Quick Start

Launching the applet you will (hopefully) see the following image

In the text area in the Query Input group you can write compose your query (either XML-QL or SEQL ). Press Execute Query to get results. In the Query Result group you will see the results in tree form (JTree). The get next button is used to obtain the results in batches.

You can pose queries on the data so far.

If you press the Query Button you will see a simple interface for constructing XML-QL queries.

To choose the dtd on which to base a query press the Choose DTD button. A list box will appear allowing you to choose one or more dtd's. The dtd is displayed in tree format and features like sets and choices are not yet incorporated in the interface. The idea is to quickly generate a query body and then probably fine tune the query by hand.

By right-clicking on an element the element is projected. Double clicking causes a dialog to appear where predicates can be specified. The OK button generates an XML-QL Query and returns to the main frame.

Joins are performed using drag and drop. This feature is still a little problematic in the applet: One has to make sure that before performing the drag and drop the target element is selected. We will try to fix this problem. The application client does not have this problem.

By pressing the Search button in the main frame you get an interface which allows you to generate search engine queries.

The usage is similar to the XML Query Interface with the excpetion that there are containment operators and there are no joins.

How to install a Continuous Query

To construct a continuous query, you may first construct a common XML-QL query as illustrated above using the GUI. Then you click on the install trigger button. You will see following window to let you specify the values of the time property of your continuous queries.

All the values in this windows are optional. Unless you type in some values, default values will be used.

  • Start Date: The date from which you want your continuous query to become effective. For examples: "Wed Sep 22 17:25:47 1999" or simply "2/1/2000".
  • Interval: you may choose a unit and type in a value. You specify this value as how often your continuous queries are going to be fired. If 0 is specified, continuous queries will be fired whenever related file changes.
  • Expiration Date: some date you want to remove your continuous queries. It is not implemented yet. By default, it will not expire unless you delete it.
  • Action: Continous query actions on the query result. By default, the query result will be sent back to the client GUI. You may also specify Mailto: your email address. Then you will get the XML file of the continous query result through your email.
  • Trigger Name: You may specify a name for your continuous query. System will add a timestamp on it to make sure it is unique.
  • Execute Now: if you check it, your continous query will be run as a regular query first to give you the results on current data. Otherwise, only new data will trigger the execution of continous queries.

    After you finish above setting, or if you don't want to change the default setting, click on Ok, you will see time information and trigger action is added to your XML-QL query automatically.

    You can then click on Execute query to install the continuous query into the system.

    Data set to be used to test continuous queries

    We use real-time stock quote data to demonstrate one possible usage of continuous queries. You may construct XML-QL queries on the Quote.dtd and Profile.dtd. Stock quotes from the Computer Software & Services industry are downloaded about every 5 minutes (depending on the network delay). There are about 1000 stocks totally. Profile.dtd contains the company and share information of those stocks. You may ask Join queries over Quote and Profile information. Note: Profile information is updated very infrequently.

    Warning: Currently your continuous queries will not be stored persistently in the system . Thus once the system is down, your installed continuous queries will be lost. :-(

    Have FUN :-)

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