S

SCO

See Second class object.

SDK

The Software Developer's Kit refers to the compiler, tools, and runtime downloadable from Java suppliers including IBM and Sun. Also known by the older name Java Developer's Kit (JDK).

Second class object

An object in memory whose state is not stored independently in the datastore. In some cases, the second class object maps to a subset of field values belonging to a first class object in the datastore, but in other cases the mapping is more complex. In JDO, all supported system classes, such as String, Date, HashSet, and so forth, are generally stored as second class objects.

See also Embedded object.

Serialization

Defined by the Java I/O library, serialization provides a way to store the current state of an object to a byte stream. Serialization follows the references in an object's member variables and serializes those objects as well. By reading the byte stream, serialization can also re-create the graph of objects that was stored.

SQL

Acronym for Structured Query Language, the query language for relational databases.

Supported system class

Any of 22 classes in the java.* libraries that the JDO implementation either must or may support. The following are the supported system classes: arrays (optional), ArrayList (optional), BigDecimal, BigInteger, Boolean, Byte, Character, Date, Double, Float, HashMap (optional), HashSet, Hashtable (optional), Integer, LinkedList (optional), Locale, Long, Short, String, TreeMap (optional), TreeSet (optional), and Vector (optional).