Data Access Language
Encyclopedia
Data Access Language, or simply DAL, was a SQL
-like language parser released by Apple Computer
in 1990 to provide unified client/server access to database management system
s. It was known for poor performance and high costs, something Apple did little to address over its short lifetime at Apple. DAL was later sold off in the early 1990s. DAL is used as the native SQL dialect of the PrimeBase
SQL server, as well as the now-defunct Butler SQL
.
, and followed with other versions over the next year or so.
DAL suffered from most Apple problems of the early 1990s, notably an alternating level of support in which Apple would aggressively promote the product and then ignore it. DAL's release was also coincident with Apple's fall from grace in the business world, and not coincidentally with Microsoft
's ODBC efforts.
DAL appears to have seen little use, and eventually Apple sold it to tiny Independence Technologies in 1994, during a sell-off of a number of "high-end" packages such as their X.400
server and an SNA
client. In 1995 BEA Systems
bought the company, and in turn sold it to Uniprise in late 1996. During this period it was basically a dead product.
or Microsoft's Transact-SQL
, DAL is essentially an extended version of SQL supporting basic query functionality and adding clean syntax for cursor operations, logic, and loops.
When sent a command, early versions of Apple's DAL interpreter broke down the statement and re-built it into subqueries for the underlying data sources. This translation took place on the server-side, just like PL/SQL and Transact-SQL, but required a fairly expensive "adaptor" program of often dubious performance. This adaptor made DAL considerably less appealing than later systems like ODBC, where the translation normally takes place on the client side and is typically included for free with the database engine. The downside to the ODBC approach is that more network bandwidth is used up to pull the "raw data" to the client machine for processing.
On the client end, DAL was originally accessed directly through a "system extension", but DAL was later rolled into a single ODBC-like driver layer, the Data Access Manager
(DAM). DAM was ODBC-like in concept, but did not include the SQL layers, it was strictly a system for sending "opaque" queries and receiving result sets. DAM also included the concept of a "query document" that allowed the DAL (or other) queries to be written in an authoring system and then easily used in any client application.
For much of the 1990s a direct-DAL database server was available on the Macintosh, Butler. However, like any server software on the "classic" Mac OS, Butler was seriously hampered by the Mac's single-user file system
and multitasking
and could never really deliver the sort of performance the same server would have on Windows NT
or Unix
.
One of the more common clients for DAM was HyperCard
. The combination of HyperCard and DAL presented a serious challenge to existing vendors who could offer nothing with a GUI. Apple gave a series of demos of HyperCard/DAL, and soon Oracle Corporation
purchased a HyperCard-clone, PLUS
from Spinnaker Software
, to produce Oracle Card.
The PrimeBase
division of German software developer SNAP Innovation GmbH continues to support DAL in their cross platform SQL database server. Their extended version of DAL is called PrimeBaseTalk (PBT) and is fully backward compatible with DAL. Their architecture does not include Data Access Manager and the resulting performance gains are considerable.
SQL
SQL is a programming language designed for managing data in relational database management systems ....
-like language parser released by Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
in 1990 to provide unified client/server access to database management system
Database management system
A database management system is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators and other specialists. A database is an integrated...
s. It was known for poor performance and high costs, something Apple did little to address over its short lifetime at Apple. DAL was later sold off in the early 1990s. DAL is used as the native SQL dialect of the PrimeBase
PrimeBase
A number of database related products and projects go under the name of PrimeBase. Classic PrimeBase is a SQL database server developed and maintained by PrimeBase Systems GmbH of Hamburg, Germany...
SQL server, as well as the now-defunct Butler SQL
Butler SQL
Butler SQL is a now-defunct SQL-based database server for the "classic" Mac OS from EveryWare Development. For much of its history it was partnered with another EveryWare product, Tango, that built dynamic database pages from SQL data...
.
History
DAL started as a 3rd party product, CL/1 (Connectivity Language One), from a small vendor, Network Innovations. Apple purchased the company in 1988, about the time that client/server databases were becoming a hot issue in the industry. They released their first version of the re-branded software in 1989, for MVSMVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
, and followed with other versions over the next year or so.
DAL suffered from most Apple problems of the early 1990s, notably an alternating level of support in which Apple would aggressively promote the product and then ignore it. DAL's release was also coincident with Apple's fall from grace in the business world, and not coincidentally with Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's ODBC efforts.
