Windows Live Agents Team Blog : dynamic content

An advanced look at Web Services and DataSources - Part II

imiluk — Mon, 11 Aug 2008 22:00:00 GMT

This is a continuation on An Advanced Look at Web Services and DataSources. The original entry is located here: http://windowsliveagents.spaces.live.com/blog/cns!5BCD45E519E07634!711.entry

Now let’s take a look at the datasource itself. The datasource essentially is a function itself, with arguments to pass, and variables to return. In the preprocess section, the POST_DATA variable where the XML SOAP request string was built is put into here. In addition, the actual web service URL is stated here as well.

In the preprocess section, there are also two built-in variables that can be used, LIMIT and OFFSET. These two variables are used to ‘page’ results in a cursor. In the example above, we look at LIMIT to populate a variable called MAXRESULTS. The MAXRESULTS variable is then used in the COUNT element (in this case 10) to bring back 10 results per request. If the user needs more, then the datasource then starts at the next row and retrieves 10 more results.

The simple xml section is a hierarchical representation of the XML response from the SOAP API, to be flattened out into a 2-dimension look when the data is retrieved. Indentation is used to signify a parent-child relationship. The {loop=content} statement acts as a loop within the XML, iterating through the XML. The end nodes (highlighted in BOLD) are the fields that is used to capture information and passed back to the calling routine. Note that fields can be skipped in the simple xml section if the user does not need it.

It should be noted here that by using simple xml to represent the XML response, there is no provision for providing a “dynamic” representation of the XML using simple xml. So in essence, you would have to potentially write a different datasource function for each different search type in this case. For generate an advanced datasource that could output differently depending on the search type would require outputting a datasource in Buddyscript. We’ll cover this in a different blog.

datasource LiveSearchAPI(SEARCH, CULTURE_INFO) => Title, Description, Url, Source, NewsYear, NewsMonth, NewsDay, NewsHour, NewsMinute, NewsSecond {expire="in 1 hour" continue_on_error="true" timeout="15" }

preprocess

if LIMIT>10 || LIMIT<=0

MAXRESULTS = 10

else

MAXRESULTS = LIMIT

FIELDLIST = "Title Description Url Source DateTime"

POST_DATA = BuildSearchAPIPostData(SEARCH, "News", OFFSET, MAXRESULTS, CULTURE_INFO, FIELDLIST)

http

http://soap.search.msn.com:80/webservices.asmx

header

Accept: application/soap+xml

postdata {encode=no}

POST_DATA

simple xml

Envelope

Body

SearchResponse

Response

Responses

SourceResponse

Offset => RESULTOFFSET // Where we're starting from.

Total => TOTAL // Total number of results.

Results

Result {loop=content}

Title

Description

Url

Source

DateTime

Year

Month

Day

Hour

Minute

Second

postprocess

INFO.Offset = RESULTOFFSET

INFO.MaxCount = TOTAL

return INFO

There are other datasource properties that should be considered to either increase performance and or deal with potential errors in accessing/retrieving information from the datasource. The first one is the Timeout property. You can specify this time in order to lengthen or shorten the time it takes before the datasource quits accessing the web service. The default value is 10 seconds. In our case, we have it at 15 seconds. The next property is the continue_on_error property. By changing this property to ‘yes’, execution will still continue and the datasource caller can retrieve the error message in the SYS.Data.Error variable. This is only on those sources that call the ABErrorProc. The final property is very important. It is the Expire property. This determines how long retrieved data should be valid, i.e. kept in cahsed memory. The ability to cache retrieved data in memory will improve performance on retrieving information in the datasource. You should consider these factors:

1) how often does the data change?

2) how often will the same retrieved data be asked again?

3) how large is the retrieved data set?

4) server memory cache size (N/A on hosted applications)

5) how fast does the web service perform?

All of these are considerations. In our case, since news items change frequently, we’ll set it for a relatively short time period, say 1 hour.

