Data Access Language: Difference between revisions

Revision as of 12:19, 25 May 2005

Revision as of 12:27, 25 May 2005

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'''Data Access Language''', or simply '''DAL''', was a [[SQL]]-like language parser released by [[Apple]] in 1990 to provide unified [[client/server]] access to [[database management system]]s. It was marginally supported in an on-and-off fashion until the mid-90s, when management apparently grew bored of it and sold it off.

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 [[MVS]], and followed with other versions over the next year or so.

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DAL suffered from most Apple problems of the early 1990s, notably a alternating level of support in which Apple would present the product and then ignore it. DAL's release was also coincident with Apple's fall from grace in the business world, and not coincidentially with [[Microsoft]]'s ODBC efforts. It appears to have seen little use, and eventually Apple sold it to Independence Technologies in 1994, during a sell-off of a number of "high-end" packages such as an [[X.400]] server. 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.

DAL was essentially a cut-down version of SQL, supporting only the most basic functionality, but adding clean syntax for cursor operations, logic, and loops -- at that time no real standards existed for this side of SQL programming. When sent a command the 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, unlike most similar tools, requiring a fairly expensive "adaptor" program of dubious performance. This bit of architechture made DAL considerably less appealing thatthan similarlater systems like [[ODBC]], where the translation normally takes place on the client side and is typically "free".

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, [[Data Access Manager]]. One of the more common clients was [[HyperCard]]. The combination of HyperCard and DAL presented a serious challenge to existing vendors who could offer nothing with a GUI, and soon [[Oracle]] purchased a HyperCard-clone, PLUS from [[Spinnaker Software]], to produce [[Oracle Card]].