What is ADO?
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Learn how ActiveX Data Objects (ADO) fits with existing data access strategies in this introduction to ADO. Other topics covered include the origins of ADO and its role in the .NET future, the problems with OLE DB, the benefits of UDA, Microsoft’s strategy for accessing data in comparison to Oracle's. (From the book
ADO Programmer's Reference, by David Sussman, published by Apress, ISBN: 1590593421.)
ActiveX Data Objects (ADO) and Object Linking and Embedding Database (OLE DB), its underlying technology, currently play a big part in data access. Microsoft has unequivocally committed its future to it, and rightly so. The paperless office has yet to appear, but the amount of data stored on computer systems increases every day. This is illustrated by the rate at which the Web is expanding—and that’s just the public face of data. Much more data is hidden from general view in corporate applications or intranets.
This chapter describes the terms and technology behind ADO. If you need to start coding straight away, you could skip to the relevant chapters, but your understanding will be better if you have a good foundation.
So, to give you that good foundation, there are several important topics I will discuss in this chapter:
- What I mean by “data”
- What I mean by a “data store”
- How ADO fits with existing data access strategies
- Data access in the client/server world
ADO is central to Microsoft’s data access strategy, so it’s important to understand why it came about and what sort of a future it has. I’ll be looking at these issues too.
What is Data? If you’ve got a few spare minutes some time, open Windows Explorer and have a look around your hard drive. Make a mental note of how many separate pieces of information you’ve got: databases, documents, spreadsheets, e-mail messages, HTML and Active Server Pages (ASP) documents, etc.
Quite a lot, eh? They are all pockets of data, but are stored in different forms. This might seem obvious, but traditionally data has been thought of as being stored only in a database; if you built a business application, the data had to be in a database. Although a large proportion of existing data may be contained in databases, why should the remaining data be excluded from our grasp? In fact, as computers become more powerful, the term “data” is starting to include multimedia items such as music and video, as well as objects and the more typical document-based data.
So, by “data” I mean any piece of information whatever its contents. Whether it’s your address book, your monthly expenses spreadsheet, or a pleading letter to the taxman, it’s all data.
What Are Data Stores? Now that I have established what I consider data to be, the definition of a data store might be fairly obvious—it’s a place in which data is kept. However, there is much more to data stores than you might think. Instead of looking at your hard disk, let’s look at mine to see what I’ve got installed:
- Databases: I consider these the traditional store of data—I’ve got both SQL Server and Access databases, which I use to store everything from accounts and invoicing to sample databases for books.
- Spreadsheets: Financial data with year-end figures for my tax returns and bills.
- Mail and News: I use Outlook and Outlook Express to handle my mail and Internet news.
- Documents: This is the largest portion of data on my machine, containing all my personal letters and documents, and chapters for books (including this one).
- Graphics: Screen captures and pictures for books.
- Internet: HTML and ASP pages containing samples and applications.
- Reference Material: Including MSDN and encyclopedias.
So that’s the actual data, but how is it stored? Well, the databases are self-contained, so they are their own data store. The reference material is, by and large, stored in its own format, so that could also be considered a data store. The mail and news hold data on their own as well, so they are data stores. Everything else is stored as files; therefore, the file system itself becomes a data store (OK, the data it stores is in myriad formats, but it’s all stored in the same way: folders and documents).
You could even include my CD-ROM drive and tape backup unit. The CD-ROM uses the standard documents and folders format, so this could be considered part of the file system data store, but the tape backup has its own format, so it could be considered a data store too.
Numerous other data stores exist, from mainframe file systems to databases and mail. As an enterprise becomes bigger it also must include user-account databases and other machines attached to the network, such as printers and scanners. Each of these things may not be data stores themselves, but as items of data, they’ll be contained in a data store somewhere.
 This is from ADO Programmer's Reference, by Dave Sussman (Apress, ISBN 1590593421). Check it out at your favorite bookstore today. Buy this book now. |
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