Examples of the Expire property:

Expire=”never” /* this is the default expiration for most non-Buddyscript datasources */

Expire=”in 1 hour”

Expire =”now” /* no caching at all, same as “never” */

Expire=”tomorrow at 5am” /* Note that this time is the server time, not the client time. In hosted applications, this is in GMT time */

The postprocess section is important for returning a range of information. For datasources that do not handle the processing of data using offsets and limits (i.e. simple xml), if the postprocess section is missing, the processing QueryServer will process the data coming back from the datasource in its entirety. In cases where the output coming back is one entity or one row, or if the amount of data needed to be processed is small, the postprocess section is not needed.

postprocess

INFO.Offset = RESULTOFFSET

INFO.MaxCount = TOTAL

return INFO

Looking at the postprocess section, this section is used to set the offset and total count of rows in a variable. This variable is then used by Buddyscript to control the display of output.

In this case, INFO is the name of an object variable. The names of the variables inside the object is Offset and MaxCount, and these values are populated from the datasource:

Offset => RESULTOFFSET // Where we're starting from.

Total => TOTAL // Total number of results.

Finally, here is a crude routine to pass a request to the Live Search API, access the web service and display the contents of the data, using Buddyscript code to control the amount of data coming in.

? Tell me some news about STRING=Anything

LOCALE="en-us"

TITLE, DESCRIPTION, LINK, SOURCE, YEAR, MONTH, DAY, HOUR, MINUTE, SECOND = LiveSearchAPI(STRING, LOCALE) show 10

* Here are the results:

- TITLE, SOURCE

* <blank/>

else

- Sorry, no news sites were found for your input.

In the input, you could ask a question such as “Tell me some news about Baron Davis” for example, and get back results that looks like this (notice that the output only contains 2 out of the 10 arguments returned, Title and Source):

Here are the results:

Baron Davis Going South, San Francisco Gate

The Baron Davis, Gilbert Arenas Switch-a-roo?, San Francisco Gate

Clippers set sights on Baron Davis, Los Angeles Times

Baron Davis on verge of signing with Clippers, Washington Post

NBA: Warriors trying to woo Brand, Newsday

Baron Davis becomes free agent, Chicago Sun-Times

Report: Davis to ditch Warriors for Clippers, FOXSports.com

Logo? Colors? History? Don't mean a thing if you ain't got that team, CBS Sportsline

Davis on verge of joining Clippers, CNN Sports Illustrated

Davis on verge of signing with Clippers, Salon

Type “more” for more news.

Notice that in the pattern routine, there is an option called SHOW 10. This means to output 10 rows at a time. Buddyscript will go to the output datasource to retrieve the information, which in this case happens to be exactly 10 rows, since the request was to buffer 10 rows per datasource request. If the user were to type in “more”, another 10 rows will be retrieved from the datasource and 10 more rows will be displayed, and so on. (Note that there is a Buddyscript variable named SYS.Presentation.Maxlength that also controls the number of characters that can be displayed on an IM client. Depending on what this is set to, this number will also control the number of rows displayed back.)

With the SHOW command, this allows the user a quick and equivalent way of emulating a forward read-only cursor, i.e. displaying x number of rows of output at one time. The other option would be to put the data into an object and loop through the object, displaying each row, which involved more coding. It’s very possible that for control purposes, the latter method is the right way to go, but for quick coding and display, SHOW is very powerful.

Hopefully you have gotten a chance to absorb the intricacies of using datasources by accessing a really powerful web service. Thanks for your attention!

An advanced look at Web Services and Datasources - Part I

imiluk — Mon, 11 Aug 2008 21:59:00 GMT

An advanced look at Web Services and Datasources

Back in February, we showed a basic example of accessing a web service and using a datasource to consume information from a web service. (Refer to: http://windowsliveagents.spaces.live.com/blog/cns!5BCD45E519E07634!443.entry) Today, we’ll take a further look at a real-world web service, and some further things you can do with a datasource to make your application perform better, and to potentially reduce coding effort.

