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A new object can be created by calling a constructor. It is also possible to assign values to attributes in this context. This makes it easier to configure operators when building a query with QDL because it is not necessary to create a new statement for each parameter.

// Constructor Call
Point p1 = new Point(2, 5);
Point p2(2,5);

// Assigning values attributeto valuesattributes
Point p3 = new Point{x = 2, y = 5};
Point p4{x = 2, y = 5};

Select sel{predicate="bid.price <=200"};
Project proj(sel){attributes=[bid.PRICE]};

Expressions

An expression is used as part of other expressions or statements and produces a value as result.

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If a data type has a getter- or setter-method there will always be a corresponding attribute to access. So it is often possible to use assignment expressions instead of method calls.

Tuple tuple = createTuple();

ITimeInterval time = tuple.metadata;
tuple.metadata = time;

//is equivalent to
ITimeInterval time1 = tuple.getMetadata();
tuple.setMetadata(time1);

Metadata

Metadata               ::= ID "=" MetadataValue.
MetadataValue          ::= MetadataValueSingle | MetadataValueList | MetadataValueMap.
MetadataValueSingle    ::= INTEGER | Double | CHAR | STRING | BOOLEAN | QName.
MetadataValueList      ::= "[" (MetadataValue ("," MetadataValue)*)? "]".
MetadataValueMap       ::= "[" (MetadataValueMapEntry ("," MetadataValueMapEntry)*)? "]".
MetadataValueMapEntry  ::= MetadataValue ":" MetadataValue.

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