untitled

76 4 The Semantic Web and Bioinformatics Applications

<Protein name="Fumerase"/>

</rdf:li>

<rdf:li>

<Protein name="Malate dehydrogenase"/>

</rdf:li>

</rdf:Seq>

</usesEnzyme>

</Pathway>

The sequence is itself a resource as well as being the container of the other

resources. Notice the use of therdf:liproperty for the members of the

container. This name was borrowed from HTML where it is used for the

members of lists. There are three kinds of container:

1. rdf:Seq.A sequence contains an ordered list of resources. In HTML one
   uses theoltag for such a list.


2. rdf:Bag.A bag is an unordered container of resources. A bag can have no
   resources at all, and it can contain the same resource more than once. In
   HTML one uses theultag for such a container.


3. rdf:Alt. An Alt container is intended to represent a set of alternatives.
   The first resource is the default or preferred alternative, and there is no
   preference among the others. So an Alt container is a set with one dis-
   tinguished member. This corresponds to a “drop-down menu” in HTML,
   and is specified by using theselecttag.

More recently, a second mechanism for ordered lists was added to RDF,

called acollection. The Krebs cycle can now be expressed as follows:

<Pathway name="Krebs Cycle">

<usesEnzyme rdf:parseType="Collection">

<Protein name="Citrate synthase"/>

<Protein name="Aconitase"/>

<Protein name="Isocitrate dehydrogenase"/>

<Protein name="a-Ketoglutarate dehydrogenase complex"/>

<Protein name="Succinyl-CoA synthetase"/>

<Protein name="Succinate dehydrogenase"/>

<Protein name="Fumerase"/>

<Protein name="Malate dehydrogenase"/>

</usesEnzyme>

</Pathway>