DAL appears to have seen little use, and eventually Apple sold it to tiny Independence Technologies in 1994, during a sell-off of a number of "high-end" packages such as their X.400
X.400
X.400 is a suite of ITU-T Recommendations that define standards for Data Communication Networks for Message Handling Systems — more commonly known as "email"....
server and an SNA
Systems Network Architecture
Systems Network Architecture is IBM's proprietary networking architecture created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes the protocol and is, in itself, not actually a program...
client. In 1995 BEA Systems
BEA Systems
BEA Systems, Inc. specialized in enterprise infrastructure software products known as "middleware", which connect software applications to databases and was acquired by Oracle Corporation on April 29, 2008.- History :...
bought the company, and in turn sold it to Uniprise in late 1996. During this period it was basically a dead product.
Description
Like Oracle's PL/SQLPL/SQL
PL/SQL is Oracle Corporation's procedural extension language for SQL and the Oracle relational database...
or Microsoft's Transact-SQL
Transact-SQL
Transact-SQL is Microsoft's and Sybase's proprietary extension to SQL. SQL, often expanded to Structured Query Language, is a standardized computer language that was originally developed by IBM for querying, altering and defining relational databases, using declarative statements...
, DAL is essentially an extended version of SQL supporting basic query functionality and adding clean syntax for cursor operations, logic, and loops.
When sent a command, early versions of Apple's DAL interpreter broke down the statement and re-built it into subqueries for the underlying data sources. This translation took place on the server-side, just like PL/SQL and Transact-SQL, but required a fairly expensive "adaptor" program of often dubious performance. This adaptor made DAL considerably less appealing than later systems like ODBC, where the translation normally takes place on the client side and is typically included for free with the database engine. The downside to the ODBC approach is that more network bandwidth is used up to pull the "raw data" to the client machine for processing.
On the client end, DAL was originally accessed directly through a "system extension", but DAL was later rolled into a single ODBC-like driver layer, the Data Access Manager
Data Access Manager
The Data Access Manager was a database access API for the Mac OS, introduced in 1991 as an extension to System 7. Similar in concept to ODBC, DAM saw little use and was eventually dropped in the late 1990s. Only a handful of products ever used it, although it was used for some extremely impressive...
(DAM). DAM was ODBC-like in concept, but did not include the SQL layers, it was strictly a system for sending "opaque" queries and receiving result sets. DAM also included the concept of a "query document" that allowed the DAL (or other) queries to be written in an authoring system and then easily used in any client application.
For much of the 1990s a direct-DAL database server was available on the Macintosh, Butler. However, like any server software on the "classic" Mac OS, Butler was seriously hampered by the Mac's single-user file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
and multitasking
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...
and could never really deliver the sort of performance the same server would have on Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
or Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
.
One of the more common clients for DAM was HyperCard
HyperCard
HyperCard is an application program created by Bill Atkinson for Apple Computer, Inc. that was among the first successful hypermedia systems before the World Wide Web. It combines database capabilities with a graphical, flexible, user-modifiable interface. HyperCard also features HyperTalk, written...
. The combination of HyperCard and DAL presented a serious challenge to existing vendors who could offer nothing with a GUI. Apple gave a series of demos of HyperCard/DAL, and soon Oracle Corporation
Oracle Corporation
Oracle Corporation is an American multinational computer technology corporation that specializes in developing and marketing hardware systems and enterprise software products – particularly database management systems...
purchased a HyperCard-clone, PLUS
WinPlus
WinPlus was a cross-platform clone of the Hypercard application that enables users to run HyperCard stacks on Apple Macintosh, Microsoft Windows and OS/2 ....
from Spinnaker Software
Spinnaker Software
Spinnaker Software was a 1982 founded software company known primarily for its line of non-curriculum based educational software, which was a major seller during the 1980s. It was founded by chairman Bill Bowman and president C. David Seuss....
, to produce Oracle Card.
The PrimeBase
PrimeBase
A number of database related products and projects go under the name of PrimeBase. Classic PrimeBase is a SQL database server developed and maintained by PrimeBase Systems GmbH of Hamburg, Germany...
division of German software developer SNAP Innovation GmbH continues to support DAL in their cross platform SQL database server. Their extended version of DAL is called PrimeBaseTalk (PBT) and is fully backward compatible with DAL. Their architecture does not include Data Access Manager and the resulting performance gains are considerable.