I can find useful information here: https://jazz.net/wiki/bin/view/Main/QueryDevGuide

Here is an example that I made to find a workitem with summary starting with given string

	public List<IWorkItem> findWorkItemBySummary(String name, IProjectAreaHandle projectHandler) {

		try {			



			IWorkItemServer workItemServer = getService(IWorkItemServer.class);

			IQueryCommon queryService= getService(IQueryCommon.class);

		

			IQueryableAttributeFactory factory = QueryableAttributes.getFactory(IWorkItem.ITEM_TYPE);

		    

			IQueryableAttribute projectAreaAttribute = factory.findAttribute(projectHandler, IWorkItem.PROJECT_AREA_PROPERTY, workItemServer.getAuditableServer(), null);

			IQueryableAttribute workItemNameAttribute = factory.findAttribute(projectHandler, IWorkItem.SUMMARY_PROPERTY, workItemServer.getAuditableServer(), null);

			AttributeExpression projectExpression = new AttributeExpression(projectAreaAttribute, AttributeOperation.EQUALS, projectHandler);

			AttributeExpression summaryExpression = new AttributeExpression(workItemNameAttribute, AttributeOperation.STARTS_WITH, XMLString.createFromPlainText(name));

			

			Term term= new Term(Operator.AND);

			term.add(projectExpression);

			term.add(summaryExpression);

			

			SortCriteria[] sortCriteria= new SortCriteria[] { new SortCriteria(IWorkItem.SUMMARY_PROPERTY, true) };

			Statement statement = new Statement(new SelectClause(), (Expression) term, sortCriteria);

			

			IQueryResult<IResolvedResult<IWorkItem>> qryResult = queryService.getResolvedExpressionResults( projectHandler, (Expression) statement, IWorkItem.FULL_PROFILE);

			List<IWorkItem> matchingWorkItems = new ArrayList<IWorkItem>(qryResult.getResultSize(null).getTotalAvailable());

			while (qryResult.hasNext(null)) {				

				matchingWorkItems.add(qryResult.next(null).getItem());

			}

			return matchingWorkItems;

		} catch (IllegalArgumentException e) {

			return null;

		} catch (TeamRepositoryException e) {

			return null;

		}



	}