This sounds very doable. I don't have time to test it out today. Perhaps
later in the week...

Do you mind posting the xsd files  and the gifs as attachments?

I'm trying to do this solely with FrontPage and DVWPs.

The ProtocolSelector DVWP should look like this:

Compound1
Protocol1
Protocol2

Compound2
Protocol3

Compound3
Protocol4
Protocol5
Protocol6

When the user  clicks on a protocol, the
ProtocolSummary DVWP should display  a gif (will
eventually have more summary info).

Protocol2

+------+
| |
| |
| |
+------+

To attempt this with the following files...
1) Put all the attached files  into your test site's
"Shared Documents" library.
2) In the files, replace "hostname" and "sitename"
with values from your test setup.
NOTE: Fake protocol  summary images are borrowed from
Google to avoid sending more files.

To ensure the files  of my previous post made  it, I'll include them
inline:
(they may be uglified with line wraps)

ProtocolSelector.xml
--------------------

<?xml version="1.0" encoding="utf-8"?>
<ProtocolSelector xmlns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSelector.xsd">
<Compound CompoundName="Compound1">
<Protocol ProtocolName="Protocol1" />
<Protocol ProtocolName="Protocol2" />
</Compound>
<Compound CompoundName="Compound2">
<Protocol ProtocolName="Protocol3" />
</Compound>
<Compound CompoundName="Compound3">
<Protocol ProtocolName="Protocol4" />
<Protocol ProtocolName="Protocol5" />
<Protocol ProtocolName="Protocol6" />
</Compound>
</ProtocolSelector>

ProtocolSelector.xsd
--------------------

<?xml version="1.0"?>
<xs:schema id="ProtocolSelector"
targetNamespace="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSelector.xsd"
xmlns:mstns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSelector.xsd"
xmlns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSelector.xsd"
xmlns:xs="http://www.w3.org/2001/XMLSchema" target="_blank" rel="nofollow">http://www.w3.org/2001/XMLSchema"
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
attributeFormDefault="qualified" elementFormDefault="qualified">
<xs:element name="ProtocolSelector" msdata:IsDataSet="true"
msdata:EnforceConstraints="False">
<xs:complexType>
<xs:choice maxOccurs="unbounded">
<xs:element name="Compound">
<xs:complexType>
<xs:sequence>
<xs:element name="Protocol" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="ProtocolName"
form="unqualified" type="xs:string" />
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="CompoundName" form="unqualified"
type="xs:string" />
</xs:complexType>
</xs:element>
</xs:choice>
</xs:complexType>
</xs:element>
</xs:schema>

ProtocolSummary.xml
-------------------

<?xml version="1.0" encoding="utf-8"?>
<ProtocolSummary xmlns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSummary.xsd">
<Protocol ProtocolName="Protocol1"
ProtocolGraph="http://www.google.com/logos/olympics06_opening.gif" />
<Protocol ProtocolName="Protocol2"
ProtocolGraph="http://www.google.com/logos/lunarnewyear06.gif" />
<Protocol ProtocolName="Protocol3"
ProtocolGraph="http://www.google.com/logos/mozart.gif" />
<Protocol ProtocolName="Protocol4"
ProtocolGraph="http://www.google.com/logos/mlk06.gif" />
<Protocol ProtocolName="Protocol5"
ProtocolGraph="http://www.google.com/logos/braille.gif" />
<Protocol ProtocolName="Protocol6"
ProtocolGraph="http://www.google.com/logos/newyear06.gif" />
</ProtocolSummary>

ProtocolSummary.xsd
-------------------

<?xml version="1.0"?>
<xs:schema id="ProtocolSummary"
targetNamespace="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSummary.xsd"
xmlns:mstns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSummary.xsd"
xmlns="http://hostname/sites/sitename/Shared%
20Documents/ProtocolSummary.xsd"
xmlns:xs="http://www.w3.org/2001/XMLSchema" target="_blank" rel="nofollow">http://www.w3.org/2001/XMLSchema"
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
attributeFormDefault="qualified" elementFormDefault="qualified">
<xs:element name="ProtocolSummary" msdata:IsDataSet="true"
msdata:EnforceConstraints="False">
<xs:complexType>
<xs:choice maxOccurs="unbounded">
<xs:element name="Protocol">
<xs:complexType>
<xs:attribute name="ProtocolName" form="unqualified"
type="xs:string" />
<xs:attribute name="ProtocolGraph" form="unqualified"
type="xs:string" />
</xs:complexType>
</xs:element>
</xs:choice>
</xs:complexType>
</xs:element>
</xs:schema>

I found an answer that worked in the mix of things I tried and
retried...

1) I added both xml  files as DVWPs.
2) In the protocol  selector, I added the child  record as a subview.
3) In code view for the protocol selector, Iadded the ProtocolName
as a DataField: <DataFields
xmlns="http://schemas.microsoft.com/WebPart/v2/DataView">@CompoundNam
e,Compound Name;@ProtocolName,Protocol Name;</DataFields>
4) In design view, I selected the protocol field and chose "web part
connections"
5) In the web  part connection  wizard, I paired up the "protocol
name" fields
6) In the web part  connection wizard, I chose the "[current select:
xsl:value-of]" as the "create hyperlink on"

FrontPage seems very touchy, and I find myself having to generally
redo some steps frequently. I am also wondering why I have to edit
the code in those places I hit.

Glad you got it working. When you setup the data  source catalog entry,
did you specify the CompoundName and ProtocolName as fields?

I have the xml  files in the shared documents library, which I
dragged into a web  part zone. Then I started placing fields onto the
DVWP.

What do you mean specifying they are fields?

Well, it looks like you had to add
<DataFields
xmlns="http://schemas.microsoft.com/WebPart/v2/DataView">@CompoundName,C
ompound Name;@ProtocolName,Protocol Name;</DataFields>

which looks like the tag that you might need if the datafields were not
automatically found. If you add the xml  files into the data  Source
Catalog and then choose Show Data, do you see these two fields?

Can you then select them instead of typing them into the code behind?

See where I'm going?