of all properties that apply to a particular OLE DB object. For example, the Rowset property group specifies whether a rowset supports bookmarks and whether it can fetch backwards.

provider

A COM object that implements the OLE DB interfaces and methods. See data provider and service component.

query processor

Given a statement in some query language (that is, SQL), a query processor determines a query plan for a statement, executes the query plan, and returns a result set.

RDB

Relational database.

relational data

Data that is stored with logical relationships attached to it. For example, databases like Oracle and Sybase contain relational data. Contrast with nonrelational data.

relational database

A database that exposes its data as a two-dimensional table, that is, using rows and columns. Examples include Oracle and Informix.

relational data provider

A data provider for a relational database. Examples include Connect OLE DB for Oracle and the SequeLink OLE DB Provider.

rowset

An OLE DB COM object that exposes data in tabular format. A rowset comprises a set of rows in which each row has columns of data.

schema

A collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user ID. Each user ID owns a single schema. Schema objects, which include tables and views, can be created and manipulated with SQL.

schema rowset

A predefined rowset that provides information about the structure of a database.

SDK

Software Development Kit.

service component

An OLE DB component that exposes OLE DB interfaces for complex data processing services. For example, a query processor component exposes OLE DB interfaces for processing SQL strings sent by applications (data consumers). This type of service provider is a query processor. The query processor's OLE DB interfaces accept complex SQL strings from applications and process them to an OLE DB level that can be understood by an underlying OLE DB provider. This data provider can then process the converted SQL request to the target data store and return the results to the query processor. The query processor then converts these results to the complex data format expected by the requesting application. As the intermediary between the application and the underlying data provider, a service provider acts as both a data provider and a data consumer.

In version 1.5 and earlier of the Microsoft OLE DB specification, this component was called a service provider.

service provider

(OLE DB 1.0 and OLE DB 1.5) An OLE DB component that exposes OLE DB interfaces for complex data processing services. See service component.

session

An OLE DB object that serves as the context for a transaction.

SQL

Structured Query Language. A language used by relational databases to query, update, and manage data.

table

A database object that formats data as rows and columns. Data in the rows and columns are related. The nature of their relationship is specified by the user who requests the data.

token

The smallest independent unit of meaning as defined by a lexical analyzer or a parser.

transaction

A logical unit of work. Consumers use transactions to define units of work with atomicity, concurrency, isolation, and durability properties within a provider. You can use transactions to specify isolation levels, which enables more flexible access to data among concurrent consumers.

type indicator

An integer value that is passed to or returned from an OLE DB method to indicate the data type of a consumer variable, a parameter, or a column.

Unicode

Worldwide character encoding standard from the Unicode Consortium. String parameters for all COM interface methods are passed as Unicode rather than ANSI strings, except for getting and setting ANSI data that resides in tables. Alternatively, the component can return actual data as ANSI strings. If the data consumer requests a different binding for a particular property, the OLE DB component can perform the appropriate conversion using the OLE DB conversion routines.

Universal Data Access (UDA)

A Microsoft strategy based on ADO, OLE DB, and ODBC that lets users get to data in different data stores through a common set of interfaces, regardless of where the data resides or what type of data it is.

view

A named virtual table that represents the result set of a SQL query. A view does not store data; it only displays the data from its source table or tables. For a user, a view looks and behaves like a database table. You can use views to simplify a complex database structure or to limit the columns that a group of users can see in a table.

Virtual Table Manager (VTM)

An in-memory relational data cache that exposes OLE DB interfaces for data access and manipulation. The VTM consumes as well as exposes OLE DB interfaces.

zombie

A state in which the only valid consumer action on a COM object is generally to release that object.



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Getting Started with DataDirect for OLE DB

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