The query (2)

Some considerations:

• expressive power of any interface is limited in comparison with textual query language
• a too complex interface could be of difficult usage for the end user (and anyway fail in replacing the textual query language)
• user must be supported in formulating the elementary components of the query

Normalization:

• identify the common ancestor for clauses on elements belonging to independent paths
• naturally associated with a single navigation

Composition:

• a trade-off between expressiveness and complexity
• A composition of several queryFragments (conceptually a single navigation upon the document tree)
• A queryFragment is made by several queryTokens
• A queryToken is the elementary component (a single interaction upon the queryForm on a single element)