Apple Newton Utilities Guida Utente Scaricare il pdf (Pagina 451)

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CHAPTER 11

Data Storage and Retrieval

About Data Storage on Newton Devices 11-19

The most important factor to consider with respect to the kind of data is whether

the data is static or dynamic. You must use soups to store dynamic data, but a

number of options are available for storing static data. You will probably ﬁnd that

certain structures lend themselves more naturally than others to working with your

particular data set.

Especially for large data sets, space-efﬁciency may inﬂuence your choice of one

data structure over another. In some cases, you may need to consider trade-offs

between space requirements and speed or ease of access.

Data access issues include questions such as whether the data structure under

consideration facilitates searching or sorting the data. For example, soups provide

powerful and ﬂexible mechanisms for searching and sorting soup entry data.

Dynamic Data 11

Data your application gathers from the user must be stored in soups. Within

individual soup entries, you are free to store data in whatever manner best suits

your application’s needs.

Because each entry in a soup is a frame, the price you pay for using soup-based

storage can be measured in terms of

■ the time required to ﬁnd slots at run time

■ the memory space required to expand soup entries

■ the memory space required to store the expanded entry frames on the

NewtonScript heap

For many uses, the beneﬁts offered by soups outweigh these costs; however, other

approaches may be more suitable for certain data sets, especially large sets of read-

only data.

For example, a large, read-only list of provinces and postal codes is saved most

compactly as a single array, frame, or binary object residing in a slot in the

application base view’s template or in the application package itself. Information

stored in this way is compressed along with your application package and is not

brought into the NewtonScript heap when it is accessed. The primary disadvantages

of this scheme are that the data set is read-only and the conveniences provided by

soup queries are not available.

Static Data 11

Read-only or static data can be stored in packages held in protected memory on the

Newton. There are a variety of reasons you might store data in a package rather

than in a soup:

■ Storing static data in a compressed package rather than in a soup helps to

conserve store space and NewtonScript heap space.

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Apple Newton Utilities Guida Utente Pagina 451

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