The parameters are defined all over here:

 Searching for 'SERVICEINPUTCLASS' in 'Ens*.cls' (whole words,case sensitive)
Ens.Enterprise.MsgBank.BankTCPAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
Ens.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.DICOM.Adapter.TCP.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.EMail.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.File.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.HTTP.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.Pipe.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.SQL.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.TCP.CountedInboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.TCP.DuplexAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.TCP.FramedInboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.TCP.TextLineInboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
EnsLib.UDP.InboundAdapter.cls(SERVICEINPUTCLASS): Parameter SERVICEINPUTCLASS 
Found 13 occurrence/s in 13 file/s.

 Searching for 'SERVICEOUTPUTCLASS' in 'Ens*.cls' (whole words,case sensitive)
Ens.Enterprise.MsgBank.BankTCPAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
Ens.InboundAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
EnsLib.DICOM.Adapter.TCP.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
EnsLib.HTTP.InboundAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
EnsLib.TCP.CountedInboundAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
EnsLib.TCP.FramedInboundAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
EnsLib.TCP.TextLineInboundAdapter.cls(SERVICEOUTPUTCLASS): Parameter SERVICEOUTPUTCLASS 
Found 7 occurrence/s in 7 file/s.

But there is no case where it is used.

Looks like "reserved for future use "

The diagramm shows to me  2 object REFERENCES (oref)
oref consists of a  (local) integer@Classname  and points to an object.
in your case both are of type %Collection.ListOfObj 
by the reference you can't tell that this is the same.
any ##class(%Collection.ListOfObj).%New() will create a new oref
in your case I see a count of 1 and then a count of 2 
you should look what happens in or after (19)  and in or after (29)
looks to me like a fresh return value

set CountRow=pObject.IssuesList.GetAt(i).Count()

you assume pObject.IssuesList.GetAt(i) gives back a %Collection Object (Iist, Array, ..)
Before applying method .Count() you should check if this assumption is true.

your previous description with ASSIGN / APPEND wasn't that convincing that you always have the object you expect.

ref: "out of the scope of ENSEMBLE to an external class" 
you should save anything that you want to keep over that call in one/multiple property of %context Object.


 

to work down a collection of varying number of elements I'd use this kind of loop
in this case it's a double loop

For res=1:1:callresponse.result.Count() {
  Continue:'$IsObject(callresponse.result.GetAt(res)
  For err=1:1:callresponse.result.GetAt(res).Count() {
    Continue:'$IsObject(callresponse.result.GetAt(res).errors.GetAt(err)
    Set context.ErrorMessage= callresponse.result.GetAt(res).errors.GetAt(err).message
    - - - -
    }
 }

This is the paranoic version!
If you trust ENSEMBLE you may skip the check for $IsObject()

HTH

online docs don't give a direct hint.

so my shot from the hip: 
selection expression - $select(), $case()  where you get a value based  on a condition
data expression - anything that sets, modifies, composes data.

this is  a quite academic view since  data expressions may contain selection expressions
and selection expressions may contain data expressions.
both variants and any mix of it  are quite common in COS 

HTH

I did a short test fiddling arouned ^Samples.PersonI

SAMPLES>Do $SYSTEM.OBJ.ValidateIndices("Sample.Person","",1,2)                   
 
Checking index integrity for class 'Sample.Person'
Begin time:  08/17/2017 21:41:25
 
Verifying data from data map 'IDKEY' is indexed correctly...
Index 'NameIDX', entry ^Sample.PersonI("NameIDX"," CHANG,QUIGLEY H.",39), has differences between master map data and index map data.  Corrected
Index 'NameIDX', entry ^Sample.PersonI("NameIDX"," CHANG,DAN L.",40) missing.  Corrected
Index 'NameIDX', entry ^Sample.PersonI("NameIDX"," CHADWICK,OLGA E.",43) missing.  Corrected
Index 'NameIDX', entry ^Sample.PersonI("NameIDX"," CANNON,BARBARA W.",81) missing.  Corrected
Data Map evaluation complete, 200 rows checked, 4 errors found, elapsed time: .004733 seconds
 
Verifying data from index map "$Person" is correct...
Index map "$Person" evaluation complete, 0 errors, elapsed time: .000691 seconds
 
Verifying data from index map NameIDX is correct...
Index 'NameIDX', entry ^Sample.PersonI("NameIDX"," CEMPER,DAN L.",40), data differs for field 'Name' between data and index map.  Corrected
Index map NameIDX evaluation complete, 1 errors, elapsed time: .001331 seconds
 
Verifying data from index map SSNKey is correct...
Index map SSNKey evaluation complete, 0 errors, elapsed time: .001195 seconds
 
Verifying data from index map ZipCode is correct...
Index map ZipCode evaluation complete, 0 errors, elapsed time: .001255 seconds
 
%ValidateIndices is complete, total elapsed time: .012282 seconds
 
SAMPLES>

This looks good so far.

Similar using  Class %System.License. ...  you may reduce the number of allowed connections by USER
This might  be interesting in SaaS situation.

classmethod SetUserLimit(MaxLU As %Integer) as %Integer

$SYSTEM.License.SetUserLimit establishes the maximum number of license units that this Cache instance will consume. This permits a system manager to prevent a Cache instance from consuming all the license units in a MultiServer key shared among multiple Cache instances. The Method returns the former maximum value. In the absence of a call to $SYSTEM.License.SetUserLimit(max) a Cache instance may consume all available license units. 

Requires access to the %Admin Manage resource.

Using  Class %System.License. ...  you may reduce the number of allowed connections by instance

• classmethod SetConnectionLimit(MaxCon As %Integer) as %Integer

$SYSTEM.License.SetConnectionLimit establishes the maximum number of connections permitted per user on this instance. This enables a system administrator to prevent a user from making so many connections to a Cache instance that they consume all available license units. Calling $SYSTEM.License.SetConnectionLimit($SYSTEM.License.MaxConnections()) permits a user to make the maximum connections permitted but prevent transitioning to the license unit per connection state, insuring the user will consume no more than one license unit. A zero argument removes the limit. The failure to obtain a license will be indicated in the normal way. For example, a call to $system.License.Login() will return zero (0) while a failure to log in to a new terminal connection will receive a error. However, these license failures will not be reported in the console log. The method returns the former maximum value. 

The limit applies only to the local instance. If a Cache MultiServer license is shared among several instances it is still possible to exceed $SYSTEM.License.MaxConnections() over all instances. This can be avoided by setting the limit low enough on each instance that the combined connections to all instances will be unlikely to exceed $SYSTEM.License.MaxConnections(). 

$SYSTEM.License.SetConnectionLimit reqires access to the %Admin Manage resource. It is suggested that customers call this API from SYSTEM^%ZSTART.