Chapter 2.3-Multimedia Storage Techniques

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XPath Introduction XPath is a language for finding information in an XML

document.

XPath is used to navigate through elements and attributes inan XML document.

What is XPath?

* XPath is a syntax for defining parts of an XML document* XPath uses path expressions to navigate in XML documents

* XPath contains a library of standard functions

* XPath is a major element in XSLT( EXtensible Stylesheet

Language).

* XPath is a W3C recommendation


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In XPath, there are seven kinds of nodes: element,attribute, text, namespace, processing-instruction,comment, and document (root) nodes.

Harry

Potter

J K. Rowling200529.99


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Example of nodes in the XMLdocument above:

(document node)

J K. Rowling (element node)lang="en" (attribute node)

Atomic values

Atomic values are nodes with no children or parent.Example of atomic values:J K. Rowling"en"


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Items

Items are atomic values or nodes.

Relationship of Nodes

Parent

Each element and attribute has one parent.

In the following example; the book element is the parent of the title,

author, year, and price:

Harry Potter

J K. Rowling

2005

29.99


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Children

Element nodes may have zero, one or more children.In the following example; the title, author, year, andprice elements are all children of the book element:

Harry PotterJ K. Rowling2005

29.99


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Siblings

Nodes that have the same parent.In the following example; the title, author, year, andprice elements are all siblings:

Harry PotterJ K. Rowling2005

29.99


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Ancestors

A node's parent, parent's parent, etc.In the following example; the ancestors of the titleelement are the book element and the bookstoreelement:

Harry PotterJ K. Rowling

200529.99


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Descendants

A node's children, children's children, etc.In the following example; descendants of the bookstoreelement are the book, title, author, year, and priceelements:

Harry PotterJ K. Rowling

200529.99


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XPath uses path expressions to select nodes or node-sets in an XML document.

The node is selected by following a path or steps.

Harry Potter

29.99

Learning XML

39.95


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Selecting Nodes

XPath uses path expressions to select nodes in an XML document.

The node is selected by following a path or steps. The most useful

path expressions are listed below:


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Examples

In the table below we have listed some path expressions and the result

of the expressions:


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Predicates

Predicates are used to find a specific node or a node that contains a

specific value.

Predicates are always embedded in square brackets.


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Selecting Unknown Nodes

XPath wildcards can be used to select unknown XML elements.

Selecting Several Paths

By using the | operator in an XPath expression you canselect several paths.


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Xpath Axes

In the table, we have listed some path expressions andthe result of the expressions:


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XPath Axes

An axis defines a node-set relative to the current node.


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Location Path Expression

A location path can be absolute or relative.

An absolute location path starts with a slash ( / ) and a relative location

path does not. In both cases the location path consists of one or more

steps, each separated by a slash:


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XPath Operators


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Video, Audio and the Switch Element (SMIL)

Adding video and audio media to your presentationis just as easy as adding images. The onlydifference is that we use the and tags instead of tags. These tags also take a

lot of the same attributes such as src, region, begin,dur, etc. To add some audio, or more specifically aRealMedia (.rm) file, we add this tag to our SMILdocument, . Below is what

our code should look like now.


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When it comes to video, it's just like adding anotherimage.

First, create a region to hold the video, then specify thevideo with the tag.Include the location of the video file in the src attributeof the tag.

With the tag, we can optimize the presentationto fit the user's situation. All the content tags, i.e., , , ,, , etc., have attributes that you use along

with such as system-screen-size, system-bitrateand system-language. The SMIL parser then selects themedia that best suits the user's needs using theseattributes.


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What this does is chooses only one tag to use based on the user's bitrate. For example, if someone views this SMIL

presentation with a 28kbps modem, they'll get the "moo-28k.rm" file. On the other hand, if someone views it with something else not

specified, they'll get the "moo-other.rm" file since that has no "system-bitrate" attribute and is deemed the default.


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Metadata Processing Steps for Lecture Archive


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illustrates the metadata processing and generation components for this

application.

Spatial Layout for a Simple SMIL Example


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Spatial Layout for a Simple SMIL Example

Replay Interface for a SMIL Presentation Lecture


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Replay Interface for a SMIL Presentation Lecture

P t ti C t


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Presentation Capture

1. Filming a lecturer giving a PowerPoint

presentation;2. Digitizing and encoding the video footage to

MPEG format (for analysis) and RealMedia

format (for streaming);

3. Analysing the digitized footage or logging datato determine the times at which slide changes

occur;

4. Using the temporal information to generate a

SMIL presentation which integrates synchronized

digital video and PowerPoint slides with a timeline

for browsing and jumping directly to a particular

slide.

Overview of System Components and Process Flow


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Ove v ew o Syste Co po e ts a d ocess ow

PresentationIndexer application


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PresentationIndexer application.

Presentation Archive Search


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Presentation Browse and Replay Interface


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Chapter 2.3-Multimedia Storage Techniques

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