Canonical String Format

Each type in a 5800 system has a canonical representation as a string value. The canonical string representation of each type is shown in Table 4–1.

Table 4–1 Canonical String Representation of Data Types

Data Type	Canonical String Representation
STRING	The string itself.
CHAR	The string itself.
BINARY	Hexadecimal dump of the value with two hex digits per byte.
LONG	Result of Long.toString. For example, 88991 or -7975432785.
DOUBLE	Result of Double.toString. For example, 1.45 or NaN or -Infinity or -1.56E200.
DATE	YYYY-mm-dd. For example, 2001-01-01.
TIME	HH:mm:sss. For example, 12:02:01.
TIMESTAMP	YYYY-mm-ddThh:mm:ss.fffZ (time relative to UTC). For example, 1969-12-31T23:59:59.999Z.
OBJECTID	60-digit hexadecimal dump of the objectid.

This canonical string encoding is used in the following places:

• When exposing the field as a directory component or a filename component in a virtual view

• When converting a typed value to a string as the result of the getAsString operation on a NameValueRecord or a QueryResultSet operation

• When parsing a literal value as described in Literals for 5800 System Data Types to create a typed query value from a string representation of that value.

The Canonical String Decode Operation

The inverse of the canonical string encoding is used in the following places:

• It is always allowed to store a string value into any metadata field, no matter what the type of the field is. The actual data stored is the result of applying the canonical string decode operation to the incoming string value.

• On a virtual view lookup operation, the canonical string decode operation is used on the supplied filename to derive the actual metadata values to look up, given their string representations in the filename.

  The decode operation is allowed to accept incoming string values that would never be a legal output for an encode operation. Some examples of this include:

  • decodeBinary of an odd number of hex digits. The convention is to left-justify the supplied digits in the binary value. For example, the string "b0a" corresponds to the binary literal [b0a0].

  • decodeDate of a non-standard date format.

  • A double value encoded with a non-canonical number of digits. For example, .00145E20 instead of 1.45E17.

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Example 4–1 Virtual View Lookup Operation

If you take a value V and encode it into a string S, and then perform the canonical decode operation on S to get a new value V’. Does V always equal V’? The answer is yes in most cases, but not always.

What is actually guaranteed is the weaker statement that if encode(V) = S and if decode(S)=V’, then encode(V’) is also equal to S.

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