Many agents rely on rich content in order to create a solid user experience. Many times, this involves accessing an external data store, such as a web service. With some web services, you can parameterize your request in the URL itself, for example http:/URL?<input>. More often, web services involve using request and response model via a SOAP API.

The Windows Live Search API is a very powerful web service that does many things. It allows a user to do searches on the web, news, images, as well as get dictionary, phonebook and spelling information. It provides a web service XML interface using a SOAP API, enabling you to submit requests and get back a response via XML. For more information on the XML, refer to this link: http://msdn.microsoft.com/en-us/library/bb251794.aspx

Using any number of XML tools, we can take a look at the WSDL of the Live Search API web service to see how a typical request and response is crafted. The WSDL endpoint is this:

http://soap.search.msn.com/webservices.asmx?wsdl

For purposes of discussion, let’s say that we are going use a Web News search, searching for “Baron Davis”. The query of “Baron Davis” is put into the Query element. There are numerous other elements that are part of the response. They are highlighted in red. The XML response would look like this:

<?xml version="1.0" encoding="utf-16"?>

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<soap:Body>

<Query>Baron Davis</Query>

<SafeSearch>Moderate</SafeSearch>

</Location>

<ResultFields>All DateTime</ResultFields>

</SearchTagFilters>

</SourceRequest>

</Requests>

</Request>

(Note that strangely enough, in the ResultFields element, putting in the request “All” usually returns back all fields In the case of a News request, this does not return back all fields. “All DateTime” will return all fields, plus the datetime in this case.)

The XML response looks like this, with output fields in bold:

<?xml version="1.0" encoding="utf-16"?>

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<soapenv:Body>

<Title>NBA free agent roundup: Baron Davis to L.A.?</Title>

<Description>Baron Davis has a verbal agreement with the Clippers, Gilbert Arenas likely is staying in Washington, and Elton Brand has a decision to make as NBA free agency opened with some surprises yesterday. The dominoes began to tumble when Davis surprised ... </Description>

<Url>http://www.newsday.com/sports/basketball/knicks/ny-spnba025749266jul02,0,2266274.story </Url>

<DisplayUrl>http://www.newsday.com/sports/basketball/knicks/ny-spnba025749266jul02,0,2266274.story</DisplayUrl>

<Source>Newsday</Source>

</DateTime>

</Result>

<Title>Later Daze, Baron: Davis leaves Warriors for Clippers</Title>

<Description>del.icio.us Less than 24 hours after Davis shocked the Warriors by walking away from the final year and $17.8 million left on his contract, the franchise guard delivered a second strike Tuesday afternoon. Davis agreed in principle with the Clippers ... </Description>

<Url>http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/07/02/SPCF11ICKB.DTL</Url>

<DisplayUrl>http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/07/02/SPCF11ICKB.DTL</DisplayUrl>

<Source>San Francisco Gate</Source>

</DateTime>

</Result>

</Results>

</SourceResponse>

</Responses>

</Response>

</SearchResponse>

</soapenv:Body>

</soapenv:Envelope>

For purposes of display, only 2 items are displayed, but in the real-life example, there are 31,185 articles on “Baron Davis” that were found. The 31,185 is indicated in the <TOTAL> element in the response. Note that not all 31,185 rows are retrieved. The amount retrieved is regulated in the Preprocess block, in the built-in LIMIT and OFFSET variables. More on this later, when we describe the datasource.

Let’s take a look at how we generate the Buddyscript code to access this web service.

