Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 441)

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CHAPTER 11

Data Storage and Retrieval

About Data Storage on Newton Devices 11-9

You can create your own specialized indexes for any soup. You need to create an

index for each slot or set of slots on which the soup will be searched frequently. It

is preferable to deﬁne your indexes in the appropriate soup deﬁnition, but you can

add indexes to an existing soup if necessary.

An index generated against a single key value is called a single-slot index. A

single-slot index selects and sorts soup entries according to the value of a single

slot speciﬁed when the index is created. An index generated against multiple key

values is called a multiple-slot index. A multiple-slot index can select and sort

soup entries according to the values of multiple slots. A multiple-slot index can

associate up to a total of six key values with each entry it indexes. You can create

multiple indexes for any soup.

The characteristics of an index are speciﬁed by an index speciﬁcation frame or

index spec. The values in the index spec frame indicate the kind of index to build,

which slot values to use as index data, and the kind of data stored in the indexed

slots. The precise format of the index spec frame varies according to whether it

deﬁnes a single-slot index or a multiple-slot index. For complete descriptions of

index specs, see “Single-Slot Index Speciﬁcation Frame” on page 9-5 and

“Multiple-Slot Index Speciﬁcation Frame” (page 9-6) in Newton Programmer’s

Reference.

A tag is an optional developer-deﬁned symbol used to mark one or more soup

entries. Tags reside in a developer-speciﬁed slot that can be indexed, with the

results stored in a special index called the tags index.

The tags index is used to select soup entries according to their associated symbolic

values without reading the entries into memory; for example, one could select the

subset of entries tagged

'business from the ROM_CardFileSoupName soup

used by the built-in Names application. In fact, “ﬁling” Newton data items in

“folders” is a user-interface illusion—the data really resides in soup entries and its

display is ﬁltered for the user according to the tags associated with each soup entry.

Note that the system allows only one tags index per soup. Each soup can contain a

maximum of 624 tags. The system treats missing tags as

nil values. For more

information, see “Tag-based Queries” on page 11-14.

A tags index speciﬁcation frame, or tags index spec, deﬁnes the characteristics of

a soup’s tags index. Like an index spec, a tags index spec can be used to create a

default tags index on a new soup or add a tags index to an existing soup. For a

complete description of the slots in a tags index spec frame, see the section “Tags

Index Speciﬁcation Frame” (page 9-8) in Newton Programmer’s Reference.

To better support the use of languages other than English, soup indexes and queries

can be made sensitive to case and diacritical marks in string values. (Normally,

string comparison in NewtonScript is insensitive to case and diacritics.) This

behavior is intended to allow applications to support the introduction of non-

English data easily; for example, the user might insert a PCMCIA card containing

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Apple Newton Utilities Guide de l'utilisateur Page 441

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