Professional InfoPath 2003 [Electronic resources] نسخه متنی

Resource Meta Data

Before you begin your analysis of the key form elements, we’d like to introduce the concept of resource meta data. It underlies the examples in this chapter, where you’ll work with a simple schema, based on the DCMI recommendations. When you get to the case study later on in the book, you’ll formalize the schema and develop it to include elements from other meta data vocabularies.

What do we mean by resource meta data? Meta data means data about data. Resource meta data describes a set of properties about information resources and, specifically, about addressable resources. By addressable resources, we mean those that we can access on the Internet, using Uniform Resource Identifiers (URIs). Typically, the meta data describes the title and content of a resource, when it was published, and so on. It represents a Web page or a music download, rather than the HTML or MP3 file itself. If you’ve used a news feed or a Web portal, you’ve worked with meta data.

The object of defining this meta data is to make it easier to retrieve useful information about Web resources by being specific about their properties. In an ideal meta data world, if you specified a search with publisher=wrox & title contains asp.net & type=book as query parameters, you’d probably just get hits from Wrox Press, Amazon, and other book vendors’ Web sites. You shouldn’t, however, get articles from the MSDN site or ASP Resource Index, because you didn’t want articles or either of these publishers.

Meta Data Vocabularies

Several XML vocabularies have been proposed for resource meta data. Nearly all of them use the DCMI recommended core set of 15 elements in some respect or another. You won’t use every one of the elements here—just enough to get you started shaping an InfoPath form.

One of the reasons that the DCMI recommendations are widely accepted is that they focus on achieving interoperability. The specification is extremely simple and straightforward to implement. The International Standards organization has recently approved the core elements as an international standard: ISO 15836:2003.

DCMI advocates the 1:1 principle, whereby one meta data record describes a single resource. So different editions, translations, and formats get separate descriptions. Thus, an image of a famous painting on a Web site is distinct from the physical object it represents, just as it is distinct from a stock negative in the picture library, or the audio guide that comments on the painting. Possibly the only common factor will be the title, but they can easily be related to one another.

Meta Data Example

Suppose you work for an imaginary online information service, NewsLine Inc., that handles a range of media and syndicates it to customers. You have to design an InfoPath form that will handle the creation of meta data about news, features, reviews, and other information categories. The meta data describes the content of the stories that the service publishes. Users of the form will save each instance of the meta data as a separate XML file.

Here’s an example of the sort of meta data instance you might need to capture when a story is created, in this case a book review by a staff writer:

<meta>
   <identifier>http://newsline.net/reviews/0261.xml</identifier>
   <creator>Maria Grant</creator>
   <title>Stealing Time by Alec Klein</title>
   <description>The downfall of AOL Time Warner was a sensational tale of
dotcom boom and bust. Here is the full story by Washington Post reporter
Alec Klein, the man who exposed the scandals, and has now documented them in
a book published this month by Simon and Schuster.</description>
   <type>Book review</type>
   <format>text/xml</format>
   <date>2003-06-24</date>
   <subjects>
      <subject>AOL Time Warner</subject>
      <subject>Washington Post</subject>
      <subject>Klein, Alec</subject>
   </subjects>   
</meta>

Most of the element names are self-explanatory.

The identifier gives the URL of the review itself, using a fictitious Web site. An identifier could use other formats, for example, an industry-standard serial identifier like an ISSN (International Standard Serial Number).

creator is the generic DCMI name for the person responsible for the intellectual creation of the resource, so it covers roles like composer, photographer, and artist, as well as author. (Secondary roles like editor, translator, and so on are relegated to the contributor element.)

DCMI type defines either the genre—that is, the intellectual type—of the resource or its presentation (there will be scope to clarify this somewhat ambiguous property in the case study).

The format states the Internet Media Type (IMT) of the file. You can read about IMT at [www.isi.edu/in-notes/iana/assignments/media-types/media-types] .

date means the date of publication or availability of the review. The recommended format of the date is yyyy-mm-dd, where dates (and times) are encoded with the W3C Encoding rules—a profile based on ISO 8601. See Date and Time Formats, W3C Note, [www.w3.org/TR/NOTE-datetime].

Note the repeating subject element. The DCMI recommendation allows for the use of repeating elements in any order. This example puts subjects in a subjects wrapper element for convenience. These subjects are simple text labels. In the case study you’ll enhance the design to use a consistent vocabulary of terms.