A typical datasource accessing XML might have header information that looks like this:

datasource dsSample(ARG1, ARG2, ARG3) => A1, B1, C1

http

http://someurl/sample.xml

simple xml

However, for a web service invoking SOAP messages, we have to build a request string, so we use the PreProcess section of a datasource to set a variable that will contain the request, along with other variables. Thus, the beginning of the datasource would look like this instead:

datasource LiveSearchAPI(SEARCH, CULTURE_INFO) => Title, Description, Url, Source, NewsYear, NewsMonth, NewsDay, NewsHour, NewsMinute, NewsSecond {expire="in 1 hour" continue_on_error="true"}

preprocess

if LIMIT>10 || LIMIT<=0

MAXRESULTS = 10

else

MAXRESULTS = LIMIT

FIELDLIST = "Title Description Url Source DateTime"

POST_DATA = BuildSearchAPIPostData(SEARCH, "News", OFFSET, MAXRESULTS, CULTURE_INFO, FIELDLIST)

http

http://soap.search.msn.com:80/webservices.asmx

header

Accept: application/soap+xml

postdata {encode=no}

POST_DATA

simple xml

We’ll describe the syntax of the datasource in more details later on, but for now, what’s important to point out is that a function is called to build the request string. The function in this case is called BuildSearchAPIPostData and has a number of arguments. Let’s take a look at the function:

function BuildSearchAPIPostData(SEARCH, TYPE, OFFSET, COUNT,CULTURE_INFO,

FIELDLIST, RADIUS, LATITUDE, LONGITUDE)

if (LATITUDE eq "")

LATITUDE = 0

if (LONGITUDE eq "")

LONGITUDE = 0

if (RADIUS eq "")

RADIUS = 5

POST_DATA = '<?xml version="1.0" encoding="UTF-8" standalone="no"?>\n'

POST_DATA = StringConcat(POST_DATA, '<SOAP-ENV:Envelope xmlns:SOAP-ENV="http:/\/schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:tns="http://schemas.microsoft.com/MSNSearch/2005/09/fex" > <SOAP-ENV:Body>')

POST_DATA = StringConcat(POST_DATA, ' <tns:Search xmlns:tns="http:/\/schemas.microsoft.com/MSNSearch/2005/09/fex"> <tns:Request>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:AppID>', GetLiveSearchAPIAppID(), '</tns:AppID>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Query>', SEARCH , '</tns:Query>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:CultureInfo>', CULTURE_INFO, '</tns:CultureInfo> <tns:SafeSearch>Moderate</tns:SafeSearch> <tns:Flags>None</tns:Flags>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Location>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Latitude>', LATITUDE, '</tns:Latitude>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Longitude>', LONGITUDE, '</tns:Longitude>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Radius>', RADIUS, '</tns:Radius>\n')

POST_DATA = StringConcat(POST_DATA, ' </tns:Location>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Requests> <tns:SourceRequest>\n')

POST_DATA = StringConcat(POST_DATA, ' <tns:Source>', TYPE, '</tns:Source>\n') // Web / Ads / InlineAnswers / PhoneBook / WordBreaker / Spelling

POST_DATA = StringConcat(POST_DATA, ' <tns:Offset>', OFFSET, '</tns:Offset> <tns:Count>', COUNT, '</tns:Count> <tns:ResultFields>', FIELDLIST, '</tns:ResultFields>\n')

POST_DATA = StringConcat(POST_DATA, ' </tns:SourceRequest> </tns:Requests>\n')

POST_DATA = StringConcat(POST_DATA, ' </tns:Request> </tns:Search>\n')

POST_DATA = StringConcat(POST_DATA, '</SOAP-ENV:Body> </SOAP-ENV:Envelope>\n')

return POST_DATA

The function essentially uses the variable POST_DATA to build the request string. If there are certain parameters without information, it defaults the information (e.g. LATITUDE). The function also calls another function to get the Windows Live APP ID. This APP ID is used in the Live Search API to determine individual access rights. (See the Windows Live API for more information on obtaining this APP ID.) The function itself simply looks like this:

function GetLiveSearchAPIAppID()

return "ABCDE12345"

where “ABCDE12345” is the App ID.

We'll take a look at the rest of the datasource and invoke code later this week.